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HomeMy WebLinkAbout03112004 BSC Agenda Item 2 • • Ordinance No. AN ORDINANCE RELATING TO FOUNDATIONS AND STRUCTURAL FRAMING; AMENDING THE CODE OF ORDINANCES OF THE CITY OF WEST UNIVERSITY PLACE, TEXAS; AND CONTAINING FINDINGS AND PROVISIONS RELATING TO THE SUBJECT. WHEREAS, the Building Official of the City, being an appropriate City official, has proposed an amendment to the City's standard codes regarding foundations and structural framing; and WHEREAS, the proposed amendment has been referred to the Building & Standards Commission, which has recommended adoption; NOW, THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF THE CITY OF WEST UNIVERSITY PLACE: Section 1. The City Council finds and determines that the matters set out in the preamble are true and correct and adopts them. The Standard Code Schedule of the Code of Ordinances of the City of West University Place are hereby amended as shown in Appendix A, which is attached to this ordinance and made part hereof for all purposes. Section 2. All ordinances and parts of ordinances in conflict herewith are hereby repealed to the extent of the conflict only. Section 3. If any word, phrase, clause, sentence, paragraph, section or other part of this ordinance or the application thereof to any person or circumstance, shall ever be held to be invalid or unconstitutional by any court of competent jurisdiction, neither the remainder of this ordinance, nor the application of such word, phrase, clause, sentence, paragraph, section or other part of this ordinance to any other persons or circumstances, shall be affected thereby. Section 4. The City Council officially finds, determines and declares that a sufficient written notice of the date, hour, place and subject of each meeting at which this ordinance was discussed, considered or acted upon was given in the manner required by the Texas Open Meetings Act, as amended, and that each such meeting has been open to the public as required by law at all times during such discussion, consideration and action. The City Council ratifies, approves and confirms such notices and the contents and posting thereof. The City Council officially finds, determines and declares that sufficient notices of the joint public hearing were given, and the City Council ratifies, approves and confirms such notices, including the contents and the method in which they were given. Section 5. This ordinance shall become effective on the tenth day following its publication as provided in the City Charter. • • CONSIDERED, PASSED AND APPROVED on first reading on Councilmembers Voting Aye: Councilmembers Voting No: Councilmembers Absent: CONSIDERED, PASSED AND APPROVED on second reading, AND SIGNED, on Councilmembers Voting Aye: Councilmembers Voting No: Councilmembers Absent: Attest: Signed: City Secretary (Seal) Mayor Recommended: Reviewed: City Manager City Attorney • a STATE OF PRACTICE OF GEOTECHNICAL ENGINEERING FOR DESIGN OF CUSTOM HOMES IN THE HOUSTON AREA BETWEEN 1990 AND 2001 BY BY DAVID A. EAST FOOD, BY FRANK OONG, P.E.' PRESENTED AT FOUNDATION PERFORMANCE ASSOCIATION MEETING ON JUNE 20, 2001 Abstract Practice of geotechnical engineering in the Houston area has been quite interesting during the past decade, depending on the firm, recommendations for design of custom residential homes vary quite a bit. The purpose of this paper is to look at various design approaches and recommendations. This paper summarizes the state of practice for the past decade. Furthermore, the paper recommends procedures to conduct better geotechnical exploration for custom residential projects in the Houston area. Introduction Due to the strong economy, custom homes are being constructed all over the Houston area. Most of these homes are supported on drilled footing type foundations. The focus of this paper is primarily on the design of homes on drilled footings. Many odd shaped homes (U, L shaped or houses with large slabs with notches) are supported on drilled footings. Furthermore, some of these houses have major foundation problems. The purpose of this paper is to review and summarize 99 geotechnical reports in the Houston area, look at various soil types, discussion of risks, heave computations, drilled footing depths, various slab designs, evaluation of environmental conditions, etc. These reports were conducted uy 17 different firms iocated in the Houston area. About 10% of these reports were conducted by Geotech Engineering and Testing. This paper also develops recommendations on how to better conduct geotechnical exploration for custom residential projects in the Houston area. Report Research In order to develop a State of Practice Report, research was conducted to find geotechnical reports for custom homes conducted by various Geotechnical firms in the Houston area. A total of 99 reports were located from GET's library and from various structural engineers throughout the Houston area. These reports were used as a basis of development of our findings. A map showing where these various soils reports for custom homes were conducted is shown on the site plan, Plate 1 of this paper. As indicated on this map, the concentration of these reports are located within 610 Loop area, near West University, Bellaire, Medical Center, and Kirby area. Furthermore, some of these reports are located along Memorial Drive, Hunters Creek Village, Piney Point Village and Bunker Hill area. A few data points are located outside the Loop. t Principal Engineer,Geotech Engineering and Testing, 800 Victoria Drive,Houston,Texas 77022,713-699-4000 2 Chief Engineer,Geotech Engineering and Testing,800 Victoria Drive,Houston,Texas 77022,713-699-4000 1 of 11 • • Definitions The data developed during this research study are summarized on Plate 2 of this paper. The definition of each term used in this paper is presented below: Map I.D. - The map I.D. indicates where a specific soils report was conducted. The map I.D. is key to the site plan, Plate 1. Year - This indicates the year the soils report was conducted. Company - This term identifies which company did the soils report. We have companies A, B, C, D, E F, G, H, J, K, L, M, N, 0, P, Q, and R, a total of 17. Report No. - This term designates the report number for each specific company. Expansive Soils - This term signifies whether or not expansive soils are present at the job site. Expansive soils should have minimum plasticity index of 20 (Ref. 1). Trees on Site/Site Conditions - This term signifies whether or not trees were present on the site or the firm who conducted the geotechnical report had a Site Condition Section in the report. Sometimes, these soils reports did not even discuss the site conditions. In this case, a dashed line is put in this space for the segment "trees on site/site conditions". Effective Plasticity Index (PI) - This column presents the effective plasticity index of the soils developed by BRAB method (Ref. 2). Discussion of Expansive Soils - This column signifies whether or not the geotechnical report discussed the presence of expansive soils on the site. Discussion of Risks - This column describes whether or not the geotechnical report discussed various risks that are associated with different types of foundations used for residential foundations built on expansive soils. For example, a structural slab with void would be low risk foundation. However, a slab-on-fill pier foundation will have a higher risk than a structural slab with void type foundation system. A discussion of foundations and risk is given on Plate 3. Heave Computations - Most of the heave computations for residential projects (if computed at all) were computed by using Potential Vertical Rise method (Ref. 3). This column signifies whether or not a heave computation was computed for the soils report. 2 of 1 I • Drilled Footing Depth - This column signifies what was the recommended pier depth for the specific soils report. Structural. Slab •- This column signifies whether or not recommendations on a low risk foundation, which is a structural slab with voids/crawl space, was given in a specific geotechnical report. Furthermore, if recommendations on structural slab was given, whether or not recommendations on voids under the floor slabs was given. Therefore, this column signifies whether or not recommendations on structural slabs were present and if recommendations on structural slab were present what was the recommended void size under the floor slab (not under the grade beams). Slab-on-Fill - This column defines whether or not recommendations on slab-on-fill were given in the specific geotechnical report. Furthermore, whether or not a specific fill thickness was given. Some reports presented a very vague fill thickness recommendations. Void Box - This column signifies whether or not recommendations on void boxes were given under the grade beams. Drainage - This column signifies whether or not recommendations on site drainage around the house were given. Sprinkler - This column signifies whether or not recommendations on the presence of a sprinkler system, and their location around the house were given. Trees - This column signifies whether or not recommendations were given on planting a tree next to the foundation. Furthermore, it indicates whether or not recommendations were given on the existing trees next to the foundation. Tree Root Removal -- This column signifies whether or not the specific geotechnical report discussed how to treat the tree removal from a specific site. What would be the ramifications of tree removal (heave). Construction Monitoring - This column signifies whether or not the geotechnical report gave specific recommendations on quality control such as conducting of testing including drilled footing observations, concrete testing, earthwork testing by the design geotechnical engineer. Review of Foundation Drawings - This column signifies whether or not the geotechnical engineer of record required that for the foundation drawings be reviewed by him/her to make sure his/her design recommendations are properly interpreted by the structural engineer and other design team members. 3of11 1 •• • Soil Variability - This column indicates whether or not the geotechnical report indicated that the soils across the site could be variable (from a standpoint of stratigraphy or properties) and there might be a need for design modifications if different soil conditions were encountered. Analysis of the Data General. The contents of all of these reports were reviewed and analyzed. The specific recommendations on analysis are presented in the following sections. Expansive Soils. Many of the reports acknowledged that expansive soils were present on the site. In general when the effective soil plasticity index is above 20, expansive soils are present on the site. Trees on Site/Site Conditions. About 64% of the reports did not discuss site conditions. Specifically, they did not discuss whether or not trees were on the site or any other site features were located on the property. This is an extremely important part of a geotechnical report where many firms failed to discuss. Effective Plasticity Index. About 82% of the reports discussed how expansive the soils were at the specific site and gave plasticity index data in the report. About 91% of the sites reviewed had expansive soils on them. Discussion of Expansive Soils. About 82% of the soils report reviewed did have a discussion of expansive soils within the body of the report. Discussion of Risks. About 40% of the reports did not have a discussion on risks of using different types foundations. For example, they did not discuss whether a structural slab was better than a slab-on-fill type foundation supported on piers. Again, this is extremely important because, by discussing the risk associated with each different type of foundation, the soils engineer brings in the architect, the structural engineer, the builder and the owner into the decision making process. Heave Computations. About 74% of the reports did not discuss or calculate the heave. It is not customary to estimate the heave for design of custom residential foundations in the Houston area. One of the reasons for that is, it's not a consensus on the correct method for estimation of heave. Furthermore, it could be expensive. Therefore, most geotechnical consultants use their experience in specifying how much fill is required under the floor slabs to reduce heave on various types of residential foundations. The required fill thickness is usually determined based on the experience and engineering computations of the heave, such as Potential Vertical Rise, PVR (Ref.3). Drilled Footing Depth. An average pier depth of about 9-ft was specified after reviewing all of these reports. Review of reports from 1996 to 2001 indicated an average pier depth of 10.5-ft. Depth of drilled footings is very important in areas where expansive soils are present. Shallow piers can push up against the grade beams and lift the foundation system, if expansive soils are present at the site. The pier should be placed below the zero movement line. The zero movement line is a line below which no movement (heave) of expansive soils occurs due to weight of the colum of the soils. The piers should be anchored below the zero movement line. Currently, we recommend piers to be placed 12-ft to 15-ft in the Houston area where expansive soils are present. 4of11 S Structural Slab Recommendations. About 55% of the reports discussed structural slab systems. The other 45% did not discuss it at all. Furthermore if they were discussed, most of them did. not specify any kind of a void space that should go under the structural slab system. We believe that there should be a detailed discussion about the use of a structural slab. Furthermore, the recommended void size should he specified. In addition, recommendations on venting of the air underneath the slab should also be discussed. 'ao limit moisture migration through the slab. This is only applicable to a structural slab with a void/crawl space. Slab-on-Fill. About 97% of the reports did specify a slab-on-fill type foundation or drilled footings ..------------------ system as the type of foundation that should be used to support the structural loads for a typical custom residential foundation. Some of these reports were vague, because they specifically say whether or not fill is required under the floor slabs. The vague statements given did not specify exactly how much fill should he placed under the floor slabs. Majority of the soils reports reviewed indicated the required fill thicknesses of about 24-inches or less. In general, a maximum of 48- inches of select structural fill was specified in the areas where the soils were highly expansive. Our experience indicates that about four-ft of fill will generally reduce the movements to an acceptable level, provided positive environmental controls (drainage, trees, sewer/plumbing leak, etc.) are implemented. Void Boxes. About 38% of the reports specified the required void box size under the grade beams. Void boxes are recommended by many geotechnica.l firms in Houston as a way of reducing foundation movements. Expansive soils once swelled up can theoretically move into a void space area (void box) without lifting the grade beams. The discussion on whether or not void boxes should be used under grade beams on residential foundations was conducted by the Foundation Performance Association. It is generally believed that void boxes under grade beams provide channels for water to flow underneath the foundation system. Therefore, the use of them are discouraged. This discussion and idea was developed in 1996. Drainage. About 93% of the reports discussed that positive drainage was extremely important to the performance of the custom foundation system. Drainage was discussed in a majority of the reports. Sprinkler Systems. About 86% of'the reports reviewed did not discuss the sprinkler system. They did not discuss how the sprinkler system (if used at all) should be placed around the structure to minimize moisture variations and therefore, differential movements. Trees. About 59% of the reports did discuss trees. Specifically, all the reports that discussed trees, described planting trees next to the foundation system and how they would affect the foundation system. It is understood that if the tree is left in place or planted next to a foundation system, it may cause the soil to shrink and the foundation to settle if clays are present. In all of the reports the word planted was synonymous with trees left in place. Tree_Removal. About 70% of' the reports did not discuss the tree root removal in their reports. This is an extremely important section of a report, because tree removal in areas where expansive soils are present, can cause significant heave. Therefore, the reports should address this condition and warn the client. This has not been customary in the Houston area until the year 1995. A detailed study of tree removal and its effect on foundation systems was presented in 1997 by Eastwood and Peverley (Ref. 4). 5 oft] • . Construction Monitoring_ About 85% the reports suggested following up the design with construction monitoring. Construction monitoring is an important part of any design. Review of the Plans and Specifications. About 75% of the reports suggested review of' the foundation drawings after the design was completed. The review of the foundation design drawings by the geotechnical engineer of the record is important. This review will provide the client with the confidence that the initial designer (architect, structural engineer, owner) understood the soils report and followed the recommendations, It is possible once the drawings are reviewed by the geotechnical engineer of the record, mistakes are found that are reported to the structural engineer. Furthermore, foundation and risks are discussed. Soil Variability_ About 99% of the reports discussed the potential variation of soil stratigraphy and properties across the site. This is a true condition. Subsoils may vary across the lot from a standpoint of stratigraphy and soil properties. Conclusions and Recommendations Based on the review of the 99 reports written between 1990 and 2001 for custom homes in the Houston area, the following conclusions and recommendations can be made: o The soil reports reviewed from 17 companies represent a cross section of the geotechnical firms in the Houston area that do residential work for custom homes. o Many of these soils reports indicated the presence of expansive soils in the vicinity of the project site. Most of them discussed the presence of expansive soils. o Only 36% of the reports reviewed discussed site conditions. The rest of the reports did not even address site conditions. The site conditions should be discussed in all reports. Perhaps a picture of the site should be included in the report. o Foundation types and risks must be discussed. o A review of the reports indicates an average pier depth of about nine-ft. Pier depths have been increasing in depth in the Houston area since 1995. In the 1970's and early 80's, piers were placed at a depth of about eight-ft. However, due to new understanding of the active zone depth and the effect of trees on foundations, deeper piers have been recommended. However, most geotechnical firms in Houston are not taking account the effect of tree removal in their foundation system. This condition was known to the Houston area after 1995 or 1996. Furthermore, the use of deeper piers is resisted by some designers, builders, owners, etc., because this may add some to the cost of the construction of the foundation system. However, we believe that increasing the depth of' the piers by a few feet, the cost of the foundation system should not increase significantly. Furthermore, the risks of' putting shallow piers in the area where expansive soils are present are too great. These shallow piers can actually be grabbed by the expansive soils and be pushed against the foundation system, resulting in floor slab heave. Considering that most of' the distress of the newly constructed foundations in Houston is heave, the piers should be deep enough to resist uplift due to expansive soils. 6 of 11 o Almost all of the reports discussed the slab-on-fill on drilled footings. However, many of them did not suggest the required fill thickness. We believe that if this type of foundation system is recommended, the fill thickness should be clearly defined. Unfortunately, some soils reports are very vague about the required fill thickness. This has caused foundation problems, because inadequate fill thickness has been placed underneath the floor slabs. o About one-third of the reports did discuss the use of void boxes underneath the grade beams. Many of' them did not. The use of void boxes is a controversial issue today. We do not recommend the use of void boxes under the grade beams. o Nearly all of the geotechnical reports discussed positive drainage as a major component of foundation design in their report. This should be covered in all reports. o Not very many reports discussed the presence of sprinkler systems around a house. We believe that the sprinkler system, if used, should be placed all around the house to provide uniform moisture conditions at the edge of the foundation. A non-uniform moisture condition will result in differential movement of the slab and foundation distress. o The area of the geotechnical reports that requires most improvement is the section that has to do with removal of' existing trees. This issue must be further discussed in geotechnical reports. Currently, most geotechnical reports in Houston do not even discuss the effect of tree removal. In the event that a drilled footing foundation system is to be used, minimum boring depths should be 20-ft. Root fiber depth should be logged in the borings. Furthermore, the depth of active zone should be estimated. The effect of' tree removal should be clearly discussed in the report. o Structural engineers who are designing a custom home must make sure the effects of tree removal have been considered in the geotechnical report prior to conducting a design of a residential slab. Some structural engineers blindly disregard this issue and they claim, they followed an erroneous soil report. Knowing the site conditions is also the responsibility of the structural engineer of'the record, o None of the reports reviewed had any suction data or used suction to estimate heave. o The authors hope that in the future, the concepts, such as the use of'suction will be implemented in the design of' lightly loaded structures. Currently, most firms in the Houston area do not run suction tests on their soils samples due to costs associated with conducting this type of test and analyzing the data. Due to the extremely competitive nature of' doing residential geotechnical work, it is almost impossible to do a detail geotechnical exploration and testing for residential projects. We believe that by providing a minimum standard in conducting geotechnical explorations, more firms will be interested in conducting more advanced and up to date geotechnical explorations and therefore, saving the client from the risks and spending too much money during construction and repair. Having a minimum standard is the only way, we believe, that the practice of design of a custom foundation system for lightly loaded structure in Houston can be improved. 7 of 11 H . . References 1. David Eastwood and Others "Methodology for Foundations on Expansive Clays" Published in December, 1980 Edition of ASCE Journal of Geotechnical Engineering Division. 2. Building Research Advisory Board, National Research Council, "Criteria for Selection and design of Residential Slabs on Grounds," National Academy of Science Publication 1571, 1968. 3. "Method for Determining the Potential Vertical Rise, PVR," State Department of Highways and Public Transportation, Test Method Tex 124-E, Austin, Texas. 4. D. Eastwood and D. Peverley "Design of Foundations with Trees in Mind", presented before the ASCE, Texas Section, Spring Meeting in Houston, April 1997. 8of11 L • - 0 I 0 r.....,'".......'M'..,..,',.. "...V.ar.....-,..n..........a..°MIPi:r.LarArAe.nvosx4aew..,rev.aner-u.ev-aw--1,-...Z.Z.Safaiamii.netwiakelleigespossame*m,,•,-‘0....mr,,,ea...sgs.,..vnts.s.,....re,ant..e,,,,..sel 2 g 4 kt. 441 i ! • 1 '7-• IE ^'' ''■ ' ,v 1 N --- -, ,.',...%41/„.■•,,, , 4 , 1 N - ,„. . ■ 1, _- ! , i i t , r - -..„ 'vg ;,... --- ,---- ...„.. . i k - .... i -: ', 1„.,„,„_,,,_._.. ......tr.--, 1 - '',, - 4 t‘'..... ,., •trr" i = ' iy4.-, ,,_ ,A ""''. //f I ; •.'" ; . 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',.• -.. , riZ':,,,,, ! ° '-'---— I 1 , ‘ ,› .f.-.A _.,, -4 > .---'" ! ■i ....... ;..., ‘-kk, 1 4 i i ,..11.1.;'-'-' Site Plan Plate I 9 of I 1 I .e • • • STATE OF PRACTICE,RESIDENTIAL FOUNDATIONS 1900 THROUGH 2001 _ r- 'RnYoeeeentlaiions on Ethan- frees Ettertive Gso,e<e2 Does,, Heave billed straahaa 5ret� Slab on Flt Vo41 Tree Corsl- Resler Of Soil d r Map F I Repro I slue ( on F'Iaeithth 01Exyanslve 1 sicn CnnIle,- ;Mine Rep-memo-I Vold Rel en-I FD I Bon f Drnir.- Sydnk- - 4401 I NNW I Fl,,ndaeon I Varna JD Ye' ICon.,■ een. Sops? 5,2 e:Ue%PI sod, ol_Risks la0m D. h,0 doNons S e dello. 790 MS,I. Sue, 1 a•- ler T1ees Reese!,I MoNtoen• Ihetin-s hie 2 1590 K J�A�__ Yes 30 Yes No � ' 4 0 Yes 49 4 0 r Yes flf No Yee I' 1900 _H lG1 0 Yes_ 45__ •Y Yes Yee �� �s���® v4 1'!11 B .101021 Yes 'f e-.. 40 Y Ye No Yxs 5 109'• H C'at-eU/ Yes 79 No No Yes ��0 6 1195 li 091-157 _Vas 24_ N0 Nn Y: _ -_% IA1 Fi.-- 0!11410 Yes 4l Yes Yas Yes I'—M ���� I_5- 19_9 I- 1-__I__091-12 �v 40 Yes —� Ye. ® Yes _`'•1 �� _� 0 1991 1 91931 3f Ye_ Ye_ �� Y� _ 1 -' �1_ �O 24 - Ynv 111 19.31 11 1091 H •001-2 2' ® ® Yes Yes Y. 12 1991 ._ 191074 Yes 13 1901 - 0104-1002 No II=1 24 -- e 4 1001 ,n- HE-91-077 Yes - Nn Ye:: 15 _2 A 92-469E Yes Yes M Yes MI Yes 24 Yes No Yes 24 Yes Millnilli es Yes �1_ 1992 0 9202026 Yes Yee 41 Yes yes a�a� 0624_ .1 _ Yes ©_ �M 17 11102 4 2111025 Ya_ - 40 Yes Yes ._9 Yes -yes. -11°_ — 055 NCI Yes ���_ 10 1042 ifl2 249 Yas - 6.5 Ye_ Yes Yes a Yes _ �= 14 PG k 9"n 107C• Yaa 5 Yes I No No b Yes 4 Yes v 10 4 No Slo ,..— 20 le92 J i_ 11892E Yes 35 No No % No gm Yes 12 Yes IM®. f 21 39 _ 1 042215 No 5II No ®. �a®1111. }n - Yes ®®®®MM® 22 19921 F �� .. 38 Yes No as®� 'Yee I Yes ®����® 23 19 H _092-299 Yea Yes Yes 'Yes I _ Yes 24 1992 I 1 180002E ® N0 ® No 11111111111•1111211111 n Yes 12 a�®� �� 2ti 1 1002 G 1 9206-1011 42 Ye., Yes N� Yes _ 18 - m��® 2, 1092 L 09-92% 4% Yes No No ® 12 N�®= 27 J 2102-020 No _ No 111191•a® 12 28 1992_ C__ 02540.1 No ® Yes_ Yes I © No I ®�®® Yes- si 'Y 30 1!9'.1 M '� 2296- Yee No No 8 Yee ® es 24 No 20 5 ®u® No No el 01 1:02 K 0 Yes m tr;z G92_583 Yea Yea MINIM e.. 1__ ��m 1903 323.02 Yes_ - Yes a 0 ��� b. G82-122 ' Ye.s 149 n Ves — 1_ ` 1.0.13 G 9310_1011 Yes .. 36 Yes ®I��� ®��� 38 1993 0 _ 0003567 Yes Yes 42 Yes I�MIa ��M ���W ��IIIEIIIIII=MIIIIIIIIIIVMIII 37 1993 H 69.:211 No - 11 No 30 1993 F 93934-1 Yes No 26 No Yes Nn wria 39 1993 R _92,32%4 Yes_ _Na _T Yes Yes 30 No �va�1e; Yes 40 1913 B 03,3921 Yes Yes 48- Yes Yes 18 ®^1- y1g1© Yea 42 = 03CA N1�'1 �1 1 ��M� 24 Q ®' ® 43 1983 Cee-, ®��®�Q� ®®mMENIIIMINIMI 0003 0303471 35 �� ���®� Yas ��®��� M : i-- 9211-1021 3303689_ Nn 32 2"16-.930 '!es 2114.93E MI -- ®_ Q=a� -- 1.Yee 49 191 J 1,093E 0 •A3 J 1"12/-93E 1 199_ 142-93 Eli������� -- . �E __ 1 993 _ 23 J3E 53 1 103 N 288'38858 11121111111111110211. 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Yes ®® - Ves__ /7 1005 G95-221 Yes __.`_1 _ 79 14!!5 E 9.11400 �� 140 �® 4 No Yea _ 1 �n�_� Yes Yes 70_ 1'9.15 A le 137 Yes f 1 Yea —24 v e Ya ®� ■ 1996 05 2 SB-54:6I 0-9 e -2.i . gl Yes 1!198 H _ O66-205 : 28 Ye_ ®� 9 Y55 Yes ���IEM 1!06 F 06005.1 26 Yes ®®��• Yes Ns ®��leeen�®a}� ®© 96776.1 - eM Yes ®ete0® l 12 We lee ®CM®IIIIICEIIII_____ .6 00135-1 Yee Y e. 1 Yes 1096�__A 0660:60 Yes ° a Yes . __-_.�L yes E rVil ���� 8 Yes ea _ Yas N° NM i� Yec lal 1097 E !9X:30'19 Ye s Yes Yes 30 Yes No Yes lee 54 `9/ N 650/0.£10 . a 40 _ 11 24 L. ®� ves Yes 89 1.197 A_ 97-4160 Y Yes Si Yee MINIM Yee g Yea 48 I V Yea Es Yes Yes RE 911 148 A_ 98+100 Y Isle_ n Yes _ Yn.¢ 1E Y - fl Yee AA Yes Yee Yes Yes 01 900I r 49' ci Y Yes 31 Y.., Yes 9 Yes - _r_Yes 24 -. M0 ��• No _N1_ 92 F 9X'-MN Y :`t No 5 Yes I Y'es No i0 No ®� -0 1 es No Y. Yes No — 92 1999 E-_- 99(2'98 Yes Ye: _2 s Yes No 9 Yes 24 4 Yes NoF® Yns Yes 94 19091 E 095225 SON_ No 41 I Yes Yes 0 a No -- Yes 24_ Yes No I YRN ME Yes: ®I� 96 ®-A__ 99504E Vfee Yes 56 Yes Yes ®® Ybs_ 5 Yee 44 Yee Yes_ Yes Yes Yes Yes lel 06 211110I C 00-137 Yes -- - Ye_I s,1 No I 10 Yes -- I Yes ,� 4 -. I No No No No Ye'.: Yes _Yen 97 1.�ry _D '922E Yens Y:s .19 Yes� Ye■ N _Yea d Yes '—'.+A `Vea V S+I No es Y. _Wee Yes -'® NO i C.I.MiDendth a re m ne nd:4on„on heave comps lalion and 01 thickness. Plate 2 10 of 11 • • • FOUNDATIONS AND RISKS Many lightly loaded foundations are designed and constructed on the basis of economics, risks, soil type, foundation shape and structural loading. Many times, due to economic considerations, higher risks are accepted in foundation design. Most of the time, the foundation types are selected by the owner/builder, etc. It should be noted that some levels of risk are associated with all types of foundations and there is no such thing as a zero risk foundation.. All of these foundations must be stiffened in the areas where expansive soils are present and trees have been removed prior to construction. it should be noted that these foundations are not designed to resist soil and foundation movements as a result of sewer/plumbing leaks, excessive irrigation, poor drainage and water ponding near the foundation system. The followings are the foundation types typically used in the area with increasing levels of risk and decreasing levels of cost: FOUNDATION TYPE REMARKS Structural Slab with Piers This type of foundation(which also includes a pier and beam foundation with a crawl space)is considered to be a low risk foundation if it is built and maintained with positive drainage and vegetation control. A minimum crawl space of six-inches or larger is required. Using tins foundation,the floor slabs are not in contact with the subgrade soils. This type of foundation is particularly suited for the area where expansive soils are present and where trees have been removed prior to construction. The drilled footings must be placed below the potential active zone to minimize potential drilled tooting upheaval due to expansive clays. In the areas where non-expansive soils are present, spread footings can be used instead of drilled footings. Slab-On-Fill Foundation This foundation system is also suited for the area where expansive soils are present. This Supported on Piers system has some risks with respect to foundation distress and movements, where expansive sods are present, However,if positive drainage and vegetation control are provided, this type of foundation should perform satisfactorily. The fill thickness is evaluated such that once it is combined with environmental conditions(positive drainage, vegetation control)the potential vertical rise will he reduced. The structural loads can also be supported on spread footings if expansive soils are not present. Floating(Stiffened)Slab The risk on this hype of foundation system can be reduced sizably if'it is built and Supported on Piers. The Slab can maintained with positive drainage and vegetation control. Due to presence of piers,the either be Conventionally- slab cannot move down. However, if expansive soils are present,the slab may move Reinforced or Post-Tensioned up,behaving like a floating slab. In this case,the steel from the drilled piers should not he dowelled into the grade beams. The structural loads can also be supported on spread footings if expansive soils are not present. Floating Super-Structural Slab The risk on this type of foundation system can be reduced significantly if it is built and Foundation(Conventionally- maintained with positive drainage and vegetation control. No piers are used in this type Reinforced or Post-Tensioned of foundation. Many of the lightly-loaded structures in the state of Texas are built on this Slab) type of foundation and are performing satisfactorily. In the areas where trees have been removed prior to construction and where expansive clays exists,these foundations must be significantly stiffened to minimize the potential differential movements as a result of subsoil heave due to tree removal. The beauty of this foundation system is that as long as the grade beams penetrate a minimum of six-inches into the competent natural soils or properly compacted structural fall,no compaction of subgrade soils are required. The subgrade sails should;however,be firm enough to support the floor slab loads during construction. The structural engineer should design the floor slabs such that they can span in between the grade beams. The subsoils within which the grade beams are placed must have a minimum shear strength of 1000 psi and a minimum degree of compaction or 95 percent standard proctor density(ASTM D 698-91)at a moisture content within 2%optimums moisture content. Floating Slab Foundation The risk on this type of foundation can be reduced significantly if it is built and (Conventionally-Reinforced maintained with positive drainage and vegetation control. No piers are used in this type or Post-'Pensioned Slab) of foundation. Many of the lightly-loaded structures in the state of Texas are built on this type of foundation and are performing satisfactorily. in the area where trees have been removed prior to construction and where expansive clays exists,these foundations must he significantly stiffened to minimize the potential differential movements as a result of subsoil heave due to tree removal. However, fiaundation tilt can still occur even if the foundation system is designed rigid. The above recommendations, with respect to the best foundation types and risks, are very general. The best type of foundation may vary as a function of structural loading and soil types. For example, in some cases, a floating slab foundation may perform better than a drilled footing type foundation. Plate 3 iI of1l • • Appendix A Standard Codes Schedule Adoption. Subject to the amendments and deletions indicated beneath each code, each of the following codes, including all of its published appendices and attachments, is adopted,ordained and made a part of the Code of Ordinances of the City and of each chapter where it is referenced, except as otherwise expressly provided. Procedure for amendments,etc. The procedure for adopting new codes, updated codes, local amendments and provisions for administration and enforcement of these codes is as follows: (1)proposal by the building official or other appropriate City official, (2)referral to the Building&Standards Commission, (3)consideration by the City Council, after giving required meeting notices, and(4) adoption and publication, as required by Article II of the City Charter. International Building Code,2000 Ed.,International Code Council,Inc.. 1. The administrative officer is the building official. All hearings,variances etc.are handled by the BSC. 2. All roofs must have Class C or better fire resistance,as determined under Sec. 1505.1. 3. All foundations and structural framing for new buildings and fvuiidativi,.cya:,�with a gross floor area of 450 sq. ft.or more must meet the following criteria:shall b.,designed by a i..gist.,ied yivfessivual eiigiucci ("RI'E")and the vuo.k shall Lc. a. They must be constructed in accordance with illu,tiatcd in complete plans and specifications prepared,signed and sealed by tire RPE a licensed professional engineer("LPE"). The plans and specifications must be prepared specifically for the site of the work, and they must meet criteria as to scope,content and form specified by the building official. b. The plans and specifications for each foundation must be based on a written soils report f.e.,,a Icrugniacd and icpulablc fiiui ui agcu.,y meeting criteria as to authorship, scope,content and form specified by the building official. The building official may adopt criteria published by the Structural Committee of the Foundation Performance Association,Houston,Texas. (Exception:no soils iepo,t is icqui.ed fo,a sii,gl.,-Aoiy ae..esbO.y budding with less than 450 o.i. ft.of glum fluvi a..,a), and c. Foundations must be one of the following types: (i)pier and beam, (ii)voided slab, or(iii)slab on grade with at least 48 inches of compacted select fill beneath it(Exception: If the soils report indicates a plasticity index less than 50, and if the report specifically recommends a smaller thickness of select fill,the smaller thickness is allowed, but there may never be less than 24 inches of compacted select fill beneath a slab on grade). The BSC may issue a special exception for another type of foundation,but only upon a showing of engineering data and opinion to demonstrate that the other type will be as stable, strong and enduring as the specified types. d. Each foundation and all structural framing must be professionally observed inspccb,d and must be certified by an RPI?LPE, why.,eitifies pope' coastit<cti011r,before work proceeds further. Observations must:(i)be performed either by the certifying LPE or by a person under that LP E's supervision and control whose professional qualifications are approved by the LPE,(ii)include actual measurement of piers,fill,compaction,reinforcement, forms,materials,dimensions, structural elements, stressing,tendons,attachments,etc.before the work is covered or concrete is placed,and (iii)be documented in a form and manner approved by the building official. Certifications must: (1)refer to and be based upon the professional observations required by this section, (2)state that the work complies with the approved plans and specifications (with any modifications approved by both the LPE and the building official)and complies with sound engineering practices,(3)comply with guidelines as to form and content as may be specified by the building official, and(4)be signed and sealed by an LPE. 4. All concrete piers,footings and foundations must be cured for at least 72 hours before any significant load is placed on them. 5. All walls and ceilings within a R-1,R-2, R-3 and R-4 type occupancy shall be sheathed with Type X gypsum board at least 5/8-inch(15.9 mm)thick. Exception: Where this code(IBC)requires otherwise for • • moisture protection. 6. Delete: Appendices A(Employee Qualifications),B(Board of Appeals)and D (Fire Districts). 7. Notwithstanding Section 907.2.10.2, a household fire alarm is permissible if it complies with Chapter 11 of NFPA 72—National Fire Alarm Code, 2002 Edition,published by the National Fire Protection Association and incorporated herein by this reference. International Energy Conservation Code,as it existed on May 1,2001,International Code Council,Inc. 1. The administrative officer is the building official. All hearings, variances etc.are handled by the BSC. 2. In lieu of inspection by City employees,the building official may require a written certification that a building meets or exceeds minimum requirements, if the certification is: (i)signed by a code-certified inspector(as defined in Section 388.02,TEX.HEALTH& SAFETY CODE)not employed by the city,and (ii)accompanied by an approved inspection checklist,properly completed,signed and dated by the inspector. If the fees of the code-certified inspector are paid by the City,the amount shall be added to the building permit fees otherwise payable. With approval from the building official,a permittee may pay such fees directly to an independent inspection firm. Only code-certified inspectors may perform inspections and enforce this code in the City. International Fire Code,2000 Ed.,International Code Council,Inc. 1. The fire official shall be the fire chief or acting fire chief,who may detail other members of the fire de- partment or the building inspection division to act as inspectors. Chapter 6 of this Code shall apply to enforcement and administration of the fire code in the same manner as it applies to the building code (except that the fire official shall have the powers and duties of the building official under such articles). • 2. The BSC shall have the same jurisdiction and authority with respect to the fire code as it has with respect to the building code. 3. The limits of the fire district referred to in Section 902.1.1 are coextensive with the City limits. 4. Explosives and fireworks, as defined in Chapter 33, are prohibited within the City limits. 5. Notwithstanding Section 2206.7.6(relating to service stations),"latch-open"type devices are prohibited. 6. Section 603.8.4 (hours for burning) is amended to read in its entirety as follows:"An incinerator shall not be used or allowed to remain with any combustion inside it:(i)at any time from an hour preceding sunset on one day until sunrise the following day;or(ii)at any time when unattended." (7) Delete: Appendices FA(Board of Appeals),FE(Hazard Categories),FF(Hazard Ranking)and FG (Cryogenic Fluids-Weight and Volume Equivalents). International Fuel Gas Code,2000 Ed.,International Code Council,Inc. 1. The administrative officer is the building official. Chapter 6 of this Code shall apply to enforcement and administration of this code in the same manner as it applies to the building code. The BSC shall have the same jurisdiction and authority with respect to this code as it has with respect to the building code. 2. Delete Sections FG103, FG106 and FG10. 3. Even if permitted by this code,copper tubing shall not be used for the yard service line. 4. Amend Section 311.2 to read in its entirety as follows:"Low pressure(not to exceed 0.5 PSI)gas piping shall withstand a pressure of at least 10 inches of mercury for a period of time not less than 10 minutes without showing any drop in pressure, except that the following shall apply in the case of new construction: The newly-constructed system must withstand a pressure of at least 25 PSI for a period of not less than 10 minutes without showing any drop in pressure as an initial pressure test, and the system must also withstand a pressure as a final test. Higher pressure piping must withstand pressure of at least 10 PSI,but never less than twice the maximum pressure to which the piping will be subjected in operation, for a period of at least 10 minutes without showing a drop in pressure,but the higher pressures required for new construction, above,shall be used to test new construction in lieu of the 10-PSI level prescribed by this sentence." 5. There must be a permanently-installed stairway, either fixed or folding,to serve attic space where appliances or equipment are located. 6. Even if permitted by this code,undiluted liquefied petroleum gas,or"LPG", shall not be used at any fixed location in the City. Exception: This does not prohibit the use of such gas in quantities of 10 gallons or less. 7. Each new or replaced gas meter shall be located on the same building site that it serves. i International Mechanical Code,2000 Ed.,International Code Council,Inc.. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. Add to Section M306.3: "There must be a permanently-installed stairway,either fixed or folding,to serve attic space where appliances or equipment are located." 3. Add to Section M603: "All return air ducts must be installed within 10 inches of the finished floor in all new residential construction and wherever possible in existing buildings." 4. Delete: Appendix MB (Recommended Permit Fee Schedule). International Plumbing Code,2000 Ed.,International Code Council,Inc. 1. The administrative officer is the building official. Chapter 6 of this Code shall apply to enforcement and administration of this code in the same manner as it applies to the building code. The BSC shall have the same jurisdiction and authority with respect to this code as it has with respect to the building code. 2. Delete:Sections P103,P106 and P109 and Appendices PA (Plumbing Permit Fee Schedule)and PG (Vacuum Drainage System). 3. Add at the beginning of Section 303.1: "Even if permitted by this code(IPC),,none of the following is allowed for use in the City:Acrylonitrile-Butadiene-Styrene(ABS)pipe or fittings,polyethylene pipe or fittings,Type M copper,lead-based pipe,aluminum DWV pipe or components,or air admittance valves." 4. Even if permitted by this code(IPC),PVC and CPVC type water pipe and fittings are not allowed for use in the City. Exception:PVC water pipe may be used where permitted by this code(IPC),but only if: (i)it is installed underground and(ii)all joints are primed and glued as required by the manufacturer's recommendations (and the primer must be purple or another distinctive color,except on above-ground pool piping). 5. Even if permitted by this code(IPC),wet venting shall not be allowed except when authorized by the BSC, as a special exception for hardship and unusual cases. 6. Amend Section 1101.2 to read in its entirety as follows: "The provisions of this chapter are applicable to interior leaders,building storm drains,building storm sewers, exterior conductors,downspouts,roof gutters and other storm drainage fixtures and facilities." 7. Maximum water meter size,unless an RPE can clearly and convincingly demonstrate the need for a larger meter in a particular case, is:3/4ths-inch for an irrigation system,or 1-inch for a single-family dwelling. International Residential Code, as it existed on May 1,2001,International Code Council,Inc.. 1. The administrative officer is the building official. All hearings,variances etc.are handled by the BSC. 2. This code,in lieu of the other"International Codes," applies to all residential structures in the City. "Residential"means having the character of a detached one-family or two-family dwelling that is not more than three stories high with separate means of egress,including the accessory structures of the dwelling. This code does not apply to: (i) any dwelling that has a common means of egress, such as a common hallway,or(ii)any dwelling or structure that has the character of a facility used for accommodation of transient guests or a structure in which medical,rehabilitative,or assisted living services are provided in connection with the occupancy of the structure. 3. All amendments and deletions to the other"International Codes"adopted by this Schedule are also carried forward and adopted as amendments and deletions from the International Residential Code. 4. Delete:Appendices RAF(Radon Control Methods),RAI(Private Sewage Disposal), and RAE (Manufactured Housing Used as Dwellings). 5. This code does not apply to installation and maintenance of electrical wiring and related components. See National Electrical Code,below. 6. Notwithstanding Section R317.2,a household fire alarm is permissible if it complies with Chapter 11 of NFPA 72—National Fire Alarm Code, 2002 Edition,published by the National Fire Protection Association and incorporated herein by this reference. (BOCA)National Building Code, 1996 Ed.,Building Officials&Code Administrators International,Inc. Only Sections 3108 (Radio And Television Towers)and 3109 (Radio And Television Antennas),together with any necessary definitions or interpretative aids,are adopted. See Subchapter G of Chapter 6 of this Code. National Electrical Code, as it existed on May 1,2001,National Fire Protection Association,("NEC"). 1. The administrative officer is the building official. All hearings,variances etc.are handled by the BSC. 2. See Chapter 8 of this Code for various provisions which override or supplement the NEC. Standard Housing Code, 1997 Ed.,Southern Building Code Congress International,Inc. 1. The administrative officer is the building official. All hearings,variances etc.are handled by the BSC. III II Technical Papers Page 2 of 3 • • DEVELOPMENT OF DESIGN AND REMEDIAL MEASURES FOi LiGHTLY-LOADED STRUCTURES FOUNDED ON EXPANSIVE SOILS WITH TREES IN MIND David A, Easheiored, FE and Richard W Peverley, PE Geotech Engineering and Testing. Inc. Peverley Engineering, Inc_ 800 Victoria Drive 7207 Regency Square, Ste. Houston, Texas 77022 Houston, Texas 77036 73-699-40D° 7 i3.977-0328 ABSTRACT I iew of ckirreiiriTfiiaTuTe"477—i t e Lir";IFF..g.-Te-i-show's there may be an absence 4 approaches for the design of lightly-loaded structureS founded on expansive clay s I trees are InVikeed. As a result, many such structures which nave experienced distress of thi.,.*lack of the consider ..ttion of the effect of tree4 in the design of these structures T of this paper are a part or a Houston organization called the Foundation Performance One of the activities of this Committee is the trivesttgation of the adverse effect that IN and/or the removal of trees can have on lightly-loaded structures This paper inctudes of this activity,and also includes the results of a literature survey,a review of the failuri foundations whose cause has been attributed to the presence of and/or the rerriovi I desiue, reciemoteedailoos, arid OthpattS where trees have been identified as the pomart INTRODUCTION mCaI Note which prOvided data which st Oak trees lOCated South of Arlington,Te*e A eignificant number of residential buildings were con- local movements varyieg from 1.2'eche sheeted in the greater Houston are in the 1950 ifiroutth between the end of the summer months 1970 time periods, Mere,of these buildrnos were founded the winter months, The University of Te on expansive soils and on building lots,which were void conducted art investigation of 69 abaft& of vegetatloe. Trees were then planted after these build- buildings which were founded on clay sou ing were Sold and eventualy the trees matured and caused among otter things, that the extraction C foundation failure io CCCUr. Corrective measures gener- the soil ihrough the toots of trees, caus ally included the underpientog of the louridatioe penile severe denecliorrs ii 100fidatiOnS.01 11) 1 eter beam using drided piers and later praseie Oki& When preseetee data which :showed damage Piers were used,this approach hack al best,a limited de, caused by trees. Kraher and Kozlowski gree of suctess. The type of taiture anode,wherebetrees comparatively high eaneelretton rates 0 cause,the settlerteet of the perimeter ef residential,and 1960. et 1987, Pevertey anti Marlys* Other low-rise beddie4S,has ree4ereel a egeificarit amount suree tie harts in a rreerdentiM found: of publicity in recent times and, as a result; eome owe- been produced by near-by trees ers,buildiry remodeling contractors;home builders,etc. have Wnfile aware of this problem. From Mrs,an entire The menace in wheel trees cart cause dc industry has grown which provides measures to control lions in residential slatecteeereund founda this oroblem, fore, been well documented. Simply sta satisee their need for soil water, trees ca Some Mite of the manner in which trees can produce soil upon which the outer edge ot a tom downward detimtions in residential siab-ongretind faun. suiting in the shrinkage of the soil with Chi datiorts began to appear in the early 1970e. For example, of soil support. Foundation distress Mei in 1972,Davis",summarized existing papers which inde causes have occurred with such regulae cated that near-ey trees coot adversely affect lewd& Houston area as to have caused a major lion performance. Davis and likereee puttlishea a Tech- fundamentai totiniiation ilit)n arid cons!: t the Spring,Sf,$!ion ref the Tens Semen ASOF Click here to continue http://geotec h en g.corelpapers/tech papers _light 1yloaded I.litm I 2/10/2004 Technical Papers Page 1 of 2 • 1 s :€ .C — R x r`'54 a s 3' '4T.a�.;-�a:.a t.•cy,'$x �3 r.s. �1.'E°r a -t yt am `Y #` ' rx-( r/ � Y. ?y. rtv f ? y x � t s c . ce ^, - - . f ye not as well understood, eicale +krgt for a month per at of kern l;r in ex, rr�nt rtfl:t�f� +' i3+ ver,Ws the alversis efitott t the renvivot of iezge cess r3f 2 dY ttici n(Wars If r were to 44w,41 �€ a1 � tr, �f�i ir even tar that `�+, � i 6r weft mey are tee on etrrlie d wry. Egualy returreforstood =sod t'y trees,the costs woul be obvortly encerrious, tho r intie nstep b growth tree root grow under, :` slat] rYVkf 104:s: 'Trees are the largest act punts in the vroddA floes r.atti, generally be classified as n ad a-teal or brood leaf trte- Cf The purpom of ttvs Paper is to explore the adverse el- iufv) The essential pails a 2800 are the 0'0 044,the ry 4 �; s that loans to have on resideneal fourioaten odor, bunk,2tki tre toots, The clown=tans tree loans,when r r r b i on the ex perierioe el othces as ro eland essent4ty&art, aid converts if irk t food t f � , rn the kterakile.based on the per r l experi�of the roots we the-lase t OrvelIV part of a tee. °1f+r+y ocked withers, art based on an ac :umutatilia of rodormaten water and transport it through the trunk to the leaves in form the Pounflatiern Performance Corrvnitlees This per: the form of sap, The trunk provides the kanspoding per wit be presented m the three Wowing bad pails; rtt natu:�rn bet Bert letwes end the roots,and Is Made . , seurrdatittan edge setterrvard produced by sell shrinkage, foundation dam' ca ,i soil� �of the heartwood in the center,the cambium layer at tkrg,and l the erne-r art of the trunk awl the bark,sodded provides eat r'Center t. ra 'ir .rset inlicracted ,_ the c protector i fs fro ornty OS fast 8S they, tevert tree roots argil slap sewer leaks. The,aid- we provided enwgy horn the leaves. The bee system r = thanics of such sonditons Wong with proposed coffee, corigsls of the emulation of water from the roots uperad Uittolt five mewares wdl be discuss x s wilt be ire through their trunk WI the tore"of sap. When the sap seated. reaches a leaf, the water evaporates into the air The sap brings mineral sets from the earth to the le es, Tire SOIL MECHANICS AS AFFECIEO BY TREES Wttorophyltin the leaves acts with sunlight to convert the sails into food through ehreta+ayntlaesdds This feed then Y WatQf TRIO nows t into the tree sysierm system through pOis Oct beikav the ba`k. his kis systwn which makes a tee tyre. Trees hai e long boon ol:dared k bo a t t 3 3122 kind, Trees ham been widen about ag many as 4000 Eta eetafr oraaq t<erfra%we ale PrffrogY orthowhtti with the yews 30.01Trees absorb heal as they lrari' o a term evapotransperaorr,i.e.,the withdrawal of moisture, T t t vide Made, and reduce sciar radiation They enhance from the soil and Its eventual tram , *"r�8a ineeri ig f tdC 41r4tf!the taboo. air punk-ail-on,all in the control at erasion, and can,tea where, Attests have been mares 10 ttueribfy he term; • tf as e s fit �,r�,T knifed degree, provide swot)r ;n rrdueads n ben fis, tamer,the results have not ays ta n uniformly? Polh2ps most;fir ate Omsk is Uw qty to tilted in the engineering!'atheist can ouriee pry eh-thence the beady oh the s1812iir4n landscape. One oily because of the la thy acrairettity measure the can appreciate die beauty of old oaks whose branches moisture tectireplacernents to the mil under most trams: prow at!ti o a for many of the reeds In the old South t'tri!r oltm presented a ranking of trees in terms of their or whose soulphrte enihanee, the skyline of the Pacific damage potential,A modified cony of this ranking Is con- Co eat tined in Table,WI Trees do have lr downside Then Loan f t miirring to the greater fin area, we into not have an : ofrt- p+Oper file In the Gitif west,people have been elarva al Poplar trees;however,there welt may be more injured or killed by lalfirtr-lees. Tree roots clog sewers Oak trees than any others, Also contained to this doer- and and br tk siduvelks Trees can also evease the ozone meet is are exarpts of oaf on:t rcoistt re eintent Yana content of the ail,damage electrical power linos, and in bans,which rs shown In Figure 1. Of Interest Is the kd ,- forfere with UHF �tiorl. Perhwhs the highrist cosi of locator el a zone ofporreahord moisture deficiency, This teas is intiob d r ago torerieferrti;elf-xan„Tatir ns In 1973, concept was hither r e; r by aiddlem who meowed red Holtz rt estimated tine annual cost of exp the soil moisture content in the close proximity of various live soils in the US to be 72 Mtion dfl rs in 1562, kinds of bees ehich two tyvaNino in a vie iety of day N AN &WOWS nyS€d, ;.' T eve-1st to roper arty theexe of wh2ch no in England_ A combined frOttUri5 rer ideal al toreld,erier in `s+ rooter t tou.;te,i-,Texoc rr-;i reductii-ointoisture defeit curve for a Pow tree ar i l 2 ttp://geotecheng.com/papers/techpapers lightlyloaded2.htm1 2/10/2004 Technical Papers Page 2 of 3 III ill Table 1. Risk of ilarriage by different varieties of tree o --1-----7----1-----— –1 7-7--------- Rarikeig Species Maximum helot ot 1 Separabon oetweali 1 mirerntro rw_orronnel tree WI.i ROC& 1 Lite&kJ vux4r4/tvi 1 irp 44 I,il,i,..aLAti 6...kair ii 1.1 75%ot casas:metes I Ac ,..k. i 41 I 1 .4.4 I 1 Oak et...At4 tv 1 2 Nplat _24 I 15 ill lime 16-24 a P. ki ._. Como?)Ash 23 10 1 0.5H 5 Plane 25-30 7.5 1 0.5H 6 _ Willow 15 Ii I 1H li 12 rHElawthon't rn :25 7 :551.1H [ q 7.--m,;"1-0 SVCatTOre 17,24 9 _ ....._,..... 0,5H ----I C-71— i la i ____J_________hern I I 11 Beech 20 9 0,5H I 12 Birth 12-14 7 r , as I 1 13 While&ram'Rowan 1 6112 7 1 ii , 14 C 0 es ,, 16-2o J.J 0.6H 641\Ni ,61,C PI itaN 4tAikR7iI-6,--, 'T —L ,J, 11...~00, t.P. ,-4LT.- Sk gl.o'w i ' ai _t .....7" — 1......... ORRIT...... &SO i 1 ausimar MI savor :"- ':, ,, :,, ,,--= . r tv +FP lot .0 i0 30 30 MI Malta..Ammo.04) M3s03345.3 avow-3.1 1'3 Figure 1.Seasonal yanaiforo M moisture content with aria with- Figur*2. An example ei loll noisiere and irk out teaea rwedion ci.a-raz far popular Item erg:,bat Lemke%England in a Bolder Clay (Pi = 29%)is shown In Figure 2. The moisture deficit curves are calculated by multiplying the trees closet to buildings,assuming the i Change in moisture content by the,,,k propriate layer thick- these curves are considered. They also rkess, in reviewing this curve, it is signikent that it does folly of simply removing existing trees it represent the most severe condition for a tree which has for the construction of a new residential been judged to be of a ikksser threat than would be an Oak tree growing in a sou whose Plasticity Index Is less WHAT CAVSES EXPAN$1VE SOILS I than some of the major was in the greater Houston, SWELL Texas area, The availability of such data krk ingiariii has had significant impacts on the constrochen business, As clay particles are formed, there err Whereas it was considered to be inprectioai to plant any points in the parlicia arrarigernenl where tree doser to a inundation than its ultimata height,these ilical imbalance; the elealcal ittobalar data do provide some bases for the pianhing of certain whenever iefit-ing'el day particles is tat: 3 Glick neie to continue http://geotec herkg.com/papers/techpapers 1 i gh tlyloaded3.htni I 2/10/2004 'fechnical Papers Page 2 of 3 • the result is that a clay particle typically has a negative negative pressure (expressed as a pc: net eleeLrical charge on its surface. SIAM nature likes all tive lo ambient atmospheric pressure things to be balanced,whenever a water rrolecule drills Mich solution identical in oornposition dose enough to the surface of a clay particle,the nega- must be subjected in order to be in aqui lively charged surface of the day panicle caysee the pcsi- porous permeable wall with soil water; tve end of the water molecule to turn toward the particle lent to permeable wall with the soil wet If it is close enough to the particle,the water molecule is equivalent to that measured by test mei attracted to the clay particle surface sulkiently strongly D.3152. that the water molecule becomes trapped. Also, unat- tached or free'positively charged particles, called'cat- The osmotic suction is the negative pre tone,tend to acquire a spherical-shaped arrangement or pool of pure water must be subjected water molecules mien have their negative ends directed equilibrium through a sena-permeable r toward the positively charged cation (and their positive pool containing a solution identical in ends directed away from the Cation). When the free cat- soil water; decrease in relative humidity ion is'captured%water molecules approach a clay par- sue of eissoived salts in pore-water. tioie. ins attraction between the negativeiy charged day particle eurtace arid the P4SiliVeili charged oulsido cii ihe OUNDATIONS AND RiZ, ciiioii wiiete ur water ljj ifltu1ioij to captured'by It)e day particle,thus;Fiera a)ing tee amount Many lightiy loaded foundations are Ut el water i=1:i'Cialed pith the day particle. atructed on the basis of aeOcienliCS, risk daisn snaps and structurd.leading. M. Clzy particl es. aro very s,•rall. A typical itactinite parade economic considerations, higher risgs might have a total aurfarm ares(tLT, bottom are,1 edges) fouridetiort design. Wet of the ire,th of app roximately 1 x 10-5 mrn' (1 x 11:1-10 ft , r aresedbyLhenet , it 0.000O000001 112)„ As areas go, this is yery sm.ea. that sorr fevels of ete-k ere eeerazialed Sreectite pearkles have a diameter that is 100 to 1,000 fridonsandiereisr,i milt thing A! airier Etntietr than tc.Aelinlie nartielee and a thie,kness that !team ika of these folindaSens meet h te 4ori rin-ns thinner than kaolinitent and; exinse- Areas where expansive soils are presto quently:typically have a larger surface area per particle. been removed prior to construction, The Thus, a single pound of montmorillonite particles would typically used in the area with increas have an incredible total surface area of approximate!,BOO and decreasing levels of cost are discu acres(325 hectares)114 with which to attract water. The above recommendations, with ref, Thus,expansive soils are very small in size and have a foundation types and risks, are very g( large surface area that attracts free water. Because of type of foundation may vary as a fund these characteristics, it is easy to see why it is said that loading and soil types. For example, i expansive soils are those days that exhibit an extreme floating slab foundation may perform be change in volume. footing type foundation. Soil suction Is a measure of free energy of the pore-water FOUNDATION PROBLEMS CAUS or tension stress exerted on the pore-water by soil ma- trix. Soil suction Is, in practical terms, a measure of the FOUNDATION SETTLEMENT FFODl. affinity of the soils to retain water and can provide infor- SHRINKAGE matron on soil parameters that are irtfluenced by soil wa- ter;e.g„volume Crlat100,deformation,and strength oriel- several authors as tar back as 1960 h acteristics of soil. The soli suction is measured using the this type of distress.1"1 fiuckley4.1 pro filter paper method in accordance with ASTM D-5213, be piaoed no closer to a residential fiaa Ultimata .height_ The basis for this roc _ , e • .1 / I 1.1t1 into Mee DorfiliOn6fii.5; contained in Figure 3.it was not, howev end Liziait,i4k dkrl. The suoiltni Lbi nized by the designers and coestructore 4 Ulick here to continue ttp://georec hen e.corn/pa pers/tec h pa pers I ightl y oad cd4.h ti n I 2/I 0/2004 Technical Papers Page 2 of 3 411 40 141br., U. pie ,r.,f,'Ilic;RI r, V:tZ.:2!feiglejtcfl abs'-','-trjud...L.4c.al.pou arid b Stixtsai Stab edit rs 1 I roundatiori.vast a crawt scram)4 mitsidered ic be a mini 1 tooridelSon A minimum it space of six•imiles or tag I required Using his(condition,he boor slobs aio no in i w(h'iie sAitifiada sc.i. .. Ttills typo of td.irdstan 4 park' 1 stiitad fur hie ant,**hem expansive snits are present an Ihoes haVti been rainoteat pr to construction. The dila I lath%roust b0 placed below the potential active zone 1 I minimize potential tallied tooting op.(tenet dee b evens ! id'beams vitwo ralare ((Winks reP he used instead of drilled foottegA b-iea-On-Fiii-Fourdisticri'Supported co Pats 1 This foondaton system is alsn suited kr he area abera 1 soils are present This system has some risks with repf fouricktion&teas aed mcwerrents,where expansive S4 I pet iioviever,ii positive dadage and vogetailon a I ,trot.i&d his tyx ef flxin&lidnstioultlpd-ftt,n1 r..-etistacJ 110 thicknedi 4 evaluated such dust once it id cornbined e tat contilions{positive drainage,vegetation cohinol)the 1 voice'.ri$e airil be minimum. The shictural loads tam ix dapciieti oil speak;l'oolinito.ilexperisrve!W er 1 k■,-....T.-aumwsmemaansairamowmanar...........eam............. ..a.... s e nal,... Fleeting(fitifteneri)Slab Striparladon PieTS. The Slab cen i The iiik tiii li"Ifea' tAjc oi iiou—oddico 5Wieiri can be ratiot abet no Gcroiectioneily+leinkrced cv Posi-Terisiaitki. 1 it.1.4 b MI Mittt4leri'Oh NE*0 CirVilttle WO Sie.. 1 MIMI DIM ID presence of piers.testi*can move up I everisive soits re;resent but not dawn. tit this case, 1 km the drilled piers should nit be dOtieied Ode the gra, i Tito saochital bait oaf(atiz be siapprith;dl weal fo i evneesive sc...*are rinl nieserit lckwbitg Slab Fv.Inredjoil(Corfuontiairifett--cd nr Post- i The nek en this 41i,a 04 foundation Can be reduced signif Tensioned Slaig 1 is taunt and triainbined Wel pose(helve and vegeb 4 Conte( *pars are used in this type a toutwiaton ik 1 lotty-k.-a&d&hem-3 in an stok of To= built On of kairidotion ond are performing satisfactorily, In the er tees have been removed;do In onnstruction and whet expansive obys exist,tiese founifations must be sighific stieried to minitniZe he poiential daunt/Its(movement =It of stbrzil Item do In tee firtz-ist ......____ homes built on concrete slab-on-ground'foundations in "— the 1950 time period In Houston,loxes,as an example, the post World War II building boom included upwards or 0.40 1,- .1 •••., 100,000 homes constructed in the Southwest part or the k r •\ : City,where the soils were typical!y very exparisive. in i 0- -1-- 114, . ■4- Tr most cases, these homes were initially constructed in 1 r • k• - subdivigions outside or the City limits,but were later an- ; 6." r - V e fiend try the City. Thus,no building codes were applied. 9 1- . &nos this real estate was imply farm fend eolith was i " t - 2,..- '•!-- — .. barren of kens,Ma of tie things that were tiOrle bi ifirli• al. .. - . ii idijid hCaTiElOWitafS(and aver Sono subdivision devel- 1- - • - • - - • . pets)was to plait trees in the yard olow to to rounda. L ..,_....F.,.....„_, t..,,....4.A.......„.,4 i i. tiori. Trees suo ii 21Z OrAs,China Barry,and Pecan Vitc4-4, popular becalm they W6te hardy. When the tress en-• itvw him° ;ao thoir period of 41,4401, %oriel, their wolof de_ Figure 3, A corn of foundation vertical enovernevd 1 da m ..c ond; adity irocrovsed and founddon a problems he hI e- gan.. ,--if 1;do:iodated et be PAPA el corztuotion wilt rie.,-lre toward the center of the eigh 20-:,,r4 SItAiP0111 he ShOt.ittll that when a KI 3h, is pared Oro hfghin ittftn et,the edge. Trees nes)soil rTyktio ground, ekrvorlooti, of soil moisture is retarded, 11 the Thiririulatia, durirtil wet piaridd.5, aiitmiarit soon s http://geotecheng.com/papers/techpapers light]yloaded5.html 2/10/2004 Technical Papers Page 2 of 3 • 4110 tijo3 is Neilehle for tree growth and soil moisture con- Figure 4 shows an example of a home twat tents. may not be substantially affected by veoelation, Southwest part of Houston,Texas„whOele slab--ci During dry summer months,when evaporation rates are bundation was underpinned using drilled pier high,the trees will obtain large quantities of moisture from the 19:: to 1990 drought.the foundation incur already dry soils. If these trees are located in close prox- tional deflections. At our GUggestion,a root ban irnity to liehtly-loaded structures such as houses, their biped vilth an automatically actuated soaker sy: root system will move toward the etructures,in an attempt applied,and the foundation not only etabilized, to find a moisture supply. if trees are too dose to a house, rebound occurred. The example contained in F. desiccation of the soils below the dab may occur,caus- not, unfortunately, an isolated example, Heel ing settlement of the slab have been obtained in the recent past using pre merited piles and helical piers,f'41 Vertical moist ers have enjoyed a very heeled use, 4;46mItuRS OM%DPI r-" ..1.. 7 1 E ' .....,,...,......., 11 \ \,1 FOUNDATION EDGE HEAViNC.;QAPSED Eli Are' I it/el S\”/CLUJ 4 0 I I \I E-1 _.... ...i 1 ,. ... I It)eleepensale for the settlement of t,,,,a cuter I ----..„... \ I, I foundation due to the extraction of mpisturo fro et. \ I through the Teets of nearby toes,tee accepted live moesure was to place the foundetien en lee I ..--.'"----------'--, -..-'--- ‘ .....\ I ors Most recently,however,a conditlen has Ir /- ------....77---„,-..- ,, / ,-----,----,--N N where the piers LieCalls3 _1 detrimeit In the in the city of !entre:tore Texas, there are subdiVI4 —4—A.. irl 'i \\I comparatively small building kits,which often elealli older homes; became very desirable ti r . , ts \ .$ their location. In many cases, the lots contair f 0 prolific trees,which were removed to make w i j 1 ci construction of larger homes. In many such ca \‘,.-A ) ‘`-'•---- ing was done to compensate for the inevitable i the soils which would occur when the tree, r77 i t wee eeeeeree,-ea. IIIARAInt tlAttlADIT 1 k - desiccated the soil in its near vicinity, was goo te t, \I I suction forces moved soil water Into the desk I I I ____m—L ill \\II eas. It does not take much imagination to ir mood of a horneowner who, in many cases, i - \ / moneys to have a sturdy foundation construct I It I have it begin to move soon after the owner ITV I ( \ ....4°''-... I example of such a condition is shown in igu foundation,in this example,was founded an 10 I le,..._„._ -',..,....s. drilled piers,which had 42-inch diameter beds I r-1 -....\. inspected during construction, The pier shafts 1-----Le .e1 4--------1 \, I to the COACIT4118 perimeter beam The soils had. 5AN.-..,,lv,. index in the 60%range. A Pecan tree was re ing the construction process,or shorty illefeai C o k ? 0 ot foundation induced damage bocaf au ii1lif61 _I ‘ ) the firsi year of eenseuetiori and have, in it j iirrottraikid uielaiily. A literature search ! ale doeureentedilieeuesicin of this phcnorronc Fivr,/,4, An""wsrelpf,p %-!?.‘ilurti Eir fniirkijOirsrl as 4 Irgsult Of i5 Tie stele U ,613 , bee in tic tereeed Stets the depletiura V?moiVate at the edges because el trees. Sc .A;.,,,,,,.1...,..,e...,ro.., k,meotialif or found Ind i ro lifer Measurements were lawn eller pier installation and eller Erect '3"4-'1'"1' '''''''--"'-'"'3"‘"''.'''-' '''', "-- - '- • barrier insleltation (..,''Aside of llio United Seeee. A Listing ef 6 keee eeee :2,,eereeee littp://geoteeheng.cone/papers/teclipapers lightieloaciede.htrill 2/10/2004 - Technical Papers Page 2 of 3 • • contained in the Bibliography Secton of this paper_ This / significanoe of the troo removal situation is perhaps test illustrated in Figure,6'"). to this case, the removal of a 1 Poftar tree caused over 6 inches of heaving which was 1 i monitored over a Si-year period of tire, 1 a r I - 1\0 rnar. , l ; 1 ./)/1 I r hp 1 i . ( ea I.. 11)\._ . ' —- - (1-1--- t -/ *if' {„t:4),..., J .**4 1 r . 44 4---..a aim .l Ms Figure _ Ana m to of a h e which 1 ,.., .„,,„„=,„„..;=,_.,,,,=2.,■„*„.7r,..,,,z;\.,.. ,,,_„,,._____: : fled been adversely a effected tyre rem oval of a Pecan try -.- °» r r ,11." In 1? : f f _e,4,1:40,_4* .f Figure?. M example of a home to Houston,Thus,which had " f , been constructed on a roadway that was tined with Post CIA 10 I 7--______-------,1 trees r I _A Figure 7 shows how a residential building was placed of �' the edge of a roadway, which, before the time of con struction,had Post Oak trees on either side. The rernova , — – of the tress caused s gnikant heaving of the foundatioi `''''- • 7 t t a is s uread t hsg,and a trrveatr ed o nt ur Wi d sf r gcues whs ch n d,e r itbr i construce � this roadway_ have been able to _. �_ , x,..� . .,; fir results are stained in Figure R. to comparing our dat{ t two woman with that st1� ► In Figure 9,we can see that the slope d F� ,gy p- q'" our data is sleeper,even though of the curves sett 1 s 17 to level out after 7 years. (F********.• 1 mentioned earlier,tree roots tend to desiccate the SOUS ia . In the event that the tree has been removed prior to build Figure C. A copy of a verficat movement that occurred as a irk construction,during the useful life of the structure,o result of the removal of a Poplar eta to London,England if a tree dies,subsoil melting can oCour in the expans€'+i 7 http://geotecheng.com/papers/techpapers lightly loaded7.html • 2/10/2004 Technical Papers Page 2 of 3 • • — h) Ihe pier depth grouid be wan that it could resist the I ——KNAT,...0 NP.AN4 KAN*SAN K1/4N:r......N..,• ---..c....1 TZA NOUN-N■NN iNNIN,NraTNN N,Nk -----.NUNTNNO 4c..ox 4.3W1 114..1,0**C.'km uplift loads due to expansive soils that extend along the shaft perimeter. — i N „......,-**4- I i . .,•-• 1)2 4 / .., ....-- ' ....-....... C) Moro extensive soil tests are required_ Soil borings 1 4 --- — — near a tree must be, as a minimum, 26 k. 30 feet 1 — ,,,-- deep. The depth to vitich,tree roof fibers exist must . . I ii fe.,,,,f te:vddtalen7pthnt'otrvaloanduvessneetaltont 1.1sliiilYstalar.isofe:obe2nb.acPsiaolcu8te*Infatilidca,diellirtitYino.1 IA,. .--"'''' . t 0 I 4 . 4 1 N N IN ME/4 YEAJNN i In the event that a floating slab foundation is used, we — recommend the gab be stiffened to resist the subsoil Figutt e. movements due to the presence of trees. In addition,the area vath' iri the tree root zone may have to be thernically statAized to reduce the potential movenvnts Meirlatively, , i ttil the site should be left alone for several years so that the ,... '''' lama ...".. aa . 1... I ''''' - ----'------'-*- 1. 0 a a a 0. a ar ,a__, , MO( 'shire regirrie in the desiccated areas of the soils(where tree roots used to be)become equalizedistabilized to the surrounding subsoil moisture conditions. The length of lime required for subsoils to regain their moisture is de- __ _ ___, , i _....--- pendent on the tree spades,soil type and the amount of rainfall, For most trees,one wet season may be enough --------,..s., as Live O Poplar etc.may result in for the subwits to regain their moisture;however,removal ,, --\\ of trees such alt, , mois- $4. / ./Z----- Y,Z,,K\ 47/ ,if/ irs,y7j) ik P tura deficits to the soil profile that may require several years to stabilize. Remedial measures to correct the adverse effects of this , , type of soil heaving are somewhat lotted.One method is (, , _ to raise the entire foundation out of the potential verb-cal ry ()I —"xi rise of the soil using underpinning techniques. Soil test- a trig will generally show the PVIVI(Potential Wrtical Movei merit)values in the soil where the trees were removed. It ( o may then become necessary to raise the foundation out I , of this zone. An alternative is to use a vertical moisture _ barrier, A combination of partial underpinning and the Figure 9.. use Of moisture barriers may also have to be used to stabilize the foundation system. soil areas for several years. Studies have shown that this process can take several years in the area where FOUNDATION CENTER SETTLEMENT highly expansive clays are present In this case,the foun- dation for the structure should be designed for the antici- There has been an ever-increasing problem with regard paled maximum heave. Furthermore,the drilled footings, i 14, interaction between trees and foundation perfor- if used, must be placed below the zone of influence of 'o '"49 Aterac 111310e, i.e., foundation performance induced by under- free roots. This depth should he evaluated as follows: slab sewer leaks. Many of the homes constructed in the 10,411 e a) The pier should be piaald below the depth of con- , ,lime periled had cast iron, under-slab sewer pipes buried in clay soil. Over the past 40(+)years the erred of Stant suction or the zero movement line this unfortunate marriage has produced a proliferation of a Click here to continue It Lp://geotec heng.c orn/papers/tec hpapers light]yloaded 8.htm I 2/10/2004 Technical Papers Page 2 of 3 • • • wider-ean sewer leaks Since most Of not ail)of the home the ultimate remit that the foundation subeded instead insurance poletes allow a homeowner to melect on darn- of heaving, as one might anticipate, ages caused by such leaks,there has been an attendant number of such claims filed. This opinion does,of course,involve a number of assunee- bons for Witch no proof exists in fact,there is little of no Typically the Inswaoce ca net litres a plumbing testing real proof that any sewer teak did,or did not,cause fount company and an Engineer to determine if the leak has dation dettectems to occur More testing and study is caused any foundation'elated damage, It Is likewise type required. cal that this same Engineer will observe that the founda- ton has deflected downward in its venter&mettle which CONCLUSIONS AN RECOMMENDATIONS is the opposite of what one might anticipate if water were to be induced into expansive soits. Otte' contradictions The design and rrtanufwture of most of the Illatetial things may be observed which included the following: we use in our lives is based,to at least some degree, on some type of research. Automobiles are designed and o The timing of the damage appeared cointedentaf to extensively tested before they reach the market, mu- the occurrence of the sewer leek faeturets of appliances subject them to extensive testing before new models are put up for sale, new food prod - o Theme were plumbing leaks;yet where soil tests were ucts must be given extensive testing,etc,it is then some- temductod, the soils were comparatively dry. what ignominious that the design and construction of the fundamental part of what is perhaps the most expensive o There was always a reasonable degree of correta- investment for most of us Is based on lite,if any,current on between the presence at the sewer beaks and research;at least in the United States, Instead,we fend the points of deflection to team in the roost fundental, and in the crudest, of ways-by trial and error. The cast of this process is born o in a majority of cases,the soils were expansive,the by the builders,homeowners,and engineers much to the foundation was, constructed on drilled piers or was delight of many attorneys. underpinned using drilled piers subsequent to the time of original construction, and there were trees grow- We have,in this paper,pointed out some of the problems ing near the foundation which were almost *ways that can be caused by our tak-e to learn to live with trees mature, It is a known fact that the water demands of in an urban envirornenit Although much of this disms- mature treeetend to stabilize. Could these trees than sion was based on Houston,Texas, expertence, this tri suddenly become the source of additional founda- formation certainly applies to much of Texas and to other lion deflections? pals of the country,as welt All of us who are involved in the design and construction of residential and other low- o In the 20(4)cases which we examined,the forego- rise buildings need to be oognizant of these problems and ing conditions existed and the foundation sewed in to conduct ourselves accordingly. This may require add- the center instead of heaving, as was anticipated. bonal pre-construction testing and may necessitate the An example is shown in Figure 9, in this case,the need for more expensive designs. Some may say that sewer system could not be tested since it would told ow clients may not be willing to pay the price for such no water extra work. So long as there are engineers who are will- ing to do cheap work,the problems we dimmed herein We are of the opinion that the introduction of the sewer will recur and we will be left to ponder why some people water spurred the growth of the tree roots to grow to- are more witting to pay their attorneys more than they are wards the tiource,"'. The tree roots then extracted not their engineers and or builders, only the moisture provided from any sewer leaks Which occurred,but also any moisture welch was in the soil be- We have pointed out the need for research. To the best fore the leak 0Oatrfed The presence of an under-slab of ow knowledge,the last 2 large research studies con- sewer teak then resulted in a net soil moisture loSs where ducted on residential foundation issues were the SRAa large trees were growing adjacent to the foundation with in the 1960ts and the University of Texas at Arlington stud- 9 Click here to continue ittp://geotecheng.com/papers/techpapers lightl yloaded9.html 2/10/2004 Technical Papers Page 2 of 3 • • les in the 1970& We do know of mine smaller studies, Texas Sezion of the American Society al CMI Engtheers, Mich have been conducted at some Universities,but we October 2, 1987. believe that larger studies are needed not only on the 7 Hem. Richard I&Arhojculture & issues presented herein but on sister in LteS, as we!, Prentice Hai Calmer e Some of the study areas are listed be Tectvlogy, 1992,Pg low: Jones,D. E. Holtz,W.G.:Expansive Soils The Hid- c A rolation,ship needs to be developed that would ad- den 5sastrx., ' , - N-ASCE,16,41.43,No,8,New dress the tree type(species),distance from the foun- York.NY,August, 1973.pp 49-51. dation, and height of the tree. o Studies similar to'those conducted by Biddle should 9. Tree Bock Encyclveria 1967, Volume T, Pg be done using trees more typically found in the United 34 States(Oaks, Pecans,China Berry,elO),tri clay soils and varying weather patterns that are typical of this 10, R. Driscoll:The influence of vegetation on the awaiting and shrinking of day soils in Britain, The influence of coin try, VocotojagnAliat The Institution of Civil Engineers, Thomas lollord,Lid,1984, o How to better design floating slabs that would resist the effect of trees. 11. T.I Freeman,et at Has Yeti House Got Cracks;Institu- tion of Cr 'Engineers&Bulking Research EstabliStvnerit, o Devotee a simple mathematical rnixtule that would Thomas Telford House, 1944,Pg.2(1 relate sewer leaks,tree moisture removal, and tub- s/oil movements 12. P,G.Skile;Patterns of sal dryirig arid moisture clafidi the vicinity of trees on day sods,.The Influence of vgq. Perhaps the information contained herein will help in the eAlre_t_onays,The Institution of Civil Engineers,The- search for reward)dollars. m Telford, 13 Wray,Warm K;So Your HOire 1$tiudi on&Derisive 5,0 SIBUOGRAPHY Soils,ASCE Pr,trilication,1995. 1. Rotten C.Davis,Resilientis4 Foundation Perfonahrefs 14. Godfrey,IC A.,Jr.:Evansive and Shrinking Sells The Construction ReSearth Center, The Um-varsity of tng problems being attacked,?CiVil Texas at Aningtm September 1,1972. October-1978, 2. Robert C.Davis g Richard)._Tucker The 1-lge ot Tfee3 15, Tucker,RithardL&Pea,Arthur R:6-g-kgai-gatlat 1.4Cf as Bella Marks in Expansive Clays Technical Note, of SiglafoLvided on Active Clay Sols, ...bumf of the Mapping DiviSiOn Journal of the American society of Civil Gegtechnical Divicaon of ASCE,AM, 197B, Er4rvaers 16 Dutton,Sm.:Foundation Repair Techniques.$Okl-Sew- a. Ernest L Buckley,Netting Bulking Loss and Damage tumtnteraction Seminar of 1996, Foundation Parfor- on Residential Slab-on-Grounil Fountions,College of marice Committee, 1966. Engineering, University of Texas at Arlingldn,March 12, 1974, 17 T.1.Freeman,at al:Has Your House Got Cracks;insatu. ton of Cniii Encineers&Sulking Research EstAnlishinent, 4. Ernest L,Buckley;i_oss arid Damage on Resickin6a1 Stab- Thomas Telford HM13441944,P.20 on-Ground Foundations,Constiuotion Research Center, College of Engineering,University of Texas at Arlington, 18. Lawson,.M.&0?Celleghan,0:A Critical Arsalysie of the March 12, 1974. Role of Trees in Damage to Law Rise&pricings,Journal Arberictillore,Vet,21(2),Pgs 90-97, 5 Paul J.KiWileff&Theodore T Kozlowski:Flisas4cm: PP 292- 5,McGraw Hill Book Corr 1966. 19, Personal conlmunicationir4111 Dr.Ronakf Newton,Texas ABM.Urtan Forestry, Department 6. Pevertey,FbdorclW&Hams his G,Resiutal Con- strucecn Probionis Presented at the Fall Meetrig of the 10 Click here to return to first page http://geotecheng.com/papers/techpapers lightly loaded10.html 2/10/2004 (ieotechnical Engineering and lhesting provides Soil Testing Enviromental Engineering Geotechnical En... Page 1 of 2 • • 0-1 -rt ' 4.40. tl %&% 1 fir-"°3 , O ,'r�'x,�` £�; ;,3'", �`r'.'. ;�; -'ffi,'e� .. .. .�,.v ,.*.:"�: ,..`M.�... -r.�..:_'` `,`�� k s a:-r€ s:.at-r.. �:::-fi. .e..,,,.�. ,�, .**0*- : £T welcome to Geotech Engineering and Testing ff Founded in 1985, Geotech Engineering and Testing (GET) is a multi-disciplined organization of registered engineers, geologist, field and laboratory technicians, and clerical personnel who combine their technical capabilities, past experience, , dedication, and enthusiasm to offer the finest service through integrated team effort. GET has a staff of about _ _ _ # _ 50 engineers, geologists, technicians, and support staff. a a f : } Our services include the following: 'E to„ enf tea,• Geotechnical Engineering including soil borings - .P Abou Hous t ton and laboratory testing, engineering analysis and • recommendations regarding foundations, paving, Contact Us construction, slope stability, faulting, etc. • Construction Materials Engineering including earthwork, asphalt, steel, and concrete testing during construction. 6 Forensic Engineering, including foundation,retaining walls, slopes and paving distress studies. ® Environmental Engineering including environmental site assessments, monitor well installations, and underground storage tank contamination studies. Copyright t jf iii r isadvaf?ta_gzr Enterprise and Testis i Aft ' hfs Rosorved GET has been certified as a Historically Underutilized Business(HUB)and Disadvantaged Business Enterprise(DBE)with the State of Texas, Texas Department of Transportation, Houston Independent School District and the Cities and Transit Authorities in Houston, Dallas, San Antonio, Austin and Beaumont. �w - insurance Our insurance coverage includes$1,000,000 general a � Y liability insurance; auto, and worker's compensation. In addition,we carry professional liability insurance with errors and omissions with a $1,000,000 limit. GET maintains worker's compensation and employers liability fi insurance in conformance with applicable state law. Furthermore,we maintain comprehensive general liability and automobile liability insurance with bodily injury and property damage. A certificate of insurance can be supplied evidencing such coverage htp://geotecheng.coin/index.htnnt 2/10/2004