Soil-Structure Interaction Seminar - Foundation Performance ...

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Design Plasticity Index 40 and above Floor Slabs The floor slabs for foundations supported on drilled footings should consist of (a) structural slabs with crawl space, (b) slab-on-fill or (c) slab-on-grade. A structural slab should be used when a minimum risk foundation is to be used. This type of floor slabs are generally expensive. A slab-on-fill will be less expansive than a structural slab • with crawl space. The fill thickness in areas where expansive soils are present should be about 18-to 36-inches. The higher fill thickness should be used in areas such as Bellaire, Tanglewood, New Territory, etc, where highly expansive clays exists (plasticity indices above 50). The floor slabs can be supported at grade on drilled footings if the subsoils are non-expansive. All of the subgrade soils should be prepared in accordance to the site preparation section prior to fill placement. Void Boxes Void boxes are historically used under the grade beams to separate the expansive soils from the grade beams. The void boxes collapse once the underlying expansive soils swell up; thereby minimizing uplift loads as a result of expansive soils on the grade beams. This can be an effective feature for reducing potential pressures on grade beams. In areas of poor drainage, void boxes may act as a pathway for water to travel under a foundation system. This condition may result in an increase in subsoil moisture contents and subsequent swelling of the soils. This may result in uplift loads on the floor slabs, and subsequent distress to the foundation and structural system. We recommend that the decision on whether or not to use void boxes be made by the owner/builder after both the positive and negative aspects of this issue are evaluated. Based on our personal experience with void boxes, it is our opinion that they provide an effective feature for reducing swell pressure on the grade beams. However, the validity of void box usage is presently being questioned because of the frequency of observed effects which may outweigh its benefits. It should be noted that void boxes should be utilized if a structural slab foundation is used in the design. Site Drainage It is recommended that site drainage be well developed. Surface water should be directed away from the foundation soils (use a slope of about 5% within 10-feet of foundation). No ponding of surface water should be allowed near the structure. GEOTECB ENGINEERING AND TESTING, INC. ____________ _. 13
Vegetation Control We recommend trees not be planted closer than half the canopy diameter of mature trees from the grade beams, typically a minimum of 20-feet. Alternatively, root barriers must be placed near the exterior grade beams to minimize tree root movements to under the floor slab. This will minimize possible foundation settlement as a result of tree root systems. In the event that sprinkler systems are used, we recommend that the sprinkler system be placed all around the house to provide a uniform moisture condition throughout the year. Residential <strong>Structure</strong>s Constructed near the Bayous Many large residential structures are being build near the bayous. Portions of the slopes on the bayous are very steep with slopes steeper than 3{h): l(v). The foundations for reside11ces near the bayous 1nust be provided by the use of deep drilled footings/piling. The geotechnical boring depths should be at least twice the height of the bayou. Any foundation which falls within the hazard zone which extends from the top of the slope, extending backward on a 4(h): l(v) slope to the existing grade should be supported on deep foundations. <strong>Foundation</strong>s outside the hazard zone should be supported on shallow piers. The floor slabs in the hazard zone should consist of a structural slab. The floor slabs outside the hazard zone should consist of slab-on -fill or slab-on-grade. No skin friction should be used for piers within the hazard zone from the surface to the toe of the slope elevation. We recommend the stability of bayou slopes are evaluated using a slope-stability analyses, using computer solutions. The house should be placed on top of the slope and the stability of the slope for global stability should be evaluated. The slopes should then be flattened and covered with erosion protection to minimize potential sloughing and erosion problems. Site Preparation CONSTRUCTION Our recommendations on site preparation are summarized below: 1. In general, remove all vegetation, tree roots, organic topsoil, existing foundations, paved areas and any undesirable materials from the construction area. Tree trunks under the floor slabs should be removed to a root size of less than 0.5-inches. We recommend that the stripping depth be evaluated at the time of construction by a soil technician. GEOTECH ENGINEERING AND TESTING, INC. ____________ _. 14
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SOIL STRUCTURE INTERACTION SEMINA
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FOUNDATION FAILURE DEFINED IN TERMS
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FOUNDATION FAILURE DEFINED IN TERMS
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FOUNDATION FAILURE IN THE HOUSTON A
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FOUNDATION FAILURES IN THE HOUSTON
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Inspections of the foundation had b
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J CASE NO. 10 - THE USE OF SPREAD F
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GARAGE 0" ·-0.2" -0.8 11 -0.3" •
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V) IJ.J u
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Page 40 and 41: CURRENT PRACTICES FOR DESIGN OF TRA
Page 42 and 43: INTRODUCTION CURRENT PRACTICES FOR
Page 44 and 45: and rigidity to control, dissipate
Page 47: 4.0 DESIGN PARAMETERS 4.1 General T
Page 62: I I. I I APPENDIX B TYPICAL GENERAL
Page 66: FUTURE OF POST-TENSIONED SLABS ON G
Page 72 and 73: GUIDLINES FOR GEOTECHNICAL DESIGN,
Page 74 and 75: GEOTECHNICAL GUIDELINES FOR DESIGN,
Page 76 and 77: INTRODUCTION The variable subsoil c
Page 78 and 79: South, Southwest, Southeast, and pa
Page 81 and 82: Geotechnical Foundation Design Crit
Page 83: Foundation Design Considerations In
Page 87 and 88: 8. The subgrade and fill moisture c
Page 89 and 90: Concrete Placement Monitoring The c
Page 91 and 92: Area drains can be used around the
Page 93 and 94: Inspections Every homeowner should
Page 95 and 96: Moisture Barriers Moisture barriers
Page 97: RECOMMENDED QUALITY CONTROL AND INS
Page 108 and 109: FOUNDATION REPAIR TECHNIQUES FOR RE
Page 110 and 111: PROFESSIONAL RESUME of DONALD E. LE
Page 112 and 113: FOUNDATION REPAIR TECHNIQUES PAGE 1
Page 115: FOUNDATION REPAIR TECHNIQUES PAGE40
Page 119: A P P E N D I X- DRAWINGS SAMPLE FO
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EXAMPLE OF HELICAL ANCHORS Pipe Typ
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RESIDENTIAL SOIL AND FOUNDATION REQ
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Section 6-52. Exceptions CITY OF WE
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Soil Structure Interaction Seminar
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July 21, 1994 Page3 corporation, as
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Residential Construction Liability
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July 21, 1994 Page 8 E. Defenses to
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The Texas Deceptive Trade Practices
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construction or design of the house
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(5) Arguably, implied warranties do
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(3) Includes any diminution in mark
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D. Who Is a Proper Plaintiff? 1. An
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a. claimant's damages are limited t
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a. May be based on hearsay (i.e., e
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d. The Broker (1) Absent specific a
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VI. More Honored in the Breach HORA
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