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J. H. KLEINFELDER & ASSOCIATES File No. 5-2599-1 <br /> March 3, 1983 <br /> Page 6 <br /> consist of soil either totally or partially obtained from the removal of the existing <br /> native materials, and replacing them as a compacted engineered fill. The material <br /> should be compacted to at least 90 percent of the maximum dry density as determined <br /> by ASTM D-1557-70 test procedure. A portion of this fill could result from regrading <br /> of the sites resulting in a rise in the elevation of a particular building pad. With this <br /> alternative, we recommend that the foundations be designed based on a bearing value <br /> not to exceed 2,000 pounds per square foot. The footings should be at least 12 inches <br /> wide regardless of load and be at least 12 inches below lowest finished adjacent grade. <br /> This load could be increased by one-third for a short duration of winter seismic loads. <br /> This aternative does have an additional margin of risk, in that there could be <br /> shallow localized pockets of relatively compressible materials with higher percentages <br /> of debris. As a result, differential settlement could result requiring maintenance and <br /> repair required beyond the normal. <br /> Post-Tension Slab and Foundation _System <br /> An alternate foundation system would be to use a post-tension slab and <br /> foundation system. This alternative uses a slab thickness similar to a conventional <br /> slab, and continuous strip footings are normally used with this alternative. The system <br /> is reinforced with post-tensioned steel cables. <br /> The information presented in this report will assist the design of a post-tensioned <br /> slab-on-grade. The design procedure was developed by the Post-Tensioned Institute, <br /> whose research was conducted at Texas A&M University. This design procedure has <br /> been used successfully for many years for slabs-on-grade resting on expansive soils and <br /> on other subsoil conditions where potential differential settlement exists. <br /> Reference used for this design of a post-tensioned slab-on-grade system is the <br /> Post-Tensioned Institute's publication entitled, "Design and Construction of <br /> Post-Tensioned Slabs-on-Grade", copyright 1980. We recommend a consulting structural <br /> o <br />