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The foundation subgrade soils should also be properly moisture conditioned to 2 to 4 percent <br />above the Modified Proctor optimum, to a depth of at least 12 inches below bearing grade. <br />Since it is typically not feasible to increase the moisture content of the floor slab and foundation <br />subgrade soils once rough grading has been completed, care should be taken to maintain the <br />moisture content of the building pad subgrade soils throughout the construction process. <br />Estimated Foundation Settlements <br />Post-construction total and differential settlements of shallow foundations designed and <br />constructed in accordance with the previously presented recommendations are estimated to be <br />less than 1.0 and 0.5 inches, respectively, under static conditions. Differential movements are <br />expected to occur over a 30-foot span, thereby resulting in an angular distortion of less than <br />0.002 inches per inch. These settlements are in addition to the liquefaction-induced settlements <br />previously discussed in Section 6.1 of this report. <br />Lateral Load Resistance <br />Lateral load resistance will be developed by a combination of friction acting at the base of <br />foundations and slabs and the passive earth pressure developed by footings below grade. The <br />following friction and passive pressure may be used to resist lateral forces: <br />• Passive Earth Pressure: 300 lbs/ft3 <br />• Friction Coefficient: 0.30 <br />These are allowable values, and include a factor of safety. When combining friction and passive <br />resistance, the passive pressure component should be reduced by one-third. These values <br />assume that footings will be poured directly against compacted structural fill. The maximum <br />allowable passive pressure is 3000 lbs/ff. <br />6.6 Exterior Flatwork Design and Construction <br />Subgrades which will support new exterior slabs-on-grade for sidewalks, patios, and other <br />concrete flatwork, should be prepared in accordance with the recommendations contained in the <br />Grading Recommendations section of this report.As noted previously, flatwork <br />supported on the existing medium expansive soils will be subject to minor to <br />moderate amounts of movement as the moisture content within the subgrade soils <br />fluctuates. This movement may cause cracking or other distress within the flatwork. <br />If additional protection against flatwork cracking is desired, consideration should be given to the <br />placement of a 1 to 2 foot thick layer of very low expansive structural fill beneath all flatwork <br />sections. Assuming that the flatwork is supported on the existing soils, exterior slabs on grade <br />may be designed as follows: <br />• Minimum slab thickness: 41/2 inches. <br />• Minimum slab reinforcement: No. 3 bars at 18 inches on center, in both directions. <br />SOUTHERN <br />CALIFORNIA <br />' GEOTECHNICAL <br />G&M Convenience Store #72 - Santa Ana, CA <br />Project No. 16G 123-1R <br />Page 23