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The caissons may be designed wing an allowable end bearing capacity of 25 kips per square <br />foot (ksf) and an allowable skin friction of 3 ksf. The allowable end bearing capacity may be <br />increased by one third for transient loads from wind or earthquakes. A design diagram presenting <br />the allowable capacity of Iv •h straight shaft and belled caissons as a function of the shaft diameter <br />is presented in Plate 10. This chart assumes that the diameter of the bell is twice the diameter of <br />the shaft, and that the straight caissons are embedded 5 feet in the bestial material. For straight <br />caissons with embedment depth greater than 5 feet, additional capacity an be calculated with the <br />allowable skin friction of 3 ksf. <br />Any calm= located immediately adjacent to the existing building should be drilled with <br />straight shafts to avoid possible interference with the existing caissons. A minimum distance of <br />Ill inches should be maintained between the sidewalis of the new and existing caissons. When the <br />Il-inch spacing is observed, the bottom elevations of the new and existing caissons should not <br />differ by more then I foot in order to avoid possible undermining of the existing caissons during <br />construction. This restriction an be reined somewhat for increasing disame" between adjacent <br />caissons. <br />Uplift capacity may be calculated using an allowable skin friction of 2.3 bf applied only to <br />the straight portion of the shaft embedded in the glacial wits. An additional 0.5 ksf applied to <br />the portion of the shaft embedded in the fill may be utilixad. The weight of the caisson may also <br />be used in estimating the total uplift capacity. For be' led caissons, uplift capabilities of 200 kips <br />and 330 kpa an be used for bell diameters of 6 and t feat, respectively. The weight of the <br />caissons an also be included. <br />5.2.2 (dLgtiL,LAgQjpg <br />Lateral load capacities of the caissons will be directly proportional to their diameter. <br />Recommended allowable lateral dad capacities for selected caisson diameters are presented in <br />Table 1 below. <br />a • OOS - 00695.016\sw W 700. rep <br />00695•50 -016 9 <br />