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^ I <br /> i � <br />� TABLE l: ALLOWABLE LATERAL LOAD CAPACITY OF CAISSONS(In Tont) <br /> " <br /> — 3.5-Foot Diemerer 4-Foot Diameter <br /> I/2 inch 25 30 <br /> — Deflection <br /> 1 inci� 50 60 <br /> i <br /> — Deflection <br /> I , <br /> j "i We recommend thet caissons loceted immediately adjecent the existing building be drilled <br /> I with straight shafts to evoid eny possible interference with the existing caissons. A minimum <br /> distance of IB inches should be meinteined between the sidewalis of the new and the existing <br /> ^,. caissons. When the 18-inch spacing is observed, the botrom elevations of the new end existing <br />; ,... ceSasons should not differ by moro than : foot in order to evoid possible uudermining of the <br /> existing caissons during construction. 'fhis restriction can be relaxed somewhat for increasing <br /> distances between adjecent caissons. The depth to the bottom of caissons along the north weil <br />� �i of the exieting building cen be obteined from data sho�+n on Plate l. The assumed depth to the <br /> top of the glaciei till is listed tor esch caisson location. The top-of-tiil information presented <br />� - on Plate 1 wes obtained by subtracting 4 feet(i.e., the assumed caisson embedment in till) from <br /> I the actual depth to the caisson bottom that was obtained from caisson instellation records. <br /> $!ctl14IDGOSg <br />' Totel settlements for individual ceissons will be proportional to the diametar of the caisson. <br />� � ' We atimate that a totel settlemenc for a 3-foot diameter caissan witl be approximetely 1/4 inch <br />� � and for n 6-foot diameter caisson will be 1/2 inch under the deaign load. Differentiel settlement <br /> between adjecent columns in the fumre extension is estim�ted at t/4 inch or leas. <br />{ ^ Ceissons oi�thr south column tine of the proposr.d extension will impose some stresses on soils <br /> � beneath the sxisting caissons elong the north wall o'' the existing building, thereby inducing <br />+ " ' settlements of the existing columns. We estimete that induced settlements wilt be i/B inch or less <br /> I if the 18-inch well-to-well spacing between caissons is maintained. <br /> I ` <br />� ^ ' These aenlements ere expected to be elastic in nemre end wilt occur essentially <br />� - simultaneously with the epplicetion of load. Negligibte time-dependent settlements flre <br /> enticipated. <br /> Construction <br />, _, <br />� The static water table hes not been encountered at depths Iess than 100 feet in this area. <br />� � Water inflow problems erc therefore not anticipated during construction. Local zones of percheJ <br />� _ water may be encountered within the fill or within granuler pockets in the glecial till. The wTter <br /> H.{ may contribute to local sloughing of the wall of the ceisson hole, but is not eapected to require <br /> ., <br /> 5 <br /> , <br /> Dames& Muore <br /> _ � <br />