GUIDE TO CONE PENETRATION TESTING - SPGEO

CPT Guide - 2006Cone Penetration Test (CPT)A raft is an inverted slab, designed to distribute structural loads fromcolumns and walls, while keeping deformations within acceptable limits.Structural characteristics of rafts are optimized by accounting for theinteraction between the raft and the supporting ground. Structuralengineers usually perform an elastic analysis using elastic (Winkler)springs. Hence, they would like the spring constant, k s .k s = coefficient of subgrade reaction (kN/m 3 )k s = spwhere:p = net applied stresss = settlement resulting from applied stress, pThe process is governed by the relative stiffness of structure and theground. The coefficient of subgrade reaction is not a soil parameter, sinceit depends on the size of the footing and degree of loading. Oftenestimates are made from global tables (Terzaghi; see Table 10).64