Engineering Classification of In-Situ Rock

Abstract : An engineering classification for in-situ rock is proposed which is based upon the results of field exploration and laboratory testing. The field program included a study of more than fifteen construction projects from which data were obtained from geophysical testing, borehole photography, water pressure testing, and geologic mapping. Laboratory analyses of 530 samples taken from these projects included physical and mineralogical descriptions, unit weights, absorption, strength, modulus of elasticity, and sonic velocities (saturated and dry). The rock types investigated included granite and basalt, gneiss, schist, sandstone, limestone, and siltstone. Geologic discontinuities such as joints, faults, and weathered rock are of major importance in an engineering evaluation of in-situ rock because of their effect upon the deformability, shear strength, and permeability of the mass.