Large Scale Direct Shear Box Tests on Gravels

The determination of shear strength characteristics of gravelly soils is difficult through the use of conventional small scale, triaxial or simple shear testing devices in the laboratory due to membrane compliance and boundary effects; or due to inconsistent penetration resistances measured as part of standard or cone penetration testing in the field. These limitations require the use of available empirical or semi-empirical relationships or the execution of large scale laboratory or field tests. In the literature there exists inconsistent, and large range of recommendations for shear strength parameters. Within the confines of this study, direct shear box test results performed on poorly- (GP) and well-graded (GW) gravel samples with initial void ratio ranging from 0.42 to 0.53 are presented, which are tested under effective normal stresses ranging from 77 to 205 kPa. The estimated peak secant-angles of shearing resistances vary in the range of 49 to 54 degrees. On the basis of volumetric change vs. shear strain responses, the peak angle of dilation and elastic Poisson’s ratio are estimated to vary in the range of 10-16 degrees and 0.28-0.39, respectively. These estimated values are compared with available literature.