The results of three Osrsct Sftar tests co.ucted on a coarse grained soil from Isle of Wight Virginia are given below Remember that the direct shear test is a drained test Each sample rs con tructed by first adding portions of the soil to a direct shear box and then compacting o’reachsa relative density D,. of 80% that correspo.e. to a Relative Compaction of 95% of Standard Proctor maximum achieve. in the field The relative dens, was the same for each sample A normal stress was then applied to the sample that remained constant during the test Finally the shear test was conducted by moving the upper box at a constant rate of displacement with respect to the lower box (see the class handout) The stress-displacement and volume change curves were recorded us, automated data acquisition
Part 1. Use the resulting stress displacement information to determine the peak state effective stress strength parameters 0′ a. c’ The normal stress for each stress displacement curve is indicated in the figure
P., 2. The lower plot shows how the samples changed in height (therefore volume) dur, the test Positive values indicate an increase in volume and negative values indicate a decrease Explain the volume change behainor shown how does it relate to the stress displacement curti;res? In engineering practice is this volume change behavior desirabte? Why or why
