Physical simulation of aquifer compression due to groundwater fluctuation

To investigate the compression of granular aquifer induced by fluctuations of pore pressure, series of repeated pore pressure induced loading-unloading tests on specimens made of Ottawa sand mixed with mica were conducted in a K-o-triodal consolidation system. To simulate the stress paths in the field, the vertical displacements of soil specimens were monitored while maintaining a constant total vertical stress and applying sinusoidal fluctuations of pore pressure to specimens under K-o conditions. Shakedown theory is applied to interpret the testing data. The paper describes the laboratory setup, test procedure and findings from the test results. The results reveal that a shakedown behavior existed in saturated granular specimens and the accumulated permanent axial strains are 5 to 56 times of the values for conventional, monotonic loading. The finding evidently proves the significance of aquifer compression to ground subsidence due to repeated ground water fluctuations.