The influence of withdrawal-recharging pattern on the deformation characteristics of sand in confined aquifer

Land subsidence caused by excessive groundwater withdrawal has become a global hazard, which demands further researches and the potential measures to control. Using the FlowTrac Ⅱ consolidation test system, six compression tests were designed to investigate the stress state and stress paths of sand within confined aquifers under conditions of withdrawal and recharging. The deformation characteristics of aquifer sand were studied under different withdrawal-recharging patterns. During pumping and recharge processes, sand deformation responses were observed to lag behind changes in applied stress. The characteristics of this hysteresis effect on deformation were summarized. The alternating phenomenon of rebound and compression of sand deformation under the recharging process is analyzed. When the recharging effect was relatively small than withdrawing effect under the stable withdrawal-recharging pattern, the compression deformation was observed in the recharging process. The research results provide a rational explanation for the continuous compression deformation of the aquifer during groundwater level recovery and offer experimental evidence for the rational design of artificial groundwater recharge in engineering construction.