Abstract: With increasing utilization of urban underground spaces, large underground structures have clear influence on the
development of regional land subsidence. To reveal the mechanisms for the effect of pile group foundations on pumping-induced land subsidence, physical model tests were conducted in this paper and the effects of pile spacings and pile arrangement patterns on pore water pressure and soil subsidence were analyzed. The experimental results indicate that pile spacing and layout have effects on the hindrance of pile groups to water flow and soil subsidence. Smaller pile spacings and checkerboard arrangements result in higher area replacement ratios and longer seepage paths, effectively obstructing seepage and soil subsidence. Owing to the blocking of pile group, groundwater in the zone between the pile group and a pumping well is hardly replenished when pumping, causing the pore water pressure to decline obviously and the gradient of subsidence to increase. 

Key words: underground structures, physical model test, land subsidence, pumping, pile-group effect