Research on Stratum Settlement Analysis under Multi-well Pumping Conditions in Complex Soft Soil Areas

The hydraulic parameters obtained from pumping tests are critical indicators for evaluating hydrogeological characteristics of deep foundation pit strata and controlling environmental impacts. This study, based on a deep foundation pit project in Shanghai, conducted single-well and multi-well pumping tests combined with site-specific engineering geological and hydrogeological conditions. The analysis of multi-aquifer water level variations and surface subsidence during pumping revealed significant hydraulic connectivity between Layers ②_3-3, ⑤_2-1, and ⑤_2-2. The permeability coefficients remained consistent across aquifers during pumping, while notable interlayer differences existed in transmissivity and storativity coefficients. Post-pumping water level recovery showed rapid restoration, with 90% of initial water levels recovered within 28 hours across all aquifers. Surface subsidence exhibited distinct spatial effects during pumping operations. The maximum cumulative settlement at central monitoring point D0 reached 37.91 mm, with subsidence attenuating to 33.46 mm and 17.76 mm at 10 m and 30 m from the pumping wells respectively. Ground rebound initiated after multi-well pumping cessation, demonstrating 36%~74% settlement recovery at monitoring points within 120 hours, while groundwater levels recovered to 96.2%~98.6% of initial values. This contrast highlights the irreversible nature of soil consolidation deformation despite substantial water level restoration. The findings provide empirical references for deformation prediction and environmental control in similar hydrogeological conditions of deep excavation projects.