VISCOELASTIC-PLASTIC CONSOLIDATION MODEL FOR DEEP AQUIFER COMPACTION WITH TIME

Shanghai had suffered severe ground subsidence, mainly due to the shallow soil consolidation caused by shallow aquifer exploitation. Thereafter, pumping aquifer is adjusted from the shallow aquifers to deep ones. The land subsidence was effectively controlled. However, in the early 21 century, through water level and borehole extensometer monitoring, it found that deep aquifer will become the major compaction layer with the increasing exploitation. The deformation of the deep aquifer shows a significant nonlinear compaction characteristic. Even if the water level is generally uplift, the compaction continues. It is very necessary to research the consolidation mechanism model for the ground subsidence prevention and control. The traditional Terzaghi theory regards sand skeleton as instantaneous materials, ignoring the rheological nature. So there is no way to explain the above-mentioned phenomenon. Based on the studies of scholars at home and abroad, taking into account the differences in rheological properties before and after the pre-consolidation pressure, the viscoelastic-plastic consolidation model for deep aquifer is established. The deep fourth aquifer long-term compaction deformation is simulated based on the test parameters, combined with the Tangqiao F16 borehole extensometer monitoring results. The simulation result shows that the model used well reflects the aquifer long-term nonlinear compaction behavior. The study result is helpful to guide the prevention and control of ground settlement.