深部含水层黏弹塑固结模型及压密模拟

VISCOELASTIC-PLASTIC CONSOLIDATION MODEL FOR DEEP AQUIFER COMPACTION WITH TIME

上海市曾遭受了严重的地面沉降灾害,主要由于浅部含水层开采引发浅部土层固结所致。之后采取了回灌浅部含水层并转向开采深部含水层的措施,地面沉降得到了有效控制。但21世纪初,通过水位及分层沉降监测,发现随着开采量增加,深部含水层也会成为主要压密土层。其变形呈现出显著的非线性压密特征,即使水位普遍抬升,压密仍然持续,开展其固结压密机理模型研究对地面沉降防治十分必要。传统太沙基理论认为砂土骨架是瞬时变形的,忽略了流变性本质,因此无法解释该现象。基于国内外学者的研究,考虑了前期固结压力前后流变性的差异,建立了深部含水层黏弹塑固结压密模型。通过试验获取了相关参数,结合塘桥F16分层标监测结果,对第四含水层长期压密变形进行了模拟。模拟结果很好地反映了含水层长期非线性压密行为,研究结果对指导防治地面沉降有实际意义。

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 ex- tensometer monitoring, it found that deep aquifer will become the major compaction layer with the increasing exploi- tation. The deformation of the deep aquifer shows a significant nonlinear compaction characteristic. Even if the wa- ter 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 in- stantaneous materials, ignoring the rheological nature. So there is no way to explain the above-mentioned phenome- non. Based on the studies of scholars at home and abroad, taking into account the differences in rheologieal proper- ties 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.