Studies On The Theories Of One-dimensional Consolidation Of Soft Soils With Threshold Gradient Induced By Groundwater Pumping

Land subsidence, primarily caused by excessive groundwater pumping, is a kind of widespread geological disaster that occurs in more and more countries and regions all over the world, which brings serious harms to people and human habitat. Up until now, Darcy’s law has been incorporated in evaluating land subsidence. However, some investigators suggest that Non-Darcy’s flow should be applied for deep soft clays exists in China’s coastal areas widely. Based on Non-Darcy’s flow that taking the existence of a threshold gradient, the thesis studies land subsidence caused by consolidation of soft soils due to groundwater pumping. The main original works and achievements are as follows:(1) Analytical solution to one-dimensional consolidation of soft soil layer induced by instantaneous decline of groundwater level due to pumping are obtained considering threshold gradient. A comparison is made between the present solution and the existing one ignoring threshold gradient, and the influences of threshold gradient and groundwater decline level on the consolidation of soft soil are analyzed.(2)General analytical solutions are derived for one-dimensional consolidation of soft soil layer with threshold gradient induced by time-dependent groundwater drawdown. Especially, the analytical solutions are given in detail for different cases when groundwater is linearly drawdown. Based on the solution, the influences of the threshold gradient, the groundwater decline level and the time of the groundwater decline on the consolidation of soft soil are investigated.(3)Analytical solution for one-dimensional consolidation of double-soil layers with threshold gradient under instantaneous decline of groundwater level are derived. Moreover, the effect of the ratio of coefficients of permeability, the ratio of modulus of compression, the ratio of thickness and the relative value of threshold gradient, of the two layers, on the consolidation of the soft soils are discussed in detail.