Three dimensional simulation of groundwater exploitation and land subsidence based on variable permeability

Porosity and permeability of soil keep on changing during the process of land subsidence. However, these are often ignored in order to reduce the computation in the simulation, thus the simulation results may deviate from the actual situation. In order to examine the influence of variable porosity and permeability on the simulation results of subsidence, a 3D consolidation model considering the variation in permeability during consolidation is established based on the coupling of the Biot consolidation theory and Kozeny-Carman equation. Pumping simulations are carried out under the condition of considering and neglecting the variation of permeability in the typical aquifer structure in the Beijing plain. It is found that the change in the layer permeability after pumping is uneven, and the permeability is reduced near the well wall. Considering the change in permeability, the final deformation of the surface is larger than that of ignoring the variation in permeability. The simulation error caused by neglecting the variation in permeability is smaller and has a tendency to develop in the early stage of settlement, and it is larger and more stable in the middle and later stages. This error is positively correlated with the pumping volume and is negatively correlated with the compression modulus and permeability of confined aquifer. With the increasing thickness of the confined aquifer, the error first increases and then decreases.