Analytical Study On Two-dimensional Viscoelastic Consolidation Of Overlying Weakly Permeable Layer Under The Change Of Confined Water Level

The over exploitation of groundwater resources will cause the change of water level in the soil layer,which will lead to the change of effective stress in the soil and the compression and consolidation of the soil layer,which is an important factor leading to regional land subsidence.Land subsidence is an environmental geological disaster that has developed for a long time and affected a wide range of areas.This phenomenon has brought great adverse effects on the high-quality development of China's economy.At present,the analytical research on consolidation settlement caused by water level change mainly focuses on one-dimensional consolidation.In the case of multi-dimensional consolidation,numerical methods are used more,and less consideration is given to the rheological factors of soil that lead to the long-term development of land settlement.In view of this,in order to more efficiently and accurately evaluate and predict the settlement of the aquitard when the confined water level changes,this paper combines the Terzaghi rendulic two-dimensional consolidation theory and the definite solution conditions of the aquitard under the water level change,establishes the mathematical model of the two-dimensional consolidation of the aquitard,and uses the merchant rheological model to simulate the creep,stress relaxation Then,the semi analytical solution of the consolidation model in the real physical domain is obtained by integral transformation and inverse transformation.The main research work of this paper is as follows:(1)Combined with Terzaghi rendulic two-dimensional consolidation equation and the initial and boundary conditions of aquitard when the water level of confined aquifer changes,a two-dimensional elastic consolidation model of single-layer aquitard is established.On this basis,the single-layer aquitard is extended to multiple layers and combined with merchant rheological model,A two-dimensional viscoelastic consolidation model of multi-layer aquifers is established.The semi analytical solution of the consolidation model of aquitard in the real physical domain is obtained by Laplace Fourier transform and corresponding numerical inverse transform.(2)The semi analytical solution of the consolidation model is programmed by MATLAB,and the solution in this paper is compared with the one-dimensional consolidation analytical solution and the two-dimensional finite element numerical solution of the aquitard through a specific example to verify the correctness of this method.Then,combined with the example,the elasticity,permeability,thickness,viscosity and stiffness ratio of the aquitard are further analyzed,And the influence of water level decline of confined aquifer on consolidation development.(3)The consolidation settlement calculation method proposed in this paper is used to analyze the settlement development of the surrounding ground in the dewatering project of foundation pit confined layer,and the calculation results are compared with the settlement monitoring data.The results show that the calculation results of this method are in good agreement with the actual development of surface settlement.It can be seen that on the basis of determining the reasonable stratum model and mechanical parameters,The semi analytical solution established in this paper can accurately and efficiently analyze the land subsidence under the change of water level.