Numerical Modelling the Effect of the Groundwater Table Variation Type on Land Subsidence

A decrease in ground water level would cause an increase of effective stresses at clay layers that results consolidation of lower layers and land subsidence. For control of this phenomenon it is necessary to prevent from extensive ground water table level lowering that could be applied with seasonal pumping and dewatering of underground aquifers. This would introduce the ground water table to oscillate periodically. Therefore, clay layers consolidation will be under the influence of cyclic consolidation. In this study Biot s three-dimensional consolidation theory has been used for finite element modeling. Formulation was achieved based on element equilibrium and fluid continuity equations. In this analysis, inelastic behavior of soil is applied in calculations and bilinear model is used for stress-strain behavior of soil under cyclic loading. Analysis has done in various loading conditions. Results of these analysis indicates that in the same conditions with a same maximum decline of ground water, the rate of settlements decrease with lowering of under area of loading-time graph. This model can be used for optimization of type of withdrawal of ground water for decreasing of land subsidence. Comparison of model results with laboratory results shows the correction of model

Keywords:

Land Subsidence , Consolidation , Ground Water , Nonlinear , Finite Elements