Numerical Simulation Of Surface Rupture Caused By Buried Normal Fault Movement And Pumping

Ground fissures are usually formed initially on the basis of fault structures,and then intensified by pumping-water.It is important to study the effect of rupture and deformation of surface soil under the action of the fault bedrock diastrophism of buried fault and pumping,which is of great significance for ensuring the safe operation of engineering construction,and also provides scientific basis for the analysis and evaluation of engineering geological environment.By establishing three-dimensional finite element numerical model,the deformation and failure effects of soil under the action of the diastrophism of buried normal fault,pumping and combination of them are studied respectively.Through in-depth analysis of stress-strain characteristics,deformation and failure process and influencing factors of soil,the following main results are drawn:(1)By the analysis of stress Lode parameters,the change of stress state of overlying soil in the process of diastrophism of buried fault is studied.The results show that in the process of diastrophism of fault,the stress state of soil on the two sides of fault varies alternately via compression-shear ? pure shear ? tensile-shear ? pure shear ? compression-shear.(2)By changing the properties and thickness of soil layer,fault diastrophism mode and dip angle,the width and starting position of “avoiding zone” and "attention zone" in engineering construction are studied.The results show that “avoiding zone” is most affected by the thickness of soil and the dip angle of fault,and "attention zone" is most affected by the elasticity or plasticity of soil.(3)Using the method of controlling variables,the influence of the pre-rupture of soil,the depth of pumping and the position relationship between well and pre-rupture on the surface deformation during pumping is studied.The results show that the pre-rupture aggravates the differential subsidence of the surface,and the influence is greatest when the dip angle is 60?.The influence of pumping on the rupture on the hanging wall firstly increases and then decreases with the increase of the distance between the well and the pre-rupture.The depth of pumping is larger,the influence of pumping formation is greater.(4)By the analysis of soil stress-strain state,the effect of surface deformation under the combination of the diastrophism of buried normal fault and pumping is studied.The results show that the deformation of the surface near the fault zone is the largest,especially when pumping water from the hanging wall side,the soil under the combined action is more prone to deformation than the soil only affected by the diastrophism of fault,and the soil of bottom near the fault zone is prone to rupture and extends up to the sand layer.