Study On Sand Liquefaction Of Weihe River Based On Unsaturated Shear Deformation Characteristics

Sand liquefaction is a common seismic geological phenomenon,and the judgment of sand liquefaction is the key and difficult problem in the field of geological engineering and geotechnical engineering.From the perspective of the nature of sand liquefaction,the liquefaction of sand is due to the shear shrinkage of the soil volume under drainage conditions,and the pore water pressure cannot be dissipated under undrained conditions,which makes the soil lose its shear strength.Therefore,in order to understand the mechanism of sand liquefaction,we must first analyze its shear deformation characteristics.In the past,our research on sand liquefaction mainly focused on strength changes,and mainly used the physical experiment of saturated sand as the research method.However,the triaxial volume deformation test of saturated sand is usually more complicated,and the indoor physical experiment research has a certain degree.limitation.This paper takes the fine sand of the first terrace on the north bank of the Weihe River in Xi’an,Shaanxi Province as the research object.It uses a combination of physical experiment and numerical simulation as the research method.To study the characteristics of the shear deformation when saturated,and then to study the liquefaction of saturated sand.The main results of the thesis are as follows:(1)Through conventional triaxial shear tests on Weihe sand,the stress-strain relationship curve law of loose sand,medium-density sand,and dense sand and the characteristics of shear deformation are obtained.(2)Through the PFC3D particle flow numerical simulation test,the stress-strain curve,volume-strain curve,porosity change curve and shear body deformation of unsaturated sand under different compactness,water content,and confining pressure conditions are obtained.feature.(3)Based on the critical void ratio theory,the CVR line of saturated sand based on the CVR line of unsaturated sand is established,and a method for evaluating the liquefaction of saturated sand based on the deformation characteristics of unsaturated sand is proposed.