Experimental Study On The Characteristics Of Seismic Subsidence Of Lanzhou Unsaturated Loess

There is a significant seismic subsidence in the loess,what many examples and loess seismic subsidence damage studies have shown in the earthquake.Because of the special characteristics of Lanzhou loess,earthquake subsidence phenomena existed widely in Lanzhou area,therefore,it is necessary to study the seismic subsidence of Lanzhou loess,which is of great significance for earthquake prevention and disaster reduction.There are fewer large earthquakes in the loess area recently,and fewer cases suitable for seismic subsidence study,the current research on loess seismic subsidence mainly relies on laboratory methods.This thesis based on summarizing and referring to the previous studies,the dynamic simple shear apparatus independently developed by Xi'an University of Technology is used to study the seismic subsidence characteristics of unsaturated loess in Lanzhou,and the improvement is made on the basis of the original pressure chamber.In this paper,the dynamic simple shear apparatus is used to carry out single shear tests on Lanzhou undisturbed loess specimens with different water content,under different compressive stress and shear strain amplitudes.The dynamic shear stress-strain relationship,dynamic strength curve and seismic subsidence deformation law are tested and analyzed,and the Curve of Dynamic Shear Stress with shake frequency,the variation law of dynamic shear modulus and dynamic damping ratio with dynamic shear strain and its relation parameter are obtained;the influence of water content,lateral confined consolidation compressive stress and dynamic shear strain amplitude on the variation of seismic subsidence coefficient with shake frequency are analyzed,the relationship between seismic subsidence coefficient and water content,compressive stress,dynamic shear strain amplitude and magnitude of vibration are also analyzed.The mathematical model of the relationship between seismic subsidence coefficient and water content,dynamic shear strain and vibration number is established,and the accuracy of prediction of seismic subsidence deformation by the mathematical model is demonstrated.The side limit plate mechanism of the pressure chamber was improved,and the difference of the test results between the two kinds of pressure chamber mechanism was compared and analyzed.The research results have gained a new understanding,which has a certain significance for the research on seismic settlement deformation testing and earthquake disaster reduction of loess.