Damage Quantification And Crack Propagation Of Ground Fissures Under Earthquake

As a kind of external earthquake disaster,ground fissures have increased the frequency and the scale of disasters,which not only caused damage to various engineering buildings,transportation facilities,urban lifeline projects and land resources,but also may lead to a series of serious ecological environment problems.At present,researches on the genetic mechanism,distribution law,activity characteristics and dynamic response of ground fissures have been carried out in large numbers,but there is still no research data on ground fissure site damage and concealed ground fissure propagation caused by earthquake.Under the action of earthquakes,generally,the soil in the ground fissure site will accumulate damage and cause secondary cracks.Crack propagation will also caused in the overlying soil layer of the buried ground fissure,which will cause the ground fissure to appear on thke surface.These catastrophic behavior will directly affect The safety of the building.Therefore,it is of great theoretical significance and engineering practical value to carry out research on damage quantification and crack propagation of ground fissure sites under earthquake action.In this paper,the Xi'an ground fissure site is taken as the research object.Based on the shaking table test,the damage analysis of the ground fissure site is carried out.The extended finite element method is used to study the crack propagation of the concealed ground fissure under earthquake action.The main work and research results are as follows:Firstly,the Hilbert-Huang transform spectrum analysis method is introduced to explore the physical meaning of Hilbert's marginal spectrum,and the program to realize this function is written by MATLAB.Secondly,using the advantage of Hilbert-Huang transform in seismic time history analysis,the damage quantification method based on Hilbert-Huang transform is determined.By analyzing the relationship between surface damage index,peak acceleration and test phenomena,the applicability of the damage quantification method is verified,and the damage development law of different locations of ground fissure sites under different ground motions is analyzed.Thirdly,using the ABAQUS nonlinear analysis software,the finite element model of the ground fissure site and the concealed ground fissure site was established.By comparing the acceleration response of the crack expandable model with the nonexpandable model,the advantages and disadvantages of the two simulation methods are compared,and the feasibility of the finite element modeling method is verified.Finally,the rupture propagation law of concealed ground fissures under different intensity seismic waves is obtained by finite element simulation.Based on the three aspects of soil tensile strength,overburden thickness and crack inclination,the effects of different soil parameters and soil layer structure on the propagation of ground fissures are analyzed.