Study On Seismic Dynamic Response Of Loess-Mudstone Slope With Antidip Fault Zone

The loess plateau in western China is located in the northern part of the north and south seismic zone,and the tectonic movement is so strong,and that the historical earthquake has caused many large-scale loess landslides such as the M=7.5 magnitude earthquake of Tongwei in gansu province in 1718,the M=8.5 magnitude earthquake of haiyuan in 1920,and the M=7.1 magnitude earthquake of yushu on April 14,2010,which induced large scale loess landslide geological disaster,and caused significant casualties and great economic losses,and above all seriously restrict the development of China's western region economy.These seismic loess landslide were almost controlled by active fault zone.From the geological structure,active faults control the formation of loess landslides in the space.Therefore,the study on the formation mechanism of loess landslide induced by the occurrence of earthquake-induced by active fault zones is of great significance for the cause and control of loess earthquake landslides.This paper taking the loess-mudstone slope of the typical anti-dip fault zone of Tianshui area in Gansu province,as the main research object,and uses the similarity theory as a guide to establish the geology of loess-mudstone slopes geological mechanical model,with different inclination angles(?=50° and 80°).Through the large-scale physical model test of the shaking table,the seismic dynamic response characteristics of the loess-mudstone slope in the anti-dip active fault zone are revealed,including the slope acceleration,dynamic earth pressure response and the deformation and failure characteristics of the slope;the FLAC3 D numerical software is used to establish the Calculation model for the loess-mudstone slope of non-fault zone and the antidip fault zone(fault zone angle ?=50° and 80°),the dynamic response of the loess-mudstone slope is analyzed by numerical simulation,and the vibration table Model tests and results were compared and verified.The main research results are as follows:(1)The dynamic responses of loess-mudstone slopes with inclination angles of ?=50° and 80° all exhibit “elevation effect”,“lithologic combination effect”,“fault magnification effect” and “hanging wall effect”,The smaller the dip angle of the fault zone,the greater the dynamic response of the loess-mudstone slope;the horizontal dynamic soil pressure of the interface between the loess and the weathered mudstone increases first,then decreases,and then increases with the horizontal distance from the front edge of the slope.(2)Under the action of horizontal seismic force,tensile plastic zone occurs at the slope shoulder of the non-fault zone,and the shear plastic zone first appears in the slope fault zone of the anti-dip fault zone.As the amplitude increases,the shear plastic zone extends upward along the fault zone to form the lower shear upper tensile crack;the horizontal permanent displacement of the lower plate of the anti-dip fault zone slope is greater than that of the upper plate,and the difference between the upper and lower disc displacement of the slope of 50° is greater than 80°.(3)Under the action of seismic forces,the loess-mudstone slope in the anti-dip fault zone is the first to produce fractures and extend upward along the fault zone to the surface of the loess.With the increase of the amplitude,the fissures on the surface of the slope increase and penetrate through horizontally.Horizontal and vertical fissures are staggered.The slope failure phenomenon is more obvious at 50°,and the deformation failure mode of the loess-mudstone slope in the anti-dip fault zone is tensile-Shear-vibratory slip damage.