Analysis Of The Slope-Tunnel Dynamic Interaction And Its Influencing Factors

With the further development of the "The belt and road" initiative,part of the transportation infrastructure in the loess region in western China is increasingly planned,and it is also inevitable to be located in high-intensity seismic areas.The loess slope is characterized by steep slope and rich fissures,which are the reasons for frequent earthquake disasters and loess landslides.Therefore,the loess tunnel traffic construction across the region has attracted much attention because the tunnel entrance section is a vulnerable part.In view of the coupling effect of the loess slope,supporting structure and tunnel,the stability and seismic performance of the slope at the mouth of the loess tunnel need to be emphatically studied,which has important practical significance for the normal use of the tunnel after completion and rapid post-earthquake repair.In this paper,particle flow PFC is used for numerical simulation and large-scale shaking table model test.The factor of slope support structure or not is mainly considered to study the response rules of slope,support structure and tunnel under the same working conditions,and analyze the relations among them,the rules of instability and damage,and the characteristics of force deformation.The following researches are mainly carried out:(1)Domestic and foreign literatures on the modeling,parameter calibration and selection of slope particle flow under the action of earthquake and tunnel failure and ground motion are reviewed to provide references for the modeling calculation of subsequent numerical simulation and the modeling and result analysis of shaking table model test.(2)With the help of particle flow(PFC5.0)numerical simulation,the slope body of loess tunnel with or without slope protection structure is analyzed.Analysis results show that the effect on seismic dynamic displayed "hasten table" and "magnifying effect",the characteristics of the slope protection and the coupling of the tunnel,inhibits the irregular movement of soil,the stress transfer and displacement speed,to a certain extent,attenuation,attenuation is more obvious horizontal displacement,slope protection can largely horizontal vibration resistance,prompting the loess tunnel slope from osteoporosis tend to be more closely as a whole.(3)A large-scale shaking table model test of a high and steep loess slope with a ratio of 1:80 has been designed and completed.By inputting seismic waves of different types,amplitudes and frequencies,the dynamic response law of the slope body at the mouth of the model under the action of earthquake and the influence of ground motion parameters on the dynamic response are discussed.The PGA of the slope increases undulately with the increase of the height of the measuring point.At the tunnel position,the PGA has a process of sudden decrease.It shows that the existence of the tunnel has a certain inhibitory effect on the amplification of slope acceleration.The slope of the loess tunnel with slope protection structure can keep the stability of the slope body in a long vibration sequence,so that the PGA constraint of the slope measurement point is within a relatively small range.In terms of soil pressure response,the soil pressure at the slope protection is negative and fluctuates in a "seesaw" manner with the increase of working conditions.The soil pressure here is passive.On the contrary,if there is no slope protection,the soil pressure is positive and points to the frontage.(4)Summarize and analyze the numerical simulation data and the vibration table test data,and propose the fitting formula.In the complex seismic wave field formed by superposition of seismic waves,the scope of the first failure of soil mass can be calculated by formula.Under the influence of the distance from the center of the tunnel and the elevation of the slope,it can be estimated that it is approximately 1.25-1.5 times the radius of the tunnel from the center of the tunnel.The conclusion is helpful to reveal the instability mechanism of the loess tunnel slope under the action of earthquake and provide useful reference for the seismic design of the project.