Analysis Of Seismic Dynamic Characteristics Of Tunnel Crossing Fault Zone Based On Discrete Element Method

Due to its special geographical location,China is located just between the two major seismic belts in the world--the Pacific Rim seismic belt and the Eurasian seismic belt.Many fault fracture zones have appeared in China and are widely distributed,especially in the Western mountainous areas where fault fracture zones are relatively dense.The frequency of earthquakes is high and the risks are great.Therefore,when the tunnel crosses the fault zone,the study of different forms of faults and resistance and damping measures has important theoretical value and engineering application value.In this paper,the seismic dynamic characteristics of some tunnel structures in fault fracture zone are studied by discrete element method.The influence of different faults(different dip,different dd,different width)and different resistance and damping measures(different buffer layer strength,different reinforcement ring strength)on the seismic dynamic characteristics of tunnel structures is analyzed.The vibration response laws of the tunnel structure after the applied buffer layer or reinforced ring are analyzed with the engineering example.The findings are as follows:(1)The condition dip=90° is the most unfavorable to the vertical deformation of the tunnel cross section,but it is the most favorable to the horizontal deformation.Under this condition,the arch shoulder is the most unfavorable position.With the increase of fault dd,the maximum vertical compression value of the tunnel cross section is increasing.The condition dd=0° is the most favorable for the maximum vertical and horizontal deformation of the tunnel cross section.With the increase of fault width,the maximum vertical deformation and horizontal deformation of the tunnel cross section are increasing,and the arch shoulder is the most unfavorable position.(2)With the increase of fault dip,the shear plastic area of tunnel structure in fault is gradually transformed into the vicinity of the fault layer,and the shear effect is transformed from dispersion to concentration.With the increase of fault dip direction,the shear plastic area of tunnel structure in fault gradually increases from the vicinity of the fault layer to the distribution of most fault areas,and the shear effect changes from concentration to dispersion.With the increase of fault width,the shear plastic zone of the surrounding rock undergoes aprocess of less and more and less,and the shear plastic zone of the tunnel structure in the fault undergoes a process of more and less and more.(3)The application of buffer layer and the increase of buffer layer strength,the application of reinforcement ring and the increase of reinforcement ring strength can obviously weaken the deformation response of tunnel lining structure.Except for the vaults,the maximum velocity response peak decreases obviously due to the application of buffer layer.With the application of the reinforcement ring,the maximum speed peak value of the monitoring points of the vault and left and right arched shoulders increased,and the maximum speed peak value of the monitoring points of the left and right arched waist,left and right arch foot and upward arches decreased significantly.(4)In a tunnel engineering example,when the model is applied to the buffer layer,the horizontal deformation at the arch foot is the largest,which is the most unfavorable position,and the maximum speed response peak at the right arch shoulder is the largest;when the model is applied to the reinforcement ring,the horizontal deformation at the arch shoulder is the largest,which is the most unfavorable position,and the maximum speed response peak at the right arch foot is the largest.