Study On The Damping Effect And Parameter Optimization Of Rubber Damping Layer In Shallow Bias Tunnel

With the rapid development of China’s economic construction in the reform and opening up,the scale of traffic infrastructure construction is increasing,and more and more shallow buried and biased underground projects appear in the field of traffic infrastructure,especially in mountain tunnels,urban tunnels and underground powerhouse of hydropower stations.In the few research results of underground structure earthquake,most of them focus on the seismic dynamic response characteristics and seismic performance of underground structure,and the research results on how to reduce the dynamic effect of earthquake on underground engineering structure,especially on how to reduce the effect of small earthquake on underground structure by setting damping layer are very rare,At present,there are few reports about the application of damping layer in practical engineering at home and abroad.Therefore,it is of great significance to study the seismic dynamic characteristics and damping mechanism of the damping layer of the shallow bias tunnel in order to clarify the seismic response mechanism,failure mode and damping mechanism of the shallow bias tunnel,reduce the earthquake action,reduce the engineering repair work and improve the seismic safety.Therefore,through the shaking table model test,this paper discusses the dynamic response law and failure mechanism of shallow buried bias pressure tunnel with rubber damping layer under the earthquake,studies the damping effect of rubber damping layer,and optimizes the parameters of rubber damping layer through the combination of numerical simulation and shaking table model test.In this paper,based on the National Natural Science Foundation Project "seismic catastrophic behavior and seismic performance evaluation of rock slope including underground caverns(groups)"(No.:51204125),a group of shaking table model tests of shallow bias tunnels with or without rubber damping layer and a geometric similarity ratio of 1:20 are completed according to the similarity theory and the discrimination criteria of shallow bias tunnels The damping effect of rubber damping layer is studied,and the parameters of rubber damping layer are optimized by midas-gts/NX numerical analysis method.The research contents and conclusions are as follows:(1)Study on the damping effect of rubber damping layer.Through the shaking table test of the shallow bias tunnel model with rubber damping layer,the stress-strain response law of the shallow bias tunnel model with rubber damping layer under different conditions of Wenchuan earthquake wave is obtained,and its failure mechanism is analyzed.Based on the shaking table model test results,the damping effect of rubber damping layer is discussed.It is considered that the rubber damping layer has the effect of obviously weakening the tunnel lining under the earthquake dynamic action,and the damping effect of the damping layer at the arch top is the best under the action of different excitation intensity,but the exertion of the damping effect is related to the monitoring position and excitation intensity of the tunnel.In addition,the damping effect of the rubber damping layer is more fully played in the low intensity excitation than in the high intensity excitation.(2)Based on the numerical simulation of rubber damping layer thickness optimization.The method of locally increasing the thickness of the damping layer in the arch foot area of the tunnel can not change the inherent stress state of the tunnel structure under the seismic dynamic load.However,under the action of different intensity of seismic waves,the amplification coefficient of horizontal acceleration at the arch foot of the tunnel tends to be constant.Therefore,increasing the thickness of the damping layer at the arch foot of the tunnel can increase the energy absorption reserve at the arch foot of the tunnel.In addition,the method of locally increasing the thickness of the damping layer in the corresponding area of the left arch foot and the right arch shoulder is adopted.The overall response trend of the horizontal and vertical acceleration is close to that of the uniform arrangement of the thickness of the damping layer.The amplification coefficient of the acceleration of the left arch foot and the arch shoulder is large,and the response of the left area of the tunnel lining is slightly larger than that of the right area.Under the action of the vertical seismic wave,By increasing the thickness of the damping layer in the corresponding area of the left arch foot and the right arch shoulder,not only the amplification coefficient of the vertical acceleration in the corresponding part can be reduced,but also the vertical acceleration of the rest measuring points of the tunnel can be greatly affected.(3)Optimization of elastic modulus of rubber damping layer based on numerical simulation.Under the action of different intensity of one-way earthquake wave in Wenchuan,the horizontal and vertical acceleration amplification coefficients of left arch foot and arch shoulder of tunnel lining with three different setting of damping layer elastic modulus are larger than other monitoring points,and the acceleration response of left area of tunnel lining is larger than that of right area.With the gradual change of the elastic modulus of the damping layer,the acceleration amplification coefficient of each monitoring point of the tunnel lining decreases greatly when the elastic modulus changes from E=3000mpa to e=1000MPa,while the acceleration amplification coefficient of each monitoring point of the tunnel lining decreases slightly when the elastic modulus changes from E=1000MPa to e=300mpa.Generally speaking,the damping effect of the damping layer is the best when the elastic modulus of the damping layer is e=300mpa,but the damping effect is the best The change of the layer elastic modulus can not change the response trend of the overall horizontal acceleration of the tunnel.