Seismic Dynamic Response Laws And Shock Absorption Measures Of Shallow Buried Bias Multi-Arch Tunnel

Double-arch tunnels have many advantages,such as convenient wiring,less floor space,smooth route alignment,and easy connection with bridges or special projects.These advantages make the double-arch tunnels more and more widely used in practical engineering.Under certain engineering conditions,shallow-buried bias double-arch tunnels will inevitably occur.The shallow-buried bias tunnel has the characteristics that thin overlying soil and asymmetry of surrounding rock pressure,which is more likely to destroy in earthquakes.At present,there are few studies on the seismic damage mechanism and shock absorption measures of shallow-buried bias double-arch tunnels.Therefore,the study of seismic dynamic response law and Shock Absorption Measures for shallow-buried bias double-arch tunnels has become an urgent problem to be solved.Based on the large-scale shaking table test and numerical simulation,the seismic dynamic response law and shock absorption measures of shallow-buried bias double-arch tunnels were studied.The effectiveness and reliability of the numerical simulation were verified by comparing the results that the shaking table test and the numerical simulation.Using numerical simulation,the dynamic response of the shallow-buried bias double-arch tunnel under different excitation directions,different excitation strengths and different loading conditions was studied.Then the damping effect of the damping layer and the seismic joint on the shallow-buried bias double-arch tunnel was studied.Finally,the damping effect was discussed that the different thickness of the damping layer and the different width of the seismic joint.The conclusions obtained are as follows:(1)In the calculation results of MIDAS-GTS/NX,the variation trend of the acceleration for the shallow-buried single-hole tunnel is same as the result that the shaking table test,and the acceleration values are also close.The double-arch tunnel model is established by the same modeling method.It is effective and reliable to analyze the seismic dynamic response law and shock absorption measures of shallow-buried double-arch tunnels by this model.(2)The acceleration response of the shallow-buried bias double-arch tunnel is greatly affected by the type of seismic wave,and the acceleration response law and the acceleration response peak are significantly different between different seismic waves.In Darui artificial wave,Wenchuan wave and Kobe wave,Wenchuan wave has the strongest dynamic effect on tunnel lining.As the excitation intensity increases,the peak response of the lining increases.However,the law of the change in acceleration at the lining position does not change as the excitation intensity increases.Different excitation strengths only affect the response peak of acceleration and do not affect the overall law of the acceleration of the lining.Under the action of X-direction seismic waves,the acceleration response of the arch shoulder,arch foot and vault are the strongest.Under the action of the Y-direction seismic wave,the acceleration response of the vault and the arch shoulder is the strongest.Under the action of Z-direction seismic waves,the acceleration response at the vault and the shoulder is the strongest.Under the action of XZ-bidirectional seismic wave,the acceleration response in the X direction is stronger than the acceleration response under the action of a single seismic wave.(3)The internal force response of the lining for shallow-buried bias double-arch tunnel is greatly affected by the type of seismic wave.Under the action of different seismic waves,the internal force response law of tunnel lining is different,and the maximum internal force is not in the same position.Under the action of Wenchuan wave,the internal force response of the lining is the strongest.The moment and the shearing force of the lining are less affected by the direction of seismic wave loading,and the axial force is greatly affected by the direction of seismic wave loading.(4)The displacement response of the lining of shallow-buried bias double-arch tunnels is greatly affected by the type of seismic waves.Under different seismic waves,the displacement response law of the lining has great differences,and the maximum displacement is also at different positions.Among the three seismic waves,the lining displacement response under the action of Wenchuan wave is the strongest.The seismic wave loading direction has a great influence on the displacement response in the X direction and has little influence on the displacement response in the Z direction.(5)The dynamic response of the shallow-buried bias double-arch tunnel is affected by the thickness of the damping layer.Under different thickness of the damping layer,the difference that the response peaks for the acceleration,internal force and displacement of the measuring points are large.Under the condition that the thickness of the damping layer is 10cm and 15cm,the damping effect is better.As the thickness of the damping layer continues to increase,the peak response of acceleration,internal force and displacement have been an increasing trend.(6)The damping effect is best under the condition that the seismic joint width is 10cm.In the X-direction,the damping effect of the damping layer is better than that of the seismic joint.The width of the seismic joint does not affect the acceleration dynamic response characteristics in the X-direction.Under different seismic joint width,the law of change of the acceleration response for the lining's measuring points is similar,but the response peaks are slightly different.