Study On Anti-seismic Technology Of Shallow Tunnel Structure Crossing Soft And Hard Surrounding Rock In Meizoseismal Areas

With China's economic construction and rapid social development,tunnel construction has gradually been in the highly seismic areas.Due to the restrictions of some complex topography such as alpine valleys,tunnels have been extensively constructed in China's highly seismic areas and have a wide range of application prospects.Although tunnel does not generally show the natural vibration characteristics of the structure itself,and tunnel has long been considered to have good seismic performance.However,several major earthquakes that have occurred since the last century.Among them,the tunnel damage through the bad geologic section is particularly prominent.In this paper,we study the problem of crossing soft and hard surrounding rocks in tunnels passing through bad geologic sections.The main results and conclusions of this paper are as follows:(1)The theory of elastic foundation beam and reactive displacement method are described.The partial elastic foundation beam model is used for derivation and analysis,combined with the formula of reactive displacement method.The formulas for the lateral and vertical forces acting on the partially elastic foundation beam are obtained.(2)The dynamic response under different conditions when the tunnel crosses the soft and hard surrounding rock is studied,which include different surrounding rock parameters,different lining thickness,different damping layer selections,and different interface inclination angles.The results show that the stress extremes are basically located in the left arch,and the lining of soft rock is greater than the hard rock section.(3)The portal of the tunnel is regarded as a free end,and the cavern section is regarded as a fixed end.The tunnel is regarded as a cantilever beam supported on a flexible foundation with known displacement.The corresponding vertical force formula can be derived.Compared with the numerical solution,the theoretical solution of the dome is close,which can provide a reference for seismic design of the tunnel.(4)Through the shaking table model test of soft and hard rock tunnels,the action of dynamic response through tunnels of soft and hard surrounding rocks was studied.The seismic damping effect of tunnels across soft and hard rock tunnels was conducted.The strain increment and acceleration amplification factor were compared and analyzed.