| Underground tunnels have shown an irreplaceable role in alleviating traffic pressure,facilitating the maintenance and repair of municipal facilities,and promoting the connection of roads in various countries.It is essential to maintain the safe and stable operation of underground tunnels.my country is a country with frequent earthquakes,and the seismic fortification intensity in most areas is 7 degrees or above.Earthquakes often cause damage to underground tunnels.The more common damages include end wall rupture,tunnel cracks,ground uplift,etc.Due to earthquake damage,disasters such as groundwater leakage,tunnel water inrush,mud outburst,and water permeation will also occur in areas with high water content.In the past,when many scholars studied the problem of tunnel scattering of seismic waves,they often simulated the medium around the tunnel as an elastic single-phase medium.In fact,the study of tunnel scattering in saturated soil is quite different from the mechanism of single-phase medium.Therefore,using the theory of saturated soil medium to study the scattering problem of tunnels in water-rich areas is closer to the actual engineering environment.Aiming at the seismic damage problem of tunnels in saturated soil areas,the complex variable function method,wave function expansion method,etc.are used to complete the process of solving the tunnel scattering problem through calculation formulas,programming solutions,comparison verification,and case analysis.In the calculation process,This paper introduces two kinds of conformal mappings and uses conformal mapping to replace the radius of the circle in the Bessel function.Therefore,the scattering analytical solution of the curved-wall horseshoe tunnel is obtained.This paper has certain significance for optimizing the tunnel design and proposing seismic damage prevention measures.The main results achieved include:(1)The power concentration of the permeable boundary of the deep horseshoe-shaped tunnel is much greater than that of the impervious.Under permeable conditions,the stress concentration in the vertical and horizontal directions is greater.Under impervious conditions,the power concentration is only in the vertical direction.(2)Low-frequency waves will cause greater power concentration and pore pressure concentration in deep-buried tunnels.When low-frequency waves are incident,the power at the top and bottom of the tunnel is concentrated.The concentration of pore pressure at the waist on the left and right sides of the tunnel is significantly higher than that at other locations.When the degree of coupling between porosity and surrounding rock and soil viscosity increases,the concentration of pore pressure here also increases faster.(3)The stress concentration of the shallow horseshoe-shaped tunnel under the incidence of low-frequency waves is significantly higher than that of high-frequency waves.The peak stress concentration of low-frequency waves appears at the left arch waist,while the stress concentration peak of high-frequency waves appears at the right arch.The power concentration of the curved-wall horseshoe-shaped tunnel section is significantly higher than that of the circular tunnel section,and the location of the peak will also vary depending on the section form.(4)Under the incidence of low-frequency waves,the displacement of the arch waist on both sides of the shallow horseshoe-shaped tunnel increases,but the top and bottom displacements do not change much.However,if the incident waves are high-frequency waves,the displacements on both sides of the tunnel will shrink instead.At the same incident wave frequency,the greater the degree of viscous coupling between the surrounding rock and soil,the lower the displacement of the top,bottom and sides of the tunnel,but the tunnel displacement will increase at the arch shoulder and foot of the tunnel.(5)Under the incidence of low-frequency waves,the shallow horseshoe-shaped tunnel adopts different porosity and Poisson’s ratio parameters.The pore pressure concentration map shows obvious symmetry along the vertical direction,and the pore pressure concentration values on the left and right sides of the tunnel are significantly higher than other positions.There was also a small increase in pore pressure concentration at the top and bottom of the tunnel,and the change in Poisson’s ratio would lead to a greater increase in pore pressure concentration. |
