| During the construction of the tunnel,the slope terrain on the surface of the tunnel is very common,and due to the structure of the rock itself,the inclined interlayer surrounding rock is also appears during the excavation process.The bias load caused by the combined action of the strata and slope will cause uneven forces on the structure.In this type of geology,coupled with the degradation of interbedded rocks by hydrology,the safety of the tunnel will be greatly affected.The current research focuses on a parameter of the tunnel in slope terrain and bedding rock strata,and rarely considers the influence of the water content of the rock at the same time.This article relies on the Wudouwan Tunnel Project of the Yuqian Railway,using literature research and triaxial experiments to study the relationship between the mechanical properties of the surrounding rock and the saturation coefficient.And uses the software numerical simulation based on the strength reduction method to calculate safety factor and structural internal force of the tunnel in slope terrain and bedding rock strata.By analyzing the data,the following conclusions are obtained:(1)Based on literature research and engineering practice,the factors affecting the stress characteristics of the tunnel in slope terrain and bedding rock strata are the slope angle of the slope,the thickness of the interbedded surrounding rock,the rock saturation coefficient and the buried depth of the tunnel.(2)Through triaxial test and literature reference,the degradation function of rock mechanical parameters with respect to saturation coefficient is obtained.Mudstone is a water-sensitive surrounding rock,and its mechanical parameters deteriorate significantly with the change of saturation coefficient.The deterioration of the mechanical parameters of limestone is not obvious with the change of saturation coefficient.Finally,numerical simulation proves the applicability of Mohr-Coulomb ’s constitutive(3)Under the geological conditions of in slope terrain and bedding rock strata,introduced several criteria for the strength reduction method.Based on the comparative analysis of the geological conditions the incremental mutation of dissipated energy is selected as the basis for determining the overall instability of surrounding rock.Through comparative analysis,the applicability of the dissipated energy incremental mutation method in the tunnel in slope terrain and bedding rock strata is proved.Finally,by changing the stress release rate of the surrounding rock,the research shows that the lining support timing has little effect on the overall safety factor of the tunnel.(4)Based on the strength reduction method,by changing the properties of the rock strata,the study found that in the interbedded surrounding rock,the safety factor is controlled by the "weak" surrounding rock,and the "strong" surrounding rock can improve the safety factor.Subsequently,the influence of the four parameters on the safety factor and the internal force of the tunnel was obtained qualitatively through combined working conditions.On the one hand,for the safety factor:as the saturation factor increases,the safety factor shows a non-linear decrease.As the inclination angle increases,it shows a process of increasing from large to small,and the 45°inclination angle is the minimum point of safety factor.The buried depth is negatively correlated with the safety factor in the range of 10m～50m.The layer thickness within 0.5m～2m has no obvious influence on the safety factor.On the other hand,for the internal force of the structure: the axial force and bending moment increases with the increase of the saturation coefficient.As the inclination angle changes in the counterclockwise interval of 0～60°,the internal force of the lining occurs clockwise compared to the horizontally symmetrical stratum tunnel.When the inclination angle increases to 45°,the position of the point of maximum axial force changes,and the tunnel failure mode begins to change.The buried depth is within the range of 30m～50m,the axial force and bending moment are positively correlated with the buried depth.The thickness is within the range of 0.5m～2m,which has little influence on the internal force,but the inclination angle of the interlayer surrounding rock and the slope rock together determines the location of the lining failure.(5)Based on the strength reduction method,through quantitative calculations,the influence of the four variables on the safety factor of the tunnel in slope terrain and bedding rock strata,from large to small,are: saturation coefficient>buried depth>slope rock inclination>interbedded surrounding rock thickness. |
