Impact Study On Bedding Rock Slope To The Stability Of Supporting Structure At Tunnel Entrance

With the rapid development of traffic construction in our country,it is very common for the highway tunnel to pass through the mountain slope.And the surface of the tunnel entrance section of the mountain,often for the accumulation of soil or weathered rock layer,so the surrounding rock is broken,poor stability.The deformation field and stress field in the rock slope of the entrance section will be redistributed,and even the stress concentration occurs in the different joint parameters and the change of the yield.Under the action of gravity,water seepage or other overload,the slope is more likely to be unstable.After the stability of the slope appears to be reduced or unstable,the sliding thrust will become larger,and the force acting on the tunnel supporting structure will become larger,and the stability of the tunnel support structure will be affected.In this paper,the Chongqing Zhong Liangshan tunnel expansion project,the use of numerical simulation,theoretical analysis,field measurement and other means to carry out the rock slope on the stability of the supporting structure of the tunnel portal.First of all,this paper introduces the current situation of the research on the limit equilibrium theory and the stability of the rock slope,and then,according to the three-dimensional discrete element software 3DEC,the deformation law of the bedding slope is determined.Secondly,the displacement and stress state of the surrounding rock and the tunnel supporting structure of the tunnel are calculated by using the three-dimensional discrete element software 3DEC,and the influence of different joint parameters on the supporting structure of the tunnel portal is discussed.Finally,based on the above research results,the paper puts forward some suggestions for slope reinforcement and reinforcement of retaining structures.Though the study of this paper,several conclusions are drawn as follow:1 Combined with previous studies,according to the slope and tunnel position relationship defined in two ways: the orthogonal relationship(bedding joint inclination and tunnel axis vertical)and the parallel relationship(bedding joint inclination and tunnel axis parallel);and analyzes the two kinds of position relations of tunnel lining under supporting force model.2 Through the three-dimensional discrete element software 3DEC calculation and analysis,draw the following conclusions: under the condition of parallel relationship between joints,friction angle changes have great influence on the stability of tunnel structure,20 degrees below is obvious;the higher the level of the surrounding rock(rock more complete),the structure of the tunnel below the smaller effect;change the joint stiffness has limited effect on tunnel lining stability;joint angle is small,the greater the effect of tunnel lining;using the elastic foundation beam theory and numerical simulation results show that the parallel relationship of longitudinal deformation in the range of 25m~55m into the hole.3 In orthogonal conditions: the tunnel and slope pile distance in 18m(that is 1.5 times the diameter)when landslide excavation has great influence on the tunnel;and in the above range,the central tunnel floor stress concentration,except the bottom lining,the maximum tensile stress value at the arch,which is less than the ultimate tensile strength of the upper value;landslide deposits,found that although the tunnel lining structure is the maximum principal stress value had a significant decrease in landslide,but there are large vertical displacement.