Study On Mechanical Characteristics And Parameter Optimization Of Rock Column In Tunnel Strengthened By Expansion And Slip Anchor

As a new type of tunnel arrangement,the small net distance tunnel can meet the special requirements of complicated terrain Geological conditions,general line layout and construction operation conditions,and has a broad application prospect.Due to the small net distance between the small net distance tunnel and the disturbance of the tunnel structure by excavation,how to ensure the overall structure of the tunnel and the stability of the middle pillar is one of the key problems to be solved during the construction and development of the small net distance tunnel.Based on the research on the mechanism of tunnel bolt support,a new type of dilated slip-resistance plastic anchor rod was developed.The working principle and mechanical characteristics of the new bolt were studied systematically through the indoor drawing test.Based on the similarity theory,a similar material model test was carried out for the small net distance tunnel middle rock column.The failure mechanism of the tunnel middle rock pillar under vertical load and the influence of different supporting parameters on the vertical bearing capacity of the middle rock column were studied.The calculation theory of Wall rock pressure of small net distance tunnel under different buried depths is studied on the basis of the theory of pressure of surrounding rock and the calculation formula of surrounding rock pressure in highway tunnel design specification.Using MIDAS numerical simulation software to simulate the structural forces and deformation characteristics of small net distance tunnel under different construction schemes and net distance of different tunnels,the reasonable construction scheme and net distance of small net distance tunnel in Hanjialing are optimized.Through the above systematic research and in-depth analysis,the following main innovative results are obtained:the new type of dilated slip resistance plastic anchor rod is developed,the mechanical characteristic index of the new type of dilated slip resistance plastic anchor rod is obtained through the indoor drawing test,the numerical model of the new dilated slip resistance plastic anchor rod is established,and the change law of the maximum displacement with the angle of the inner wall of the sleeve and the external wall of the embolus body and the nonlinear regression equation.And the optimized index of new type anchor rod structure size;A model test device for small net distance tunnel similar material is developed.Based on the model test results of small net distance tunnel similar material,a theoretical formula for the vertical bearing capacity of the middle rock column reinforced by a double linear bolt is presented;Considering the influence of the crossing and overlapping of rock mass on the wall rock pressure of tunnel,a theoretical formula is established to calculate the vertical pressure and the lateral pressure of the surrounding wall rock in the tunnel excavation.Considering the influence of the crossing and overlapping of rock mass on Wall rock pressure,a theoretical formula is established for the calculation of Wall rock pressure of small net distance under different depth.The vertical pressure and lateral pressure of surrounding surrounding wall rock in tunnel excavation can be calculated respectively,and the change law of small distance tunnel pressure and the numerical model of Wall wall pressure can be obtained under different depth and net distance method.At the same time ensure the construction safety and stability of the optimal construction plan and tunnel net distance range.