Study On Stability Of Surrounding Rock Of Tunnel Near Water-rich Gallery

With the implementation of the National Southwest development strategy plan,highways and railways have been developed unprecedentedly,tunnel becomes the main choice for crossing the mountain.China is also a big energy country,and its resources have been greatly exploited and disorderly,leaving a large number of rich water tunnels.In a resource-rich region,for various reasons,the tunnel inevitably passes through the adjacent rich water tunnel section and its affected area.Tunnel excavation can easily cause mud inrush,water inrush,and even engineering accidents such as collapse and roof fall,which have a great impact on construction safety,construction schedule and construction cost.Therefore,it is great importance to deeply study the influence of adjacent rich water tunnels on the stability of tunnel surrounding rock.In this paper,based on the Shui Qing tunnel of Bi Zhen highway in Guizhou province,the relative location of the rich-water gallery and Shui Qing tunnel is detected by using the pre-geological survey data and supplementary survey of on-site engineering,based on this,derived the influence of adjacent rich-water tunnels on the stability of surrounding rock of Shui Qing tunnel by carring out on-site testing of Shui Qing tunnel and numerical simulation of on-site conditions;then the indoor model tests,numerical simulations,and theoretical analysis work were conducted to further explore the general laws affecting the stability of surrounding rock of adjacent tunnels.The main contents of the study were:(1)Three methods,including on-site geological survey,high-density electrical method and TSP detection,were used to conduct additional on-site engineering surveys of the shallow buried section of Shui Qing Tunnel to determine the approximate location of the water-rich gallery,and targeted drill holes were accurately positioned.The location and scale of water-rich gallery and Shui Qing Tunnel.It shows that "on-site geological survey + high-density electrical method + TSP detection" can achieve good results when detecting a water-rich gallery.(2)On the basis of inferring the spatial position of the water-rich gallery and the Shuiqing tunnel,the test on site and the numerical simulation of field conditions was carried.The results was show that the overlying water-rich gallery began to affect the Shuiqing tunnel is at ZK15+604.5,and the impact was basically completed at ZK15+639.5;the sink of the arches of ZK15+604.5 zone was obviously,and the maximum settlement was 32.01 mm.Relative to the unaffected zone,the maximum accumulated settlement of the arch in this zone increased by 58.3%.The difference between the field test and the numerical simulation results is small,and it also proves the feasibility of the numerical simulation.(3)Conducted an indoor tunnel model test to study three types of conditions of tunnels with no adjacent gallery,overlying water-rich gallery,and obliquely above 45°water-rich gallery.By changing the relative distance between the water-rich gallery and the tunnel,discussing the effect of adjacent water-rich gallery on the surrounding rock stability,the affect partition table of water-rich gallery on the surrounding rock was obtained.(4)FLAC3D numerical analysis software was used to analyze six types of conditions,including tunnel-free tunnels,overlying water-rich tunnels,obliquely above-water 45-degree tunnels,horizontal parallel-rich water tunnels,obliquely-lower 45-degree water tunnels,and underlying water-rich tunnels.Based on numerical simulations,the relative stress and deformation of surrounding rock under various conditions were obtained,and the divisional maps of the influence of adjacent rich water tunnels on the tunnel surrounding rock were divided.Comparing the numerical simulation with the indoor test results,the two conclusions are similar,thus verifying the feasibility of numerical simulation.(5)Based on the limit analysis upper bound method,the failure mechanism of active two-dimensional multi-blocks on the face of shallow tunnels is constructed by introducing the nonlinear H-B failure criterion.The power of each part is obtained through the principle of virtual work,and the power balance equation is established to obtain the implicit function including the safety thickness.The Fmincon function of Matlab is used to optimize and solve,and the optimal upper bound solution of the safe thickness under different influencing factors is obtained.Then we explored the influence of the number of triangle blocks,tunnel size,water pressure and geological strength index on the safe thickness.