The Interaction Research Of Karst Area Surrouuding Rock And The Tunnel Initial Support Structure

Based on the Luheshan tunnel of Qin Chong freeway,this paper investigates interaction between surrounding rock and support of karst area tunnel, adopting numerical simulation with field tests, and analyzes that hydraulic pressure upon lining in karst area have influence on surrounding rock and support structure. The main research contents are as follows:(1) The principle of interaction between seepage field and stress field of tunnel surrounding rock have been expatiated, derivating rock stress and deformation formula when taking consideration of seepage and not.(2)The mechanism of support structure have been expatiatied, drawing the rock convergence curve and support resistance curve theoretically with deduced formula and Luheshan tunnel.(3)The two dimension model of Luheshan tunnel have been established by MIDAS/GTS, comparing the development of plastic zone and the rock displacements when applie to supporting structure or not, show that Supporting structure can be obvious limitation the deformation of the surrounding rock, delay the development of plastic zone; simulating seepage and stress coupling, analysis of the impact seepage on surrounding rock stress, displacement, plastic zone, bolt stress, shotcrete stress.The results are that the seepage increases, so does the surrounding rock stress, displacement and the zone of plastic. Through the lining by applying different size external water pressure, it has great impact on surrounding rock and support. Using load release coefficient method, the rock convergence curve have been made.Finally using load release coefficient method to draw the don’t consider seepage and consider seepage circumstances surrounding rock convergence curve, consider seepage role to move right curve has the trend, it indicated that in the same load is released, consider the seepage water effect, the displacement of surrounding rock increase with trend; When the same displacemen happened,it required supporting force also increased.(4) The Luheshan tunnel have been measured, gathering vault displacements, bolt stress, shotcrete stress which are compared with theoretical value and numerical value. The result is that these values are above the value when don not taking consideration of seepage, and between the value when considering seepage without water pressure and when considering seepage with water pressure. It provides theoretical fundament for water shut off and emission limits.