滇藏铁路香格里拉—邦达段地应力状态及工程效应分析

IN-SITU STRESS STATE AND ENGINEERING EFFECT IN SHANGRI-LA-BANGDA SECTION OF YUNNAN-TIBET RAILWAY

滇藏铁路香格里拉—邦达段沿线断层发育,构造运动强烈,为提高沿线工程的稳定性,基于构造形迹、震源机制解和实测数据的多元综合分析法,对研究区主应力方向进行了分析;基于Hoek-Brown强度准则和修正的Sheorey理论,结合实测数据,对研究区岩体强度参数和主应力量值进行了估算和预测,最后对研究区的地应力场特征及其工程效应进行了分析。结果表明:香格里拉-德钦应力区的水平最大主应力方向N0°W~N40°W;芒康-邦达应力区的水平最大主应力方向为N60°E~N80°E;铁路沿线埋深1000 m处,水平最大主应力范围为24.23~37.30 MPa;埋深2000 m处,水平最大主应力范围为47.29~66.69 MPa;香格里拉-德钦应力区隧道轴线设置为N80°W~N40°E有利于围岩稳定,芒康-邦达应力区隧道轴线走向设置为N10°E~N130°E有利于围岩稳定;铁路沿线高地应力显著,埋深超过400 m就可能处于高地应力状态,硬质岩埋深超过700 m会有岩爆风险,软质岩埋深超过1400 m会有大变形风险。

The faults along the Shangri-La-Bangda section of Yunnan-Tibet railway are well developed. The tectonic movement is strong. Research on the present in-situ stress field in this area is conducive to the construction of the Yunnan-Tibet railway. A multisource comprehensive analysis method based on geomechanical trace analysis, focal mechanism solution, and measured data is utilized to analyze the orientation of in-situ stress field of the Shangri-La-Bangda Railway. Based on the Hoek-Brown strength criterion, the modified Sheorey theory and the measured data, the rock mass strength parameters and in-situ stress values along Shangri-La-Bangda section of Yunnan-Tibet railway are estimated and predicted respectively. And the characteristics of in-situ stress field and its engineering effect in the research area are analyzed. The results show that the orientation of the maximum horizontal principal stress is in the range of N0°W~N40°W in the Shangri-La-Deqin stress district while it turns into N60°E~N80°E in the Mangkang-Bangda stress district. The maximum and minimum horizontal principal stresses ranges are 24.23~37.30 MPa and 14.81~22.79 MPa, respectively when the buried depth is about 1?000 m. Their ranges are 47.29~66.69 MPa and 28.90~40.76 MPa when the buried depth is about 2?000 m. The tunnel axes are N80°W~N40°E and N10°E~S50°E in Shangri-La-Deqin stress district and Mangkang-Bangda stress district, which are conducive to the stability of surrounding rock. The effect of high in-situ stress is obvious when the buried depth is more than 400 m. Rockburst risk is high when the depth of hard rock is more than 700 m. Large deformation risk is high when the depth of soft rock is more than 1400 m.