成兰铁路地应力测量与构造应力场分布规律研究

成兰铁路位于青藏高原东部边缘高山峡谷区,由于印度板块与欧亚板块碰撞,区域内构造变形强烈,构造应力场十分复杂。为研究成兰铁路工程区地应力分布规律及断层稳定性,在铁路沿线茂县、松潘县以及宕昌县境内4个深孔水压致裂地应力测量基础上,获得了不同位置区域地应力实测值的大小和方向,并建立工程区应力参数随深度分布规律。分析表明:工程区应力随深度变化呈现出较好的线性关系,在测试深度范围内,水平应力普遍高于垂直主应力,地应力值总体上属于中—高地应力级别,在750 m深度内,最大水平主应力达25 MPa,反映出工程区构造应力占主导地位,侧压系数随深度呈缓慢衰减趋势。成兰铁路在不同构造单元上最大水平主应力方向有所不同,在东昆仑断裂以北甘南块体内,最大水平主应力为北北东向,在东昆仑断裂以南川青块体内最大水平主应力为北西向。根据实测的地应力数据并结合库伦滑动摩擦准则,对工程区内的断层稳定性进行了分析。文中取得的认识对成兰铁路工程区的构造应力场、断裂活动性的研究以及隧道工程的建设具有重要的参考意义。

IN-SITU STRESS MEASUREMENT AND RESEARCH ON TECTONIC STRESS FIELD DISTRIBUTION LAW OF CHENGDU-LANZHOU RAILWAY

Chengdu-Lanzhou Railway is located in the alpine valley area at the eastern edge of Qinghai-Tibet Plateau. Due to the collisions of the India plate and Eurasian plate, regional tectonic deformation is severe. The railway line stretch across the Sichuan-Qinghai and the southern Gansu block, across the Longmenshan fault, Minjiang fault, East Kunlun fault, Diebu-Zhouqu-Bailongjiang fault and other active faults, and the regional tectonic stress field is very complicated. In order to study the in-situ stress distribution law and fault stability of Chengdu-Lanzhou Railway, hydraulic fracturing in-situ stress measurements were carried out in four boreholes along the railway area, the magnitude and direction of the in-situ stress in different positions are obtained, and the distribution law of stress parameters with depth-variant is established. The results show that in-situ stress presents a good linear relationship with depth-variant, and the horizontal stress is generally higher than the vertical stress within the measurement depth ranges, indicating that the regional stress field is dominated by tectonic horizontal stress. Within 750 m depth, the maximum horizontal principal stress is 25 MPa, belonging to middle-high stress level, and the lateral pressure coefficient decreases slowly with depth. The directions of maximum horizontal principal stresses are different in different tectonic units. The direction of maximum horizontal principal stress is NNE in the southern Gansu block while NW in the Sichuan-Qinghai block. According to Coulomb frictional failure criteria, the stability of the fault in the engineering area is analyzed. The results provide meaningful information for further research on tectonic stress field, fault activity and tunnel construction.