两水隧道地应力测量及三维地应力场多元回归分析

Geostress Measurement and 3D Multivariate Regression Analysis of the Geostress Field of the Liangshui Tunnel

文章针对兰渝铁路两水隧道选择1个测孔、7个试验段进行水压致裂地应力测量。测试结果表明两水隧道的现今应力场以水平应力为主导,应力量级属于极高应力水平。最大主应力方向为N80°W^EW,与区域构造应力场方向一致。该测点的最大水平主应力方向与隧道轴线方向夹角较小,利于隧道围岩稳定。结合实际的地质条件和地层参数,在实测地应力结果的基础上,建立隧道区两个大规模三维计算模型,通过有限元分析软件ANSYS对重力、水平挤压和剪切等4种工况的自重应力场和构造应力场分别进行数值计算,根据多元回归方程,宏观扩展分析两水隧道区域的原岩地应力场。分析结果表明,两水隧道大部分区段的水平横向地应力值为7.0~9.0 MPa、水平横向侧压力系数为1.0~1.5。宏观地应力场的分析结果对工程设计与施工具有重要参考价值。

A hydraulic fracturing test was conducted on a selected testing hole and seven test sections in the Li- angshui tunnel of the Lanzhou-Chongqing railway. The results show that the present stress field of the Liangshui tunnel is dominated by a horizontal stress whose magnitude of stress is extremely high, and the maximum principal stress orientation is N80°W - EW, the same as that of the regional tectonic stress field. Due to the small angle between the tunnel axis and the maximum horizontal stress orientation at the testing point, this is a great advantage to the stability of the sun-ounding rock. Using the practical geological conditions and tormation parameters, two large- scale 3D computational models were established based on measured geostress values; the gravity stress field and tec- tonic stress field wre calculated by ANSYS under four condions regarding the gravity, horizontal compression and shear; a macro extended analysis on the protolith geostress field was carried out by a muhiple regression equation. The analysis results show that the horizontal lateral geostress value is between 7.0 and 9.0 MPa, and the horizontal lateral pressure coefficient is between 1.0 and 1.5 in most sections of the Liangshui tunnel.