基于中国西部构造应力分区的川藏铁路沿线地应力的状态分析与预估

Analysis and prediction of stress fields of Sichuan—Tibet railway area based on contemporary tectonic stress field zoning in Western China

基于中国西部构造应力分区和地质力学迹线分析方法,利用Anderson断层力学理论分析工程区可能的主应力方向,并结合地应力数据,分析新建川藏铁路沿线的地应力场方向。基于Hoek-Brown强度理论估算工程区范围内的岩体强度,利用修正Sheorey模型对川藏铁路沿线深埋区域的地应力值进行预测分析,综合分析评价新建川藏铁路沿线地应力状态及可能导致的高地应力现象。研究结果表明,新建川藏铁路沿线区域最大水平主应力优势方向为NE向,但在东构造结附近和青藏高原东北边缘应力区,应力场方向较为复杂多变,其中东构造结区域最大水平主应力优势方向为NNW^NEE向,东构造结以东,最大主应力方向范围较大,优势方位范围20°~140°。地应力预测结果显示,考虑岩性差别,川藏铁路沿线埋深1000 m左右时,最大、最小水平应力量值范围分别为26.19~38.41和13.88~21.81 MPa;埋深2500 m左右时,最大、最小水平应力量值范围分别为66.44~86.48和35.02~49.11 MPa。高地应力情况下,埋深超过1000 m时,硬质岩可能存在岩爆风险,软岩可能发生严重的大变形现象。基于中国西部构造应力分区,利用地质力学迹线分析、Anderson理论和修正Sheorey模型等方法,结合有限的实测资料,可以较好地解决线状工程的工程区应力场状态及应力量值预测问题。

Analysis and prediction of stress fields along the Sichuan-Tibet railway area is of important significance and high application value.Combining the tectonic stress field zoning,geomechanical trace analysis method and Anderson’s theory of faulting mechanics,the stress orientations along the new Sichuan-Tibet railway area were analyzed based on the databases from WSM and Crustal Stress Database of China Mainland.The strength of rock masses in the engineering area was estimated by using Hoek-Brown criterion,the stress magnitudes of this area were predicted by the modified Sheorey model,and consequently,the stress state and potential high stress were comprehensively evaluated.The results show that the regional dominant orientation of SH is NE while that the orientation of the stress field varies around the Namche Barwa Terrane,Eastern Himalayan Syntaxis and the northeastern margin of the Qinghai-Tibet Plateau.The dominant orientation of SH near Eastern Himalayan Syntaxis is NNW–NEE,and the range of the orientation is 20°–140°at the northeastern margin of the Qinghai-Tibet Plateau.The predicted results indicate that the maximum and minimum horizontal principal stresses at a burial depth of 1000 m along the new Sichuan-Tibet railway are respectively up to 26.19–38.41 MPa and 13.88–21.81 MPa and,at a burial depth up to 2500 m,are 66.44–86.48 and 35.02–49.11 MPa respectively.It is also pointed out that,under such high stress,brittle failure or rock bust of hard rock and large deformation of soft rock would occur in the case of the overburden over 1000 m.According to an application case,the proposed method works well combined with the databases and limited stress measurement results.