摘要
藏东贡觉地区位于金沙江断裂带北段,经历了复杂的地质构造演化.本文基于水压致裂法地应力实测数据,通过计算评价主应力量值、侧压力系数、主应力方位及构造应力等地应力特征参数,分析了贡觉地区现今地应力场分布规律及其影响因素.结果表明:藏东贡觉地区实测主应力随深度增加而增大,浅部(<500 m)数据较为离散,深部(>500 m)数据呈线性分布,表现为S_(v)>S_(H)>S_(h),水平主应力随深度变化梯度低于背景地块相应梯度水平;实测最大水平主应力优势方位为NNE向,与区域应力场优势方位NE—NEE向呈现逆时针偏转;通过对研究区侧压力系数、水平应力比、剪应力相对大小(μ_(m))以及Sheorey模型分析得出,研究区水平构造应力积累程度和活动程度均较低,区内字嘎寺—德钦断层处于稳定状态.研究区地应力场影响因素主要为重力作用、地形特征以及构造作用.岩体自重对地应力的影响主要遵循静水压力规律;地形地貌的影响主要体现为浅部(<500 m)水平向主应力值较离散,在深切峡谷区侧压力系数由谷底至坡顶逐渐减小;构造作用对研究区地应力场的影响主要集中在字嘎寺—德钦断层两侧一定范围内,表现为局部地应力场的主应力方位偏转及主应力量值异常.研究结果可为藏东贡觉地区及类似地质环境区域稳定性评价以及地下工程选址建设提供理论依据.
Gonjo region of eastern Tibet which is locatedin the northern section of Jinshajiang fault zone hasundergone complex geological tectonic evolution.Thedistribution and influencing factors of in-situ stress fieldare discussed through the characteristic parameters analysisof the main stress value and orientation,lateral pressurecoefficients,tectonic stress value based on the measureddata of in-situ geostress using hydraulic fracturing method.The results show that the measured main stress increaseswith depth.The stress are scattered at the depth less than500 m but manifested asSv>SH>Shin linear at the depthmore than 500 m.The gradient of horizontal main stressversus depth is lower than that of the regional backgroundblocks.The regional dominant orientation of maximumhorizontal principal stress is NNE,which shows acounterclockwise deflection comparing with the dominantNE-NEE regional tectonic stress direction derived fromother tectonic stress indicators.Based on the analysis oflateral pressure coefficients,horizontal stress ratio,ratio ofmaximum shear stress and average horizontal stress (μm)and Sheorey model,it is indicates that the horizontaltectonic stress accumulation is in the low level and theZigasi—Deqin fault is stable in this region.Theinfluencing factors of the in-situ stress field mainly includegravity,topography and tectonic action.The influence of gravity action on geostress follows the law of hydrostaticpressure.Under the influence of topography the horizontalgeostress is discrete in superficial crust( < 500 m) andthe lateral pressure coefficient decreases from bottom to thetop of slope in deep-cutting gorge.The tectonic actionmainly concentrates on the range of Zigasi—Deqin fault onboth sides,where the values and directions of the mainstress are abnormal in local area.It is expected to providetheoretical basis for regional stability evaluation,siteselection and construction of underground engineering.
作者
廖昕
吕改杰
陈仕阔
王虎
赵晓彦
黄涛
LIAO Xin;LÜGaiJie;CHEN ShiKuo;WANG Hu;ZHAO XiaoYan;HUANG Tao(Faculty of Geosciences and Environmental Engineering,Southwest Jiaotong University,Sichuan,Chengdu 611756,China;Sichuan Province Engineering Technology Research Center of Ecological Prevention and Control of Geological Hazards in Transportation Corridor around Qinghai-Xizang Plateau,Chengdu 611756,China;China Railway Design Corporation,Tianjin 300142,China)
出处
《地球物理学进展》
CSCD
北大核心
2024年第3期938-950,共13页
Progress in Geophysics
基金
四川省重点研发项目(2022YFWZ0009)
四川省自然科学基金青年学者项目(2022NSFSC1117)
西南交通大学地质工程与测绘工程创新实践基地(YJG-2022-JD04)联合资助。
关键词
贡觉地区
地应力场
分布特征
地形特征
构造应力
Gonjo region
In-situ stress field
Distribution characteristics
Topography characteristics
Tectonic stress
