三维地应力测量及地质力学分析

THREE-DIMENSIONAL GEOSTRESS MEASUREMENT AND GEOMECHANICAL ANALYSIS

针对地应力场测量给出的区域最大主应力方向常常有争执,且不同的测量方法结果也不同。采用现场测试和地质力学对地应力场进行分析,以研究工程两侧坝肩岩体的稳定状况并为其设计与施工提供可靠的理论依据。现场测试采用套孔应力解除法,使用36-2型钻孔变形计采集数据,结合室内弹模试验,分析计算得出坝肩岩体地应力的大小、方位、倾角,并对计算结果进行分析,得出工程区地应力的分布特征。地质力学分析方法对场区共轭剪节理和断层面的产状、擦痕侧伏角及移位等地质信息进行分析,引入赤平投影分析计算原岩主应力方向。通过这两方面的对比研究,结果表明:(1)实测原岩应力与地质力学分析结果基本吻合,可靠性较高;(2)场区测点处应力作用方式以地形地貌与构造应力综合控制为主导,最大主应力大小为11.8～20.8MPa,总体方位左岸为NW～NNW,右岸为N～NNE,方向在坝肩两侧基本上与峡谷壁面平行,向峡谷侧下方倾斜;(3)场区三向应力状态应属潜在走向滑动型。

For there is dissension in the maximum principal stress orientation obtained by in-situ measurements by different means, geostresses in the three directions are presented by in-situ measurement and geomechanical analysis, to investigate the status of stability of rock mass of bilateral dam abutment and get reliable theoretical foundation for its design and construction. The in-situ measurement adopts stress relief by overcoring method, using bore strain gauge 36 - 2 to collect data. And the elastic modulus experiment is conducted indoors. In terms of these experimental data, the magnitude, azimuth, inclination of the geostress of rock mass of dam abutment can be figured out, through which the distribution character of the ground stress of rock mass of the hydraulic engineering can be determined. By geomechanical method, the in-situ geological information about conjugate joints, fault occurrence, rake angle, shift symbol of fault slip and so on are analyzed, through which the principal stress orientation can be elicited by stereographic projection. By the study of the above two aspects, some conclusions are drawn： （1） The in-situ metrical results accord with the geomechanical results well, which indicates better reliability. （2） The mode of stress action in the region of measurement point gives priority to terrain and tectonic stress control. The magnitude of the maximum principal stress is between 11.8 and 20.8 MPa, and the direction as a whole is NW-NNW in the left bank, and N-NNE in the right bank, parallel to the bilateral cliff faces approximately and inclining to the bottom of the cliff. （3） Three-dimensional stress state in the region belongs to the potential strike-shift pattern.