基于钻孔形态分析的地应力测量方法研究

地应力作用下的钻孔孔壁会发生一定程度的变形，导致钻孔横截面形状会发生变化，变形后的钻孔几何形态也反映了钻孔受力状态。在经典岩石力学理论的基础上，研究钻孔在平面二维应力作用下的几何形态，建立应力与变形后圆孔几何参数的关系，实现基于钻孔椭圆参数的应力解算，并提出钻孔椭圆参数的测量方法和测量技术，形成一种新的基于钻孔形态分析的地应力测量方法。结果表明，（1）在平面二维应力作用下圆孔变形后的几何形态为椭圆，推导了椭圆参数与应力的关系表达式；（2）利用3个不同方向的孔径值可以实现椭圆参数的解算，研发触头式显微光学孔径测量技术，实现了钻孔形态的测量，从原理上分析了技术实现的可行性，并就该技术进行地应力测量过程中可能存在的问题进行了探讨；（3）通过室内模拟试验，验证了技术原理的可行性，并通过误差分析和实例计算对该方法测量结果的准确性进行了讨论。

An in-situ stress measurement method based on borehole shape analysis

The wall of borehole tends to deform under in-situ stress state, resulting in a change in the cross-sectional shape of the borehole. Accordingly the morphology of borehole after deformation also reflects the stress state of borehole. Based on the classical rock mechanics theory, the geometric shape of borehole under the plane two-dimensional stress is studied, and the relationship between the stress and geometric parameters of the circular hole after deformation is established. The stress solution based on the elliptical parameters of the borehole is realized. The measuring method and measuring technology of borehole elliptical parameters is proposed, forming a new in-situ stress measuring method based on borehole shape analysis. The conclusions are as follows: (1) under the action of plane two-dimensional stress, the geometric shape of the circular hole turns to be ellipse, and the relationship between the ellipse parameter and the stress is derived; (2) the parameters of ellipse can be resolved by using the diameter values in three different directions. Besides, the contact micro-optical aperture measurement technology is developed to measure the morphology of borehole. The feasibility of this new measurement technology is analyzed from the principle point of view. Furthermore, the possible problems of this technology in measuring the in-situ stress were discussed; (3) based on the indoor simulation tests, the feasibility of the technical principle is verified. The accuracy of measurement results is also discussed through error analysis and example calculation.