基于孔内立体像对成像的地应力方向测量方法研究

摘要

深部岩体地应力的测量对岩土力学与工程地质具有重要的意义.由于传统的地应力测试过程较为复杂,在深孔中更是难以实现,因此本文提出一种利用全景立体钻孔成像技术和受力状态下钻孔形态特征快速、有效、准确地确定地应力方向的测量方法.该方法利用基于双锥镜成像原理的全景立体钻孔成像技术获得钻孔孔壁同一位置不同视角的两幅立体像对图像,通过对像对图像构建钻孔孔径形态数值以刻画钻孔孔壁的几何形态特征.根据地应力的作用下圆形钻孔孔壁变成椭圆形孔壁,进而推导出圆形孔壁变成椭圆之后的标准椭圆方程,并建立椭圆形态参数与地应力方向的关系.据此,结合全景立体钻孔成像技术获得钻孔孔壁的几何形态(椭圆形孔径),计算出椭圆长轴与坐标轴的方向,进而测得孔内的地应力方向.最后利用标准模型进行模拟测试.结果表明该方法测量的钻孔几何形态与实际的应力方向保持一致,验证了该方法的正确性和可靠性.该方法应用了最新的钻孔成像技术,在不依赖岩体物性参数的前提下,实现了基于钻孔形态的地应力方向的直接获取,为深部岩体地应力的测量提供一种新的途径和测试方法.%The measurement of geostress of deep rock masses is of great significance to rock and soil mechanics and engineering geology.Tradi-tional geostress testing process is complicated and more difficult to perform in downhole.Hence,a testing method,which can rapidly,effectively and accurately determine geostress direction was proposed based on panoramic stereo-borehole imaging technology and borehole morphological characteristics in stress state.The principle of this method is to obtain two stereopair images of the same position of borehole wall in different visu-al angles with the panoramic borehole imaging technology based on double-conic mirror image-forming principle,and construct the aperture vari-ation values of the borehole wall based on the image pairs,to describe the geometric characteristics of the borehole wall.Under the action of geo-stress,a circular borehole will turn elliptic,thus the standard equation of ellipse is given out,and the correlation between the morphological para-meter of ellipse and geostress is established.Besides,the geometric shape (ellipse) of the borehole wall is obtained in combination with the panor-amic stereo borehole imaging technology,and the direction of geostress is solved on the intersection angle of the ellipse macroaxis and x axis.It is verified by a simulation model and the testing results show that the measured geometric shape of the model roughly agrees with the actual direc-tion of borehole.In this method,the latest borehole imaging technology is applied,and the ground stress direction is obtained based on borehole morphology without consideration of the physical property parameters of rock mass,which provides a new approach and testing method for the measurement of deep rock mass geostress.