Abstract:The measurement of geostress of deep rock masses is of great significance to rock and soil mechanics and engineering geology.Traditional 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 visual angles with the panoramic borehole imaging technology based on double-conic mirror image-forming principle,and construct the aperture variation values of the borehole wall based on the image pairs,to describe the geometric characteristics of the borehole wall.Under the action of geostress,a circular borehole will turn elliptic,thus the standard equation of ellipse is given out,and the correlation between the morphological parameter of ellipse and geostress is established.Besides,the geometric shape (ellipse) of the borehole wall is obtained in combination with the panoramic 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 direction 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.