Abstract: The measurement of deep ground stress is widely applied in shale gas extraction, conventional oil and natural gas exploration, large hydroelectricity and irrigation projects, deep mining and fundamental earth science research areas. The borehole wall local stress relief method is suitable for the rock stress measurement at a great depth. This paper presents an improved three-dimensional deep rock stress measurement apparatus based on the existing ground stress measurement device, BWSRM-H01 in a horizontal borehole. The improved device can perform the locating, installation of the strain gauges at the borehole surface, relieving of the borehole surface and strain measurement. The design approach of key components of the device is introduced in this paper. The in-situ rock stress measuring procedure of the improved apparatus is also briefly presented. The design and development of the apparatus has the in-house owned intellectual property. Currently, the pressure and temperature resistance of the instrument is suitable for the measurement of 1 200 m deep borehole. 

Key words: Deep Borehole, Ground Stress, Borehole Wall Stress Relief Method (BWSRM), Testing Equipment, Design, High-Temperature and High-Pressure Environment