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Abstract It is important to conduct a research on the stress state of the rock masses in the upper earth′s crust. In-situ rock stress measurement is the basic and reliable access to obtain the stress state of the rock masses. The development of in-situ rock stress measurement and state-of-art of research on it are overviewed. Then，several in- situ rock stress measuring methods and techniques are briefly analyzed in rock mechanics and engineering. A new method，borehole wall stress relief method(BWSRM) to determine the in-situ 3D rock stress tensor in a single drilled borehole is deliberated. An original geostress measuring instrument typed by BWSRM-H01 is designed and manufactured based on the principle of in-situ rock stress measurement with BWSRM. The in-situ test for rock stress with BWSRM is carried out at an experimental tunnel in Jinping II hydropower station，China，where the buried depth of overburden is about 2 430 m. It is shown that the two principal stress components close to the horizontal direction are the maximum and intermediate principal stress respectively；while the stress component close to vertical direction is just the minor principal stress in the testing site. The magnitudes of the maximum and the intermediate principal stress are high；and both of them are very close.
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Received: 28 September 2011
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2011, Vol. 30 
