(1. National Institute of Natural Hazards，Ministry of Emergency Management of China，Beijing 100085，China；
2. School of Engineering and Technology，China University of Geosciences(Beijing)，Beijing 100083，China；
3. College of Geological Engineering，Institute of Disaster Prevention，Sanhe，Hebei 065201，China)
Abstract：The conventional hydraulic fracturing(HF) method is greatly limited in the in situ stress measurements of inclined boreholes，especially in three-dimensional stress measurements. Moreover，the hydraulic tests on pre-existing fractures(HTPF) requires a large number of pre-existing fractures to obtain reasonable results. By optimizing the assumption of shear stresses on the primary fracture surfaces and using Monte Carlo algorithm，the three-dimensional stress tensor inversion in the inclined borehole was realized by combining the conventional HF and the HTPF tests. The reliability and accuracy of the proposed method were verified by three-dimensional stress measurements of an inclined borehole in a pumped storage power station in Jizhou，Tianjin. The results show that the proposed method can determine the three-dimensional stress tensors of the inclined borehole only by selecting 1 or more test intervals for conventional HF tests in intact rock mass and 1 or more test intervals for HTPF tests. Compared with the HTPF method that only adopts pre-existing fractures in stress determination，the proposed method greatly reduces the requirement of the number of pre-existing fractures. The inversion results have little dispersion and high stability，which are also consistent with the regional stress state. The proposed method provides a new idea and a reliable approach to determine the stress tensor using a single inclined or vertical borehole.
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2024, Vol. 43 
