Analysis of Initial Geostress Field of a Hydropower Project without Measured In-situ Stress

Abstract

Initial geostress field is an important factor affecting the stress distribution, displacement and failure mode of surrounding rock of underground engineering, and is also one of the important indexes of design for underground works, especially large hydropower projects. At present, the method to obtain the geostress field is mainly based on measured in-situ stress, however some projects are lack of in-situ stress measurement data. To solve this problem, we inversed regional tectonic stress field firstly, and then extracted the boundary load of the project area from the fitted regional tectonic stress field and embedded the underground cavern to be studied in the calculation model to carry out the numerical calculation of the geostress field of the project area. The results show that the direction of regional tectonic principal stress is NNE∼NE, and the average maximum horizontal tectonic stress is about 5.0MPa. The direction of the maximum principal stress in the project area is generally the same as that of the regional tectonic stress field, which indicates that the valley stress field is determined by the regional tectonic stress field. However, due to the influence of river incision, the geostress field of the project area redistributes, and has the basic characteristics of principal stress direction deflection and stress differentiation. The research results provide a basis for the subsequent study of the stability of underground caverns, and have a certain reference value for the method of obtaining initial geostress field of a project without measured in-situ stress.