Prediction of stress field of super-long deep-buried tunnel area and case analysis

The prediction of stress field of deep-buried tunnel area is a tough problem that many scientists and engineers have to face with. Herein, a solution is put forward for this problem. The databases from the WSM and the Crustal Stress Environment of China Mainland and the previous research findings can offer indications of stress orientations of an engineering area; at the same time, the Andersonian theory can be used to analyze the possible stress orientation of an engineering area. After the limited in-situ stress measurements are obtained, the Hoek-Brown criterion can be used to estimate the strength of rock mass in the engineering area by utilizing the geotechnical investigation data, and then the modified Sheorey model can be employed to predict the stress field of areas without stress data by taking the existing in-situ stress measurements as input parameters. One planned hydroelectric power plant is located on the western edge of Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicate that the stress state of the engineering area is S_H>S_h>S_V or S_H>S_V>S_h. The measured orientation of S_H is NEE (N70.3°—89°E), and the regional orientation of S_H from WSM is NE, which may imply that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model is utilized to predict the stress state along the water sewage tunnel for the plant. The predicted results indicate that the maximum and minimum horizontal principal stresses of the place with the greatest burial depth are up to 56.70 and 40.14 MPa, to which the relevant organizations pay more attention. According to the application case, the proposed method works well.