Abstract:

In order to reduce the influence of geological structures such as faults on the local stress field in the underground engineering area, an expressway tunnel project in Honghe Prefecture, Yunnan Province was taken as an example to analyze the initial ground stress field in the tunnel site selection area. Firstly, a three-dimensional geological model of the tunnel site selection area was established, and the initial stress data of 10 measuring points were collected by the hollow inclusion method. Then, according to the measured in-situ stress data, the initial in-situ stress field of rock mass in the tunnel site was obtained by multiple linear regression inversion analysis. At the same time, the influence of faults and fracture zones in the area was considered on the basis of this method, and the influence of faults on the distribution of in-situ stress was summarized. Finally, according to the geological structure conditions (mainly faults) obtained from field investigation, the fault dislocation was simulated by applying compressive and torsion forces to the fault zone, so as to adjust the local in-situ stress and obtain the actual in-situ stress field. The results show that the stress in the horizontal and vertical direction of the tunnel axis in the study area is the largest, which is σ_y>σ_z>σ_x. The stress value decreases inside the fault and increases at the edge of the fault zone. In the high ground stress hard rock tunnel project, the edge of the fault with stress concentration has the possibility of increasing the probability of rockburst, andprevention and control should be strengthened to ensure the safety of the construction process.

Key words: faults, high ground stress, tunnel, initial stress field, ground stress inversion, multiple linear regression, hollow core inclusion method