Construction of 3D geological model and multi-scale numerical analysis of in-situ stress field of long tunnel in fault development area

Affected by faults of different scales, there is a big difference between the local stress and regional stress in the crust. The Xianglushan tunnel of Central Yunnan Water Diversion Project is located in the Sichuan-Yunnan block with violent tectonic activity, and the tunnel passes through complex strata and fault development areas. Due to the limitations of testing methods, the measured stress data in Xianglushan tunnel project are mainly distributed in the relatively intact rock mass, so it is difficult to reflect the stress characteristics in the fault-affected area. Therefore, based on the tectonic geological data of Xianglushan tunnel, this article explores the construction method of multi-scale 3D geological model of fault development area. The corresponding information processing mechanism is established to realize the interactive interpretation, supplement and correction of fault data, and then gradually approach the actual situation of the geological body in the modeling process. According to the modeling method, a generalized large-scale model and a refined sub-model were established separately for the whole Xianglushan tunnel project area and the Longpan-Qiaohou fault affected area. At the same time, combined with the stress test data of Xianglushan tunnel, the first-stage stress field inversion calculation of large scale model is carried out based on multiple regression analysis method. The macroscopic stress field distribution characteristics of the strata and fault zones along the tunnel are preliminarily explored. From the first-stage inversion result, the displacement boundary conditions of the sub-model can be obtained by interpolation in the displacement field, which is applied to sub-model for the secondary elastic-plastic iterative calculation. Finally, the construction of the refined sub-model and the secondary elastic-plastic iterative calculation not only optimize the detail features of the initial stress field obtained by the first-stage inversion analysis, but also reveal the disturbance law of the complex strata and the Longpan-Jiaohou fault on the initial stress state, which has a high guiding significance for the construction and support of tunnel engineering.