| Abstrakt: |
Under complex geological conditions of fault system, stratum and terrain, an accurate inversion of the in-situ stress field is a challenging and hot issue in the study on engineering geology. Focusing on the accurate inversion of fine in-situ stress field for deep-buried tunnel under complex geological conditions, and the influence of major geological factors on the stress state, we took the Jiangranshan tunnel of the express way from Shuangjiang to Cangyuan in southwest Yunnan as a case to perform the study. We first established the fine geological model of the Jiangranshan tunnel area by integrating the fine DEM data and the geological survey data. Then, taking the measured in-situ stress data in the tunnel site and the measured GPS data of velocity field as the integrated constraints, we carried out the inversion of fine in-situ stress field in the engineering region of Jiangranshan tunnel. On the basis of the inversion results, we analyzed the characteristics of fine in-situ stress field in the tunnel site and the influence of main geological conditions on the current in-situ stress field. Finally, we estimated the engineering geological stability of the surrounding rock mass of the Jiangranshan tunnel. The results show that the simulated displacement velocity field in the Jiangranshan tunnel area is basically consistent with the GPS observation results, revealing that the inversion model adopted in this study can well reflect the current tectonic stress environment of the engineering region. The simulation results show that the level of the in-situ stress field in the western part of the study area is relatively high, while it is low in the eastern part. The direction of the maximum principal stress shows partial deflection in the study area. The influence of the nearly E-W-striking Xiaoheijiang fault--the largest fault in the study area--on the in-situ stress is that it causes the slight deflection of the direction of the maximum principal stress; however, it does not cause abrupt change of the in-situ stress magnitude. The secondary faults and topography show little effect on the in-situ stress field, which is limited to very small area and does not cause notable disturbance of the in-situ stress field. The results reveal that the maximum, intermediate, and minimum principal stresses along the tunnel mainly distribute in 7.47--27.23 MPa, 1.59--15.12 MPa, and 0.01--6.71 MPa, respectively, and does not show obviously abnormal characteristics. The engineering geological stability of the surrounding rock mass of the Jiangranshan tunnel is estimated by the stress intensity index (i.e., the ratio of the maximum tangential stress to the uniaxial compress strength of rock). The estimation results, which are determined by integrating the stress field simulation results and the mechanical properties of the typical rocks obtained from the laboratory tests, show that the stress intensity indexes of the Jiangranshan tunnel mainly range between 0.20--0.48. It indicates that the surrounding rock masses of the Jiangranshan tunnel are mainly in a stable state or in a slight rockburst risk under the current in-situ stress conditions. The conclusion can be drawn from the case study that under the complex geological conditions, the fine geological model suitable for the scale of engineering area can be established by using the fine DEM and actual fault and strata data, which can effectively reveal the characteristics of the in-situ stress field in engineering area and the influence of the main geological conditions. This study provides not only the profound understanding of the in-situ stress field of the Jiangranshan tunnel area, but also the implications for the fine inversion of in-situ stress field under complex geological conditions in Yunnan and other similar areas. In addition, this study can directly support the stability evaluation of the surrounding rock of the deep-buried Jiangranshan tunnel. [ABSTRACT FROM AUTHOR] |
