Study On Geo-Stress Evaluation Method Along Sichuan-Tibet Moraine Transportation Corridor

Geo-stress is an important parameter in the long and big deep-burying tunnel engineering design. And on-site drilling examination is a reliable method to get it. But in the feasibility stage of the route selection, it is inadvisable to do large scale geo-stress on-site drilling examination along the route due to the route is not determined. And it hopes to draw lessons from existing data or empirical formula to figure the geo-stress situation.Tectonic earthquakes often occur in Tibetan tectonic zone. Based on the existing records of historical earthquakes Tibetan Plateau, the seismic activity parameter b-value’s spatial distribution nephogram was confirmed, then the dynamic activity of the tectonic belt active degree were analyzed. We can get the conclusion that the dynamic activity within Yarlung Zangbo suture zone is less than the active tectonic zones. So the dynamic activity within Brahmaputra suture zone does not belong to the controlling factor when the Sichuan-Tibet railway crossing the Yarlung Zangbo suture zone.Research has shown that the inverse relationship between power exponent b-value and geo-stress. So a correction method of adding b-value to the maximum horizontal principal stress varying with the depth formula is proposed. Taking Sichuan-Tibet moraine transportation corridor earth stress analysis as an example, the seismic activity parameter b-value’s spatial distribution nephogram was confirmed. Based on existing measured stress data, b-value, and depth H-value as independent variables, the evaluation model of geo-stress was developed. Compared with the current method using the depth as the only independent variable, the evaluation precision is significantly increased.By analyzing the distribution rule of geothermal anomalous area, and comparing with the distribution rule of geo-stress anomalous area of Sichuan-Tibet moraine transportation corridor. There are overlap phenomenon of two regions, and the bigger scale region is geothermal anomalous area. Based on the relationship between geothermal energy and geo-stress, a correction method of adding geothermal energy value to the maximum horizontal principal stress varying with the depth formula is proposed. Based on existing measured stress data, geothermal energy value, and depth H-value as independent variables, the evaluation model of geo-stress was developed. Results show that the evaluation precision less than the method using the b-value and depth as the independent variable. The number of historical earthquakes existing records is very important to calculate the seismic activity parameter b-value, so the method using the b-value and depth as the independent variable is not for the weak areas of seismic activity level. And it hopes to use the method that using the b-value and depth as the independent variable to figure the geo-stress situation.