Prediction of Rock Bursts for Sangzhuling Tunnel Located on Lhasa-Nyingchi Railway Under Coupled Thermo-Mechanical Effects

Coupled thermo-mechanical effects on the prediction of rock bursts for tunnels with special geostress and high geotemperatures is a new problem that needs to be solved. During the excavation of the newly built Sangzhuling tunnel in the Lhasa-Nyingchi railway project, the geotemperature at different buried depths was obtained by field temperature test data inversion. The gradually changing hole stress during the excavation process was clarified by coupled thermo-mechanical numerical simulation. The range and intensity of rock bursts throughout the entire calculation scope of a typical section under various stress-relieving coefficients and geotemperature conditions, combined with different of rock burst criteria, such as Russense, TAO Zhenyu, WANG Yuanhan, and FAN Jianping criteria, were predicted. Finally, the prediction results were compared with the field measurements. The results show that the geothermal gradient of Sangzhuling tunnel is 5.5℃/100 m. As the buried depth of the tunnel increases, so does the geotemperature. The maximum compressive stress is concentrated in the vault and the arch springing in the deep-buried tunnel section with the gravity stress field. At 45-85℃, the maximum tangential and principal stresses increase linearly with an increase in the stress-relieving coefficient, and the maximum tangential and principal stresses increase by 84-96 MPa and 93-96 MPa, respectively, when the stress-relieving coefficient reaches 100%; the intensity of rock bursts will increase under these conditions. The analysis using the four methods for predicting rock bursts compared with rock burst data from results in field tests shows that the occurrence of rock bursts will be accelerated during stress release by coupled thermo-mechanical effects. The prediction of middle level and greater intensity rock bursts using the TAO Zhenyu criterion shows great sensitivity for the earlier stages of stress release. In the mid-late periods of stress release, the rock bursts prediction results using the WANG Yuanhan criterion are in accordance with the measured results.