Abstract: Due to the existence of high geostress and high geotemperature, the rockburst disaster is highly possible during the excavation of the newly-built Sangzhuling tunnel in the lasa-Nyingchi project. According to the unloading-temperature drop coupling action, the numerical model was conducted to simulate the stress release process during the tunnel excavation at different temperatures. At the same time, the secondary stress field was measured on site. The influence of high geotemperature on the circumferential stress was comparatively analyzed. Finally, the effect of high geotemperature on rockburst occurrence was discussed by considering different criteria. The results show that the indices of stress release rate and large temperature drop are used to reflect the excavation unloading-temperature drop coupling function, which can reasonably describe stress characteristics and rockburst occurrence law under high-geostress and high geotemperature in the excavation process. When the temperature drop exceeds 55 ℃ and the stress release coefficient is greater than 40%, and linearly increase with the increase of stress release coefficient. The and achieve maximum values when the stress release rate reaches 100%. It is found that the stress at the arch foot increases fastest, following at the vault. With the increase of the stress release coefficient, the rockburst occurs earlier due to the high geotemperature, and the grade of rock burst also increases.

Key words: tunnel engineering, high geotemperature, rockburst, numerical simulation, stress release rate