Abstract
In China, rockburst disaster occurs mostly in construction of underground engineering in Qinghai-Tibet Plateau and its adjacent region. Previous research on deep-buried tunnels has indicated that tunnels stability is related to in situ stress state. To quantify these relationships, three-dimensional finite element modeling was done to analyze the influences that the angle φ between the maximum horizontal principal stress orientation and tunnel axis, and the lateral pressure coefficient KH, had on the tangential stress σ θ in a deep-buried-curved tunnel. Based on the in situ stress condition in Qinghai-Tibet Plateau and its adjacent region, 50 different simulation conditions were used to analyze the relationship that φ and KH had on σ θ for the rock mass surrounding the tunnel. With the simulation data produced, predictive equations were generated for σ θ as a function of φ and KH using multivariate regression analysis. These equations help estimate σ θ at various key positons along the tunnel boundary at Qinghai-Tibet plateau and its adjacent region. The equations were then proved by a set of typical tunnels to ensure validity. The results concluded that the change in φ has a significant impact on σ θ , and thus, the stability of the tunnel, when 30° < φ < 60°, with the most obvious influence being when φ is about 45°. With the equations, the rockburst potential at a certain location within a curved tunnel can be quickly estimated by calculating φ and KH on σ θ , without need of geo-stress background knowledge and heavy simulation, allowing for the practical value in engineering at design phase for the projects in Qinghai-Tibet Plateau and its adjacent region.
Highlights
Rockburst is a sudden and violent failure of the rock mass, caused by highly stressed brittle rocks and the rapid release of accumulated strain energy [1]
Due to the failure of surrounding rock mass developing from the boundary of the tunnel to the interior rock mass along radius direction [61], σθ in surrounding rock mass of the deep-buried-curved tunnel from numerical simulation based on in situ stress state of Qinghai-Tibet Plateau and its adjacent region is analyzed in this study
Practicality and availability of predictive equations for σθ at the key positions in the deep-buriedcurved tunnel are based on Qinghai-Tibet Plateau and its adjacent region, and it is essential to verify the accuracy of rockburst intensity of predictive equations
Summary
Rockburst is a sudden and violent failure of the rock mass, caused by highly stressed brittle rocks and the rapid release of accumulated strain energy [1]. Previous research on construction of deep-buried tunnels in areas of strong tectonic activity indicated close correlation between the stability of tunnels and in situ stress state [2, 22,23,24]. The coupling effect of the influence mechanism of the angle φ between the maximum horizontal principal stress orientation and tunnel axis, and KH, on the deep-buried tunnel is unclear. Erefore, the in situ stress measurement for most deep-buried tunnels was taken before tunnel construction [15, 44, 45], rockburst still occurred frequency during construction due to lack of professional interpretation in the design stage. E coupling effect of φ and KH on the stability of the deep-buried-curved tunnel in Qinghai-Tibet Plateau and its adjacent region is investigated in this study.
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