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Research on the Characteristics of In-situ Stress Field and Rock Burst Risk in Eastern Qinling |
CHEN Xingqiang1, LIU Jin2, MENG Xianglian1, ZHANG Wenzhong1, HUANG Yong1, WANG Huajiang1, ZHOU Fujun1, LI Yubo1, LI Limin1, WANG Kai1, QIU Shili3 |
1. China Railway First Survey and Design Institute Group Co. Ltd, Xi′an, Shaanxi 710043, China; 2. Xi′an Technological University, Xi′an, Shaanxi 710021, China; 3. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China |
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Abstract Research purposes:Different from the typical rock burst prone area which is a strong compressive tectonic area, the eastern Qinling, which is dominated by the extensional structure in present, also has the characteristics of high in-situ stress and strong rock burst risk. In order to guarantee the construction and route selection of deep ground projects such as railway tunnels, this paper makes a preliminary study on the characteristics of the in-situ stress field, the tectonic causes and the overall control of rock burst. Research conclusions:(1) The measured extrusion direction of the maximum horizontal principal stress SH in the eastern Qinling is consistent with the direction of the current extensional structure in the area, both of which are NW-SE. This indicates that the in-situ stress is not controlled by current regional tectonics. The average variation gradient of SH is as high as 2.94 MPa/100 m, which is equivalent to that of the Tibet Plateau. Therefore, the area is dominated by the tectonic stress formed by squeezing during Yanshanian, which belongs to the residual stress. This feature indicates that the strain energy of intact rock mass can be retained for hundreds of millions of years, and the strain energy in large rock mass is not easily changed by extensional structure. (2) Regionally, SH in the eastern Qinling is always the maximum value of the three-way principal stress, which is the main control factor of rock burst risk. In the stage of railway route selection, the eastern Qinling needs to focus on the rock burst risk of hard rocks such as granite and diorite. Medium rock burst is easy to occur above 700 m, and strong rock burst is easy to occur above 1 400 m. It is recommended to avoid tunnels buried more than 1 400 m.(3)This research achievement can be popularized and applied to the geological route selection of Qinling and similar mountain railways and the prevention and control of tunnel rock burst risk.
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Received: 20 December 2022
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