Abstract
Double primary support structures could effectively solve the problem of large deformation of surrounding rock for soft rock tunnels. However, the mechanical behavior of this new support structure is still incomplete, and the design method should be revised. Based on the theory of energy conversion, this paper analyzes the support characteristic curve of double primary support and puts forward the dynamic design method of double primary support. Considering that the secondary lining can be set after monitoring the deformation amount and deformation rate of the first primary support, its support parameters can be dynamically adjusted according to the actual situation. By applying the double primary support design method in the Maoxian tunnel of Chenglan Railway, the field monitoring results show that the double primary support has a significant effect on the energy release of surrounding rocks, greatly reducing the load acting on the secondary lining and ensuring the safety and reliability of the tunnel structure.
Highlights
Zhe LiuTechnical Standards Institute, China Railway Economic and Planning Research Institute, Beijing 100038, China
Due to the compression of Qinghai-Tibet Plate, Yangtze Plate, North China plate, and Tarim plate, the western plateau and its marginal areas are prone to form high ground stress zones and often cause rockburst, large deformation, and other related geological disasters, which bring significant challenges to the construction of the tunnel. e traditional support theory of “timely support and strong support” is often unable to effectively solve the problem, and the deformation and support failure of surrounding rocks can always be controlled only after experiencing multiple cycles of support, failure, and replacement [8]
Because the double primary support allows the surrounding rock to do work on the support structure by allowing greater deformation, compared with the single primary support, the surrounding rock deformation energy absorbed by the support structure is increased
Summary
Technical Standards Institute, China Railway Economic and Planning Research Institute, Beijing 100038, China. Double primary support structures could effectively solve the problem of large deformation of surrounding rock for soft rock tunnels. The mechanical behavior of this new support structure is still incomplete, and the design method should be revised. By applying the double primary support design method in the Maoxian tunnel of Chenglan Railway, the field monitoring results show that the double primary support has a significant effect on the energy release of surrounding rocks, greatly reducing the load acting on the secondary lining and ensuring the safety and reliability of the tunnel structure. To solve the above technical problems, the concept of “yield control” support has been gradually developed to make the support structure deform along with surrounding rock before failure. The steel frame is difficult to retract after spraying concrete, and the sudden sliding is
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