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Design Optimization of the Support Reinforcement at the Portal Section of a Highway Tunnel
(1 Beijing General Municipal Engineering Design and Research Institute, Beijing 100082; 2 Guangxi Hualan Geotechnical Engineering Co. Ltd., Nanning 530001)
Abstract In light of the existing problems regarding the reinforcement design of support at the portal sections of highway tunnels, and based on the characteristics of surrounding rock and its loading at the portal and shallow-buried tunnel sections, this paper analyzes supporting features under different rock conditions by considering the action mechanisms of pipe-roof support, primary support, and secondary linings, and gives relevant suggestions for the above two sections. The results show that due to fractured surrounding rock and its poor self-stability at the portal section, the advance support plays an important role in enhancing the early stability of the rock, the primary support serves as the main bearing structure, and the secondary lining can be used to share part of load with a certain safety reserve. Thus, for the portal section it is better to strengthen the advance support and the primary support instead of the secondary lining, since the loads at the portal section are less than that at the shallow-buried section. Additionally, because of the intact surrounding rock and its certain self-stability at the shallow-buried section, the secondary lining serves as the main bearing structure and the primary support gives play to adhesion for better coordination between the surrounding rock and the support structure. Consequently, it is better to strengthen the secondary lining at the shallow-buried section and choose the best time for installation.
Abstract：
In light of the existing problems regarding the reinforcement design of support at the portal sections of highway tunnels, and based on the characteristics of surrounding rock and its loading at the portal and shallow-buried tunnel sections, this paper analyzes supporting features under different rock conditions by considering the action mechanisms of pipe-roof support, primary support, and secondary linings, and gives relevant suggestions for the above two sections. The results show that due to fractured surrounding rock and its poor self-stability at the portal section, the advance support plays an important role in enhancing the early stability of the rock, the primary support serves as the main bearing structure, and the secondary lining can be used to share part of load with a certain safety reserve. Thus, for the portal section it is better to strengthen the advance support and the primary support instead of the secondary lining, since the loads at the portal section are less than that at the shallow-buried section. Additionally, because of the intact surrounding rock and its certain self-stability at the shallow-buried section, the secondary lining serves as the main bearing structure and the primary support gives play to adhesion for better coordination between the surrounding rock and the support structure. Consequently, it is better to strengthen the secondary lining at the shallow-buried section and choose the best time for installation.
WU Jin-Gang-1,
SONG Yan-Bin-1,
CHEN Ren-Dong-1 etc
.Design Optimization of the Support Reinforcement at the Portal Section of a Highway Tunnel[J] MODERN TUNNELLING TECHNOLOGY, 2014,V51(6): 12-18
2014, Vol. 51 