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Study on the Mechanical Behaviors of High-filled Loess Arched Open Cut Tunnel under Different Load Reduction Measures
(1 College of Civil Engineering, Lanzhou Institute of Technology, Lanzhou 730050; 2 Track Maintenance Section of Beijing High-speed Railway, Beijing, 100071;3 National and Provincial Joint Engineering Laboratory of Road & Bridge Disaster Prevention and Control,Lanzhou Jiaotong University, Lanzhou 730070; 4 Key Laboratory of Road & Bridge and Underground Engineering of Gansu Province,Lanzhou Jiaotong University, Lanzhou 730070；5 China Railway First Survey and Design Institute Group Co.,Ltd., Xi′an 710043)
Abstract Compared with the conventional open cut tunnel, the applied load is larger and the structure is more complex concerning the high-filled open tunnel. It is not clear if the soil pressure change after load reduction is favourable for the tunnel structure in terms of mechanical behaviors. A Study on the mechanical behaviors of trench type high-filled arched open cut tunnel in loess under two load reduction measures is conducted through in door model test, and the law of soil pressure and lateral stress varying with fill height around the open cut tunnel and the load reduction effect are obtained. The test results show that the soil pressure above the arch can be transferred to the two sides of open cut tunnel due to the load reduction measures of EPS plate, EPS plate and geogrid, which reduces the soil pressure on the vault and arch bottom and increases the soil pressure on both sides; the stress on each section outside tunnel is reduced, and the orders in terms of effect of the load reduction materialon external stresses at different sections are haunch, side wall, vault, spandrel and arch bottom. A numerical simulation analysis on the test procedure is under taken by FEM strain model, with the results indicate that the average relative errors between the soil pressure, lateral pressure and the test results are 11.7% and 14.6%; load reduction of internal force increases with an increase of fill height and its change rate increases. For the load reduction of trench type open cut tunnel,it is necessary to reasonably select load reduction material and foundation stiffness under the condition of guaranteeing the safety of lining structure of open cut tunnel.
Abstract：
Compared with the conventional open cut tunnel, the applied load is larger and the structure is more complex concerning the high-filled open tunnel. It is not clear if the soil pressure change after load reduction is favourable for the tunnel structure in terms of mechanical behaviors. A Study on the mechanical behaviors of trench type high-filled arched open cut tunnel in loess under two load reduction measures is conducted through in door model test, and the law of soil pressure and lateral stress varying with fill height around the open cut tunnel and the load reduction effect are obtained. The test results show that the soil pressure above the arch can be transferred to the two sides of open cut tunnel due to the load reduction measures of EPS plate, EPS plate and geogrid, which reduces the soil pressure on the vault and arch bottom and increases the soil pressure on both sides; the stress on each section outside tunnel is reduced, and the orders in terms of effect of the load reduction materialon external stresses at different sections are haunch, side wall, vault, spandrel and arch bottom. A numerical simulation analysis on the test procedure is under taken by FEM strain model, with the results indicate that the average relative errors between the soil pressure, lateral pressure and the test results are 11.7% and 14.6%; load reduction of internal force increases with an increase of fill height and its change rate increases. For the load reduction of trench type open cut tunnel,it is necessary to reasonably select load reduction material and foundation stiffness under the condition of guaranteeing the safety of lining structure of open cut tunnel.
MA Li1 LIU Yapeng2 LI Sheng3,
4 LV Wenda5 XIE Chao3,
4 DAI Jinpeng3 etc
.Study on the Mechanical Behaviors of High-filled Loess Arched Open Cut Tunnel under Different Load Reduction Measures[J] MODERN TUNNELLING TECHNOLOGY, 2020,V57(3): 75-84
2020, Vol. 57 