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Analysis of Mechanical Properties and Influencing Factors of High-filled Cut-and-Cover Tunnel in Trench
(1 College of Civil Engineering, Lanzhou Jiaotong University, Lanzhou Gansu 730070; 2 Beijing High-speed Railway Works Maintenance Division of China Railway Beijing Group Co., Ltd., Beijing 100071)
Abstract As for few studies on the stress state of the arched open cut tunnel under high backfilling, the mechani? cal characteristics of high-filled open cut tunnels with arched cross-section in the cutting trench is studied through laboratory tests, the earth pressure distributions around open cut tunnel and stress variations outside tunnel arch ring along with backfilling height are obtained. The results show that the earth pressure distribution at the arched section on the top of open cut tunnel is in the shape of being large in the middle and small on both sides. When the backfilling height is low (less than 1.2 times of the tunnel height), the equivalent vertical uniform load is greater than the value specified in specifications, while being less than this value specified in specifications when the backfilling is high (equal to or greater than 1.2 times of the tunnel height). With the increase of backfilling height, the distribution pattern of earth pressure on both sides of open cut tunnel changes from "positive trapezoid" to "rectangular", and the earth pressure on bottom of open cut tunnel is uniformly distributed. With the increase of backfilling height, the external stress of the section at the spandrel varies little, but increases obviously at the vault, side wall and the bottom of the open cut tunnel. Subsequent numerical simulation analysis shows that the average relative error of earth pressure around open cut tunnel is 11.3%, and the average relative error of external stress is 14.5%, verifying the correctness of experimental data and the rationality of the numerical simulation parameters. Finally, the effects on the internal force of lining structure induced by sensitivity of the influential factors are discussed, such as the backfilling height, slope angle, backfill properties and the trench-width ratio. The results show that the slope angle and trench-width ratio have the most significant effect on the internal force of lining structure. To improve the me? chanical properties of the open cut tunnel in the practical engineering, the slope angle should be increased, and the trench-width ratio should be reduced as much as possible.
Abstract：
As for few studies on the stress state of the arched open cut tunnel under high backfilling, the mechani? cal characteristics of high-filled open cut tunnels with arched cross-section in the cutting trench is studied through laboratory tests, the earth pressure distributions around open cut tunnel and stress variations outside tunnel arch ring along with backfilling height are obtained. The results show that the earth pressure distribution at the arched section on the top of open cut tunnel is in the shape of being large in the middle and small on both sides. When the backfilling height is low (less than 1.2 times of the tunnel height), the equivalent vertical uniform load is greater than the value specified in specifications, while being less than this value specified in specifications when the backfilling is high (equal to or greater than 1.2 times of the tunnel height). With the increase of backfilling height, the distribution pattern of earth pressure on both sides of open cut tunnel changes from "positive trapezoid" to "rectangular", and the earth pressure on bottom of open cut tunnel is uniformly distributed. With the increase of backfilling height, the external stress of the section at the spandrel varies little, but increases obviously at the vault, side wall and the bottom of the open cut tunnel. Subsequent numerical simulation analysis shows that the average relative error of earth pressure around open cut tunnel is 11.3%, and the average relative error of external stress is 14.5%, verifying the correctness of experimental data and the rationality of the numerical simulation parameters. Finally, the effects on the internal force of lining structure induced by sensitivity of the influential factors are discussed, such as the backfilling height, slope angle, backfill properties and the trench-width ratio. The results show that the slope angle and trench-width ratio have the most significant effect on the internal force of lining structure. To improve the me? chanical properties of the open cut tunnel in the practical engineering, the slope angle should be increased, and the trench-width ratio should be reduced as much as possible.
MA Li1 WANG Qicai1 LI Sheng1 LIU Yapeng2 NING Guixia1 HAN Guoqiang1
.Analysis of Mechanical Properties and Influencing Factors of High-filled Cut-and-Cover Tunnel in Trench[J] MODERN TUNNELLING TECHNOLOGY, 2020,V57(6): 133-141
2020, Vol. 57 