| 地层渐进成拱对浅埋隧道上覆土压力影响研究 |
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| 引用本文： | 汪大海,贺少辉,刘夏冰,张嘉文,姚文博.地层渐进成拱对浅埋隧道上覆土压力影响研究[J].岩土力学,2019,40(6):2311-2322. |
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| 作者姓名： | 汪大海 贺少辉 刘夏冰 张嘉文 姚文博 |
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| 作者单位： | 北京交通大学 土木建筑工程学院，北京 100044 |
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| 摘 要： | 砂土及完整性较差、黏聚强度较小的破碎岩体中，浅埋隧道地层拱作用机制随地层变形发展而变化，受此影响隧道松动土压力也相应变化。常规方法忽略了地层拱不同阶段力学机制的不同，同时未考虑剪切面转动与大主应力旋转之间的相互关系，因此，不能解决浅埋隧道地层能否成拱、地层拱何时贯通至地表以及地层拱发展对隧道松动土压力影响等问题。针对这一情况，提出渐进地层拱力学模型以反映不同阶段地层拱的力学机制；其次，同时考虑主应力旋转、剪切面转动及二者相互关系，确定拱内土体应力分布；随后，优化了传统主应力偏转与地层差异沉降间的数学模型。在此基础上确定了渐进地层拱对隧道松动土压力的影响。改进方法结果与传统方法结果及试验结果的对比验证了改进方法的有效性与适用性。通过参数分析研究了隧道初始松动压力、随地层变形发展的松动压力以及地层拱贯通至地表时的极限变形等关键参数。最后，对下北山超大跨浅埋隧道的研究说明了改进方法的实用性。结论显示：（1）初始松动压力为初始松动区内土体重力，初始松动区范围不受覆跨比影响，而受地层强度影响，随内摩擦角增加而减小；（2）最大拱效应阶段以后，松动土压力随地层变形发展而增加，深埋、小跨度隧道（ ）增长速率较慢，反之较快；（3）极限变形随覆跨比、内摩擦角增加而增加，深埋、小跨度隧道地层拱效应更明显；（4）对于下北山隧道，初始地层拱存在，初始松动土压力为0.37 ，极限松动土压力为0.41 ，最终松动土压力为0.54 ，隧道变形应控制在5.7%以下避免地层拱贯通至地表。
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| 关 键 词： | 浅埋隧道 松动土压力 渐进地层拱 |
| 收稿时间： | 2018-10-24 |
Studies of the progressive ground arching on the loosening pressure above shallow tunnels |
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| WANG Da-hai,HE Shao-hui,LIU Xia-bing,ZHANG Jia-wen,YAO Wen-bo.Studies of the progressive ground arching on the loosening pressure above shallow tunnels[J].Rock and Soil Mechanics,2019,40(6):2311-2322. |
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| Authors: | WANG Da-hai HE Shao-hui LIU Xia-bing ZHANG Jia-wen YAO Wen-bo |
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| Institution: | School of Civil Engineering，Beijing Jiaotong University, Beijing 100044 |
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| Abstract: | For underground excavations in sand and blocky rock masses with low cohesive strength, the loosening pressure above a shallow tunnel varies with the developing ground deformation due to evolutions of ground arching. However, the normal ground arching method fails in determining the existence of the ground arch, resulting in critical deformation when the ground arch reaches the ground surface and the variation of the loosening pressure as a function of the developed arching effect. This paper presents a modified method by introducing a continuously developed ground arching mechanism. Rotations of the principal stress and the correlation between orientations of the principal stress and the shear surface are used to determine the stress state within the arch. Previous methods determining the rotation of the shear surface as a function of the ground deformation was also modified to better reflect the test results. On the basis of the above three steps, a modified method is proposed. Comparisons of the results among the previous methods, the proposed method and the experiments examined the validity of the proposed method. Parametric analysis studied the initial loosening pressure, the evolution of the loosening pressure and the critical deformation. A case study by the proposed method indicates its practical use. Some important conclusions are: (1) the initial loosening pressure comes from the weight of the ground within the arch. The area of the initial-loosening zone is independent on the cover-depth ratios. Instead, the area is controlled by the friction angle of the ground. Grounds with low friction angles tend to have large initial-loosening zone with a high initial loosening pressure; (2) the loosening pressure increases with the developing ground deformation, and a lower raising rate is found for a deeper, smaller tunnel ( ); (3) the critical deformation increases with the raising cover-depth ratio and the increasing friction angle, indicating that a stronger arching effect is expected in such grounds; (4) for Xiabeishan tunnel, the arching effect exists, the initial loosening pressure is 0.37 , the critical value is 0.41 , the ultimate is 0.54 , and the critical relative deformation is 5.7%. |
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| Keywords: | shallow tunnels ground loosening pressure progressive ground arching |
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