| 大跨度绿泥石片岩隧道大变形机理与控制方法 |
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| 引用本文： | 陈建勋,陈丽俊,罗彦斌,王传武,刘伟伟.大跨度绿泥石片岩隧道大变形机理与控制方法[J].交通运输工程学报,2021,21(2):93-106. |
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| 作者姓名： | 陈建勋 陈丽俊 罗彦斌 王传武 刘伟伟 |
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| 作者单位： | 长安大学 公路学院，陕西 西安 710064 |
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| 基金项目： | 国家自然科学基金项目41831286国家自然科学基金项目51808049 |
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| 摘 要： | 依托宝鸡至汉中高速公路连城山隧道(双洞六车道)，基于隧道变形和支护结构受力现场测试，分析了大跨度绿泥石片岩隧道大变形灾害特征和机理，总结了隧道大变形灾害综合控制方法，建立了大跨度绿泥石片岩隧道大变形分级标准，提出了各变形级别对应的支护参数。分析结果表明:大跨度绿泥石片岩隧道在开挖过程中以沉降变形为主，主要表现为拱部初期支护的整体沉降；在初期支护闭合后，主要表现为边墙的挤出变形和墙脚下沉引起的仰拱底鼓；大变形灾害主要表现为掌子面失稳垮塌、初期支护变形侵限破坏、锁脚锚管脱焊失效、二次衬砌开裂、边墙下沉以及仰拱回填隆起开裂；绿泥石片岩极其软弱、破碎及仰拱基底遇水软化，是造成隧道大变形灾害的根本原因；隧道开挖跨度大(最大开挖跨度为19.6 m)、断面扁平、拱脚地基承载力不足而缺乏有效约束，加剧了隧道支护变形侵限和失稳破坏；初期支护承载能力有限，围岩荷载不断传递至二次衬砌，是导致二次衬砌开裂的直接原因；围岩变形机制为拱部岩体黏聚力难以克服自重而产生不断向下的滑移和松动机制，以及墙脚和仰拱部位围岩低强度应力比引起的软岩塑性流动机制；通过采用“三台阶留核心土法+大预留+双层HK200b钢架分次支护+大直径锁脚锚管+围岩径向注浆+加深仰拱”的大变形灾害综合控制方法，同时对隧道大变形进行分级管理，有效避免了隧道大变形灾害的发生。
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| 关 键 词： | 隧道工程 软岩 大跨度隧道 变形机理 控制方法 |
| 收稿时间： | 2021-03-25 |
Mechanism and control method of large deformation for large-span chlorite schist tunnel |
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| CHEN Jian-xun,CHEN Li-jun,LUO Yan-bin,WANG Chuan-wu,LIU Wei-wei.Mechanism and control method of large deformation for large-span chlorite schist tunnel[J].Journal of Traffic and Transportation Engineering,2021,21(2):93-106. |
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| Authors: | CHEN Jian-xun CHEN Li-jun LUO Yan-bin WANG Chuan-wu LIU Wei-wei |
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| Affiliation: | School of Highway, Chang'an University, Xi'an 710064, Shaanxi, China |
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| Abstract: | Based on the field test of deformations and stresses of supporting structures in the Lianchengshan Tunnel of Baoji-Hanzhong Expressway (double-hole six-lane), the characteristics and mechanism of large deformation disasters of large-span chlorite schist tunnels were analyzed, the comprehensive control method of large deformation disasters of the tunnel was summarized, the classification standard of large deformation of large-span chlorite schist tunnel was established, and the corresponding support parameters of each deformation grade were proposed. Analysis result shows that the large-span chlorite schist tunnel mainly has the settlement deformation during the tunnel excavation, which is mainly manifested as the overall settlement of the primary support. After the primary support is closed, the tunnel deformation is mainly manifested by the extrusion deformation of the side wall and the bottom heave of tunnel invert caused by the settlement of tunnel foot. The large deformation disasters are mainly as follows: the instability and collapse of tunnel face, primary support invasion and failure, the unsoldering and failure of feet-lock pipe, the cracking of secondary lining, the sinking of side wall, and the uplift and cracking of invert backfill. The chlorite schist is extremely weak and broken, and the invert base is softened by water, which are the fundamental causes of large deformation disaster of the tunnel. The large span of tunnel excavation (the maximum excavation span is 19.6 m), the flat tunnel section, and the lack of bearing capacity and effective restraint for arch foot foundation aggravate the deformation intrusion and instability failure of tunnel structure. The limited bearing capacity of primary support, causing loads to be continuously transmitted to the secondary lining, is the direct cause of the cracking of secondary lining. The deformation mechanism of surrounding rock can be summarized as the continuous downward slipping and loosening mechanism caused by the difficulty of the cohesion of arch rock mass in overcoming its own weight, and the plastic flow mechanism of soft rock caused by the low-strength stress ratio at the tunnel foot and invert. The large deformation disaster of the tunnel can be effectively avoided by adopting the comprehensive control method of "three-step core soil method+large reservation deformation+double-layer HK200b steel frame+large-diameter feet-lock pipe+radial grouting of surrounding rock+deepening tunnel invert", and managing the large deformation hierarchically at the same time. 5 tabs, 18 figs, 32 refs. |
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