【作者】 赵勇；

【导师】 王梦恕；

【作者基本信息】 北京交通大学 ， 地下工程， 2012， 博士

【摘要】 当前我国大规模的隧道建设中,软弱围岩隧道的设计与施工难题一直困扰着广大隧道建设者。软弱围岩隧道通常表现为围岩变形大,甚至发生坍塌等安全事故；施工进度缓慢,严重制约工程的工期。出现这些问题的主要原因是对隧道围岩特别是软弱围岩的变形机制、发展演化规律等认识不足,采取的控制技术与方法缺乏针对性等。针对这一系列问题,本论文对软弱围岩地质特征与工程影响评价、变形机制与时空效应、支护结构与围岩作用体系、隧道软弱围岩变形控制技术等进行了系统深入研究,取得了以下主要研究成果：(1)系统总结提出隧道工程软弱围岩的含义；分析了软弱围岩的地质特征、变形特征和强度特征；根据软弱围岩的力学特征,提出了铁路隧道软弱围岩的分级标准建议,将软弱围岩分为软岩I级、软岩II级和软岩III级共三个等级。(2)隧道断面尺寸对围岩的变形机制和变形控制基准有较大影响,为方便研究软弱围岩隧道的变形控制对策,本文提出了铁路隧道断面等级和跨度分级建议,将隧道断面分为小断面、中断面、大断面和特大断面4级,将隧道跨度分为小跨度、中跨度、大跨度和特大跨度4级。(3)分析提出了围岩变形的分布规律。围岩变形在空间上可分为三部分,即掌子面前方的超前变形、掌子面挤出变形和掌子面后方变形,这三部分变形是同时发生的。软弱围岩隧道变形量大、变形持续时间长、掌子面前、后方变形影响范围大、变形速度快是软弱围岩隧道变形的特点。(4)基于隧道施工过程中应力释放与应力控制动态作用关系的研究,建立了由围岩、超前支护、初期支护和二次衬砌组成的软弱围岩隧道结构体系,并阐述了各个构件在该结构体系中的力学作用。支护结构分为超前支护、初期支护和二次衬砌,其中超前支护和初期支护与围岩体共同形成承载结构,二次衬砌仅作为安全储备,主要承担附加荷载和残余变形引起的荷载。(5)建立了考虑围岩应力释放的隧道结构体系理论模型,并采用数值方法验证了其正确性,指出为避免或尽量减小出现过量围岩塑性变形,一方面要及时支,护,减小支护结构施做前的围岩应力释放；另一方面要使支护结构具有一定的刚度,尤其是早期刚度,以提供足够的支护抗力来抵制过量围岩塑性变形的发生。(6)开挖方法和支护措施是围岩变形控制的两个方面,开挖使得围岩释放应力,支护则是控制应力释放的方法,支护结构和围岩的稳定是变形控制的目标。围岩变形控制原理就是根据围岩变形的时空分布规律,采取合理的开挖方法和支护措施,控制掌子面前方、掌子面、以及掌子面后方变形,使围岩变形控制在变形基准值以内,以保持围岩和隧道结构的长期稳定。(7)软弱围岩变形预测分为施工前的变形预测和施工过程中的变形预测两个阶段。数值法和基于自身量测数据的统计分析法是比较接近实际又便于实施的变形预测法。研究提出了我国铁路隧道净空位移、拱顶下沉、掌子面前方超前变形、掌子面挤出变形、掌子面后方变形速度的管理基准建议。(8)提出了软弱围岩变形控制的方法和支护结构设计原则。即采用超前支护,控制掌子面的超前变形和拱顶下沉；采用掌子面支护,控制掌子面挤出变形；加强初期支护,控制开挖掌子面后方变形；采用辅助支护措施,控制掌子面的稳定和初期支护的拱脚位移；采用二次衬砌,合理预留支护结构的安全储备,控制隧道建成后的残余变形。研究提出了软弱围岩隧道支护结构设计的原则、设计流程和支护结构设计参数。(9)以兰渝铁路桃树坪隧道和贵广铁路天平山隧道为例,阐述了软弱围岩隧道掌子面前方变形和掌子面后方变形的控制实践,按照本课题的研究成果,均取得了很好的控制围岩变形效果。更多还原

【Abstract】 In the current China’s large-scale tunnel construction, one of the main problems which puzzled the majority of tunnel builders is the design and construction of tunnels in the soft and weak rock. It usually presents a great deformation, or even collapse and other accident; and a slow construction progress which is a severe restriction of the construction time. Such problems are mainly due to shortage of knowledge on the deformation mechanism and law of development and evolvement of tunnel surrounding rock, especially the soft and weak surrounding rock. Another reason for the problems is that the technical measures and methods which have been taken are lack of pertinence. This article studied in a system and deep-going way on soft and weak surrounding rock, including the geological features, evaluation of engineering influence, deformation mechanisms and time-space effect, interaction system of supporting structure and surrounding, and deformation control technique. Following key achievements have been achieved in the article.(1) The meaning of the soft and weak surrounding rock tunnel has been expatiated systemically, and itsgeological features, deformation characteristics and strength characteristics have been analyzed. The soft and weak surrounding rock has been classified three levels, grade I soft rock, grade II soft rock and grade III soft rock according to it mechanical characteristics.(2) The deformation mechanism and the deformation control criteria of the soft surrounding rock are influenced by the size of the tunnel-section. The recommended classification of tunnel sections and span of railway tunnel are proposed for the convenience of the study on deformation control of soft and weak surrounding rock. The tunnel sections are classified as small, medium, large and extra-large size, and the span of tunnel are also distributed into small, medium, large and extra-large span.(3) The deformation distribution of surrounding rock is divided into three parts in space, which are deformation ahead of the tunnel face, at the tunnel face and back from the tunnel face. And all of them occurred at the same time. The large-value, long-lasting deformation, the large change range ahead of the tunnel face and high change rate back from the tunnel face in initial excavation period are considered as the main characteristics of the soft surrounding rock tunnel.(4) Based on the study of the stress release and the dynamic relationship of stress control in the process of tunnel construction, the structure system of the soft rock tunnel, which is composed of surrounding rock, support in advance, primary support and lining, is established. The mechanical role of each component is explained. The support structure is divided into advancing support, primary support and lining. The advancing support and primary support forms the load bearing structure together with the surrounding.rock and the lining serves as safety margin, mainly supporting the additional load caused by the residual deformation.(5) Establish the tunnel structure theory model considering the rock stress release and verify the exactness with the numerical method, then point out that there are two sides should be careful in order to avoid or reduce the rock plastic deformation, for one is timely supporting, reducing the rock stress release before the construction of the support structure, and another is enough stiffness of support structure, especially the early stiffness to provide enough support force to resist the occurrence of rock plastic deformation.(6) Excavation method and support measure are two sides to control the rock deformation. Excavation causes the rock stress release and the support is the method to control the stress. Stability of the support structure and rock is the destination of deformation control. The control principle of rock deformation is to keep the rock deformation, including deformation ahead of the tunnel face, at the tunnel face and back from the tunnel face, under the deformation control criteria and make the surrounding rock and support structure stable for a long time by using appropriate excavation method and support meausure according to the time-space distribution regularities of rock deformation.(7) The deformation predictions of weak surrounding rock are distributed in two stagesas prediction before the construction and after the construction. Numerical method and the statistic method based on its original measure data are the deformation prediction methods approaching the reality. The management reference suggestions of clear displacement, crown settlement, precession displacement of excavation face, extrusion displacement of excavation face, arch subsidence and displacement velocity behind the excavation face have been presented in the article for the railway tunnel in our country.(8) The control method of weak surrounding rock and its design principle of support structure have been presented. That is using the advanced support method to control the displacement before the excavation face and the excavation face, using the primary support to control the displacement behind the excavation face, using the auxiliary support to control the stability of excavation face and the arch subsidence of primary support, and using the secondary lining support as reasonable emergency capacity to control the residual deformation. The structure design principle, design process and design parameters have been presented for weak surrounding rock.(9) Taoshuping Tunnel of the Lanzhou-Chongqing railway and Tianpingshan Tunnel of the Guilin-Guangzhou railway have been taken examples in the article to state the control practice of deformation before and behind the excavation face in the weak surrounding rock. Perfect result of deformation control has been got in above two tunnels by using the research achievement of this article.更多还原