隧道塌方总结

1、隧道塌方总结1 （共6页）-本页仅作为文档封面，使用时请直接删除即可-内页可以根据需求调整合适字体及大小-隧道围岩大变形研究分析due to the influence of natural geological conditions, collapse accident often bring enormous damage to the tunnel construction in the large section tunnel excavation of road (or railroad) construction.engineering equipment and the safe

2、ty of personnel are seriously threatened by the collapse of tunnel which has the character of high incidence and high risk.1、primary influence factors and types of tunnel collapseThe main factors of tunnel collapseThere are many influence factors in tunnel collapse, generally can be divided into ext

3、ernal and internal factors, internal factors are mainly refer to the engineering geological and hydrogeological conditions, external factors are mainly refer to improper design and construction.unfavorable geological conditionsunfavorable geological mainly includes the weathered metamorphic rock, fr

4、actured rock mass and rock pile area, fault, karst cave, landslide, mudslide, swelling strata, the tunnel encountered to those geological condition,some slight negligence may lead to the collapse of tunnel.underground waterGroundwater is one of the important factors influencing the stability of surr

5、ounding rock. it not only reduces the strength of rock which has high softening coefficient, and also reduces the shear strength of structure plane.geostress geostress mainly includes the bias, plasticity, landslides and high ground stress area, etc.,there are many instances of collapse happened in

6、the entrance zone of the tunnel were caused by bias and landslide,extrusion destruction of tunnel is often caused by plastic pressure,and rock burst often occured in high ground stress area, etc.mproper design and construction.At present, New Austrian Tunnelling Method is used to design and construc

7、tion in most of the tunnel, However, the deviation understanding of the concept and connotation of the principle led to many failure in engineering.collapse of tunnel is induced by many factors and the mechanism is of more complex, therefore, improper treatment measures for the complex geological du

8、ring the construction will easily cause the occurrence of collapse disasters.analysis of collapse typesthere are many types of partitioning method, generally based on the cause of collapse, form, scale, mechanism, etc. it mainly divides into the following five kinds of forms.Partial collapse : Mainl

9、y happened in large blocky rock mass, the rock mass is cutted by structure surface and formed into different shapes of unstable structure. After cavern excavation, the friction direction of unstable structure surface slide and collapse occured.Arch collapse : Typically occur in layered rock mass or

10、broken rock mass, it has two kinds, one kind is in the range of the pit, only occur in the arch department; Another kind is expanding arch collapse, including wall collapse.Deformed collapse : collapse induced by special geological conditions (caves, sinkhole, etc.), shallow buried and bias.swelling

11、 rock tunnel collapse : Due to high inflation pressure acts on the shotcrete support; The expansion of the rock body reduces the friction and shear strength; High water pressure accumulation。Large deformation of tunnel the rock burst : surrounding rock large deformation problem of deep buried,long-l

12、arge tunnels and underground engineering under high geostress condition has become a problem in underground engineering and become a major issue to be solved.2、deformation analysis for surrounding rock of tunnelsWith the rapid development of tunnel and underground engineering, the characteristic of

13、its long- scale-deep are increasingly obvious, and it is prone to geological disasters , such as large deformation of surrounding rock in certain geological and environmental geological conditions. Based on a lot of literature retrieval, it is obviously that surrounding rock large deformation is a k

14、ind of great hazardous geology casualty of tunnel and underground engineering.current research of large deformation of Tunnel surrounding rockthough a lot of domestic and foreign scholars have done a lot of exploration efforts, due to the large deformation theory research is not mature, as well as t

15、he complexity of on-site geological rock mass condition, the current research work is mainly manifested in the following aspects.The concept for large deformationthere is no form a consistent and clear definition About the large deformation of surrounding rock, Some scholars according to whether the

16、 deformation of surrounding rock is within the reserved deformation of primary support to define it. Also some scholars think it shouldnt be defined by the absolute value of the deformation which is the external performance of large deformation problem. It should be defined by the essence that the s

17、urrounding rock occurs shear deformation , deflection , rupture and failure under the shear stress, and causes the rock mass squash the underground cavity.analysis of the soft rockso far, Rock engineering community has been unable toreach a consensus on the concept of soft rock, the definition of so

18、ft rock is more than a definition of soft rock of ISRM (international society for rock mechanics, 1990 , 1993) is refers to the uniaxial compressive strength of rock was 25 mpa; In 1984 coal mine term discussion (kunming) , soft rock is defined as low strength, high porosity ,poor cementation and af

19、fected by structural plane cutting and weathering or contains a lot of expansive clay minerals and loose, soft rock (body); And some scholars also divide it into geological soft rock and engineering soft rock and so on.mechanism of Large deformationPeople generally divide it into two types base on t

20、he formation mechanism of the surrounding rock large deformation. The first type is caused when redistribution stress exceeds surrounding rocks strength after tunnel excavation, which makes the surrounding rock be plasticity. the other type is caused when certain minerals in the rock react with wate

21、r and inflation. swelling mineral and water are significant for the expansion deformation.type and mechanism of Large deformation of tunnel surrounding rockTunnel surrounding rock large deformation can be defined as: a kind of plastic deformation and failure with progressive and obvious time effect

22、of tunnel and underground engineering surrounding rock, it is different from brittle failure of rock burst and distinguish it from collapse and slide, etc, which are caused by the rocks structure plane of surrounding rock loose zone.the type of Large deformation of tunnel surrounding rockAccording t

23、o the analysis of typical examples and the research on mechanism of large deformation, classification on the large deformation was carried out base on different controlled conditions: controlled by lithology of surrounding rock , controlled by the structure of surrounding rock and affected by artifi

24、cial excavation disturbance.在公路（或铁路）隧道大断面开挖施工中，由于自然地质条件、施工等的影响， 常会发生塌方事故，给隧道施工带来极大危害。塌方以其高发性、高危性严重威 胁着工程设备和人员安全。本报告从塌方的类型、塌方的影响因素进行了总 结，并对隧道中的大变形进行了一定的介绍。1、隧道塌方类型及塌方主要影响因素隧道塌方主要影响因素影响隧道塌方的因素很多，大体上可分为内因和外因，内因主要是指工程 地质和水文地质条件，外因主要是指设计和施工不当。1）不良地质条件不良地质主要包括风化变质岩体、裂隙发育岩体、崩塌岩堆地区、断层 带、溶洞、滑坡、泥石流、膨胀性地层等，当隧道

25、从这些岩体中通过时，如稍有疏 忽,就可能发生大塌方。2）地下水地下水是影响围岩稳定的重要因素之一。这不但能使岩石强度降低，特别 是软化系数较大的岩石，而且使结构面的抗剪强度减小。对于断层，地下水影响更 大，一般张性断层是储水结构，压性断层带中断层糜棱岩是隔水的，而另一侧的破 碎带为含水的，当揭穿断层后，便时常发生突发性涌水导致塌方。3）地压地压主要包括偏压、塑性地压、滑坡及高地应力区等 ，偏压和滑坡在隧道洞 口段造成的塌方实例很多，塑性地压引起隧道挤出性破坏也时有发生，高地应力区 的完整坚硬岩体常发生岩爆等。4）设计和施工不当目前，大多数隧道都号称采用“新奥法”设计和施工，由于对“新奥法”概念

26、 和原则的内涵理解有偏差，所以在许多工程中遭到失败。由于塌方诱发因素多、机理复杂，因此，在施工中针对复杂地质时若处理 措施不当，将极易造成塌方灾害的发生。塌方类型分析塌方类型的划分方法有多种，一般根据塌方的原因、形式、规模、机理、 发生的部位等进行划分，主要分为以下五种形态：1）局部塌方：主要发生在大块状岩体中，由于岩体被结构面切割后构成不同形 状的不稳定结构体。洞室开挖后，不稳定结构面的摩擦力向洞内滑移而发生塌 方。2）拱形塌方：一般发生在层状岩体或破碎块岩体中，它有两类，一类是在 坑跨范围内，仅出现在拱部；另一类是包括侧壁崩塌在内的扩大的拱形塌方。3）异形塌方：由于特殊地质条件（溶洞、陷穴

27、等），浅埋、偏压隧道等原 因产生的塌方。4）膨胀岩隧道塌方：由于高膨胀压力作用在喷混凝土支护上；岩土体的膨 胀原因使摩擦和剪切强度损失，造成很大的岩石材料重力荷载；高水压力积聚 等造成隧道塌方。5）大变形的隧道和岩爆：高地应力状态下的深埋、长大隧道及地下工程的 围岩大变形问题已经成为困扰地下工程界的难题和尚待进行深人研究的重大课 题之一。2、隧道围岩大变形分析随着隧道工程以及地下工程的迅猛发展，其长、大、深的特点日趋明显，而在 一定的围岩地质和环境地质条件下则往往易于发生围岩大变形等地质灾害。根 据大量文献检索结果显示，隧道工程围岩大变形已是困扰地下工程界的一个重大 问题。隧道围岩大变形研究现

28、状国内外学者已经做过不少的探索工作，但由于大变形理论的研究不尽成熟，加 之现场地质岩体状况复杂性，目前的研究工作主要表现在以下方面。1）大变形的定义关于围岩大变形，目前还没有形成一致的和明确的定义。有的学者提出根据 围岩变形是否超出初期支护的预留变形量来定义大变形。也有的学者认为，不能从变形量的绝对值大小来定义大变形问题，具有显著的变形值是大变形问题的外 在表现，其本质是由剪应力产生的岩体的剪切变形发生错动、断裂分离破坏，岩体 将向地下空洞方向产生压挤推变形来定义大变形。2）关于软岩的分析至今岩石工程学界仍未就软岩的概念达成共识，软岩的定义有十几种之 多。ISRM国际岩石力学学会1990,19

29、93）定义的软岩是指单轴抗压强度为 25MPa的一类岩石；1984年煤矿矿压名词讨论会（昆明）将软岩定义为“强度 低、空隙大、胶结程度差、受结构面切割及风化影响或含有大量易膨胀粘土矿 物的松、散、软、弱岩层（体）”；还有的学者将软岩划分为地质软岩和工程软岩 两类等等。3）大变形机制人们一般按形成机制将围岩大变形分为两类：一是开挖形成的应力重分布超 过围岩强度而发生塑性化。二是岩石中的某些矿物和水反应而发生膨胀。水及 某些（膨胀性）矿物的存在，对于膨胀变形是必须的。、隧道围岩大变形的类型与机制隧道围岩大变形可以定义为：隧道及地下工程围岩的一种具有累进性和明显 时间效应的塑性变形破坏，它既区别于岩

30、爆运动脆性破坏，又区别于围岩松动圈中 受限于一定结构面控制的坍塌、滑动等破坏。1）隧道围岩大变形的类型分析根据对围岩大变形典型实例的分析和对大变形机制研究，可以按照不同的受 控条件对大变形进行类型划分：受围岩岩性控制的大变形，受围岩结构构造控制的 大变形和受人工采掘扰动影响的大变形三大类型large deformation mechanism of Tunnel surrounding rock2）隧道围岩大变形机制研究围岩的变形破坏首先取决于围岩性质，其中包括围岩体的岩性、结构条件，其 次受到围岩的环境条件即地应力的大小、地下水的发育分布状况的影响 ，同时也 与围岩的支护条件密切相关。一般而

31、言，隧道变形将经历初始变形、等速变形及加速变形3个阶段。在隧道开挖初期，由于围岩变形刚开始，岩体内应力场和位移场处于线性变化阶 段，处于力学平衡状态，这时围岩处于初始变形阶段。随着开挖过程的进行、 围岩地应力释放、应力状态重新分布，引起某些区域局部变形、微裂隙产生、 应力增加，使得岩体内部微裂隙不断增加和扩展。这时围岩处于等速变形阶 段。随着围岩变形的增长，裂隙进一步扩展、连通、丛集，甚至局部贯通，围 岩发生较大的变形，变形速率持续增加，直至整体失稳坍塌，这时围岩处于加 速变形阶段。若局部变形发展过程中，围岩系统受到外界干扰（如：降雨、人 工影响、振动等），则将促使其变形和破坏过程的加速发展。

32、3、隧道围岩大变形的预测在大变形的预测方面，目前国内外尚无实用的预测大变形的方法、日本学者 viladkar（1995）提出利用地层Q值的“临界埋深法”，当实际埋深大于临界埋深时 围岩应视之为挤压性围岩，具有发生大变形的条件。但此种方法与开挖断面及支 护不发生关系，与支护变形量的大小也无内在联系，当实际埋深大于临界埋深时可 能发生的支护变形值有多大难以确定。大变形的预测另一方法是，对于一个具有锚喷支护的洞室，采用弹塑性理论解 析公式计算其在地应力作用下的最终洞壁位移，然后确定位移与地应力及岩体强 度三者的关系（绘出曲线图形）,如已知地应力及岩体强度支护位移值及大变形的 等级可从图中查得。4、隧

33、道围岩大变形的支护对策交通隧道的支护包括初期支护和二次衬砌。对于软岩隧道 ，支护的首要任务 是如何遏制初期支护的大变形。随着人们对大变形现象认识不断深化 ，提出了各 种各样的支护措施和手段，这些支护措施基本可以分为以下三大类1）刚性支护这种支护措施的核心是通过加大支护结构的强度和刚度来抵抗巨大的围岩 压力，这种支护措施无论从技术上还是从经济上 ，都是欠合理的，现在已经较少采 用。2）可缩支护这种支护的理论依据是允许围岩发生适度的变形，以降低作用于结构的支护 压力,从而减少超挖量并降低支护强度。可缩支护系统在国内外煤矿巷道支护方面已经取得一些成功的经验，但该方法只允许适度变形，若超出支护体系的允许变形范围，这类支护结构一般很难 抵挡围岩的巨大压力，该方法在交通隧道支护中的应用效果并不理想。3）锚、注一体化围岩加固-支护系统锚喷衬砌作为隧道初期支护的主要手段，也构成了永久衬砌的重要组成部 分。喷锚衬砌是一种加固围岩、充分利用围岩自承能力的一种支护衬砌形式，并且快速及时，可以节约劳