【作者】 沈乐；

【导师】 陶志平；

【作者基本信息】 西南交通大学 ， 岩土工程， 2012， 硕士

【摘要】 花岗岩蚀变岩体体是指晚期侵入的花岗岩再经热液蚀变后形成的岩体,花岗岩蚀变岩体体强度低,有吸水膨胀的特点,易松裂崩解,节理裂隙发育,岩体破碎且多呈松散碎石角砾、粉砂土状,稳定性极差。目前,这种地质现象在国内外工程建设中较为罕见,类似工程的建设经验较少,对花岗岩蚀变带隧道围岩稳定性及变形规律的研究尚无相关资料,对蚀变带地区隧道工程的设计与施工也无规律可循,因而本文所开展的研究具有十分重要的意义。本文以洛湛线铁路北岗隧道工程为依托,该隧道洞身周边存在较厚的全风化的花岗岩蚀变带,加之隧道所处区域地下水丰富,因而在隧道穿越富水软岩地段的施工中,多次出现围岩急剧变形、坍塌、突泥、突水、地下水位下降、泉水枯竭、地面塌陷、开裂等问题,最终导致整个隧道施工被迫全面停止,设计进行变更。针对以上问题,论文基于相似理论,以几何相似比q=100、容重相似比C,=1为基础相似比,建立三类力学模型,分别研究了围岩工程特性、渗流作用、围岩分界面位置三个因素对隧道变形的影响,分析了蚀变带隧道的变形机理；为研究支护结构对隧道变形的影响及其支护效果,建立了几何相似比q=30的力学模型,对支护结构的支护效果做出评价,为支护结构的设计提供有意义的参考；同时以数值模拟计算为辅助研究手段,对模型试验成果进行了进一步地验证与补充,主要得到以下有关蚀变带隧道的研究成果：1.花岗岩蚀变带地区隧道开挖过程中洞周收敛变形明显且发展速度快,如不及时支护,容易引起地表较大范围内出现开裂甚至局部塌陷,地表沉降规律符合Peck提出的理论曲线；2.地下水的渗流将导致突泥涌水的产生,对围岩的力学性质产生损伤,这是造成北岗隧道严重塌方的最根本原因；3.隧道塌方破坏主要从拱顶开始,为拱形破坏模式,这是典型的松散无黏性土的破坏模式；4.岩体分界面存在于开挖面上或其附近时,围岩容易沿岩体分界面发生相对错动或局部破坏,并导致地表沉降、围岩压力变化的不对称,当分界面的角度为45°左右时,这种不对称性的综合影响最明显,但随着分界面与开挖面的距离增加这种影响将明显越来越小。总之,隧道围岩越多部分为软弱围岩,就对隧道围岩变形及其稳定性越不利；5.北岗隧道开挖后应重点防止渗流产生并及时施作仰拱,支护设计强度应比规范中一般规定要大,在蚀变带隧道的设计计算中应采用考虑损伤的本构模型。更多还原

【Abstract】 Granite altered rock refers to the rock mass formed by hydrothermal alteration on the late intrusive original granite rock, the strength of granite altered rock mass is low, which has the characteristics of expansibility after absorbing water, and it’s easy to loosen and disintegrate, there are many joints and fissures in the granite altered rock, it is broken and loose with mostly gravel and silt like soil, whose stability is poor. At present,this geological phenomenon is relatively rare in domestic and international engineering construction,the experience of the costruction of similar projects and the relevant research on stability and deformation law of altered granite rock tunnel is rare,there are no rules to follow about the construction and design of altered granite rock tunnel currently, therefore,the research of this thesis carried out with great significance.This thesis based on project of Beigang tunnel of Luoyang-Zhanjiang railway,the tunnel exists in a thick weathered altered granite zone,where is rich in groundwater,thus in the process of tunnel construction when the tunnel through the section of the water-rich soft rock mass, the surrounding rock of the tunnel dramatically deformed and collapsed repeatedly,many other problems such as sudden mud,water burst,falling water tables,dried up springs,ground subsidence,cracking also happened again and again,which eventually led to the construction of the tunnel was forced to comprehensively stop and the design of the tunnel was changed.To solve above problems,three types of mechanical model was established in this paper according to geometric similarity ratio CL=100and density similar ratio Cy-1which was considered as basic similarity ratio,the models were respectively used to study the impacts on deformation of the tunnel caused by engineering properties of the rock,seepage effects and location of rock interface these three factors,and the deformation mechanism of altered tunnel was gained finally;To study the effects on deformation of the tunnel by supporting structure and its supporting effect,the mechanical model was established according to the similarity ratio CL=30,which was used to evaluate the supporting effect of the supporting structure and provide a meaningful reference for the design of the supporting structure; meanwhile,numerical simulation was considered as the auxiliary method to further validate and complement the results of the model tests, these two methods can complement and confirm each other,the mainly achevements about altered rock tunnel of this thesis as followed:1. Altered rock tunnel converge obviously and quickly during excavation,and this will lead to crack within a larger area on the ground surface or even partial collapse,and if it is not supported,the settlement law of cross-section of the stratum in line with the theoretical curve proposed by Peck;2. Groundwater seepage will result in the sudden mud and gushing water,and the mechanical properties of the surrounding rock will be damaged,which is the most fundamental cause of the severe collapse of the Beigang tunnel;3. The collapse mainly began from the vault of the tunnel,it is called the arch-failure mode,which is the typical failure mode of loose non-cohesive soil;4. When the rock interface exist in or near the excavation surface,the surrounding rock is easy to dislocate or destroy partly along the rock interface, meanwhile,the existence of the rock interface will also lead to surface subsidence and geotechnical pressure become asymmetric,the combined effects of this asymmetry is most obvious while the angle of the interface is about45,but with the increase of the distance between the interface and the excavation face,this impact will be significantly smaller and smaller. In short, the more part of tunnel surrounding rock is the weak rock, the more unfavorable the deformation and the stability of the tunnel will be;5. After excavating Beigang tunnel,we shoule focus on preventing seepage and applying the invert in time,the design strength of the supporting structure should be higher than the general provisions in the standard of railway tunnel design,and the constitutive model which consider the damage should be used in design and calculation;更多还原