破碎围岩条件下隧道开挖支护方法改进方案探讨

总结分析了隧道破碎围岩的力学特性，结合隧道开挖支护施工中容易出现的问题和工作经验，提出了破碎围岩条件下隧道开挖和支护方案的改进意见，以期对同类条件下隧道的施工有借鉴和帮助。     

变质岩区隧道开挖作用下围岩应力场变化及其稳定性分析

为研究复杂工程地质条件下的隧道围岩在施工过程中的力学特征,以陕西省石泉县喜河—后柳改建公路的拟建隧道为研究对象,以有限元为研究方法,基于其地形地貌、地层岩性、水文地质等工程地质特征数据,形成模型相关参数,以此建立隧道三维地质数值分析模型,利用隧道钝化模拟单向全断面开挖的施工工况,探讨其应力分布特征及变化规律。结果表明:开挖的隧道会表现出显著的应力集中现象,其对隧道顶部围岩稳定性影响最大;在本模型中,隧道开挖未支护时,天然应力处于临界状态的中风化绿泥石石英片岩和断层带整体处于破坏的应力状态,而开挖前相当稳定的微风化绿泥石石英片岩、微风化石灰岩、微风化闪长岩在开挖时大部分处于稳定状态,只有局部处于破坏状态,而微风化碳质石英片岩稳定性不受影响;在参考监测数据中,中风化绿泥石石英片岩开挖后失稳,其他岩层处于稳定状态。     

隧道工程地质评价的内容和方法

结合工程隧道实际,首先阐述了隧道工程的基本地质环境和工程地质条件,然后针对隧道工程可能出现的不良地质现象和可采取的工程措施,从大气降水、围岩稳定、围岩压力、洞口稳定、隧道比选等角度探讨隧道工程地质评价的主要方法和一般内容,进行隧道工程地质评价,为隧道施工、支护提供了依据.     

西安地铁隧道穿越饱和软黄土地段的地表沉降监测

以西安地铁一号线朝阳门站—康复路站区段饱和软黄土地铁隧道为研究对象,通过施工期现场地表沉降变形监测,分析了在饱和软黄土特殊地层条件下隧道浅埋暗挖法施工引起的该区段地表沉降变形规律以及地表沉降槽分布特征。结果表明:在饱和软黄土隧道开挖时,随着掌子面的推进,隧道顶地表沉降可分为沉降微小阶段、沉降显著发展阶段、沉降缓慢阶段和沉降稳定阶段;单线隧道开挖后的最大地表沉降量为18.89mm,双线隧道开挖后的最大地表沉降量为36.4mm;已开挖隧道对围岩土体的扰动作用使得后开挖隧道的地表沉降发展较大;双线隧道的地表沉降槽宽度接近单线隧道沉降槽宽度的2倍,因此可以将其近似为单线隧道地表沉降槽宽度与双线隧道轴线中点距离之和;单线隧道开挖后地表沉降槽宽度为8.4～9.3m,双线隧道开挖后地表沉降槽宽度为16.2～17.5m;隧道开挖施工的沉降槽宽度参数为0.435～0.467,单线隧道开挖后的地层损失率为0.765%～1.324%,双线隧道开挖后的地层损失率为1.231%～2.200%。     

地盘子水电站引水隧洞支护方案探讨

依据地盘子水电站隧洞岩性、构造、地下水等工程地质条件,对隧洞岩体完整性、稳定性进行划分及围岩进行分类,探讨了引水隧洞在开挖过程中Ⅳ类不稳定围岩及Ⅴ类围岩的支护方案及支护效果。     

沂源鲁村煤矿千米混合立井围岩稳定性分析与施工措施

基于沂源鲁村煤矿围岩稳定性差,塑性变形量大的实际情况,采用弹塑性力学分析的方法,分析了鲁村煤矿千米混合立井岩石开挖后围岩应力重新分布情况和塑性变形,进而确定是否采用临时支护措施,以确保施工安全。研究表明鲁村煤矿混合井围岩掘进深度大于780 m时,围岩变得不稳定,需要施加锚喷临时支护,同时增加井筒掘进荒断面,预留围岩变形空间。     

云南思小高速公路白花山隧道围岩稳定性研究

根据白花山隧道中导洞开挖过程的实际情况，在隧道开挖期间，采用地质素描法对隧道进行详细的地质描述，同时对地层、岩性、构造、地下水、围岩和边坡的变形破坏现象进行分析，对该隧道的地质条件有了更为详尽和准确地认识，然后提出了合理建议。     

十堰至天水高速公路磨河村隧道工程地质条件分析

通过对隧址区地形地貌、地层岩性、地质构造、岩土体工程地质特征等的调查,结合工程物探、地质钻探,岩体物理力学试验和地质测绘等勘察成果,分析了隧道洞身及进出口处围岩的稳定性,指出隧道施工过程中可能会遇到的工程地质问题,并提出了超前地质预报、支护、预防地质灾害、保护生态环境等施工措施和建议。     

关于锚索支护技术在柴达木盆地鱼卡公司采矿中的应用

锚索支护主要是将一定长度的低松弛高强度的钢绞线配以专用锚具,用树脂或砂浆进行锚固,通过液压千斤顶在其尾部施加预应力,达到对巷道锚固支护的一项技术。因锚索支护可以独立承担对巷道围岩的控制,该技术主要用于对常规支护的补强和围岩极为破碎的巷道支护,是矿压显现严重巷道的最有效支护方式,可以用于井下任何巷道和硐室,目前已成为青海海西州柴达木盆地海拔3200米的鱼卡公司煤矿7#煤层支护的主要技术手段。本文围绕柴达木盆地鱼卡公司煤矿的地质条件和回采工艺等应用背景,结合鱼卡公司10多年从事锚索支护技术的实际工作,就锚索支护在该采矿中应用进行了介绍和分析,并给出了成功的经验——应用锚索施工的整个工艺过程中存在的问题及其解决的关键技术。这对实际生产应用具有一定的指导意义和实用价值。     

浅谈镇安隧道围岩工程地质条件评价

通过镇安隧道工程地质特征分析、隧道围岩地质特征方面的论述,提出了隧道围岩分级的方法;进行了隧道围岩分级参数的选取研究,达到了隧道围岩分级合理选取的效果,解决了隧道施工对围岩稳定性预测的问题.     

水电工程长隧洞开挖造价问题的探讨

由于水电工程长隧洞受地质条件影响受勘测条件和勘探手段的限制以及施工难度大,变化因素多等原因其开挖造价问题较复杂。因此,在水电工程长隧洞开挖定额项目中应考虑短循环进尺因素,增加按围岩分类的补充调整系数,考虑长隧洞开挖艰难因素,补充洞长增加系数     

隧道围岩变形监测反演分析及稳定性研究

针对有限元方法模拟隧道开挖过程受参数取值影响导致精度降低问题,提出利用BP神经网络和数值模拟方法来对隧道围岩力学参数进行反演分析。对比实测值与模拟值,证明了反演参数的可靠性,并得到隧道的最大最小主应力和位移变化值;利用强度折减法,通过数值模拟计算相应的拱顶沉降值,通过离散点拟合来求得隧道围岩的自稳系数,分析隧道围岩的稳定性。     

Interaction analyses between tunnel and landslide in mountain area

This paper focuses on the analytical derivation and the numerical simulation analyses to predict the interaction influences between a landslide and a new tunnel in mountain areas. Based on the slip-line theory, the disturbance range induced by tunneling and the minimum safe distance between the tunnel vault and the sliding belt are obtained in consideration of the mechanical analyses of relaxed rocks over the tunnel opening. The influence factors for the minimum safe crossing distance are conducted, including the tunnel radius, the friction angle of surrounding rocks, the inclination angle of sliding belt, and the friction coefficient of surrounding rocks. Secondly, taking account of the compressive zone and relaxed rocks caused by tunneling, the Sarma method is employed to calculate the safety factor of landslide. Finally, the analytical solutions for interaction between the tunnel and the landslide are compared with a series of numerical simulations, considering the cases for different perpendicular distances between the tunnel vault and the sliding belt. Results show that the distance between the tunnel vault and the slip zone has significant influence on the rock stress and strain. For the case of the minimum crossing distance, a plastic zone in the landslide traversed by tunneling would be formed with rather large range, which seriously threatens the stability of landslide. This work demonstrates that the minimum safe crossing distance obtained from numerical simulation is in a good agreement with that calculated by the proposed analytical solutions.     

Time-dependent squeezing deformation mechanism of tunnels in layered soft-rock stratum under high geo-stress

Large squeezing deformation of layered soft rock tunnel under high geo-stress has a significant time-dependent deformation behavior. In this paper, we studied the deformation mechanism during the construction period of deep-buried softrock tunnel by means of a combination of field observations and a numerical method. First, a new classification criterion for large deformations based on the power exponent variation law between the deformation and the strength-stress ratio is proposed. Then, the initial damage tensor reflecting the bedding plane(joint) distribution and an equivalent damage evolution equation derived from the viscoplastic strain are introduced based on the geometric research method, i.e., a new rheological damage model(RDL model) of layered soft rock is established consisting of elastic, viscous, viscoelastic, viscoplastic and plastic elements. A field test was conducted on the Maoxian tunnel in Sichuan province, southwestern China, which is in broken phyllite(layered soft rock) under high geo-stress. The tunnel has experienced large deformation due to serious squeezing pressure, thus we adopted double primary support method to overcome the supporting structure failure problems. The rheological parameters of phyllite in the Maoxian tunnel were recognized by using SA-PSO optimization, and the RDL model does a good job in describing the time-dependent deformation behavior of a layered soft-rock tunnel under high geo-stress. Thus, the RDL model was used to investigate the supporting effect and bearing mechanism of the double primary support method. Compared with the single primary support method, the surrounding rock pressure, secondary lining force, surrounding rock deformation, and the depth of the damage to the rock mass was reduced by 40%-60% after the double primary support method was used.     

香丽高速公路昌格洛滑坡-隧道工程病害三维数值分析

准确评价滑坡-隧道相互作用及稳定性, 采用合理的病害防治方法, 对保障公路顺利完工具有重要意义。以香丽高速公路昌格洛滑坡为例, 利用现场地质调查、钻探等方法查明了滑坡成因机制以及变形特性, 通过数值模拟研究了昌格洛滑坡在天然、降雨和开挖等工况下的空间应力应变特征以及稳定性变化, 研究了隧道与所穿越滑坡之间的相互作用, 据此提出了相应的病害防治方案。结果表明: 昌格洛滑坡在自然条件下处于欠稳定状态; 隧道开挖难以引起滑坡整体失稳, 但会诱发滑坡局部变形, 受滑坡体变形影响, 穿越滑体的隧道部分将产生拉伸-剪切变形; 降雨严重恶化滑坡稳定性, 导致滑坡失稳, 进而使穿越其中的隧道失效破坏。原选线方案面临风险巨大, 最优防治方案为线路东移绕避, 使隧道从滑面以下穿过。研究方法和成果可为香丽高速公路类似病害的防治提供有益借鉴。      

Geotechnical investigations and remediation design for failure of tunnel portal section: a case study in northern Turkey

Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and anthropogenic impacts are generally reported as the most important triggering factors in the region. Following the portal slope excavations in the entrance section of Cankurtaran tunnel, located in the region, where the highly weathered andesitic tuff crops out, a circular toe failure occurred. The main target of the present study is to investigate the causes and occurrence mechanism of this failure and to determine the feasible remedial measures against it using finite element method (FEM) in four stages. These stages are slope stability analyses for pre- and postexcavation cases, and remediation design assessments for slope and tunnel. The results of the FEM-SSR analyses indicated that the insufficient initial support design and weathering of the andesitic tuffs are the main factors that caused the portal failure. After installing a rock retaining wall with jet grout columns and reinforced slope benching applications, the factor of safety increased from 0.83 to 2.80. In addition to slope stability evaluation, the Rock Mass Rating (RMR), Rock Mass Quality (Q) and New Austrian Tunneling Method (NATM) systems were also utilized as empirical methods to characterize the tunnel ground and to determine the tunnel support design. The performance of the suggested empirical support design, induced stress distributions and deformations were analyzed by means of numerical modelling. Finally, it was concluded that the recommended stabilization technique was essential for the dynamic long-term stability and prevents the effects of failure. Additionally, the FEM method gives useful and reasonably reliable results in evaluating the stability of cut slopes and tunnels excavated both in continuous and discontinuous rock masses.     

Model test on support scheme for carbonaceous slate tunnel in high geostress zone at high depth

The Muzhailing extra-long highway tunnel and corresponding inclined shafts in Lanzhou,Gansu Province,China passes through structurally complex carbonaceous slate that is under high ground stress.Rationally-designed and effective support is of high importance for achieving safe and efficient tunnel construction.The No.2 inclined shaft of Muzhailing Tunnel was taken as the engineering background prototype,for which,a similar model test was conducted to evaluate the effect of highly pretightened constant resistance(NPR,Negative Poisson’s Ratio)anchor cable support provision to the geologically complex carbonaceous slate at different depths.Two schemes were proposed during testing:one scheme was without support and the second was with asymmetric support from highly pre-tightened constant resistance anchor cable.Digital speckle displacement analysis system and micro-groundstress sensors were employed to measure the deformation and shear stress distribution of the tunnel.The results demonstrated that through the second support scheme,the deformation of the surrounding rock could be effectively ameliorated,while this support scheme was applied on the project site of the No.2 inclined shaft,to explore the rationality of the scheme through field engineering tests.On-site monitoring indicated that the deformation of the surrounding rock was within the reasonable design range and the problem of severe tunnel deformation was effectively controlled.The research methods and related conclusions can be used as a reference for the treatment of large deformation problems in deep-buried soft rock tunnels.     

In situ experiments on supporting load effect of largespan deep tunnels in hard rock

A section of the Nanliang high speed railway tunnel on Shijiazhuang-Taiyuan high-speed passenger railway line in China was instrumented and studied for its mechanical properties and performances. The cross section for the tunnel was 300 m2 and is classified as the largest cross section for railway tunnels in China. Through in situ experimental studies, mechanistic properties of the tunnel were identified, including the surrounding rock pressure, convergences along tunnel perimeter and safety of primary support and lining structure. Based on the field measured data, the surrounding rock pressure demand for large-span deep tunnel in hard rock is recommended as double peak type in the vertical direction and fold line type was recommended for horizontal pressure. The results suggested that Promojiyfakonov＇s theory was most close to the monitored value. Specific recommendations were also generated for the use of bolts in tunnel structures. Numerical simulation was used to evaluate the safety of the tunnel and it confirmed that the current design can satisfy the requirement of the current code.