元磨高速公路某连拱隧道围岩稳定性三维数值仿真

以元磨高速公路的一座连拱隧道作为工程背景，采用三维连续介质快速拉格朗日元模拟直墙连拱隧道的施工工况，得出了施工过程中隧道围岩位移、应力和塑性区分布规律。     

偏压连拱隧道围岩稳定性数值仿真

连拱隧道作为公路隧道新的结构型式,理论上还不成熟,特别是在复杂应力条件下隧道的应力、位移分布及稳定性研究很少.文章以元磨高速公路的一座连拱隧道作为工程背景,采用三维连续介质快速拉格朗日元模拟偏压条件下直墙连拱隧道的施工工况,得出了施工过程中偏压连拱隧道围岩位移、应力和塑性区分布规律,这对今后偏压条件下连拱隧道的设计和施工具有一定的理论意义和应用价值.     

不对称双连拱隧道施工方法研究与应用

针对不对称双连拱隧道施工中不同工况下的应力和位移情况,运用MIDAS/GTS数值模拟软件建立计算模型,对IV级围岩开挖过程进行模拟分析,得到了分别采用三导洞台阶法和中导洞台阶法开挖施工过程中的隧道应力及位移数值,通过与围岩位移、沉降、压力及二衬弯矩实测数据的对比分析,为不对称双连拱瞇道的设计和施工提供一定的理论依据及借鉴。     

软弱破碎连拱隧道松动区模型试验与分析

工程中连拱隧道围岩松动范围的确定对采取合理的支护手段和方法具有重要的理论价值和实际意义。以埋深100 m的公路连拱隧道为研究对象,利用室内模型试验,对软弱破碎围岩松动区的发展过程及范围进行研究,并采用压力盒量测围岩不同部位的应力,分析围岩松动区的应力场特征。利用FLAC软件对模型试验进行数值模拟,通过应力分析法和极限拉应变法判别松动区范围,并与模型试验结果进行对比分析,发现松动区内围岩切向应力大于径向应力,深埋条件下围岩更容易形成压力拱,应力分析法所得的松动区与模型试验结果更为接近,建议深埋隧道采用应力分析法判断松动区范围。     

双连拱隧道模型试验研究

结合某双连拱隧道实际工程,利用相似模型在Ⅱ、Ⅲ类围岩条件下,采用三导坑法、双导坑法和中导坑拓展法三种施工方法进行模型试验研究。得出：最大的周边径向位移发生于拱顶,其次为拱腰部位,径向位移收敛警戒值的范围不能超过10 mm；从洞室的失稳特征分析,衬砌最容易在隧道边墙及中墙与衬砌搭接处出现裂缝；通过模型试验得出了连拱隧道在Ⅲ类围岩中采用中导坑拓展法施工,对围岩扰动较小,有利于隧道稳定的结论。     

基于流固耦合理论的连拱隧道围岩稳定性分析

以湖南省常吉高速公路新修建的一些大跨度连拱隧道为工程背景，基于流固耦合分析理论，利用快速拉格朗日有限差分法对连拱隧道围岩稳定性进行分析。主要考虑流固耦合效应作用时，围岩级别、隧道埋深、地下水位以及施工工法和初期支护等因素对围岩稳定性的综合影响，得到Ⅲ，Ⅳ，Ⅴ级围岩在各种情况下隧道开挖后围岩最大主应力、洞周位移、塑性区、孔隙水压力分布以及喷锚支护受力特征等结果，探讨连拱隧道开挖渗流机制，并分析深埋连拱隧道开挖后的孔隙水压力场分布特征。研究结果直接指导该高速公路二期工程中的隧道防排水施工和支护措施的改进提高，为富水地层条件下的隧道工程开挖设计提供一定的理论参考。     

连拱隧道围岩压力的释放率分析

连拱隧道作为公路隧道新的结构型式,理论上还不成熟.以云南省元磨高速公路的两座连拱隧道作为工程背景,按弹性阶段相似原则进行两组连拱隧道室内模型试验,包括隧道处于常规应力状态下和偏压状态下的模型试验.采用压力盒量测施工过程中隧道围岩压力,并提出了围岩压力释放率的概念,对连拱隧道开挖过程中围岩压力的变化特征进行了分析,同时对两种应力状态下的试验结果进行了对比分析.得出的结论对连拱隧道的设计和施工有积极的指导作用.     

偏压连拱隧道渗流-应力耦合分析及处治技术研究

基于渗流-应力耦合分析理论模拟偏压连拱隧道开挖过程,分析连拱隧道在偏压条件下围岩位移变形特性及稳定性的影响,给出偏压连拱隧道施工过程中左洞上台阶与中隔墙连接处、以及右洞拱腰处为相对薄弱位置并有针对性地进行处治。     

较差地质连拱隧道开挖方案及施工顺序的探索

通过对云南富广高速公路银厂连拱隧道施工过程的分析,并对比邻近在建连拱隧道的不同施工方法,分析了偏压连拱隧道在采用不同开挖顺序施工时各阶段围岩的应力、应变状况,得出了一些结论,为今后类似连拱隧道的施工提供了合理建议。     

支护参数对大跨度双连拱隧道稳定性的影响分析

我国连拱隧道支护结构设计过程中,无现成的计算理论和相应的规范、规程,主要采用半经验半理论的方法进行荷载的计算和结构设计。本文以灯草塘大跨度双连拱隧道为依托,针对该类型隧道在不良地质情况下,是否采用锚杆支护分别进行了三维隧道数值模拟计算,研究了隧道在是否采用锚杆支护的情况下,其围岩位移、围岩应力、塑性区的分布和剪切应变率的区别,分析了大跨度双连拱隧道的中隔墙应力分布情况。结合工程实例,阐述了锚杆在大跨度双连拱隧道的稳定性中起到明显的作用,为类似工程的建设提供参考。     

Design and construction aspects of deep tunnels (with particular emphasis on strain softening rocks)

A series of railway tunnels will be dug through the European Alps at depths exceeding 2000 m over long stretches. The prevailing high stresses are expected to cause rock burst, large deformations and creep, depending on the nature of the rock. In the first part of the paper the theoretical relations between support pressure and tunnel wall displacements are briefly discussed. Emphasis is given to the post-failure behaviour of the rock mass and its influences on the tunnelling conditions. Frequently encountered strain softening rock types are shown to exhibit a strong dependence of the tunnel stability on the softening rate, which itself varies with the applied confinement pressure. Also discussed are results of laboratory tests and field observations which yield a critical deformation value for a given rock type. Beyond this value, the required support pressures are shown to increase sharply. Systematic monitoring of the rock deformations due to tunnelling can help to define the most adequate support measures and to improve the input values for static calculations by back analyses. Deep tunnels require support types able to control the tunnel wall displacements efficiently. They should oppose significant support pressures from incipient deformations up to large displacements. Various constructive solutions are discussed for-drill & blast as well as for TBM excavation. The last section briefly addresses time-dependent tunnel deformation and their influence on the time of placing the final lining.     

Case studies of groundwater flow into tunnels and an innovative water-gathering system for water drainage

Groundwater inflow into tunnels can constitute a potential hazard and also is an important factor influencing the speed of tunnel excavation. In this paper the results of numerical modelling are presented to investigate the groundwater flow and the distribution of the pore pressure around tunnels. Two types of tunnels, double-arch tunnel and twin-tube tunnel, were studied. Potential leakage places are identified for the two types of tunnels. The most permeable place in the double-arch tunnel is at the contact interface between the middle wall and the overlying rock. The results of numerical modelling are compared with field observations in the case studies. Based on the results of numerical modelling and the field investigations, an innovative water-gathering system for reducing water leakage was proposed and applied in some tunnels on ChangJi Expressway in China. The water-gathering system can be quickly glued to the rock surface and easily installed for tunnelling. It can be applied in tunnels where water-bearing fractures are well-developed in the rock mass.     

流变岩体中既有隧道与新建平行隧道相互影响的理论解

在流变岩体中进行隧道施工时,既有隧道与新建隧道的相互作用将使围岩应力、位移分布与单隧道问题有明显不同,且与时间相关。针对黏弹性岩体中深埋双圆形隧洞考虑施工顺序问题,用复变函数方法、Laplace变换、黏弹性叠加关系导出两隧道周边开挖增量位移和应力场的求解方法和理论解答,并与有限元解进行了比对。根据解答分析了既有和新建隧道孔边增量位移与全应力分布特点;隧道周边增量位移随时间的变化;周边位移随隧道间距的变化规律。可用于黏弹性岩体中双圆形隧道顺序开挖的施工分析。相比数值方法,理论解可更方便地进行参数分析和初步设计。     

Stability analysis and optimization of excavation method of double-arch tunnel with an extra-large span based on numerical investigation

The Xiamen Haicang double-arch tunnel has a maximum span of 45.73 m and a minimum burial depth of 5.8 m. A larger deformation or collapse of the tunnel is readily encountered during tunnel excavation. It is therefore necessary to select a construction approach that is suitable for double-arch tunnel projects with an extra-large span. In this study, three construction methods for double-arch tunnels with extra-large spans were numerically simulated. Subsequently, the deformation behavior and stress characteristics of the surrounding rock were obtained and compared. The results showed that the double-side-drift method with temporary vertical support achieves better adaptability in the construction of such tunnels, which can be observed from both the numerical results and in situ monitoring data. In addition, the improved temporary support plays a critical role in controlling the surrounding rock deformation. In addition, the disturbance resulting from the excavation of adjacent drifts was obvious, particularly the disturbance of the surrounding rock caused by the excavation of the middle drift. The present findings can serve as the initial guidelines for the construction of ultra-shallowly buried double-arch tunnels with extra-large spans.     

隧道浅埋段的超前地质预报与监控量测

隧道超前地质预报与监控量测是新奥法施工不可缺少的一部分,能够准确预报掌子面前方一定距离内围岩质量的好坏,并实时通过围岩变形的监测与分析检验围岩是否稳定及支护是否合理。结合杉溪隧道工程实例,通过对隧道浅埋段的超前地质预报和监控量测数据进行分析研究,得出隧道浅埋段围岩变形速率受施工干扰影响较大,钢支撑内力及围岩压力与围岩断面变形量变化趋势基本一致。通过研究隧道浅埋段的围岩变形规律和支护结构受力特征,可为以后类似项目积累经验,提供施工依据。     

剪胀对地下工程岩体位移的影响——以加拿大Donkin-Morien隧道为例

根据建立的岩石剪胀角模型,分析岩石峰值内摩擦角和剪胀角的关系,得出岩石在零围压时的峰值剪胀角小于并近似等于峰值内摩擦角,并假设岩石和岩体的剪胀角遵循相似的变化趋势,结合Hoek-Brown强度准则和GSI岩体分级系统,实现剪胀角模型从完整岩石到岩体的转化。采用程序语言在FLAC3D中编写岩体剪胀角模型程序模块。以加拿大Donkin-Morien隧道为工程实例,研究围压和塑性剪切应变依赖的岩体剪胀对隧道渐进开挖过程中围岩位移的影响,论证恒定的剪胀角值不能准确表达隧道开挖边界附近的岩体位移,而考虑围压和塑性剪切应变为影响因素的岩体剪胀角模型能够合理描述围岩的位移分布,模拟结果与实际测量值具有很好的一致性。研究成果可为岩体非线性力学行为的研究和地下工程岩体的稳定性控制提供理论和实践基础。     

A closed-form elastic solution for stresses and displacements around tunnels

A closed-form plane strain solution is presented for stresses and displacements around tunnels based on the complex potential functions and conformal mapping representation. The tunnel is assumed to be driven in a homogeneous, isotropic, linear elastic and pre-stressed geomaterial. Further, the tunnel is considered to be deep enough such that the stress distribution before the excavation is homogeneous. Needless to say that tunnels of semi-circular or “D” cross-section, double-arch cross-section, or tunnels with arched roof and parabolic floor, have a great number of applications in soil/rock underground engineering practice. For the specific type of semi-circular tunnel the distribution of stresses and displacements around the tunnel periphery predicted by the analytical model are compared with those of the FLAC^2D numerical model, as well as, with Kirsch's “circular” solution. Finally, a methodology is proposed for the estimation of conformal mapping coefficients for a given cross-sectional shape of the tunnel.     

隧道开挖引起地表下沉及其影响分析

针对地下隧道开挖引起的地表下沉问题,运用概率统计理论建立了数学模型,并根据BP神经网络理论,通过对BP神经网络算法的改进,采用反分析方法确定岩体移动变形参数。利用所建模型对隧道开挖引起的地表垂直移动(下沉)进行了具体的计算分析,将理论计算值与实测下沉值进行对比,二者十分吻合。对比结果表明,所给出的数学分析模型及参数确定方法符合工程实际,为解决地下隧道开挖引起地表下沉预计分析问题开辟了新的途径。     

地下水影响下裂隙岩质边坡变形的Fuzzy测度分析

根据裂隙岩质边坡工程实际,采用 Fuzzy 数学理论中的 Fuzzy 测度理论,将工程开挖引起裂隙岩质边坡移动变形这一客观现象视为一模糊事件,依此建立了在地下水影响下岩体移动变形预测分析的 Fuzzy 测度模型。利用该模型可对边坡岩体移动变形参数进行反分析,并可对边坡开挖过程中引起的岩体移动变形进行定量计算,进而对地下水影响下岩质边坡总体稳定性和稳定程度进行预测。对已有的矿山边坡岩体移动变形及其稳定性进行了具体的分析预测,结果符合工程实际。