A multi-purpose prototype test system for mechanical behavior of tunnel supporting structure: Development and application

A multi-purpose prototype test system is developed to study the mechanical behavior of tunnel sup-porting structure,including a modular counterforce device,a powerful loading equipment,an advanced intelligent management system and an efficient noncontact deformation measurement system.The functions of the prototype test system are adjustable size and shape of the modular counterforce structure,sufficient load reserve and accurate loading,multi-connection linkage intelligent management,and high-precision and continuously positioned noncontact deformation measurement.The modular counterforce structure is currently the largest in the world,with an outer diameter of 20.5 m,an inner diameter of 16.5 m and a height of 6 m.The case application proves that the prototype test system can reproduce the mechanical behavior of the tunnel lining during load-bearing,deformation and failure processes in detail.

Physical model simulation of rock-support interaction for the tunnel in squeezing ground

The existence of squeezing ground conditions can lead to significant challenges in designing an adequate support system for tunnels.Numerous empirical,observational and analytical methods have been suggested over the years to design support systems in squeezing ground conditions,but all of them have some limitations.In this study,a novel experimental setup having physical model for simulating the tunnel boring machine(TBM)excavation and support installation process in squeezing clay-rich rocks is developed.The observations are made to understand better the interaction between the support and the squeezing ground.The physical model included a large true-triaxial cell,a miniature TBM,laboratoryprepared synthetic test specimen with properties similar to natural mudstone,and an instrumented cylindrical aluminum support system.Experiments were conducted at realistic in situ stress levels to study the time-dependent three-dimensional tunnel support convergence.The tunnel was excavated using the miniature TBM in the cubical rock specimen loaded in the true-triaxial cell,after which the support was installed.The confining stress was then increased in stages to values greater than the rock’s unconfined compressive strength.A model for the time-dependent longitudinal displacement profile(LDP)for the supported tunnel was proposed using the tunnel convergence measurements at different times and stress levels.The LDP formulation was then compared with the unsupported model to calculate the squeezing amount carried by the support.The increase in thrust in the support was backcalculated from an analytical solution with the assumption of linear elastic support.Based on the test results and case studies,a recommendation to optimize the support requirement for tunnels in squeezing ground is proposed.

Vibration analysis of wind tunnel support

In order to enable a wind tunnel support to have a high enough natural frequency to prevent experiencing mechanical resonance and excessive vibration displacement, five kinds of wind tunnel support structures have been simulated and analyzed individually under five different load conditions by means of a nonlinear finite element numerical method. With natural frequency and three directions vibration displacement given, simulation and analyses indicated that additional supports is more beneficial than heightening the rigidity of steel reinforced concrete in support pillars and adopting steel wrappers on the pillars to increase natural frequency of support structure. Increasing the rigidity of steel reinforced concrete, adopting steel wrappers and providing additional supports are all helpful in reducing three directions vibration Max displacement. and additional supports are comparatively more effective. Therefore, a structure scheme with steel reinforced concrete support pillars, steel wrappers and additional supports should be adopted in practical wind tunnel support construction.

Optimization of construction scheme and supporting technology for HJS soft rock tunnel

For a soft rock tunnel under high stress in jointed and swell soft rock （HJS）, two construction schemes pilot-tunneling enlarging excavation and step-by-step excavation were optimized using FLAC20, and the deformation effects of the two construction schemes were verified by field tests. Based on engineer- ing geological investigation and mechanical analysis of large deformations, the complex deformation mechanisms of stress expansion and structural deformation of the soft rock tunnel were confirmed, and support countermeasures from the complex deformation mechanism converted to a single type were proposed, and the support parameters were optimized by field tests. These technologies were proved by engineering practice, which produced significant technical and economic benefits.

Tunnel behaviour and support associated with the weak rock masses of flysch

Flysch formations are generally characterised by evident heterogeneity in the presence of low strength and tectonically disturbed structures. The complexity of these geological materials demands a more specialized geoengineering characterisation. In this regard, the paper tries to discuss the standardization of the engineering geological characteristics, the assessment of the behaviour in underground excava- tions, and the instructions-guidelines for the primary support measures for flysch layer qualitatively. In order to investigate the properties of flysch rock mass, 12 tunnels of Egnatia Highway, constructed in Northern Greece, were examined considering the data obtained from the design and construction records. Flysch formations are classified thereafter in 11 rock mass types （I-XI）, according to the siltstone -sandstone proportion and their tectonic disturbance. A special geological strength index （GSI） chart for heterogeneous rock masses is used and a range of geotechnical parameters for every flysch type is presented. Standardization tunnel behaviour for every rock mass type of flysch is also presented, based on its site-specific geotechnical characteristics such as structure, intact rock strength, persistence and complexity of discontinuities. Flysch, depending on its types, can be stable even under noticeable overburden depth, and exhibit wedge sliding and wider chimney type failures or cause serious deformation even under thin cover. Squeezing can be observed under high overburden depth. The magnitude of squeezing and tunnel support requirements are also discussed for various flysch rock mass types under different overburdens. Detailed principles and guidelines for selecting immediate support mea- sures are proposed based on the principal tunnel behaviour mode and the experiences obtained from these 12 tunnels. Finally, the cost for tunnel support from these experiences is also presented.

Nonlinear Static and Dynamic Stiffness Characteristics of Support Hydraulic System of TBM

Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key components.The support system,an important part of TBM,is one path through which vibrational energy from the cutter head is transmitted.To reduce the vibration of support systems of TBM during the excavation process,based on the structural features of the support hydraulic system,a nonlinear dynamical model of support hydraulic systems of TBM is established.The influences of the component structure parameters and operating conditions parameters on the stiffness characteristics of the support hydraulic system are analyzed.The analysis results indicate that the static stiffness of the support hydraulic system consists of an increase stage,stable stage and decrease stage.The static stiffness value increases with an increase in the clearances.The pre-compression length of the spring in the relief valve a ects the range of the stable stage of the static stiffness,and it does not a ect the static stiffness value.The dynamic stiffness of the support hydraulic system consists of a U-shape and reverse U-shape.The bottom value of the U-shape increases with the amplitude and frequency of the external force acting on the cylinder body,however,the top value of the reverse U-shape remains constant.This study instructs how to design the support hydraulic system of TBM.

Assessment of Rock Mass Quality and Support Estimation along Headrace Tunnel of a Small Hydropower in District Mansehra, Khyber Pakhtunkhwa, Pakistan

The main purpose of this study is to classify the rock mass quality by using rock mass quality (Q) and Rock Mass Rating (RMR) systems along headrace tunnel of small hydropower in Mansehra District, Khyber Pakhtunkhwa. Geological field work was carried out to determine the orientation, spacing, aperture, roughness and alteration of discontinuities of rock mass. The quality of rock mass along the tunnel route is classified as good to very poor quality by Q system, while very good to very poor by RMR classification system. The relatively good rock conditions are acquired via RMR values that are attributed to ground water conditions, joint spacing, RQD and favorable orientation of discontinuities with respect to the tunnel drive. The petrographic studies revealed that study area is mainly comprised of five major geological rock units namely quartz mica schist (QMS), garnet mica schist (GMS), garnet bearing quartz mica schist (G-QMS), calcareous schist (CS), marble (M). The collected samples of quartz mica schist, marble and garnet bearing quartz mica schist are fine to medium grained, compact and are cross cut by few discontinuities having greater spacing. Therefore, these rocks have greater average RQD, Q values, RMR ratings as compared to garnet mica schist and calcareous schist.

基坑开挖导致邻近既有隧道变形的主动控制研究

采用有限元分析方法对新型支撑轴力主动控制系统进行了研究,提出了一种支撑轴力设计方法;在对支撑不施加主动轴力的情况下,研究了花岗岩残积土地层中基坑开挖对既有隧道的影响,根据基坑侧边不同位置隧道在基坑开挖作用下的位移划分了基坑开挖影响区;基于提出的轴力设计方法,研究了基坑开挖过程中支撑轴力主动控制对既有隧道位移的影响规律;获得了隧道位移控制到预警值10 mm以下的临界控制比,分析了其在不同隧道位置时的分布规律。结果表明:该地层中的影响区范围相对已有研究的影响区更小;隧道位移与地连墙位移的控制比近似呈正比关系;基坑腰部0.6倍挖深位置附近隧道的水平位移需进行最严格的控制,靠近基坑且深度较深的区域通过水平位移控制得到的临界控制比更小,应以隧道水平位移控制为主,而远离基坑且深度较浅的区域应以隧道竖向位移控制为主;花岗岩残积土中的基坑开挖影响区以及对临界控制比的量化研究成果可为类似工程提供参考。

西(宁)成(都)铁路高地应力节理发育软岩地层隧道支护体系研究

为保证西成铁路高地应力节理发育软岩大变形隧道安全修建,采用现场勘察、室内试验、地应力测试、工程类比、数值模拟等方法展开研究,结果表明,西成铁路与毗邻兰渝线地质条件类似,均以二叠系、三叠系板岩与砂岩为主,层理清晰、节理裂隙发育,地应力以水平主应力为主导,水平主应力在10~30 MPa之间,竖直主应力在4~13 MPa之间,有较强水平构造应力作用,兰渝线控制围岩变形主要采用增加预留变形量、自进式长锚杆、钢花管加固、增加初支及衬砌刚度、钢纤维喷射混凝土等技术措施。在此基础上针对西成铁路节理发育软岩大变形主要发生在垂直节理倾角方向上的特点,提出首先增大矢跨比,然后增大钢拱架刚度,对于Ⅲ级大变形在垂直节理方向设置预应力锚索的非对称大变形隧道支护体系,该支护体系相比传统支护体系能够减小13.8%~21.2%软岩变形,对于控制节理发育软岩变形效果良好。

小型岩孔喷浆机器人设计及其性能分析

为实现喷浆作业质量均匀稳定,本文针对岩孔喷浆过程中参数的影响及其控制进行研究,采用涂层建模、理论参数计算与实验验证方法,得到了喷枪参数、进给推进速度是关键影响因素结论。建立了涂层质量与喷枪参数模型和喷涂进给速度匹配方程,应用于实际喷浆机器人的设计和控制系统中。研制了小型喷浆机器人,完成了喷浆机器人的喷涂实验。实验表明:小型岩孔喷浆机器人可实现对模拟实验隧洞道的喷浆支护作业,本文设计的小型岩孔喷浆机器人能够满足使用要求。

风洞模型-支撑系统多维振动特性辨识与试验研究

针对风洞模型-支撑系统振动特性不明导致控制有效性差的问题,首先基于风洞模型-支撑系统的结构与原理,设计了系统振动特性辨识整体方案;其次建立了系统的等效动力学模型,通过引入动刚度对系统的俯仰、偏航维度振动特性进行了理论分析;进而提出了“正弦扫频-频谱细化-频响函数”振动特性辨识方法,并依据辨识结果建立了振动状态估计模型,将其引入控制闭环形成了基于辨识的控制方法;最后开展了脉冲响应试验与锤击试验,并对比了传统方法与基于辨识的控制方法的抑振效果。试验结果表明:俯仰、偏航维度频率响应辨识结果的均方根误差分别为0.084 0 g/V、0.007 5 g/V;且基于辨识的控制方法相较于传统控制方法将俯仰、偏航维度的等效阻尼比分别提升了1.48倍、3.00倍,具有明显优势。

大跨度隧道主动支护施工体系及现场应用研究

深入研究了大跨度隧道主动支护施工体系及其现场应用,探讨了主动支护技术的不同类型,包括锚杆支护、预应力支护系统以及其他创新的主动支护技术,并详细阐述了大跨度隧道主动支护施工体系的整体设计原则,聚焦于施工过程中的关键环节,如钻孔作业、安装支护结构、施工监测与调整,讨论了大跨度隧道主动支护施工中的安全措施和质量控制,包括施工现场安全管理、质量控制系统、应急响应与风险管理等方面,强调了这些措施在维护工程质量和保障施工安全中的核心作用。

隧道掘进机快速拆装举撑液压系统仿真

针对隧道掘进机(TBM)在施工现场因空间限制无法满足调试所需较大空地的问题,设计一种用于TBM洞内快速拆装变位的举撑液压系统。该液压系统由4组顶升单元构成,通过4组顶升单元同步运动实现TBM的起吊和举撑;液压顶升单元由4根四级液压缸、液压控制系统、激光位移传感器和机架构成。基于AMESim建立四级液压缸、变量泵和比例节流阀以及整个顶升单元的液压仿真模型,通过仿真分析负载下液压缸运动的速度、位移和压力曲线。结果表明:改变比例节流阀的输入信号可以实现四级液压缸速度的变化;泵出口压力可由比例溢流阀调整;在2.5×105 N的额定负载下,四级缸的换级工作腔压力逐级上升;随着换级,活塞杆伸出速度逐渐上升。与理论计算对比显示,建立的TBM洞内快速拆装液压系统顶升单元的AMESim仿真结果和理论值基本吻合。

柳梧铁路某隧道初期支护体系研究

针对高地应力软弱围岩变形大、混凝土层裂开、钢架弯曲等破坏现象,以柳梧铁路某隧道为例,分析了高地应力软弱围岩对初期支护的不利影响,通过现场监测和数据分析,揭示了某铁路隧道内围岩压力的空间分布规律和时间演变特性,以及初期支护体系及构件的变化情况,探讨了围岩压力在开挖过程中的变化阶段和敏感性特征。

软弱围岩浅埋大断面公路隧道支护结构参数比选

以乐汉高速为工程背景,借助有限元软件MIDAS分别构建地层结构模型和荷载结构模型,研究不同支护参数下隧道围岩变形及结构受力特征,结合结构安全系数,比选出隧道最为合理的支护体系。研究结果表明,不同初支厚度下结构受力均呈现边墙>拱腰>拱顶的分布规律,围岩变形呈现仰拱>拱顶>拱腰>边墙的分布规律,随着初支厚度的增加,结构受力及围岩变形均逐渐降低,但跌幅较小,在15 cm厚初喷C25支护下结构受力及围岩变形均满足工程要求。对于软岩浅埋公路隧道,结构安全系数最小值位于隧道拱顶,且随衬砌厚度增加而逐渐提高,采用45 cm,55 cm,65 cm厚C30钢筋混凝土结构安全系数及裂隙宽度均满足规范要求,为了节省经济,减少工程投资,二衬可选择45 cm厚C30钢筋混凝土。

TBM隧洞围岩分级方法及支护体系研究

目前TBM隧洞设计施工主要采用基于矿山法的围岩分级方法,但由于TBM法与矿山法隧洞施工存在很大差异,传统矿山法的围岩分级方法难以适用于TBM施工。为解决该问题,依托北疆供水二期工程,综合考虑围岩稳定性和围岩可掘性,选取围岩基本质量指标BQ、岩石单轴饱和抗压强度Rc、岩体完整性系数KV和岩石磨蚀性指数CAI作为评价隧洞围岩性质的主要指标,统计18台TBM集群施工收集的近3000组BQ、Rc、KV等岩性指标数据,分析各项岩性指标与纯掘进速度PR及安全系数FS的变化规律,将TBM隧洞围岩分为Ⅰ~Ⅴ级共10个亚级。在此基础上,分析了敞开式TBM的施工特性,进而采用数值模拟方法,对各级围岩在不同支护参数下的稳定性进行对比分析,提出了适用于北疆地区水工隧洞各级围岩的隧洞支护体系及支护参数,共形成7套支护体系设计图,并结合现场实际工程对本文提出的围岩分级支护体系进行验证。现场监测数据表明,本文提出的TBM隧洞围岩分级支护体系有较好的适用性。

隧道开挖对穿越隧道现有支护系统的影响

为研究垂直交叉隧道开挖时对现有隧道支护系统的影响,采用全三维有限元与弹塑性材料模型相结合的方法,研究了山区垂直穿越隧道间的相互作用。分析结果表明:新建隧道施工的影响下,水平应力较高的地区已有隧道喷射混凝土衬砌内侧处于受拉状态;在拱顶和仰拱处于受压状态,在离洞口地段受拉较大。新隧道掘进时顶部既有隧道锚杆的拉力减小,深埋隧洞上覆土层使现有混凝土衬砌产生压缩破坏,且在隧道顶板周围既有锚杆拉力显著增大。为保证既有隧道的稳定性,浅埋隧道优先安装时,既有喷射混凝土衬砌两侧需进行局部加厚,深埋隧道优先安装时,既有喷射混凝土衬砌顶部需进行局部加厚。

浅埋偏压隧道洞口钻爆设计及支护体系研究

洞口是浅埋偏压隧道工程的关键性控制节点,钻爆施工不当极易造成地表沉降过大、洞口塌方、边坡滑移等安全事故,提出一套系统完整的软弱围岩浅埋偏压隧道洞口钻爆设计方案及支护体系迫在眉睫。依托成都市东西城市轴线(东段)工程龙泉山二号隧道为工程背景,通过对开挖工法、钻爆参数、支护体系等的研究,形成了一套系统完整的软弱围岩浅埋偏压隧道洞口段钻爆施工方案。研究结果表明,超前管棚对掌子面前方围岩进行加固,形成类似拱壳的连续体,可主动承担上方围岩压力,同时管棚提供的抗剪力提高了整体的抗剪、抗弯能力,稳定了有滑移风险的岩体;管棚直径越大,地表沉降越小,控制效果越好,更有利于促进隧道掌子面稳定;采用“规范钻爆作业、优化钻爆参数设计以及大管棚超前支护”的施工方案可有效控制地表沉降,降低隧道拱顶塌方风险,确保施工安全和施工正常进行。

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 toslope 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.

大断面铁路隧道下穿富水堰塘浅埋段施工技术研究

针对隧道施工在遇到下穿富水堰塘浅埋段采用传统盖挖法施工效率低的问题,以成自宜铁路白云山隧道为背景,结合现场实际,成功研究了大断面隧道下穿富水堰塘段暗挖施工新技术。通过施工调查,选取优先疏干堰塘积水,清除地表淤泥,再进行地表注浆加固,最后隧道施工采用加强支护参数形成劲型支护体系暗挖法的技术措施,确保施工进度和安全质量。新技术解决了传统下穿富水堰塘浅埋段盖挖法施工速度慢的难题,创新了工艺技术,可在同样施工工况隧道中推广应用。