Interface failure of segmental tunnel lining strengthened with steel plates based on fracture mechanics

Segmental tunnel lining strengthened with steel plates is widely used worldwide to provide a permanent strengthening method.Most existing studies assume an ideal steel-concrete interface,ignoring discontinuous deformation characteristics,making it difficult to accurately analyze the strengthened structure’s failure mechanism.In this study,interfacial fracture mechanics of composite material was applied to the segmental tunnel lining strengthened with steel plates,and a numerical three-dimensional solid nonlinear model of the lining structure was established,combining the extended finite element method with a cohesive-zone model to account for the discontinuous deformation characteristics of the interface.The results accurately describe the crack propagation process,and are verified by full-scale testing.Next,dynamic simulations based on the calibrated model were conducted to analyze the sliding failure and cracking of the steel-concrete interface.Lastly,detailed location of the interface bonding failure are further verified by model test.The results show that,the cracking failure and bond failure of the interface are the decisive factors determining the instability and failure of the strengthened structure.The proposed numerical analysis is a major step forward in revealing the interface failure mechanism of strengthened composite material structures.

Case study of performance assessment of overlapping shield tunnels with a small curve radius

Due to the network planning of subways and their surrounding structures,increasingly more overlapping shields with a small curve radius have been constructed.A newly constructed upper tunnel partly overlaps a lower one,leading to the extremely complex uplift of the lower tunnel caused by the construction of a new tunnel.Based on the shield-driven project that runs from the Qinghe Xiaoyingqiao Station to the Qinghe Station in Beijing,which adopts the reinforcement measures of interlayer soil grouting and steel supports on site,in this study,the uplift pattern of the lower tunnel and the stress characteristics of steel supports were investigated through numerical simulations and on-site monitoring.The study results show that among all tunnel segments,thefirst segment of the shield witnesses a maximum uplift displacement that increases with the horizontal space between tunnels.On using either interlayer soil grouting or steel-ring bracing reinforcement,the uplift of the tunnel lining exceeds the control value;by contrast,when these two measures are jointly applied,the uplift of the tunnel lining does not exceed a maximum value of 4.87 mm,which can satisfy the requirements of deformation control.Under these two joint measures,the soil strength between two stacked shield tunnels can be enhanced and the uplift deformation can be restricted with the interlayer soil grouting.Also,the segmental deformation and overall stability of the existing tunnel can be controlled with the temporary steel supports.The deformation of circumferential supports and segments is closely related to each other,and the segmental uplift is controlled by H-shaped steel supports.With the increase in the horizontal space between twin shields,the effect of the construction would gradually weaken,accompanied by a gradual reduction of the stresses of steel supports.Thesefindings provide a valuable reference for the engineering design and safe construction of overlapping shield tunnels with a small curve radius.K E Y W O R D Sfield monitoring,numerical simulation,overlapping shields,small curve radius,steel support stress,uplift of tunnel lining Highlights•A project of twin overlapping shield tunnels with a small curve radius is introduced.•Protective measures of soil grouting and H-shaped steel supports are proposed.•A 3D model in view of overcutting soils,grouting,and steel supports is established.•The performance of the overlapping shield tunnel with a small curve radius is evaluated.

Study on the new shell bolting and shotcrete support and its application in soft rock tunnels

A new kind of tunnel support was put forward on the basis of the anchor spraysupport principle. The mechanics of the new three-dimensional steel bar shotcrete liningsupport was studied and the structure's internal forces were analyzed. The model experiment was done relying on the industrial test. The conclusion of numerical calculationsproved that the ANSYS program is reasonable and creditable. It was compared to otherkinds of support that are commonly used in soft rock tunnels. The technique and economiccontrasts of the typical tunnel with support three-dimensional steel bar were completed.

Support elements in conventional tunneling–Focus on long-term behavior

Owing to increasing traffic and the need for constructing second tunnel tubes including corresponding cross-passages,where only one tube existed thus far,sampling of tunnel-lining materials with an age of 30–40 years has been made possible.Laboratory and in situ tests were carried out to evaluate the long-term effects of the tunnel linings.This paper presents the outcomes regarding the long-term behav-ior of support elements and membranes after performing strength tests on inner and outer lining concrete samples,flat jack tests,rock bolt tests,and tests on re-extracted sheet membranes,as well as geotextiles.Furthermore,the interface connection mechanical behavior in a double-shell-lined tunnel was investigated with laboratory tests.The aim of this research was to determine the characteristics of sheet membranes and geotextiles in the case of reduced load-bearing capacity caused by degradation of the primary lining.The results provide information on the load-sharing effects of the interaction between the primary and secondary lining,depending on the waterproofing sheet membrane and geotextile properties.Based on the results,conclusions for new design approaches for underground infrastructure construction can be formulated.

波纹钢板套衬加固大断面隧道衬砌力学性能

采用有限元软件建立了江西省某座大断面隧道地层-结构数值计算模型,对波纹钢板套衬加固隧道衬砌的力学性能进行研究。结果表明:波纹钢板套衬分担了部分围岩压力,隧道衬砌的应力出现重分布;波纹钢板套衬与既有衬砌组合结构的承载力随着锚栓数量的增加而增强,建议拱顶至拱肩区间的锚栓间距为2~3 m、拱肩至拱脚位置锚栓间距为1 m;既有衬砌和波纹钢板套衬对围岩压力的承担比呈负相关;考虑经济性和波纹钢板厚度对锚栓受力的影响,建议波纹钢板厚度不超过6 mm。

TBM有压输水隧洞内张钢圈-管片-围岩组合结构联合承载力学特性分析

为探究全断面隧道岩石掘进机(tunnel boring machine,TBM)有压输水隧洞内张钢圈-管片-围岩组合结构的受荷状态,以榕江―关埠引水工程中Ⅴ类围岩TBM有压输水隧洞段为研究对象,建立内张钢圈-管片-围岩组合结构三维精细化有限元模型,研究内水压力、围岩类型对组合结构力学特性的影响。研究结果表明:采用内张钢圈加固隧洞结构能有效控制隧洞变形,减小管片拉应力及受拉区范围,提高组合结构的承载能力;内水压力作用下管片压应力、竖向变形、接缝张开度、连接螺栓应力、内张钢圈应力、锚杆应力均较无内水压力作用下有所减小,但管片拉应力和接缝错台分别增大了19.68%、39.25%,其主要原因为内水压力作用致使隧洞结构整体呈现向外膨胀,在充水运营期间应加强内水压力作用下的安全监测;在外部水土压力和内水压力共同作用下,围岩类型的改变使组合结构中连接螺栓应力、管片接缝错台、锚杆应力分别提高37.11%、15.29%、14.75%,其主要原因为围岩岩性越差承担荷载能力越弱,在围岩类型的过渡区域应进行重点监测;此外,在外部水土压力和内水压力共同作用下,组合结构中围岩、管片、内张钢圈、锚杆的荷载分担率分别为21.38%、43.08%、24.01%和11.53%,内张钢圈荷载分担率较无内水压力作用提高了34.06%,内水压力作用提高了内张钢圈分担荷载的效果;组合结构中围岩的分担率随围岩类型(Ⅲ类、Ⅳ类、Ⅴ类)的增加而减小,相同荷载下Ⅲ类围岩的荷载分担率较Ⅴ类围岩提高了16.96%。该研究成果可为类似隧洞工程的衬砌设计及后期加固措施提供理论参考。

重载铁路隧道衬砌病害套衬整治关键技术及应用

为解决重载铁路隧道衬砌空洞、剥落掉块等问题,提出适用于重载铁路衬砌病害整治的套衬技术,即波纹板套衬和钢拱架套衬。依托大秦铁路和尚坪隧道衬砌病害整治项目,从套衬结构设计、防腐处理、施工工艺等方面进行论述,建立数值模型对套衬加固效果进行分析,并论述了波纹板套衬和钢拱架套衬结构性能及适用性。结果表明:两种套衬方案均可增加隧道衬砌的承载能力,适用于大秦铁路隧道衬砌病害整治;波纹板套衬抗弯刚度较钢拱架套衬大;钢拱架套衬施工效率和经济效益大于波纹板套衬。

小转弯半径叠落盾构隧道施工相互影响研究

【目的】受地铁规划线路与周边环境的限制,小转弯半径叠落盾构隧道的应用较多,叠落段上行隧道施工引起的邻近下行隧道结构上浮规律极其复杂,相应的加固措施有待研究。为此,【方法】以北京地铁上清桥站—清河站区间隧道工程为背景,通过数值模拟和现场监测,研究夹层土注浆和钢环撑加固措施对下行隧道结构上浮的影响规律和钢环撑受力特征。【结果】结果显示:单独采取夹层土注浆或钢支撑加固措施时的下行隧道结构上浮均超过控制值,采取联合加固措施时变形为4.87 mm;下行隧道第1环管片上浮变形最大,随着盾构间距增大,隧道结构上浮呈不断减小的趋势,数值模拟得到的最大的隧道结构上浮为现场监测的1.15倍;实测的竖撑拉应力最大为5.78 MPa。【结论】结果表明:夹层土注浆提高叠落盾构井之间土体强度并对抑制下行隧道结构上浮起到一定作用,临时钢环撑施作有利于限制管片变形,其中竖撑限制管片竖向的收敛变形,横撑限制管片水平净空收敛,纵撑限制了管片的上浮。研究成果可为类似小转弯半径叠落盾构隧道工程设计与安全施工提供参考。

地铁隧道钢管片自动焊接技术研究

为解决人工焊接隧道钢管片存在的焊接质量不可控、效率低等问题,对钢管片自动焊接技术进行研究。在传统自动焊接技术的基础上,引入3D机器视觉传感技术对钢管片角接缝进行识别,实现焊接路径的补偿和纠偏;同时,结合钢管片焊缝特征数字模拟、接缝识别编码与焊接工艺,对钢管片自动焊接成型工艺进行优化。研究结果表明:1)在3D机器视觉传感技术辅助下,采用自动焊接技术可以实现对钢管片角接缝的准确识别,与人工焊接相比,自动焊接得到的焊缝外观连续、美观、均匀性好,且焊缝内部无微观裂纹、微气孔等缺陷;钢管片腹式结构底部角焊缝交叉顶角过渡圆滑美观,经0.6 MPa加压保压后焊缝未出现渗水。2)自动焊接试验效率为单工位45 h/块,在保证焊接质量的前提下,通过焊接工艺优化与多机械手协作,自动焊接效率有望提升到20 h/块甚至更高。

钢模台车在引江补汉输水隧洞出口渐变段中的应用

引江补汉输水隧洞出口渐变段顶拱受不良地质条件的影响,出现了出口边坡变形过大引起不收敛的问题。由于施工合同工期短,若采用传统支架平面模板的方式浇筑边顶拱,则该出口段施工工期不能达到合同要求。阐述了应用定制钢模台车成功完成该输水隧洞出口渐变段边顶拱混凝土衬砌施工的过程,较平面模板的施工方式节约工期7 d。采用钢制模板施工其混凝土,外观质量优于传统平面大模板衬砌渐变段边顶拱混凝土,不仅节约了施工成本,而且为后续隧洞掘进争取了时间,所取得的经验可供类似工程借鉴。

钢箱梁顶推上跨既有线路施工临时结构研究

钢箱梁顶推施工是现阶段最常见的一种跨线、跨山河的施工方式之一,但施工前需对其进行完备的安全验算,尤其是顶推施工过程中所涉及的临时施工结构。以哈尔滨东三环快速路工程某钢箱梁顶推施工为例,对该顶推施工项目所设计的6组顶推临时支墩和2组拼装临时支架进行施工验算。结果表明,临时结构中立柱的最大应力为σ_(max)=120.1 MPa≤[σ]=190.0 MPa,腹杆的最大应力为σ_(max)=114.0 MPa≤[σ]=190.0 MPa,且均发生在顶推临时支墩上,但均能满足相关规范要求。顶推支墩和拼装支架的最大挠度分别为u_(max)=28.8 mm≤[u]=22000/300=73.3 mm、u_(max)=2.0 mm≤[u]=22000/600=36.7 mm,均能满足相关规范的要求。在顶推支墩的桩基强度验算中,其轴力和弯矩也均能满足规范要求,但在进行拼装支架的浅基础强度校核中发现,基础所受的最大应力为f=F/A=1351/(5×1.5)=180 kPa>[f]=150 kPa,所以在实际施工时需要对地基进行加固处理来满足现场施工的要求。

基于钢板加固的盾构隧道管片衬砌承载性能数值模拟研究

为了提高隧道衬砌的耐久性和安全性,本研究通过数值模拟方法,评估钢板加固对盾构隧道衬砌结构损伤和变形的抑制效果,对加固和未加固的盾构隧道衬砌结构在不同荷载比下的变形和承载力进行了对比分析。研究结果表明:(1)加固后的衬砌结构在荷载作用下的变形被显著抑制,当荷载比为0.6时,加固衬砌的竖向收敛和水平扩张分别比未加固衬砌减小了71.4%和68.3%;(2)加固衬砌在不同荷载比下的性能表现出明显的优势,尤其在荷载比为1.24时,加固衬砌的极限承载力提升了24%,极限变形程度减小了30%左右;(3)通过对加固时机前后衬砌结构的破坏过程进行详细分析,揭示了钢板加固在抑制裂缝扩展和提高衬砌刚度方面的显著效果。

导卫装置在轧线除尘中的创新应用

介绍了在轧钢生产线充分利用导卫件对轧制过程中产生的粉尘进行抑制和除尘。导卫处于粉尘的源头,根据导卫的结构添加集尘罩,结合热湿交换、惯性碰撞、静电捕获等原理,把惯性力、电场力、重力、浓度梯度力等相耦合,结合异质成核凝结相变、外部空间流场组织、内部结构流场优化等方式,实现对蒸气及粉尘颗粒的高效脱除。

组合式钢模台车在长距离隧道施工中的应用

水利水电项目隧道工程采用钢模台车进行衬砌施工,常常会遇到曲线段台车就位难度大、转角处易侵占衬砌结构面等问题,影响隧道衬砌质量和使用性能。结合长距离隧道曲线特征、断面尺寸、工作面划分等特点,将钢模台车设计成标准单元模块型式,通过标准单元模块自由组合成长度为16 m、24 m和32 m的组合式钢模台车,用于隧道衬砌施工。应用实践表明,组合式钢模台车施工效率高、工作面之间协调灵活,大幅缩短施工进度和减少台车的配置,同时在曲线段将台车分离成标准单元长度使用,更容易控制曲线隧道衬砌结构面,保障工程施工进度。

超长距离小直径污水连通管道二次衬砌建造技术研究

超长距离小直径盾构污水联通管道采用二次衬砌施工工艺时,往往面临空间狭小、施工距离长、管道线形复杂、机械化程度低等难题。以上海竹园白龙港污水连通管管道工程为依托,在其内径仅4 m、单区间最大长度达2346.3 m、转弯半径250 m段数量4个,且具有连续双S曲线的盾构隧道内实施了二次衬砌。研究表明:模板台车和组合钢模板2种二次衬砌施工工艺的组合使用,能够针对性地解决不同转弯半径隧道二次衬砌的施工难题,安全高效,有效保证污水输送期间管道的结构稳定性、防水性、抗腐蚀性和抗冲磨性,可为类似工程施工提供借鉴。

全圆多模穿行式台车在长距离水工隧洞施工的应用

采用穿行式台车可有效提升水工隧洞二次衬砌施工效率。以驷马山滁河四级站干渠(江巷水库近期引水)工程为应用对象,在盾构施工的基础上,设计了一种全圆多模穿行式台车,介绍了台车工作原理和施工重、难点,研究全圆多模穿行式台车在长距离水工隧洞的应用,提出了应用免拆堵头模板的设计思路。工程应用表明:全圆多模穿行式台车对盾构施工圆形隧洞二次衬砌有较强的适应性;相较于传统针梁式台车,全圆多模穿行式台车在施工精度、作业空间、施工进度及施工质量等方面表现优异;采用免拆堵头模板,可进一步提升穿行式台车施工效率。全圆多模穿行式台车性能高效先进,可在类似工程中借鉴应用。

铣削钢纤维在盾构隧洞内衬混凝土结构防裂中的试验研究

盾构隧洞内衬混凝土结构在温度应力和内外水压等复杂荷载作用下易出现开裂现象,影响隧洞结构安全和工程耐久性,为提高盾构隧洞内衬混凝土结构的抗裂性能,研究了掺入钢锭铣削钢纤维、粉煤灰、磨细矿粉材料改进高强泵送混凝土性能的关键技术问题,结果表明,钢锭铣削钢纤维、粉煤灰、磨细矿粉的合理掺入,对混凝土抗压强度、和易性、可泵性影响甚微,但其抗裂性能显著提高,为有效解决薄壁高强泵送混凝土结构的裂缝问题提供了可行的技术路径,研究成果可为类似结构的设计和施工提供借鉴。

浅埋偏压隧道钢拱架应力分布及变化规律与合理二衬时机研究

依托北京市密云区西统路小西库隧道浅埋偏压段工程,通过理论分析、数值模拟以及围岩监测、量测技术对该隧道钢拱架在不同施工阶段下不同部位应力变化情况进行了研究,得出了钢拱架应力分布及变化规律,获得了满足软弱围岩大断面隧道围岩位移的“空间效应”和“时间效应”的钢拱架拱顶下沉及周边收敛条件下的合理二衬时机,通过比对验证确定了最佳二衬时机,为浅埋偏压软弱围岩隧道及类似工程研究提供了借鉴。

隧道钢纤维喷射混凝土单层衬砌试验研究

为了解决隧道施工中采用单层喷射混凝土作为隧道永久衬砌的问题,对不同钢纤维及外添加剂掺量的混凝土分别进行了抗压、抗拉、抗渗以及弯曲强度等室内试验。结果表明,在喷射混凝土中加入钢纤维材料,其抗拉、抗弯以及抗渗水性能分别提高了65.6%、94.7%、98.1%;并通过现场试喷,选定符合设计要求、经济合理的配合比,在摩天岭隧道通风斜井施作了湿喷钢纤维混凝土,以单层衬砌代替原设计的复合式衬砌。工程实践证明,钢纤维湿喷混凝土,其支护强度达到了设计要求,喷射作业回弹损失量减少7%～15%。研究成果可为类似隧道纤维喷射混凝土单层衬砌技术的应用提供参考。

隧道钢纤维喷射混凝土性能试验及其工程应用

根据钢纤维喷射混凝土结构力学原理,为了研究钢纤维混凝土喷层在隧道单层永久衬砌支护中适用性,先分析钢纤维在混凝土中的增强力学作用机制,然后完成钢纤维喷射混凝土合理配比、抗拉、抗压、抗折及抗折初裂强度和弯曲性能等指标的室内试验;并结合具体的隧道现场喷射试验,以及围岩应力、钢纤维混凝土喷层应力及洞周附加水平收敛等监测数据进行分析。研究结果表明,钢纤维喷混凝土抗拉、抗折强度高,韧性好,喷层中的应力分布较均匀,具有较好的让压能力,喷射作业回弹损失量减少,说明钢纤维喷射混凝土是一种理想的单层衬砌支护材料,具有较好的推广应用价值。