Fiber optic sensing and performance evaluation of a water conveyance tunnel with composite linings under super-high internal pressures

For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the deformation and failure characteristics of lining structures under internal water pressure are not well investigated in the literature,particularly for three-layer composite linings.This study presents an in situ experimental investigation on the response of two types of composite linings(i.e.separated and combined lining structures)subjected to internal pressures,in which a fiber optic nerve system(FONS)equipped with distributed strain and displacement sensing nerves was employed to monitor the performance of the two composite linings during testing.The experimental results clearly show that the damage of the tunnel lining under different internal pressures was mainly located in the self-compaction concrete layer.The separated lining structure responded more aggressively to the variations in internal pressures than the combined one.Moreover,two evaluation indices,i.e.radial displacement and effective stiffness coefficient,are proposed for describing the changes in the structural bearing performance.The effective stiffness coefficients of the two types of lining structures were reduced by 39.4%and 29.5%,respectively.Considering the convenience of field monitoring,it is suggested that the average strains at different layers can be used as characteristic parameters for estimating the health conditions of lining structures in service.The analysis results provide a practical reference for the design and health evaluation of water conveyance shield tunnels with composite linings.

3D Finite Element Simulation of Tunnel Boring Machine Construction Processes in Deep Water Conveyance Tunnel

Applying stiffness migration method,a 3D finite element mechanical model is established to simulate the excavation and advance processes.By using 3D nonlinear finite element method,the tunnel boring machine(TBM) excavation process is dynamically simulated to analyze the stress and strain field status of surrounding rock and segment.The maximum tensile stress of segment ring caused by tunnel construction mainly lies in arch bottom and presents zonal distribution.The stress increases slightly and limitedly in the course of excavation.The maximum and minimum displacements of segment,manifesting as zonal distribution,distribute in arch bottom and vault respectively.The displacements slightly increase with the advance of TBM and gradually tend to stability.

Predictive analysis of stress regime and possible squeezing deformation for super-long water conveyance tunnels in Pakistan

The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hoek–Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey's model can subsequently be employed to predict the areas' stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai–Tibet Plateau.Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH>-Sh> SVor SH> SV> Sh. The measured orientation of SHis NEE(N70.3°–89°E), and the regional orientation of SHfrom WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stresses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.

湿陷性黄土区输水隧洞盾构施工风险评估

为了提高针对湿陷性黄土区输水隧洞盾构法施工安全评估的可靠性,从人员管理、机械材料、施工技术、施工环境4个方面构建较为完善的施工安全风险评估指标体系;利用灰色-DEMATEL方法对中心度进行处理得到风险指标权重;以风险发生概率和风险损失程度两个维度为基础构建二维云评估模型,其中发生概率由主、客观方法相结合来确定,损失程度通过改进雷达图法从人员伤亡、经济损失、工期延误、功能缺陷和环境影响5个方面来综合确定。将该评估模型运用到引汉济渭工程X输水隧洞盾构法施工项目的安全评估中。结果表明:该项目施工风险评估等级为Ⅱ级,施工安全风险程度较小,评价结果符合工程实际,验证了该评估模型的可行性和有效性。研究成果可为湿陷性黄土区类似输水隧洞盾构法施工安全风险评估提供借鉴和参考。

外水压力作用下伸缩缝防渗体系数值模拟研究

基于内聚力模型,建立了复合型防渗体系的有限元计算模型,探讨了在外水压力作用下防渗体系的剥离破坏过程。研究表明,表面涂层厚度、嵌缝深度与防渗体系抵抗变形能力成正比;随着嵌缝深度的增加,防渗体系抵抗水压变形能力的增强幅度越小,涂层厚度对抵抗水压变形能力的增强幅度影响更小;防渗体系的破坏起始点有两处,当嵌缝材料厚度较小时,破坏起始点在聚脲表面涂层与混凝土的接合处;当嵌缝材料厚度较大时,破坏起始点在嵌缝材料与混凝土黏接层下部。通过定量分析,为抵抗1 MPa的水压,推荐内嵌材料深度至少1.5 cm、表面封闭层厚度至少2 mm。

显式算法中三维黏弹性人工边界应用及输水隧洞动力响应分析

为确保大型复杂三维有限元模型动力响应分析的稳定性及高效性,结合二维黏弹性边界理论及其在动力显式分析中稳定性的改善方法,提出了一种适用于ABAQUS/Explicit模块的三维黏弹性人工边界方法,并依托某输水隧洞与临近高铁隧道的立交工程,在设有三维黏弹性边界的基础上研究高速列车振动荷载对既有水工隧洞的振动影响特性。结果表明,采用动力显式分析时,稳定性改善后的黏弹性人工边界具有良好的吸能效果,满足远域地基的回弹性能;振动荷载对输水隧洞的动力影响随着作用距离的增大而减小,且各断面的动力响应极值均出现在底板中心。

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。

穿越活动断层输水隧洞病害研究进展

穿越活动断裂带及大型城镇的输水隧洞,具有洞线长、埋深大、地质条件复杂等特点。为研究穿越活动断裂带的输水隧洞病害,归纳总结了关于穿越活动断裂带的隧洞结构变形、应力和损伤特征等方面的研究成果,对汶川地震和台湾集集地震灾区位于活动断裂带影响范围内的隧洞结构破坏统计数据进行系统整理,分析隧洞病害的主要特点、产生原因、破坏机理与案例病害类型,并将病害等级分成无病害、轻度病害、中度病害和严重病害4级。最后对隧洞病害处理措施进行归纳,并提出相应处置建议。研究结果可为输水隧洞病害的归类与处置提供参考。

我国城市地下空间盾构法隧道工程技术新进展

基于盾构施工特点,对盾构法施工技术的发展过程和创新进展进行调查研究,总结盾构法施工技术在地铁、市政公路、城市铁路、城市水工隧洞、城市综合管廊等工程中的最新应用,阐述城市盾构法隧道在地质条件多样化、越江跨海常态化、结构断面多元化、地面条件复杂化、隧道结构耐久性等方面面临的技术挑战。介绍超大直径盾构装备、大直径泥水盾构常压换刀、多模盾构、类矩形盾构隧道建造、联络通道机械法施工、软硬极端悬殊地层掘进、富水砂卵石地层土压平衡盾构、地下高地震烈度盾构隧道减隔震抗震和超长距离综合施工等技术创新成果;总结不良地质识别、设备状态实时感知、同步推拼连续掘进、盾构自动驾驶技术、盾构智能化管控平台等盾构智能掘进技术进展;指出城市地下空间建设盾构法隧道工程的发展趋势,地铁隧道、城市道路、综合管廊、城市给排水等设施需要不断更新,并网络化,盾构法隧道技术需要不断发展,盾构法隧道智能化施工需日趋精益。未来盾构装备将朝着“多模式、无刀化、外星化”等多元化,多源信息感知、管片智能拼装、地质探测预报、自主感知掘进决策等智能化以及特大直径、超长距离、超大埋深、超高水压等方向发展。

富水残积土输水隧洞水平旋喷桩和超前小导管组合支护技术研究

为了研究水平旋喷桩配合超前小导管组合支护设计参数对不良地质输水隧洞预加固效果的影响,依托广西黄章水库富水残积土输水隧洞,研究了超前小导管管径、注浆加固圈厚度、外插角、环向间距、水平旋喷桩桩径、桩间距对富水残积土地层输水隧洞拱顶竖向沉降、拱腰水平变形以及掌子面变形的影响规律,并采用局部敏感性分析方法研究了支护参数的敏感性。研究结果表明:隧洞内的拱顶竖向沉降、拱腰水平收敛、掌子面位移与超前小导管和水平旋喷桩相关参数有关;小导管外插角对拱顶竖向沉降影响最大,注浆加固圈厚度次之,小导管环向间距的影响最小;小导管注浆加固圈厚度对拱腰水平位移影响最大,小导管外插角次之,小导管管径的影响最小。利用超前小导管+水平旋喷桩组合支护对富水残积土输水隧洞进行支护时,应综合考虑各参数影响,寻求最安全经济的支护参数,确保隧洞施工安全性。

输水隧洞下穿并行高速公路施工安全风险评价

输水隧洞施工环境复杂,存在诸多风险源,为降低输水隧洞的施工风险,提出一种安全辨识与数值分析相结合的评价方法。依托珠江三角洲水资源配置工程,基于熵权-模糊综合评判法计算输水隧洞下穿、并行高速公路施工安全风险等级为偶尔发生,并采用MIDAS有限元软件对评判结果进行验证,分别计算出输水隧洞在下穿和并行高速公路期间的地表位移。结果表明,下穿造成路基最大沉降为-1.115 mm,并行桥梁产生的路基最大横向位移为0.193 5 mm,均小于监测预警值,与施工实际相符。

输水隧洞混凝土表面降糙及补强研究与应用

为确保输水隧洞长期安全、稳定高效运行,采用盾构法、浅埋暗挖法等方法施工的地下引水工程,需实施一层钢筋混凝土二衬结构,对输水隧洞混凝土衬砌表面实施有效防护保护。在常用的防护保护技术措施中,存在易脱落、表面粗糙度较大等问题,不满足输水隧洞糙率要求。文章通过材料比选及现场试验,总结出了满足糙率及补强的一套施工工艺流程,目前,已在南水北调团九二期项目中应用,可为类似的新建及检修项目提供参考借鉴。

Numerical study of the mechanical process of long-distance replacement of the definitive lining in severely damaged highway tunnels

Mountain road tunnels are prone to water leakage and lining corrosion under the complex geological conditions and corrosive envi-ronments,which will reduce the strength of the lining structure until it loses its load-bearing capacity;eventually,the definitive lining will need to be replaced.In this paper,a highway tunnel in a mountainous area in Southwest China is taken as an example.Field investi-gation found that the tunnel was seriously corroded by sulfate,the strength of the definitive lining decreased,and large-scale cracks and spalling appeared on the surface,so the operator decided to replace the definitive lining by the method of interval replacement.Based on the data obtained from drilling and coring,a numerical model of long-distance replacement of the definitive lining of the damaged tunnel is established.First,the back analysis of the calculation parameters is carried out,and the modified calculation results are com-pared with the field monitoring results for verification.Then,the deformation trend of the tunnel and the development of the plastic zone during the process of long-distance replacement of the definitive lining are studied.Finally,the construction scheme is optimized.Numer-ical analysis results show that the replacement of the definitive lining of the tunnel mainly leads to the settlement of the arch crown and the uplift of the inverted arch.The deformation of the tunnel shows two rapid growth stages and two stable stages during the replace-ment process;after replacement,the deformation of the arch crown and the inverted arch is divided into two buffer zones and one stable zone.In the progress of the replacement of the definitive lining,the plastic zone does not change.Regarding the reinforcement measures,with the increase in the grouting range,the grouting efficiency decreases,and the effect of the temporary steel arch on controlling the overall deformation is not obvious.The length of the replacement of the single section should be determined according to the geological conditions of the replacement section and the monitoring data during construction.The research results can provide a reference for sim-ilar projects for the replacement of the definitive lining.

软硬互层岩体对输水隧洞围岩稳定性的影响研究

软硬互层岩体是水工隧洞施工中经常遇到的地质环境,其对围岩安全稳定性的影响研究具有重要的理论意义和工程价值。以具体工程为依托,利用数值模拟的方式探讨软硬互层岩体的层厚比和岩层厚度对围岩应力、位移和塑性区特征的显著影响,获得相应的变化规律,可为理论研究和工程施工设计提供必要的支撑和借鉴。围岩的最大压应力和塑性区出现在拱腰部位,建议在施工中加强该部位的应力和变形监测。

化学注浆在引汉济渭秦岭输水隧洞施工过程中的应用研究

水工隧洞开挖施工过程中遇到的地下水和松软岩层工程病害问题的治理是输水隧洞工程施工中的主要难题之一。因此,以引汉济渭秦岭输水隧洞工程为背景,针对该隧洞K68+835~K68+851段开挖掌子面及边墙涌水问题,提出采用化学注浆技术进行涌水堵漏处理。首先,对节理密集带2m宽初支进行凿除,准确揭示密集带。其次,给出了涌水堵漏处理区域划分方法、区域注浆堵漏处理顺序以及拱顶、边墙、底板注浆堵漏处理顺序。最后,通过化学注浆技术在引汉济渭秦岭输水隧洞开挖掌子面及边墙涌水问题处理中的成功应用,说明该技术可以做到用于指导化学注浆在输水隧洞施工过程中涌水堵漏处理,为今后类似输水隧洞工程中的涌水堵漏处理提供借鉴。

卡利瓦大坝项目输水隧洞TBM施工管片选型分析

笔者以菲律宾卡利瓦大坝项目输水隧洞TBM施工为例对衬砌管片选型进行探讨,首先通过对比分析常用的三种管片的结构特点及适用性,选出适合该项目特点的隧洞衬砌管片型式即平行四边形管片和六边形管片;然后从设计功能要求、施工速度、成本等方面对平行四边形管片和六边形管片进行综合对比分析,最终选择采用六边形管片。研究成果可为具有洞线长、洞径小、弯段少、内水压力较小等特点的输水隧洞管片选型提供参考。

浅埋长大输水隧洞下穿省道建设施工技术研究

云南省滇中引水工程楚雄段4标段下穿S218省道,位于省道正下方的最小埋深仅为20m。为最大程度减小隧洞施工对S218省道的影响,保证隧洞施工安全、质量和进度,提出了包括采用超前固结及洞周注浆、超前支护及加强初期支护等措施在内的浅埋长大输水隧洞下穿省道施工建设技术,并结合现场量测结果,分析了该技术的现场实施效果,以及该技术的效益情况。结果表明,该技术能提高滇中红层软岩的承载能力,同时恢复或构成完整的岩体结构,进而形成连续的结构体,有利于后期系统锚杆、锁脚锚杆加固时锚固力的传递,大幅度提高加固质量和效果,有效控制隧洞变形,同时实现较小超挖,大大提高施工效率和质量,节约项目成本。

输水隧洞水温模型

输水隧洞是长距离渠系输水工程的重要组成,北方输水隧洞水温的变化严重影响下游渠道冰情的发展。研究了输水隧洞水体的热交换,包括无压隧洞气体与洞壁和水面的热交换,提出了计算水体热交换的参数化方程和水温模型,并分析有压隧洞和无压隧洞水温的时空变化规律。结果表明:有压和无压隧洞水温均随着时间或者离开隧洞进口距离的增加呈指数规律变化,分别逐渐趋近于一个大于0℃的定值,其大小与围岩恒温层温度、水温及隧洞结构和热力学参数有关。

穿越城区隧洞分离式衬砌承载机理及性能优化研究

近年来我国兴建的穿越城区引水隧洞工程采用了一种新型分离式衬砌,但其承载机理尚不够明晰。以某水资源配置工程中穿越城区的TBM施工输水隧洞为对象,建立输水隧洞分离式衬砌整体三维有限元数值模型,分析了衬砌的变形、受力和承载比等特征。结果表明:设计内压作用下,钢衬和自密实混凝土径向紧密贴合,排水板铺设范围内两者径向变形明显大于管片,排水板铺设范围外三者径向同步变形,钢衬应力水平低且分布极不均匀,管片应力超过抗裂限值,内水压主要由围岩承担,钢衬承载比例明显低于预期;降低钢衬-自密实混凝土界面、自密实混凝土-管片界面的摩擦系数,均能使钢衬应力分布的均匀性增加,有利于钢衬承载性能的发挥,且对管片抗裂有利;提高排水板厚度与综合模量比值d E,可以提升钢衬承载比,控制d E在12.4~45.1 mm 3 N范围内,可以满足钢衬容许应力和管片抗裂设计的要求,同时使分离式衬砌钢衬主要承担内水压的设计理念得以实现。

TBM法施工深埋输水隧洞变形机理研究

深埋输水隧洞施工过程中的变形机理研究,对指导工程设计、施工、变形监测均具有十分重要的意义。以某实际工程为例,采用有限元计算方法,计算分析了隧洞开挖过程中围岩及喷混凝土支护结构的变形、不同工况下支护结构的受力状态以及围岩的塑性变形情况,并通过正交试验对参数明感性进行了分析。结果表明:隧洞变形以向隧洞临空面变形为主,隧洞变形开始于距掌子面约1倍洞径、结束于掌子面超过2倍洞泾,且75%的变形均发生在开挖后;支护结构受力主要以环向压应力为主,受力最大的部位主要在洞底内侧;洞边墙围岩塑性变形比洞顶、洞底大约20%;洞泾和外水压力对隧洞受力和变形的影响十分显著,喷混凝土支护距掌子面距离和掘进步长敏感性较低。