海底隧道复合衬砌水压力分布规律及合理注浆加固圈参数研究

 与普通山岭隧道不同,海底隧道深埋于海床之下,地下水的处理是其修建过程中的关键问题,而隧道渗水量控制及衬砌结构水荷载确定又是地下水处理的核心问题。采用“堵水限排”的设计理念,设计海底隧道复合衬砌结构防排水系统,可以实现以较小的排放量明显折减甚至消除作用在支护结构上的外水压力,使海底隧道衬砌结构设计更经济。基于地下水水力学理论,推导海底隧道渗水量和复合衬砌结构外水压力的计算方法,并结合厦门海底隧道工程实践,采用理论分析和数值模拟方法揭示初期支护、二次衬砌以及注浆加固圈等参数的变化对隧道渗水量和衬砌外水压力的影响规律。在此基础上,提出海底隧道复合衬砌合理注浆加固圈参数的确定方法,并在厦门翔安海底隧道穿越F4风化深槽的合理注浆加固圈参数设计中取得成功应用。研究结果可为海底隧道或富水区高水头山岭隧道工程的防排水系统设计提供借鉴和参考。     

高水压富水区隧道限排衬砌注浆圈合理参数研究

海底隧道深埋于海水以下,处于高水压富水区,隧道结构设计时需要考虑外水压力,如果采用"堵水限排"的防排水设计原则,能够以较小的排水量显著降低作用在衬砌上的外水压力,从而使隧道结构设计更加经济。注浆圈合理参数的确定是"堵水限排"的核心问题。基于穿越高水压富水岩溶区的圆梁山隧道工程,通过理论计算和分析,得到了注浆圈参数变化对隧道涌水量和衬砌外水压力的影响规律;提出了隧道排水率的概念,分析了隧道排水率与衬砌外水压力之间的关系。在此基础上提出了确定注浆圈合理参数的方法和程序,给出了圆梁山隧道注浆圈的合理参数值,并在现场得以应用,取得了理想的效果,注浆后实测隧道涌水量与理论计算值基本一致。研究结果表明:衬砌外水压力折减系数取决于隧道排水率,只有当隧道排水系统能够将渗透到衬砌背后的地下水全部排出时,衬砌外水压力才能完全消除;注浆圈的作用不是分担衬砌外水压力,而是通过封堵地下水降低隧道涌水量,从而以较小的排水量可显著降低甚至消除衬砌的外水压力。研究成果对类似高水压富水区以及海底隧道防排水设计具有一定的参考价值和借鉴作用。     

高外水压力下水工隧洞设计理念的初步探讨

高外水压力是深埋水工隧洞施工中经常遇到的难题之一,如何合理确定外水压力已成为学术界和工程界研究的重点。基于解析法和有限元法,分析渗透系数、灌浆圈厚度和排水孔对作用在衬砌上外水压力的影响,并进一步讨论外水压力作用下衬砌结构的计算模式。分析结果表明围岩渗透性越好,作用在衬砌上的外水压力越大。固结灌浆圈的折减效果受制于其渗透性及厚度,且受衬砌渗透性的影响。排水孔是减小衬砌上外水压力的有效措施,但需注意过大渗水量对环境的影响,一般可与固结灌浆联合使用。采用有限元法分析外水压力作用下衬砌结构受力时,考虑衬砌与围岩之间的接触关系是必要的。     

基于流固耦合分析的富水隧道外水压力与限量排放标准研究

隧道衬砌结构外水压力和限量排放标准是岩溶山区隧道工程建设关注的焦点。以某富水隧道为依托,借助FLAC~(3D)软件通过流固耦合数值分析,对富水隧道衬砌结构合理的外水压力取值和限量排放标准进行研究。分析了围岩无注浆条件下隧道外水压力随排水量的变化规律,进而提出了基于结构安全的隧道外水压力取值和地下水排放标准,同时分析了围岩注浆条件下隧道外水压力随注浆圈厚度和地下水排放量的变化规律,提出不同注浆厚度条件下地下水排放标准和合理的注浆圈厚度取值。     

隧道工程与水环境的相互作用

隧道工程“以排为主”的设计原则已不能适应当前水环境保护的要求,而完全封堵地下水又会使隧道衬砌难以承受巨大的水压力。从建立隧道工程与水环境的相互作用链出发,采用非稳定流法预测隧道衬砌前的涌水量,基于泰斯公式新的近似式预测洞顶含水层疏干漏斗的范围、体积和降深,基于地表水平衡方程确定恢复水环境的隧道衬砌允许渗水量,基于折减系数法计算隧道衬砌外水压力,进而归纳出“以堵为主”的“水环境平衡”的隧道设计原则,以防治洞顶水环境灾害和隧道水害,并以渝怀铁路圆梁山隧道做了算例。     

隧道外水压力确定的渗流分析方法及排水方案比较

隧道外水压力是进行隧道衬砌设计的重要因素.目前,外水压力的确定还是采用根据当地的地下水位折算外水压力的折减系数方法.这是一种粗略的折算方法,并不十分恰当.根据隧道周围岩层的水文、地质条件建立模型,采用三维拟连续介质渗流理论,通过数值计算来确定围岩衬砌上的外水压力场.工程实例计算了隧道围岩岩性为均匀的和非均匀的岩层内部的水头场分布,并设计不同的排水方案,通过计算比较了各种排渗方案的排水效果.结果显示,该方法用来确定隧道衬砌外水压力是可行的.     

泄水式管片衬砌壁后水压力分布特性模型试验研究

 基于研制的泄水式管片衬砌–围岩泄流装置,采用室内试验方法对某铁路隧道装配式泄水式管片衬砌在高水压条件下衬砌壁后水压力分布规律进行研究,重点探讨单纯限排、堵水限排等不同泄水方案下衬砌壁后外水压力分布规律。分析排泄流量、泄水孔密度、注浆与否对隧道衬砌壁后水压力的影响,揭示隧道衬砌壁后整体和各位置处外水压力折减系数、外水压力大小等与衬砌泄水孔泄流量之间的二次曲线关系。研究结果可为高水压山岭隧道衬砌的设计提供参考。     

外水荷载作用的铁路隧道衬砌结构设计探讨

本文主要运用试验分析的方法,探讨外水荷载的折减系数与渗透系数之间的关系。铁路隧道衬砌的受力模式可分为考虑和不考虑外水荷载,通过分析得知,受外水荷载较大的铁路隧道衬砌采用钢筋混凝土构成的圆形或椭圆形衬砌。     

控制排放的隧道防排水技术研究

针对控制排放的隧道防排水技术中一些关键问题,以龙潭隧道和白云隧道为依托,采用模型试验、数值仿真、现场调查等方法进行了系统研究。重点就堵水方式、防水板铺挂形式、外水压力的折减以及抗水压衬砌设计等技术问题进行了研究,提出了可通过注浆堵水圈、初期支护、防排水网格和抗水压衬砌形成综合防排水体系,它可以达到控制排放的目的。     

地铁隧道穿越城市山岭水压力取值探讨

为解决地铁隧道穿越城市山岭的水压力取值问题,对隧道设计中的勘探钻孔缺陷、水头高度取值、水压力折减系数等问题进行探讨。由于勘探钻孔不足以反映山体内部岩石的裂隙分布情况,建议对设计水头高度进行保守取值;当隧道采用矿山法施工,且设置可靠的衬砌排水系统时,可以考虑对水压力进行适当折减,其它情况不建议对水压力进行折减。     

南水北调西线工程深埋长隧洞管片衬砌结构受力分析

地应力和地下水问题对深埋长隧洞衬砌的设计及施工具有重大影响。通过数值计算对南水北调西线工程深埋长隧洞管片衬砌结构进行了受力分析,研究了围岩变形及水压力对管片衬砌结构的影响。初步研究结果表明:约90%的洞段稳定性较好,围岩变形对管片衬砌结构影响较小,可采用管片衬砌;隧洞沿线外水压力较高,是影响衬砌设计的主要因素,应采取适当的排、堵措施降低外水压力对管片衬砌结构的作用。研究结果为南水北调西线一期工程隧洞衬砌设计提供了依据。     

Design of shield tunnel lining taking fluctuations of river stage into account

Fluctuations of river stage are expected to induce changes in loads acting on the tunnel linings and cause readjustments of member forces in the segmental linings subsequently. Therefore, the evaluation of impacts of time-dependent river levels on the loads acting on the tunnel linings is of great importance in design of shield tunnel linings situated beneath the rivers. However, the loads acting the tunnel linings are generally considered as constant in most design methods available, taking no account of the influences of constantly changing river stage. In this study, the influences of river stage on design of shield tunnel linings are evaluated with respect to two common ground conditions: (a) impermeable overburden strata of low permeability and (b) permeable overburden strata of high permeability. Two earth pressure calculation models are correspondingly established. In addition, field observations in the Hangzhou Qiantang River Tunnel are described in detail to present the responses of tunnel linings to fluctuations in river stage and validate the established design model for the former case.     

深部隧洞裂隙围岩渗透特性及衬砌外水压力变化规律

高外水压岩是影响隧道开挖过岩围岩稳定及衬砌结构安全的关键因素之一,基于裂隙介质渗流经典理论,给出围岩、衬砌不同渗透系数下的外水压岩解析解,采用数值方法对隧洞二次衬砌后的外水压岩作用特性进行仿真模拟,探讨裂隙围岩岩衬砌渗透系数对渗流场的影响,围岩、衬砌渗透和排水措施岩外水压岩的相关性。研究表明岩体和衬砌渗透系数之比是影响衬砌外水压岩的关键,正确的灌浆、排水设计对外水压岩折减系数影响较大,是减小衬砌外水压岩的有效措施。结论对高压水作用下裂隙岩体渗流及衬砌外水压岩研究具有重要理论意义,对高水压下围岩注浆及衬砌结构材料选型、参数选择等具有重要岩岩实用价值。     

隧道开挖问题的水力耦合计算分析

隧道工程中的地下水问题是富水地层中普遍存在的重要问题,地下水流动对隧道围岩稳定性有重要影响。本文利用解析法给出了饱和孔隙介质地层中考虑地下水渗流力作用下的应力。位移表达式;提出了隧道水力耦合数值分析中的耦合计算模型的建立方法并进行数值模拟分析。数值计算结果表明在考虑渗流影响条件下,隧道周边位移最大增加17．0％,最大剪应力最大增加10．3％。在不考虑衬砌条件下,由于渗流引起的渗流力增加了围岩的应力、位移,从围岩-支护结构共同作用原理考虑,进行隧道支护结构设计时是应该考虑渗流效应的。     

Mechanism for buckling of shield tunnel linings under hydrostatic pressure

In this paper, the effects of segmental joints, dimensions of segments, and ground conditions on buckling of the shield tunnel linings under hydrostatic pressure are studied by analytical and numerical analysis. The results show that radial joints have significant impacts on the buckling behavior: the shield tunnel linings with flexible joints buckles in a single wave mode in the vicinity of K joint, while those with rigid joints buckles in a multi-wave mode around the linings. Hydrostatic buckling strength is found to increase with the flexural rigidity of the radial joint and the thickness of segment increasing. This study shows that ground support increases the buckling strength dramatically, while earth pressure reduces the capacity to resist hydrostatic buckling. The tunnel linings during construction are found to be easier to buckle than that during operation. Meanwhile, the buckling of tunnel linings is studied by theoretical analysis of buried tube buckling.     

The study of seepage forces acting on the tunnel lining and tunnel face in shallow tunnels

In this paper, the seepage force problems arising from the flow of groundwater into a tunnel were studied. Firstly, the effect of seepage forces acting on the tunnel lining was studied for the case of shallow drainage-type tunnels and these results were compared with the lining stresses developed for waterproof-type tunnels. This model was then reviewed through a comparison with an actual case study of the Seoul Subway Line No. 5. Secondly, the effect of seepage forces on the tunnel face stability was studied. In this study, two factors were considered simultaneously. The first factor considered was the effective stresses acting on the tunnel face, calculated from the upper bound solution of limit analysis and the other factor was the seepage forces, calculated from a numerical analysis under a steady-state of groundwater flow conditions. Consequently, reasonable design concepts applicable to the design of tunnel lining and to the evaluation of the support pressure required for maintaining the stability of the tunnel face were suggested for underwater tunnels.     

The ground reaction curve of underwater tunnels considering seepage forces

When a tunnel is excavated below groundwater table, the groundwater flows into the excavated wall of tunnel and seepage forces are acting on the tunnel wall. Such seepage forces significantly affect the ground reaction curve which is defined as the relationship between internal pressure and radial displacement of tunnel wall. In this paper, seepage forces arising from the ground water flow into a tunnel were estimated quantitatively. Magnitude of seepage forces was estimated based on hydraulic gradient distribution around tunnel. Using these results, the theoretical solutions of ground reaction curve with consideration of seepage forces under steady-state flow were derived. A no-support condition was taken into account. The theoretical solution derived in this study was validated by numerical analysis. The changes in the ground reaction curve according to various ground and groundwater conditions were investigated. Based on the results, the application limit of theoretical solution was suggested.     

隧道工程全包与半包结构防水体系受力特征试验研究

长期以来针对隧道防水该采用全包防水方案还是半包防水方案,一直是人们争论的焦点。依托厦门翔安海底隧道,对不同防排水方式（即全封堵、堵排结合及排放方式）的隧道衬砌水压力分布规律采用相似模型试验的方法进行研究,模型试验的比例尺为 1 ∶ 38.88 ,试验台架可同时施加土压和水压。通过模型试验得出结论：全封堵条件下,防水板全包、半包对衬砌背后的水压力、结构的受力无明显影响;隧道内排水后,半包段衬砌背后水压力明显减小,并随着排水量的增加,水压力基本成直线下降,并且半包段衬砌应变较全包段小,半包情况下衬砌结构受力较为有利。