软土盾构隧道纵向设计综述

软土盾构隧道纵向设计综述软土盾构隧道发生过量的纵向沉降或不均匀沉降,引起隧道渗水、漏泥或结构局部破坏,有时甚至会影响到隧道的正常运营[20][21]。

因此,深入研究软土盾构隧道纵向变形对隧道结构影响及考虑纵向变形的衬砌结构纵向设计理论是解决软土盾构隧道现存问题的关键,尤其是衬砌结构纵向设计方法。

2衬砌结构纵向设计现状目前,国内外对盾构法隧道衬砌结构设计主要采用横向设计。

在国内,我国地下铁道及铁路隧道设计规X[6]中推荐使用荷载结构模型,而未考虑纵向变形的影响。

《XX市地基基础设计规X》1999版中对盾构隧道纵向变形进行了一定的考虑[7],提出盾构隧道纵向不均匀沉降的影响是不可忽视的。

尤其是盾构工作井和区间隧道的连接处;隧道底部下卧土层特性及分层突变处;覆土厚度急剧改变处等,都会有较明显的不均匀沉降。

提出在设计中应按照预估的沉降差,设置适量的变形缝。

规X还提到在施工阶段和使用阶段,进行隧道结构的横向内力和变形计算时,在必要的时候宜考虑隧道纵向变形对横向内力和变形值的影响。

目前,国内针对软土盾构法隧道采用的设计模型主要为匀质圆环和弹性铰法[13～17],皆可用弹性方程解。

前者主要用于使用阶段的设计验算,后者主要用于施工阶段的设计验算。

在国外,国际隧道协会(ＩｎｔｅｒｎａｔｉｏｎａｌＴｕｎｎｅｌＡｓｓｏｃｉａｔｉｏｎ)在1978年成立了隧道结构模型研究组,收集各会员XX用的地下结构设计模型。

并于200 0年编写出了《盾构隧道衬砌设计指南》[8],为各国盾构隧道结构的设计指明了基本原则。

其中将结构模型分为四类:连续体或不连续体模型、作用与反作用模型、收敛-约束模型和工程类比法。

这与我国学者XXX、侯学渊[5]的分类(经验类比模型;荷载结构模型;地层结构模型;收敛限制模型)基本相同。

同时在《盾构法隧道设计指导》中提出在必要时将隧道纵向沉降的影响列入荷载类别的特殊荷载项予以考虑。

美国交通运输研究协会在2000年度报告[9]中就提到,很多处于软土中的隧道、管道的破坏或出现问题就是由于纵向不均匀沉降而产生的。

最多的一种情况就是由于下卧土层土性沿纵向分布不均匀而产生的纵向不均匀沉降。

因此美国交通运输研究协会在2000年提出了隧道“纵向设计”的概念,并计划开始进行这方面的研究工作。

由此可见,在现行的设计规X中还没有纵向设计的相关内容,但是,结构的纵向问题对结构的影响已经引起广大学者关注。

因此,开展纵向设计相关研究具有重大现实意义。

免费论文下载中心.hi138. 由于隧道纵向问题属于三维问题,其结构复杂,纵向结构计算模型尚不成熟。

但也已经取得了一定的科研成果。

在工程实测和室内试验基础上,已建立了一些隧道纵向结构计算模型。

目前对软土隧道纵向结构的理论研究主要分为:试验或实测分析法、数值分析法和理论解析法。

在理论解析法中根据隧道接缝和螺栓简化方法的不同,日本学者提出了两种隧道纵向结构理论,一种是以村上博智及小泉淳[22]为代表的以轴向、剪切和弯曲弹簧模拟接缝和螺栓、以梁单元模拟衬砌环的梁一弹簧模型,它是将横向梁一弹簧模型移植到了隧道结构纵向(见图3);纵向粱一弹簧模型中每一衬砌环均由一直线粱模拟,各衬砌环间的接缝以弹簧模拟,因而在作纵向分析计算时单元较多,它可以模拟衬砌环和接缝性能有变化的隧道段,但其缺点也是明显的,即一般适合于线性分析,并且由于以单元作为基础,分析过程为矩阵形式,需要通过数值方法实现,所得结果需要进行再一次分析才能得到管片、螺栓应力和接缝X开度等关键数据。

另一种模型是以志波由纪夫及川岛一彦[23～25]为代表的等效轴向刚度模型,该方法认为隧道在横向为一均质圆环、在纵向以刚度等效的方法将有环向接缝非连续的结构等效为连续均质圆筒。

由于是直接从分析衬砌环向接缝和螺栓的受力变形性能出发得到等效模型,因此计算结果可直接给出管片和螺栓应力,并且在很多情况下可推导得到显式理论解,应用方便,但该方法也有未考虑预应力、只简单被认为是弹性地基上的直梁等缺点,然而,根据目前国内外的研究现状来看,轴向等效刚度方法是当前隧道结构的纵向理论研究中提出的最好的方法。

该法为研究盾构隧道纵向问题奠定了坚实的理论基础。

3盾构隧道结构拼装型式盾构隧道结构是由管片在环向和纵向通过螺栓连接而成的非连续结构。

由于预制钢筋混凝土管片经济、耐久及强度高,所以成为目前国内外的盾构法隧道管片的主要形式。

盾构隧道衬砌结构拼装型式有两种:错缝拼装衬砌与通缝拼装衬砌[10][11][12][19]。

这两种拼装型式的不同之处在于;错缝拼装衬砌由于相邻环管片间结构刚度沿环向分布的不同,虽然受到的初始荷载基本相同,但结构变形却不同、引起的地层反力不同,地层反力的不同又加剧了结构变形的不同。

由于相邻环之间存在联系,如连接螺栓、环面凹凸榫槽和环面间的摩擦又阻碍了结构变形的不同,使结构变形与荷载及地层反力分布的不同限于一定的X围之内。

而通缝拼装衬砌由于相邻环管片间结构刚度沿环向分布相同,受到的初始荷载也基本相同。

因此,结构变形基本相同、引起的地层反力也基本相同。

虽然,通缝拼装衬砌每一环横向变形也受到相邻环的嵌固和约束,但这种约束和影响的效应错缝比通缝更显著。

衬砌环间的这种相互作用非常复杂,因此错缝衬砌内力与变形的计算也比较复杂,其计算模型与计算方法还在深入研究之中。

在我国,XX先期施工的盾构法隧道基本采用通缝拼装形式,而XX近期建设的隧道及XX和XX地铁盾构法隧道则全部采用错缝拼装形式,从而说明错缝拼装形式在抵抗纵向变形上优于通缝拼装形式。

既然不同的拼装形式有不同力学效果,能够改变衬砌的纵向刚度及控制纵向裂缝和不均匀变形,那么采用更多不同力学效果的拼装形式就成为解决当前软土盾构隧道结构纵向问题的另一关键问题。

4软土盾构隧道结构存在问题从当前工程设计的实际应用和理论研究进展分析可得出软土盾构隧道衬砌结构在考虑纵向问题时的不足之处:缺乏与纵向理论要求接近的衬砌形式;现有的纵向理论缺乏与工程实际的结合;衬砌拼装形式单一(不能协调纵向不均匀变形);衬砌管片材料在同一工程中单一;衬砌管片宽度在同一工程中单一;纵向线形不合理。

5软土盾构隧道纵向设计展望为克服软土盾构隧道现存问题,必须从以下两方面来解决:(1)从软土盾构隧道衬砌管片拼装形式、管片材料等方面进行创新改造。

以增大软土盾构隧道衬砌结构的纵向刚度的变化,使软土盾构隧道衬砌结构的纵向刚度具有可控性。

而不同刚度的多样的衬砌结构拼装形式是解决软土盾构隧道纵向问题成为可能。

(2)在纵向设计理论研究及其成果应用上应有所加强。

隧道纵向结构性能的研究和横向性能研究相比还处在早期发展阶段,其成果尚未应用到工程设计的实践中。

如何将已有的理论研究成果应用于工程设计(即纵向设计),使工程设计更加符合客观现实。

这不仅符合当前设计理论发展的趋势,更能实现在设计阶段上就开始着手解决软土盾构隧道现存问题(过量的纵向沉降或不均匀沉降,导致隧道渗水、漏泥或结构局部破坏而影响隧道的正常运营),避免软土盾构隧运营后再进行处理的被动状态,因此,可节约大量资金。

总之,软土盾构隧道结构纵向设计理论,不仅是软土盾构隧道结构设计理论发展的需要,也是社会发展的需要。

它不仅具有理论价值,而且更具重要的经济意义和社会意义。

Design of Shield Tunnel in Soft Soil Longitudinal SurveyAs the world economy, globalization and social progress, people have their own quality of living environment of rising demand, resulting in rapid increase in the level of ur banization, cities have been expanding. Cities bee the world's countries and regions of poli tical, economic and cultural development centers. However, to the sustainable development of urban construction, resource conservation and environmental protection, urban developm ent and utilization of more and more builders of all can take advantage of the limited livin g space, especially in urban underground space, in order to build water supply, drainage,energy and transport underground tunnel. However, with the development and utilization of underground space, a growing number of underground structures due to the use of the process of non-uniform deformation caused the excess of the underground structure itself and the surrounding environment has bee even more serious [1] [2]. For example, in the ground under the effect of hydrodynamic pressure, the Shanghai Jinshan water diversion project in the shield tunnel (see Figure 1), the horizontal layers of soil and water into the tunnels and the resulting vertical settlement and bending, resulting in circumferential seam s further open and soil erosion increased, eventually lead to devastating and destructive ho rizontal vertical deformation force status, the maximum relative differential settlement reach ed 18cm, the largest transverse diameter of more than 10cm [3]. Shanghai Metro Line in April 1995 formally pleted and put into operation. After long-term deformation monitoring found that the tunnel in the long-term operation of the settlement and differential settleme nt quite large, many of the tunnel section of settlement and differential settlement has bee n developing, and there is no trend of convergence [4]. To the end of 2001 the People's Square station - the interval between the Xinzha Station tunnel maximum total settlement of more than 200mm; Huangpi Station - the People's Square Station tunnel differences in the interval between the settlement of nearly 100mm (see Figure 2). Too much has been uneven deformation of the structure of the tunnel, joint water threat. So far, although the segment of the destruction of rare, but on the 1st line has been found between the balla st and tube sheet cracking phenomenon occurring in the Hanzhong Road Station to Statio n Huangpi of at least five have been found between the overall track bed and segment an d the gap between the cracking phenomenon, intermittent totaled 300m. After investigation found that are basically a large part due to uneven settlement of the tunnel caused by [5]. In addition, as the vertical deformation caused by uneven deformation of the segment joints increases, on the 1st line of the tunnel ranges in many areas of water seepage an d leaking points, mainly in girth, cap connected to the block of 'cross-stitch', etc., while t he ring seam leakage is the most difficult to deal with. With the development of uneven d eformation of the vertical tunnel, tunnel leakage increasing number of cases, and even affe ct the normal operation of the MTR.The current practice of building a large number of underground tunnels, the shieldconstruction method has bee a major urban underground construction method of tunnel c onstruction, particularly in metro tunnels. Shanghai's existing subway line and is being buil t using this method of construction without exception. In Shanghai, like with many coastal cities are located in soft soil strata are widely distributed on the shield tunnel structure i s the soft soil environment in which a large number of operations leading to soft soil Shi eld Tunnel excessive vertical settlement or differential settlement, causing the tunnel water seepage, leakage or structural partial destruction of mud, and sometimes affect the normal operation of the tunnel [20] [21].Therefore, the in-depth study of soft soil shield tunnel longitudinal deformation ofthe tunnel structure and consider the impact of the vertical structure of vertical deformati on of the lining of the design theory to solve the existing problems of soft soil shield tun nel key, in particular the vertical lining structure design methods.Two vertical lining structure design of the status quoAt present, the right domestic and international structural design of shield tunnel lining used mainly horizontal design. In China, China's Mass Transit Railway and the railway tunnel design specification [6] remended the use of load structure model, without conside ring the impact of vertical deformation. 'Shanghai-based foundation design code '1999 ver sion of the vertical deformation of shield tunnel, which must be considered [7], proposed shield tunnel longitudinal impact of uneven settlement can not be ignored. Especially the s hield work well and interval tunnel junction; tunnel lying under the bottom layer of soil ch aracteristics and mutation Branch; Futuhoudu drastically changed Department, will have a more significant differential settlement. Made in the design should be in accordance with t he estimated differential settlement, set an appropriate amount of deformation crack. Specif ication also referred to in the construction phase and use phase of the tunnel structure, t he horizontal internal force and deformation calculation, when necessary, should take into account the vertical deformation of the tunnel horizontal internal force and deformation effe cts.At present, the domestic soft soil for the shield tunnel design models used primarily for homogeneous ring and flexible hinge method [13 ~ 17] may apply to use elastic e quations. The former is mainly used for checking the use of stage design, which is mainl y used for checking the construction stages of the design. In other countries, the Internati onal Tunneling Association (InternationalTunnelAssociation) was established in 1978, the tun nel structure model of study groups, the collection of all Member States to adopt the und erground structure design model. And in 2000 prepared a 'Shield Tunnel Lining Design Gu ide' [8], for countries to shield the design of the tunnel structure pointed out the basic pr inciples. Structural model which will be divided into four categories: a continuum or contin uum model, the role and reaction models, convergence - a constraint model and engineeri ng analogy. This Chinese scholars Liu Hang, Hou Xieyuan [5] classification (experience in analog model; load structure model; stratigraphic structure model; convergence limit model) basically the same. At the same time in the 'shield tunnel design guidelines' when neces sary, will be proposed in the settlement of the tunnel vertical load categories included in t he special load options to be considered. U.S. Transportation Research Institute at the 200 0 annual report [9] mentions that many in the soft soil of the tunnel, pipeline damage orproblems that arise due to uneven settlement of the vertical. Up to a situation that is lyi ng under the soil due to its rural character and unevenly distributed along the longitudinal differential settlement resulting from the vertical. Therefore, the U.S. Transportation Resear ch Institute in 2000 to the tunnel 'longitudinal design' concept, and plans to start research work in this area. This shows that in the current design codes are also not related to th e contents of the vertical design, but the structure of the vertical structure of problem has attracted broad attention and scholars. Therefore, to carry out longitudinal research design is of great practical significance.Reposted elsewhere in the paper for free download .hi138.As the tunnel vertical issues are three-dimensional problem, its plex structure, vertical structure calculation model is not yet ripe. But it has also made some achievements i n scientific research. In engineering measurement and laboratory test, based on a number of tunnels have been established model of the vertical structure calculation. Present the ve rtical structure of soft soil tunnel theoretical study can be divided into: testing or measure ment analysis, numerical analysis and theoretical analysis method. In theory, analytical met hod, in accordance with the tunnel joints and bolt to simplify the different methods, the J apanese scholars have put forth a theory of vertical structure of the two tunnels, one is b ased on Chi and Koizumi, Atsushi Murakami [22] as the representative to axial, shear and bending spring simulation joints and bolts, in order to beam element simulation of ring b eam lining a spring model, which is the horizontal beam-spring model of vertical migratio n to a tunnel structure (see Figure 3); vertical beam-spring model, each lining both Centra l by a straight line beam simulation, the lining of the joints between the rings to spring s imulation, thus making a more longitudinal analysis of the calculation unit, which can simu late the performance of lining of the Central and joints have changed the tunnel section, b ut its shortings are obvious, which means they are suitable for linear analysis, and due to the unit as a basis for analysis in matrix form, achieved through numerical methods, the results of an analysis of the need to get re-segment, bolts degree of stress and open joi nts and other key data . Another model is Shiba and Yukio Kawashima, Kazuhiko [23 ~ 2 5] as the representative of the equivalent axial stiffness model, the method considers that the tunnel in the horizontal for a homogeneous ring, in the longitudinal stiffness of the eq uivalent method in order to circumferential seams are non-continuous structure is equivale nt to a continuous homogeneous cylinder. Because it is directly from the analysis of circu mferential lining of joints and bolts of force-deformation properties of the starting model t o be equivalent, so the calculation results can be directly given segment and bolt stress, a nd in many cases can be derived by an explicit theoretical solution, application convenient, but the method has not taken into account pre-stressed, and simply be considered straig ht beam on elastic foundation and other shortings, however, according to the current situa tion of the study at home and abroad, the axial equivalent stiffness method is the currenttheory of the tunnel structure of the longitudinal Research presented in the best way. Th e method to study the issue of Shield Tunnel longitudinal laid a solid theoretical basis.3 shield tunnel structure of assembled typeShield tunnel structure is a segment in the circumferential and longitudinal screwconnections made through a non-continuous structure. As the pre-cast reinforced concrete segment economy, durability and high strength, so be at home and abroad of the shield tunnel segment of the main form. Shield tunnel lining structure, assembly, there are two t ypes: the wrong lining of joints assembled themselves and the assembled seam lining [10] [11] [12] [19]. These two different types of assembly is that; wrong lining of joints asse mbled adjacent ring segment due to structural stiffness between the different distribution al ong the ring, although the initial load are basically the same, but the structural deformatio n is different strata caused by anti - force is different from the different strata reaction ex acerbated by structural deformation of the difference. Because there is a link between adja cent rings, such as connecting bolts, torus bump Mortise and torus has hindered friction between the different structural deformation, so that the structure deformation and load an d stratigraphic distribution of the different reactions within the scope be limited to a certai n . Tong assembled lining the joints due to the adjacent ring segment between the struct ural rigidity along the circumferential distribution of the same, subject to the initial load ar e basically the same. Therefore, the structural deformation is basically the same, causing t he formation reaction force is also basically the same. Although the assembled lining seam pass lateral deformation of each ring has also been mounted adjacent to Central and con straints, but the effects of constraints and the impact of the wrong seam sew more prono unced than the pass. This interaction between the lining ring is very plex, sewing lining of the wrong calculation of internal forces and deformation is also more plicated, the calcula tion model and calculation method are also in-depth studies.In China, Shanghai in advance of construction of the shield tunnel pass the basicuse of sewing assembled form, the recent construction of the tunnel in Shanghai and Gu angzhou, and Nanjing subway shield tunnel is used in all the wrong seam assembly form, which can show the wrong form of resistance to vertical seam assembly deformation is superior to pass suture assembled form. Since the assembly of different forms have differ ent mechanical effects, can change the lining of the longitudinal stiffness and control of lo ngitudinal cracks and uneven deformation, then the effect of the introduction of more mec hanical assembly of different forms of soft soil on the solution to the current issue of shi eld tunnel structure, the other vertical key issues.4 soft soil shield tunnel structural problemsFrom the current engineering design of practical application and theoretical research can be drawn from analysis of the progress of soft soil shield tunnel lining in consideri ng the vertical structure of the inadequacies of problems: lack of theoretical and vertical cl ose to the demand of the lining form; the existing theory of a lack of vertical and Engine ering The bination of the real; lining assembled form of single (can not be reconciled verti cally non-uniform deformation); lining film material in the same project in a single; lining segment width of a single in the same project; vertical linear unreasonable.5 Longitudinal Shield Tunnel in Soft Clay Design ForecastIn order to overe the existing problems of soft soil shield tunnel, we must solvethe following two aspects:(1) from the soft soil shield tunnel lining segment assembled form, tube sheet materials, i nnovation in areas such as transformation. In order to increase the soft soil shield tunnel lining structure of the longitudinal stiffness of the changes so that the soft soil shield tun nel lining structure of the longitudinal stiffness of a controllable. The different stiffness of the lining of the diverse forms of structural assembly to solve the problem of soft soil sh ield tunnel longitudinal possible.(2) In the longitudinal research and its application of design theory should be strengthened. Structural performance of tunnel longitudinal and transverse properties of the study is s till in the early stage of development pared to its results have yet been applied to enginee ring design practice. How to results of theoretical studies have been used in engineering d esign (ie, longitudinal design), so that the project design more in line with objective reality. This is not only theoretical development in line with current design trends, can help achi eve in the design stage begins to address the existing problems in the soft soil shield tun nel (an excessive amount of vertical settlement or differential settlement, leading to the tun nel seepage, leakage or structural partial destruction of mud affect the normal operation of the tunnel), to avoid the soft soil shield tunnel operations for processing after the passiv e state, therefore, can save a lot of money.In short, the soft soil vertical shield tunnel structure design theory is not only thesoft soil shield tunnel structure design theory development needs, but also social develop ment. It not only has theoretical value, but also more economic importance and social sig nificance.。