地铁盾构隧道足尺整环结构极限承载能力试验研究

为研究地铁隧道衬砌在侧向荷载作用下的极限承载力和变形能力,上海申通地铁集团有限公司和同济大学近期完成了基于地铁隧道变形治理的衬砌整环极限承载能力试验研究。介绍了地铁衬砌结构整环试验的研究内容,包括加载装置、荷载设计、测试内容以及部分试验结果等。     

盾构管片整环足尺寸模型试验研究综述

在地铁施工和运营期间,盾构管片在不良工况影响下经常出现变形过大和承载力降低等问题。以优化盾构管片受力和提高安全性能为目的,国内外学者通过整环足尺寸模型试验对管片变形性状和破坏关键性能点进行了大量研究。依据试验对象的不同,分别从未加固类管片和加固类管片对研究现状进行了总结和阐述,明确盾构管片结构整体变形、管片内力、接缝变形、管片裂缝、混凝土应变、接缝螺栓、管片错台量等发展情况,总结管片受力变形规律、极限承载力及破坏特征。明确国内外研究的不足,进一步优化加载装置、加载方式和加固技术,对未来该领域的研究提出进一步展望。     

超大隧道衬砌管片接头力学性能试验研究

国内超大隧道衬砌管片试验已进行过整环试验,文中介绍的超大隧道衬砌管片接头足尺试验在国内尚属首次.与以往隧道衬砌管片接头试验不同的是,在错缝夹片试验基础上首次增加了环缝接头剪切试验.文章简要介绍了超大隧道衬砌管片接头力学性能的试验方法,包括管片直接头试验和管片错缝夹片试验的加载装置、测试内容、试验工况等.通过试验数据分析得到隧道衬砌纵缝抗弯刚度在不同弯矩、轴力组合下的变化规律以及环缝的径向、切向剪切性能,试验结果可用于指导同类衬砌管片参数设计.     

通缝拼装盾构隧道结构极限承载力的足尺试验研究

针对轨道交通通缝拼装的盾构隧道结构的承载性能,进行结构的足尺静载试验。具体介绍试验方案和加载方案的设计,提供结构变形、管片裂缝、接缝变形和连接螺栓受力的发展情况以及破坏过程等试验结果;对结构的承载性能和破坏机理进行分析。足尺试验研究表明:试验结构的破坏由不同部位接缝混凝土先后受压破坏形成,属梁铰机制;管片接缝是隧道极限承载力的关键断面;周边卸载工况下结构的承载力安全系数比顶部超载工况小,对盾构隧道结构的承载更为不利。     

盾构隧道管片衬砌内力计算方法比较

针对广州地铁二号线三元里－越秀公署区间盾构隧道,采用弹性铰法和弹性地基梁法对管片初砌内力进行了计算,并与自由变形圆环法的计算结果作比较,得出一些对设计有参考价值的结论。     

盾构隧道管片衬砌内力计算方法比较

针对广州地铁二号线三元里～越秀公园区间盾构隧道 ,采用弹性铰法和弹性地基梁法对管片衬砌内力进行了计算 ,并与自由变形圆环法的计算结果作比较 ,得出一些对设计有参考价值的结论。     

盾构隧道纵向接头局部足尺试验研究

沿盾构隧道纵向,管片环与管片环之间的接头称之为纵向接头。纵向接头是变形的薄弱部位,在变形过程中受到相邻管片的约束,其受力特点与管片接头不同。文章首先采用数值模拟方法,研究纵向接头局部试验的可行性,然后开展纵向接头局部足尺试验,研究接头的受力变形特征,所得结论如下：对纵向接头进行分析时,对比整环模型及纵向等效刚度梁模型计算结果,两者接头张开量、螺栓应力相差在11%以内,管片结构塑性损伤区分布特征基本一致,故纵向等效刚度梁模型可作为纵向接头局部足尺试验的依据;纵向接头局部足尺试验时,纵向接头张开量的变化对轴力更加敏感,螺栓应变增长与环间力(轴力、弯矩)的增加基本保持一致。接缝转角在环间拉力下趋近于0,且追随环间弯矩的变化;各工况中构件表面混凝土最大拉应变出现在套筒侧管片外表面中部,最大压变出现在手孔侧管片的内表面。破坏试验中,纵向拉力3232kN时管片结构先于螺栓破坏,此时螺栓未达屈服强度。     

内张钢圈加固盾构隧道结构极限承载力的足尺试验研究

为提高既有盾构隧道结构的极限承载力,以通缝拼装盾构隧道结构为对象,设计了两种加固类型的足尺试验。对试件进行了模拟上部堆载作用下的静力加载试验,分析了结构整体的受力过程、破坏模式和极限承载力等,考察了内张钢圈加固方法对于提高结构受力性能的作用。研究表明:内张钢圈加固方法是一种合理有效的加固方法,能显著提高既有盾构隧道的整体刚度和承载能力;采用整环或半环方式加固后盾构隧道结构的受力性能相近,加固结构的破坏模式均是由于局部粘结失效所导致的结构破坏。     

输水隧道单层衬砌管片接头抗弯力学特性研究

因受到复杂的外部水土压力和较高的内水压力共同作用,单层衬砌盾构法输水隧道具有独特的接头构造。针对上海青草沙输水隧道(岛屿陆域段)单层衬砌管片接头的特点(铸铁手孔,双层螺栓),借助1:1足尺荷载试验及三维非线性弹塑性数值模拟对单层衬砌输水隧道管片接头的抗弯力学特性进行了研究。获得了单层衬砌输水隧道管片接头在不同接头轴力(拉/压力)、不同接头弯矩(正/负弯矩)和不同螺栓预紧力条件下接头张角及抗弯刚度的变化规律;并获得了环向螺栓轴力随接头弯矩的变化规律及管片接头的变形特性,研究成果可供类似工程借鉴。     

内水压条件下盾构隧道复合衬砌破坏机理原型试验研究

盾构输水隧道工程常采用复合衬砌结构型式,钢筋混凝土内衬具有施工便捷等优势成为常用内衬之一,但在内水压作用下容易开裂,钢筋混凝土内衬开裂后复合衬砌承载能力成为工程中设计的关键问题。本文对盾构隧洞钢筋混凝土内衬复合衬砌结构展开原型试验,研究内水压作用下复合衬砌的全过程变形破坏规律,揭示复合衬砌内压承载机理。试验结果表明：(1)内外压差达到0.22MPa时,内衬开始开裂,内衬开裂后盾构管片承担更多内水压力,随着内水压增长,接头手孔处混凝土出现损伤,最终内外压差达到1.78MPa时,管片接头混凝土断裂,复合衬砌丧失承载能力;(2)管片接头是复合衬砌薄弱环节,裂缝首先产生于内衬临近盾构管片接头处,然后沿环向均匀增加,内衬产生裂缝后,混凝土通过与钢筋的黏结作用共同承担内水压力,因此随内水压增加内衬发生多次开裂;(3)内衬开裂、接缝损伤后复合衬砌抗拉刚度分别下降为其弹性状态时的23.8%,12.3%,内衬开裂对复合衬砌承载能力影响最为显著。     

Numerical analysis of DRC segment under inner water pressure based on full-scale test verification for shield tunnel

Shield tunnel subjected to high inner water pressure is used to prevent waterlogging, and DRC (Ductile cast iron segment and Reinforced Concrete) segment has been developed for obtaining high loading capacity in the linings of underground drain shield tunnel. In general, tunnel linings resist bending moment, hoop and shear forces. Cracks will occur in tunnel linings under high inner water pressure during operating period, while tensile stress will appear at member section. On the basis of the existing experimental results, the crack pattern, relative slip, contact stress, strain distribution, and relationship between deflection and load of DRC segment were investigated by finite element method. A three-dimensional finite element model of DRC segment was proposed to simulate its nonlinear behaviors by applying MSC.Marc software package. Taking the three sources of nonlinearity into account, the proposed numerical model fully presented the complicated behaviors of DRC segment during the whole loading process. Results indicated that the numerical studies agreed well with the experimental tests, and comparisons between them demonstrated that the proposed numerical model could excellently analyze the nonlinear behaviors of DRC segment under combined hoop and bending loads.     

Squeezing loading of segmental linings and the effect of backfilling

Overstressing of the segmental lining is one of the major hazard scenarios related to shielded TBM tunnelling in squeezing ground. The present paper deals with this specific problem, addressing the key question of the ground pressure acting upon a segmental lining installed behind a single shielded TBM. Starting with a structured discussion of the influencing factors and their interactions, the paper investigates how the type, location and thickness of the backfilling play an important role with respect to the loading of a segmental lining. Secondly, it explains how to take due account of the actual thickness of the backfilling (which is not known a priori since it depends on the deformations of the bored profile) in a numerical simulation. Thirdly, the paper advances a number of theory-based decision aids which cover the relevant range of ground parameters, initial stress, segmental lining and backfilling characteristics, thus supporting rapid initial assessments of the ground pressure acting upon a segmental lining and making a valuable contribution to the decision-making process.     

水压作用对通缝拼装管片结构力学性能的影响研究

以苏通GIL综合管廊工程为背景开展了通缝拼装方式下的原型试验,从水压对管片环的受力、形变及抗裂性方面着手,对通缝拼装条件下水压力对管片结构力学性能影响进行了研究。试验结果表明：①通缝拼装管片结构在拱顶位置出现较大的位移,水压力的增大对管片结构拱顶形变和整体椭圆变形的控制有良好的效果,但管片最大单点位移相比椭圆度更易达到限值;②通缝拼装管片结构建议取单点最大形变率2‰~2.5‰作为形变控制标准;③在高水压作用下通缝拼装管片结构的纵缝张开主要发生在封顶块附近,由于该处纵缝密集、结构刚度最小、变形最大所致,水压力的增大对该处纵缝张开有明显的限制作用,且可减小相应连接螺栓的受力;④水压力的增大会较大幅度地提升管片的抗裂性能,并减小管片主筋的拉应力,但也会使主筋的压应力和箍筋应力有较大幅度的升高;⑤水压力的升高在一定程度上提高了管片结构的受力性能,但高水压使管片结构处于高轴压受力状态,易发生纵缝处的压剪破坏,该破坏具突发性。研究成果对水下盾构隧道的设计具有重要的指导意义。     

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.     

异形盾构隧道衬砌结构计算模型和受力特征研究

首先通过原型整环管片力学试验研究了异形盾构管片环向接头转动刚度随隧道埋深增加的变化规律。基于试验成果建立了异形盾构管片壳-弹簧计算模型,并将原型试验结果与修正惯用法和壳-弹簧模型进行对比,给出了异形盾构管片内力分布模式,明确了修正惯用法作为异形盾构管片设计方法的可靠性,并将壳-弹簧模型推荐为能较为科学地反映异形盾构管片实际受力特征的计算模型。最后,基于壳-弹簧模型从经济和力学两个角度对异形盾构隧道与矩形和圆形隧道进行对比,证明了异形盾构应用于浅覆土地层的科学合理性。     

无黏结预应力环锚衬砌力学特性原位加载试验研究

新型无黏结环锚衬砌具备预应力损失低、薄弱区小、施工便捷等优势,但因结构复杂致使力学特性不明确,阻碍了其广泛应用。依托引松工程总干线压力隧洞,开展了首次预应力环锚衬砌大型原位加载试验,明确了内水压加载过程中衬砌预应力重分布特征,揭示了环锚拉力、钢筋应力以及锚固应力损失变化规律,并探讨了围岩和环锚衬砌联合承载作用。原位试验表明:环锚衬砌整体预应力分布均匀,高效地利用了锚索高强抗拉性和混凝土抗压性,常规钢筋作用极小,因而整体可不配筋或仅构造配筋;锚具槽背后混凝土预应力稍薄弱,是高内水压作用下结构潜在破坏区域,但内水加载过程中衬砌环向、纵向预应力值趋于一致,将有效减缓预应力薄弱部位开裂倾向;环锚衬砌具备优越的抗拉和抗渗性能,可不依赖于围岩条件而独立承载,也可利用围岩部分承载以降低预应力设计值或增加结构安全裕度,它能为覆盖层薄、地质条件差且内水压力高的大直径压力隧洞长期存在的支护难问题,提供解决新途径。     

钱江隧道管片拼装过程中的力学行为实测分析

钱江隧道是目前世界上最大直径的软土盾构法隧道工程之一。通过在典型地层深埋段埋设全断面的隧道试验环,对盾构拼装管片的全过程及拼装后管片结构的受力特征进行了现场实测。监测结果表明,管片结构内力在拼装过程中受到管片相对位置及相互接触关系的变化影响,经历了波动、微调整直至平衡状态的变化过程。多数管片在拼装阶段的实测内力小于正常使用阶段管片理论内力的30%,但高于拼装阶段管片内力的理论值,最高可达到拼装阶段理论值的10倍以上。管片拼装过程中的内力实测值经历了波动或跳跃后逐渐逼近拼装阶段的理论值。值得注意的是,实测值的变化曲线表明:个别管片局部内力出现突变,实测突变值达到正常使用阶段理论值的3倍以上。因此,尽管管片之间通过管片间接触条件及相对位置的调整使管片结构的内力较快调整至正常状态,但该过程中出现管片内力局部过大的情形对管片结构的耐久性和长期承载性能可能造成影响,在今后的设计和施工控制中应予以充分考虑。     

Experimental investigation of the ultimate bearing capacity of continuously jointed segmental tunnel linings

The serviceability of segmental tunnel linings is attracting more and more attention within the operation of urban rail traffic. Full-scale tests are herein conducted to determine the ultimate bearing capacity of continuously jointed segmental tunnel linings, considering changes of surrounding environment. The design of tested linings and loading schemes are described. The most important results are the evolution of deformations, cracking and opening of joints and forces in bolts. The bearing capacity, role of joint bolts and failure mechanism of the tested linings are analysed. It is found that failure of these linings is caused by the failure of joints. Thus, in order to optimise structural design of tunnel linings, more attention needs to be paid to maximise the joint strength. It is also found that circumferential joint bolts could take action and offer the safety margin in connection with the response of segmental structures. What’s more, a comparison of different experimental loading conditions has shown that segmental lining structures are more vulnerable to lateral unloading than to overload conditions.