软弱围岩隧道钢纤维混凝土衬砌承载特性模型试验研究

为满足软弱围岩隧道开挖后尽快封闭岩面、适应一定变形及提供足够支护力的要求,通过素混凝土、钢筋混凝土及钢纤维混凝土衬砌力学行为室内模型试验,对钢纤维混凝土衬砌的承载特性进行研究。研究结果表明:钢纤维混凝土衬砌初裂荷载提高了20%,极限荷载得到较大提高;掺入钢纤维后衬砌结构韧性增强,初裂后仍能抵抗一定变形并较大降低变形速率,与素混凝土、钢筋混凝土相比可承受更大的变形;钢纤维混凝土衬砌初裂后承载特性曲线缓慢上升,至2倍初裂荷载时仍无收敛迹象,素混凝土快速收敛,钢筋混凝土在一定缓慢上升后快速趋于收敛,软弱围岩条件下,钢纤维混凝土初支在一定变形后可与围岩特征曲线相交,达到围岩–结构稳定状态,是一种力学性能良好的快速支护材料。研究成果对软弱围岩隧道的设计与施工都具有重要的意义。     

粘钢板加固砼双向简支板的承载力分析

基于塑性铰线理论 ,分析了正方形粘钢板加固集中荷载下的正方形砼简支板的承载力 ;改进了文献〔1〕的塑性铰线模式 ,修补了文献〔1〕的理论解的一个缺陷 ,即随着粘钢板的面积增加 ,承载力上升至无穷大。比较试验值和计算值 ,提出了的钢板内单位长度屈服弯矩的分布     

螺旋筋增强外包型钢混凝土柱偏压性能

为了研究螺旋筋增强外包型钢混凝土柱的偏压受力性能,设计并制作了22个试件(其中螺旋筋增强外包型钢混凝土柱试件19个和外包型钢混凝土柱对比试件3个)并进行偏心受压静力加载试验,观察试件的破坏过程,剖析失效机理,获取了其荷载 挠度曲线、荷载 应变曲线、截面应变分布和刚度退化曲线,并分析了箍筋间距、偏心距、径长比（D/a,D为螺旋筋约束直径,a为柱截面边长）、长径比、缀板间距、角钢配钢率和纵筋直径等参数对其承载力和抗弯刚度的影响。研究结果表明：相比外包型钢混凝土柱,螺旋筋增强外包型钢混凝土柱在破坏时混凝土的压溃剥落程度更小,荷载 挠度曲线下降段更为平缓;截面内型钢的环向应变呈线性分布,螺旋箍筋的应变呈非均匀分布;螺旋筋增强外包型钢混凝土柱的偏压承载力和抗弯刚度相比外包型钢混凝土柱分别提高了4%~25%和13%~39%;偏压承载力及抗弯刚度均随着箍筋间距、缀板间距、偏心距和长径比的增大而提高,随径长比的减小而降低;刚度退化速率随着螺旋箍筋间距、缀板间距和径长比的增大而提高。     

碳纤维补强公路隧道设计计算方法的研究

针对碳纤维补强公路隧道衬砌,按荷载结构法,以碳纤维补强钢筋混凝土偏压构件的理论为基础,提出了裂缝发展分析方法,初步形成了一套适用于碳纤维补强公路隧道衬砌结构的设计计算方法。可为碳纤维加固修补公路隧道衬砌结构提供设计依据。     

Full stress and displacement fields for steel-lined deep pressure tunnels in transversely anisotropic rock

An analytical solution is derived that provides closed-form formulations for stresses and displacements for a deep pressure tunnel in a transversely anisotropic rock, with a steel liner, and subjected to a uniform internal pressure. For the derivation, it is assumed that the tunnel support includes a thin steel liner, concrete backfill and that there is an annulus of damaged rock around the concrete. It is also assumed that all materials remain elastic and that the concrete and the damaged rock cannot transmit shear or tangential stresses. The solution is verified by providing comparisons between its results and those from the Finite Element program ABAQUS. For thin steel liners, it can be assumed that the contact pressure between the different materials is uniform, and thus the bending moments in the liner are negligible. This is due to the low bending stiffness of the steel liner. The paper is inspired by and expands the work by Pachoud and Schleiss (2015) who conducted an extensive numerical parametric analysis to obtain correction factors that, when used with an analytical solution for isotropic materials, approximate the maximum principal stress in the liner and intact rock.     

隧道衬砌后方隐伏洞穴地质雷达响应特征分析

探明隧道衬砌后方隐伏洞穴对保障隧道结构安全和隧道耐久性具有重要意义。采用地质雷达(GPR)进行隧道衬砌后方隐伏洞穴检测时,双层钢筋网的屏蔽问题、洞穴尺寸和洞穴内填充物类型判断问题一直未能得到很好的解决。将不同围岩等级的隧道二衬结构简化成双层钢筋网和素混凝土结构两种形式,分别开展双层钢筋网后方洞穴探测和衬砌后方洞穴尺寸与充填物类型识别试验。试验结果表明:同时采用天线垂直极化和尽量小的道间距进行探测能有效地降低双层钢筋网对衬砌后方目标体的屏蔽作用;衬砌后方圆形和近似圆形洞穴的尺寸可用渐近线法估算,且具有较高的精度;充填物类型的识别需要综合考虑洞穴上下界面反射波双程走时,上界面反射信号单道波相位的正负、振幅的大小和时频谱下界面反射波中心频率变化情况等特征综合分析。     

隧道纤维混凝土二衬承载机理及受力计算方法研究

充分考虑和发挥纤维混凝土的韧性性能是目前隧道二衬结构设计的热点和难点。通过素混凝土、钢纤维及玄武岩纤维混凝土的室内试验发现：纤维的掺入,对混凝土的增韧效果远超增强效果。基于纤维混凝土优异的韧性特征,将纤维混凝土二衬裂缝视为塑性铰,提出隧道纤维混凝土二衬的承载机理：围压作用下,衬砌出现第一个塑性铰,随着围压继续增大,塑性铰发生转动并引起更多塑性铰出现,至结构由超静定变为可转动机构时,二衬结构破坏。基于此,探讨了隧道纤维混凝土二衬裂后结构受力计算方法,推导了相应的计算公式,并通过模型试验予以验证。研究成果可为纤维混凝土在地下工程中的推广应用提供理论支撑。     

Simplified nonlinear simulation of shield tunnel lining reinforced by epoxy bonded steel plates

A high-efficiency simplified modeling approach based on fiber-beam elements and discrete elements is proposed for investigating the nonlinear response of shield tunnel reinforced concrete linings. The proposed approach focus on following main features: modeling simplicity and computational efficiency, the considerations of critical material and geometric nonlinearity associated with the entire loading process, including the stage of reinforcing the deformed concrete lining by steel plates. Comparison between the analysis results of the proposed numerical model and the experimental results from the full-scale structural test are presented to validate the developed model. The results show that the proposed model can capture the essential characteristics of the nonlinear load–deformation response of segmental tunnel lining. The modeling approach presents a balance between simplicity and accuracy, and serves as a viable alternative to detailed finite elements analysis.     

Damage identification of a tunnel liner based on deformation data

A new system identification approach based on tunnel deformation data is proposed to find the damage in the tunnel liner. For this, an inverse problem in which deformation data and dead load of concrete lining are known a priori is introduced to estimate the degree and location of the damage. Models based on uniform reduction of stiffness and smeared crack concept are both employed and the efficiency and relative advantage are compared with each other. Numerical analyses are performed on the idealized tunnel structure and the effect of white noise, common in most measurement data, is also investigated to better understand the suitability of the proposed models. As a result, model 1 based on uniform stiffness reduction method is shown to be relatively insensitive to the noise, while model 2 with the smeared crack concept is proven to be easily applied to the field situation since the effect of stiffness reduction is rather small. Finally, real deformation data of a rail tunnel in which health monitoring system is in operation are introduced to find the possible damage and it is shown that the prediction shows quite satisfactory result.     

Influence of segmental joints on tunnel lining

A simplified method for evaluating the moment carrying of a segmental tunnel liner was proposed using a result from a FEM analysis in which parameters were obtained by calibration against a true scale model test. Influence of segmental joint, number of segment and soil subgrade modulus on the bending moment carrying characteristics of a segmental tunnel was examined. Joint was represented by a series of springs called angular joint stiffness. Based on a set of model tests, practical range of angular joint stiffness was in range of 1000–3000 kN m/rad. It was found that jointed lining carried smaller value of maximum bending moment than the non-jointed one. The reduction in bending moment, represented by the parameter called moment reduction factor, can be simply expressed as a function of angular joint stiffness and number segment.     

突发堆载引起软土地铁盾构隧道大变形整治研究

城市地铁的快速发展难以避免频受外部工程活动扰动影响,其中突发堆载已成为突出问题。上海某地铁区间盾构隧道上方突发大量堆土,最大堆高约7 m,从而引发结构产生横向收敛大变形（ΔD）最大达到34.5‰倍的隧道外径(D),堆载严重威胁到地铁结构及运营安全。介绍了该工程案例,包括堆载引起的隧道结构横纵断面变形及相应的结构病害,提出并实施了及时卸载、堵漏及碎裂修补、后采用芳纶布及钢环结构补强的结构整治措施。卸载对于减缓堆载对隧道结构沉降影响作用明显,卸载之后隧道沉降恢复且部分产生隆起现象,后续张贴芳纶布及钢板环加固措施,可提高盾构隧道横断面承载能力,相比隧道沉降,隧道结构收敛变形状况改善并不明显,水平直径收敛最大仅回缩2.6‰D。案例对于外部扰动对盾构隧道影响及整治研究,具有重要的工程实践价值。     

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。     

纤维混凝土隧道衬砌地震动力响应特性的振动台试验研究

 为研究纤维混凝土隧道衬砌在地震动力作用下的动响应特性,对普通混凝土隧道衬砌与纤维混凝土隧道衬砌开展大型振动台模型试验,分析隧道衬砌的震害特征、地震动应变、结构内力和应变基线响应规律。试验结果表明：水平地震荷载及地层压力共同作用下,2种隧道衬砌均为仰拱最先开裂,其次为拱腰开裂,衬砌结构破坏模式主要为开裂、掉块和裂缝两侧挤压破坏;素混凝土隧道衬砌出现开裂破坏早,裂缝易贯通,裂缝两侧混凝土基体在振动过程中相对位移大;纤维混凝土隧道衬砌出现开裂破坏晚,裂缝两侧混凝土基体在振动过程中相对位移小,裂缝呈挤压破坏状;纤维延缓衬砌结构裂缝的产生和阻碍裂缝的扩展;地震波加速度峰值从0.1 g增大到1.0 g时,素混凝土隧道衬砌动应变极值和裂缝宽度显著增大,而纤维混凝土隧道衬砌动应变极值和裂缝宽度先在一定范围内缓慢增长然后迅速增大,但最终2种衬砌动应变极值和裂缝宽度大致相等,说明纤维混凝土隧道衬砌在一定地震荷载范围内可以有效避免开裂和减小裂缝宽度;纤维混凝土隧道衬砌压缩变形率较小,当输入地震波加速度峰值为0.1 g和0.4 g时,纤维混凝土隧道衬砌结构动弯矩极值较低,受力更均衡,能有效地抵御地震荷载。     

盾构衬砌整环破坏机理研究

以某盾构衬砌整环原型试验作为研究对象,利用提出的接头和管片破坏指数对盾构衬砌环的破坏机理进行了研究,研究表明：①接头破坏指数和管片破坏指数以及开裂弯矩等指标可以对盾构衬砌的实际受力状态进行追踪,可以阐述、解释盾构衬砌环的破坏机理；②对于本文所依据的盾构原型试验而言,盾构衬砌环破坏历程是由接头开始开裂、管片开始开裂、首个管片塑性铰形成、接头开始屈服（接头开始丧失承载力）、多个管片塑性铰形成、整环承载力丧失等阶段构成；③多个塑性铰的形成是导致盾构环承载力丧失的直接原因,塑性铰开始位置、发展顺序取决于关键截面及其排序情况。     

深排隧道钢纤维补强衬砌混凝土-伦敦Lee Tunnel

钢纤维补强能够极大提升混凝土结构物的耐久性能,非常适用于长寿命,高耐久性,并且供用环境腐蚀条件苛刻,磨耗严重的都市深层排水隧道衬砌混凝土。依据有关钢纤维补强混凝土结构的国际混凝土结构联合会制订的模型代码：fib model code 2010,以及欧洲的相关技术规范,结合伦敦的深层排水隧道：Lee Tunnel的具体工程实例,对如何应用钢纤维补强技术在盾构隧道衬砌混凝土管片,以及现场浇筑二次衬砌自密实混凝土进行了探讨。同时通过钢纤维补强混凝土缺口梁试件的抗折强度试验,大型梁试件的弯曲加载试验,以及试验结果的非线性有限元逆向解析,确认了钢纤维取代钢筋的结构补强性能,控制裂缝效果,以及应变硬化性能,能够满足Lee tunnel工程项目的砌筑混凝土性能要求,适用于深层排水隧道:Lee tunnel衬砌混凝土补强。     

Analysis of shearing effect on tunnel induced by load transfer along longitudinal direction

In order to analyze the behavior of load transfer mechanism of shield-constructed tunnel in longitudinal direction, tunnel is modeled as the cylindrical shell within elastic foundation (CSEF). By applying the theory of elastic cylindrical shell (ECS) with considering shear deformation and assumed displacement functions of trigonometric series, the distribution of stress and deformation in tunnel lining is obtained. In the solution, the stiffness of tunnel lining is decomposed into two components of circumferential and radial stiffness. The effects of both components on the behavior of deformation and internal forces of tunnel lining are discussed in details. By using the proposed solution, more reasonable results on the behavior of tunnel lining are obtained, e.g bending moment in tunnel cross section becomes smaller with the increase of the circumferential shear stiffness. The analytical results are verified by the results of 3D FEM analysis and field measured data. In accordance with the proposed analytical method, the tunnel lining in soft ground should be designed via considering the following aspects: (i) three dimensional effect of tunnel lining; (ii) relatively weaker shear stiffness in radial direction, and (iii) increase the circumferential shear resistance between rings.     

公路隧道偏压效应与衬砌裂缝的研究

衬砌裂缝是公路隧道施工中常见的病害之一。结合三公菁隧道各项监控量测数据和隧道实际地质情况,对裂缝产生的各种原因及其发展变化从力学角度进行正、反演分析和归纳。讨论了隧道设计规范的适用范围,并与实测及反演方法进行比较,同时提出了合理的设计施工方案。实例分析了某断面二次衬砌内力状况,并进行强度校核以解释其裂缝成因。经综合分析及力学计算,存在较大偏压是隧道衬砌产生裂缝的主要原因。最后,提出了综合处理隧道裂缝的具体措施,方案实施后,其效果令人满意。     

有衬砌隧道设计计算探讨——隧道稳定性分析讲座之三

利用有限元强度折减法结合基于有限差分原理的FLAC软件,探讨了隧道设计计算过程中初衬和二衬的计算问题以及隧道开挖的应力释放问题,并以黄土隧道为例探讨研究不同应力释放率以及不同初衬和二衬厚度情况下隧道的受力特征,计算围岩安全系数以及二衬安全系数,得出了以下结果:一是利用FLAC软件计算中的不平衡力来控制隧道开挖过程的应力释放是合适的与可行的;二是初衬作为隧道围岩的加固圈将承受较大荷载和产生较大的变形,初衬必将进入弹塑性状态;二衬作为隧道的强度储备或者承受不大的荷载,二衬视作弹性杆件可按结构力学的方法确定安全系数;三是如果初衬后围岩安全系数大于1.30,可以认为围岩和初衬都是稳定的,二衬作为安全储备;如果围岩安全系数在1.30~1.15之间或围岩为粘弹塑性材料时,表明二衬将承受一定荷载;如果初衬后围岩的安全系数小于1.15~1.20,则认为初衬不足,不能保证施工安全。最后建议对二衬后的围岩安全系数取1.3,二衬结构安全系数对无抗裂要求的混凝土衬砌取1.4,钢筋混凝土衬砌取1.35。两者综合的安全系数大约在1.8左右以供参考。     

Damage to mountain tunnels related to the Wenchuan earthquake and some suggestions for aseismic tunnel construction

Many tunnels along the Dujiangyan to Wenchuan highway, located near the epicenter of the 2008 Wenchuan earthquake in China, were damaged severely. The characteristics of the tunnel failures were analyzed and categorized as avalanches and landsliding near the tunnels, cracking of the tunnel portals, collapse of the liner and surrounding rock, cracking and dislocation of the liner, uplift and cracking of the ground, deformation and cracking of the preliminary bracing. The main geological factors influencing the tunnel damage are secondary fractures of earthquake faults, sudden change in soil and rock type, weak rocks and the variable geo-stresses in the host material. The tunnel portals and their slopes, unless fully integrated into the tunnel structures and sufficiently reinforced, are likely to suffer significant distress as a consequence of seismic events. The main mitigation measures proposed are the use of reinforced concrete in the secondary lining in the area of fault zones and injection grouting to reduce the differences where there are sudden changes in the character of the host material.     

西江引水工程盾构输水隧洞衬砌形式的选择与设计

广州西江引水工程在穿越城区的大型交通枢纽位置采用了盾构隧洞的非开挖穿越方式。该盾构输水隧洞内压高、距离长、埋置深,使得隧道衬砌结构的设计成为制约整个隧道工程安全、保证工程质量和确保按期完工的关键。通过对多种衬砌形式进行比较,最终确定采用钢筋混凝土管片加钢衬的分离式双层结构。从盾构隧洞的基本构造、外衬管片的设计和施工措施、内衬钢管的设计和自密实混凝土的浇筑等方面进行了介绍,以供类似工程参考。