基于数值评价的隧道衬砌裂缝成因分析与维修设计

地下工程衬砌裂缝是隧道工程常见病害之一。由于衬砌裂缝对隧道结构体受力、防排水等安全方面产生不良影响,有必要对裂缝成因加以分析并采取有效措施来降低裂缝对隧道的影响。以四川省某铁路隧道为研究对象,现场调查衬砌裂缝情况,分析隧道边墙纵向开裂原因。采用应力解除法对该隧道进行地应力测试,测点处围岩初始应力处于极高应力状态,分析得出高地应力作用是导致衬砌开裂主要原因。为检验这一推断,采用扩展有限元(XFEM)对该段衬砌结构性能进行数值模拟,根据XFEM得到破坏区域衬砌结构破坏演化、二衬安全系数,模拟结果与实际衬砌损伤形式一致。最后,针对隧道衬砌结构开裂提出一种具体的维修方案,根据数值计算结果及现场施作情况,验证所提维修方法的有效性及安全性。     

Hydro-mechanical interaction analysis of high pressure hydraulic tunnel

The reinforced concrete lining of hydraulic tunnel cracks under high internal water pressure and the high pressure water will leak off from the crack surface, which is a typical hydro-mechanical interaction problem. Unfortunately, the analytical and numerical methods used in current engineering practice for simulating the hydro-mechanical interaction of the lining and surrounding rock do not adequately account for the effects of the cracking of lining as well as the conditional cooperation between them. When lining cracks under high internal water pressure, the tensile strain of concrete and reinforcement presents to be nonuniformity and the lining would detach from the surrounding rock in a certain condition. In this paper, the nonuniformity coefficients of reinforcement strain and concrete strain are introduced to compute the secondary permeability of cracked lining and a water-filled joint (WFJ) element is developed to simulate the conditional cooperation between the reinforced concrete lining and surrounding rock. Thus an equivalent coupling method is adopted to calculate the hydro-mechanical interaction in hydraulic tunnel. The results show that the reinforcement stress obtained by the new method and the observed data match well. The phenomenon that the reinforcement stress stays at a lower value in the reinforced concrete tunnel with high internal water pressure is verified.     

山岭隧道受震损害类型与原因之案例研究

 以1999年台湾集集地震造成完工通车仅1 a的三义壹号铁路隧道损害为例,应用隧道受震数值分析成果及相关研究,探讨隧道受震损害的原因。研究成果显示,受震损害区段皆落于埋深接近0.25倍岩体波长的范围内,即隧道埋深与岩体特性的组合强化震波受地表自由面反射与隧道散射的效应,导致衬砌受震引起应力大幅增加而造成破坏。而衬砌损害可归纳为4种类型：纵向裂缝、环向裂缝或环向施工缝错动、环状剥落以及斜向裂缝与剥落。分析隧道施工地质记录及震后检测结果显示,衬砌纵向裂缝主要受地盘深处上传的S波垂直方向或45?入射导致衬砌轴力与弯矩受震增加而影响。环向裂缝或环向施工缝错动则受到水平方向P波造成的张力破坏以及乐夫波造成衬砌应力增加的影响。环状剥落系隧道承受较显著的水平方向应力下,S波45?入射导致衬砌应力增量以及避车洞开口结构配置的影响。而斜向裂缝则受S波通过软硬地盘互层的应变差异以及隧道衬砌结构刚度特性所致。研究成果表明隧道受震损害原因与影响因素,可为山岭隧道耐震分析与设计提供参考。     

Global sensitivity analysis of certain and uncertain factors for a circular tunnel under seismic action

There are many certain and uncertain design factors which have unrevealed rational effects on the generation of tensile damage and the stability of the circular tunnels during seismic actions. In this research paper, we have dedicated three certain and four uncertain design factors to quantify their rational effects using numerical simulations and the Sobol’s sensitivity indices. Main effects and interaction effects between the design factors have been determined supporting on variance-based global sensitivity analysis. The results detected that the concrete modulus of elasticity for the tunnel lining has the greatest effect on the tensile damage generation in the tunnel lining during the seismic action. In the other direction, the interactions between the concrete density and both of concrete modulus of elasticity and tunnel diameter have appreciable effects on the tensile damage. Furthermore, the tunnel diameter has the deciding effect on the stability of the tunnel structure. While the interaction between the tunnel diameter and concrete density has appreciable effect on the stability process. It is worthy to mention that Sobol’s sensitivity indices manifested strong efficiency in detecting the roles of each design factor in cooperation with the numerical simulations explaining the responses of the circular tunnel during seismic actions.     

Shaking table tests of tunnel linings in progressive states of damage

Tunnels have long been assumed to be able to withstand earthquakes and suffer little damage. However, investigations of tunnels after the Wenchuan earthquake in China revealed that over 30 tunnel linings were cracked. Different types of cracks were found in almost all the tunnel linings. In this study, a series of shaking table tests were conducted on scaled tunnel models under seismic excitations with increasing intensities. White noise sweep tests were interlaced with the seismic excitations to identify the damage in the tunnel linings. The accelerations and strains of the tunnel lining were measured. The test results are discussed based on the dominant frequencies, amplification factor, and lining strains. Furthermore, this paper presents the results of damage identification for various states of damage using the white noise sweep method. The dominant frequencies decreased with an increase of the input peak ground acceleration (PGA), which also reflected the damage of the tunnel lining. The dominant frequencies decreased by approximately 32% for an input PGA intensity of approximately 0.6 g, but the first cracks could still be visually detected. The cracks gradually propagate with the PGA increasing from 0.6 to 0.8 g. The effect of lining damage on the seismic performance of tunnel linings should be considered in the seismic design of tunnels.     

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。     

A method to estimate concrete hydraulic conductivity of underground tunnel to assess lining degradation

The determination of the degradation state of underground concrete tunnels is a crucial issue for maintaining and monitoring the performance of these infrastructures. In particular, if the tunnel is totally or partially submerged, concrete deterioration and consequent changes in both lining thickness and hydraulic conductivity can have dramatic effects on the amount of water inflow, leading to an increase in maintenance costs as well as to possible interruption of the infrastructure serviceability. The hydraulic conductivity of the concrete lining is here proposed as a proxy of the overall degradation state of the structure, being this property directly correlated to porosity and to the presence of interconnected fissures and cracks.The aim of this study is to propose a simple and completely non-destructive method to estimate the hydraulic conductivity of tunnel lining concrete. Provided the availability of easy-to-collect in situ geometrical and hydrogeological data (i.e. tunnel geometry, water inflow, water table level), the method relies on a back analysis to estimate the hydraulic conductivity of the concrete, performed via the finite element method to solve the seepage equations in porous media. Ground Penetration Radar technique is coupled to the modelling approach to gain accurate data about the current lining thickness.The proposed method has been applied to the study of a real case of underground tunnel, used to prove the model reliability. Moreover, once estimated the hydraulic conductivity and thickness of the concrete, the model can be used to generate curves linking the total water inflow in the tunnel as a function of the groundwater level variations, allowing a real-time monitoring of the current hydraulic state of the infrastructure.This methodology, which can be considered of general validity and easy to be extended for the study of any underground tunnel, provides a simple and effective tool useful to prioritize maintenance works and to evaluate the consequences of different hydraulic scenarios.     

城门洞型压力隧洞衬砌限裂配筋设计方法研究

以城门洞型无压隧洞改建为引水发电隧洞的限裂配筋设计方法为研究对象,综合分析衬砌开裂前后围岩–衬砌混凝土–钢筋的联合作用,建立起二维(平面应变问题)非线性有限元数值仿真分析模型,经分析得到运行期内水压力工况下衬砌中钢筋应力、衬砌混凝土拉应力、衬砌裂缝、裂缝宽度的分布规律、衬砌配筋设计结果,以及检修期外水压力工况下衬砌混凝土裂缝处的应力集中现象和衬砌配筋的验算结果。提出的衬砌限裂配筋设计方法较以往的方法考虑更多影响配筋结果的因素,使结果更符合水工压力隧洞的实际工况,对同类工程设计具有指导意义。     

Assessment of damage in mountain tunnels due to the Taiwan Chi-Chi Earthquake

Tunnels, being underground structures, have long been assumed to have the ability to sustain earthquakes with little damage. However, investigations of mountain tunnels after the Chi-Chi Earthquake in central Taiwan revealed that many tunnels suffered significant damage to various extents. This work describes the findings of a systematic assessment of damage in the mountain tunnels in Taiwan after the earthquake. It was found that among the 57 tunnels investigated 49 of them were damaged. The damage patterns are summarized based on the characteristics and the distribution of the lining cracks. This systematic investigation, involving geological conditions, design documents, construction and maintenance records of these tunnels, has been conducted to assess the potential factors that may have influence on the various damage patterns and the earthquake loading for tunnels. The results show that the degree of damage is associated with the geological condition and structural arrangement of the tunnel. A tunnel passing through a displaced fault zone will definitely suffer damage. The extent of geological weak zones, distance from the epicenter, and the existence of a slope face are also significant influencing factors. The seismic capacity of the tunnel is influenced by its structural arrangement, type of lining, invert setup, lining reinforcement, and other parameters.     

Cause investigation and verification of lining cracking of bifurcation tunnel at Huizhou Pumped Storage Power Station

A wide range of cracking happens in concrete lining at the crown of the lower adit and high-pressure bifurcation in the water-filled test of bifurcation tunnel at Huizhou Pumped Storage Power Station. Then a field investigation is undertaken to explore the main reason of such prominent lining cracking. Through investigating several possible inducing factors, it is found that mass defects exist in the concrete lining in constructing bifurcation tunnel, and insufficient thickness of concrete lining is probably the main factor causing lining cracks. In order to verify if this conclusion is reasonable, comparative analysis through numerical simulation is utilized to assess the influence of different concrete thicknesses on tunnel stability for the lower adit and high-pressure bifurcation. And then the fracturing process of concrete lining with the increase of internal water pressure during the water-filled test is simulated. The results reveal that the displacements and tensile strains in the lining crown are significantly bigger than other parts of tunnel, with deficiency in concrete thickness considered. It is also concluded that whether the cavities exist or not in the crown, rather than the cavity thickness, is the main factor influencing the values and distributions of the tensile strains and displacements for tunnel lining. Besides, the distribution of tensile-strain-concentrated zones is approximately in good agreement with the in-situ fractured status of concrete lining. Finally, a conclusion can be drawn that deficiency in concrete thickness in the crown is the primary triggering factor for lining cracking.     

渗水高压引水隧洞衬砌的设计研究

在借助渗流体积力考虑渗流场的力学效应，并由室内试验获得渗透系数随应力水平而变化的关系式的基础上，建立了裂缝混凝土衬砌和渗水围岩地层中渗流场与应力场的耦合计算模型，然后根据衬砌混凝土裂缝出现和开展后的受力变形的特征，提出了一种可供高压引水隧洞衬砌配筋采用的计算方法，并将其应用于广蓄电站二期工程高压引水隧洞衬砌的设计研究。     

受荷状态下盾构隧道管片锈蚀劣化破坏过程研究

为研究服役期盾构隧道衬砌结构性能衰退演变规律,从隧道结构长期处于水土荷载和周围离子侵蚀环境耦合作用下的特点出发,根据服役盾构管片压弯荷载受荷特征,采用弯矩、轴力导入的方式,等效地模拟盾构隧道管片的实际受力状态,结合围堰式的电化学加速锈蚀方式,研发了可实现压弯受荷状态下进行盾构管片加速锈蚀劣化的试验系统,重点分析不同工况下盾构隧道管片锈蚀劣化发生发展规律。主要结论有：未锈蚀管片裂缝形态主要以受拉横向裂纹为主;未加载锈蚀管片在锈蚀阶段仅产生顺筋锈胀裂纹,裂纹宽度体现出先增大后趋于稳定的特点,加载破坏阶段锈蚀区混凝土在锈胀裂纹和受拉裂纹共同作用下将出现混凝土局部剥离与错动现象;压弯受荷状态下,管片裂缝的扩展是钢筋锈蚀与外加荷载共同作用的效果,管片受拉裂纹与锈蚀裂纹体现出相伴发生发展的规律,管片承载能力存在较大降低。研究成果可为设计基准期内盾构隧道管片衬砌结构长期安全性能评价提供重要参考。     

铁路隧道衬砌极限状态法设计验证研究

为了验证极限状态法在隧道衬砌设计中的可操作性,分别采用极限状态法和破损阶段法对铁路隧道衬砌进行了试设计,并对比分析了两种方法的试设计结果。研究结果表明:(1)当衬砌为素混凝土结构时,极限状态法的计算厚度均比破损阶段法计算厚度大,最大相差20 cm,需对极限状态法抗裂验算公式中的调整系数γ_d重新校核,校核后γ_d=1.55;(2)针对钢筋混凝土衬砌结构及明洞结构,极限状态法的设计结果与破损阶段法设计结果基本相同,钢筋混凝土结构的极限状态方程中相关分项系数及调整系数取值是合理的。(3)采用极限状态法(γ_d=1.55)与破损阶段法试设计工程投资相当,极限状态法较破损阶段法工程投资增加237万元,增加1%。     

隧道二衬混凝土裂缝的成因分析和修补及预防

指出在隧道工程施工过程中,衬砌混凝土的裂缝问题始终困惑于工程技术人员,是一个普遍存在而又难于解决的质量问题,针对隧道衬砌混凝土工程中常见的一些裂缝问题进行了探讨分析,并提出了一些修补方案及预防控制措施,以便在工程实践中得以应用。     

既有地下结构安全性鉴定研究

上世纪70年代初哈尔滨市按照当时地铁限界标准修建了一条地下人防工程(即7381工程),隧道穿越粉质粘土、细砂土层,埋深10～20 m.为了评价7381工程现在用于地铁运营的安全性,从结构承载能力、构造、变形和裂缝等方面进行了详细检测,主要内容包括混凝土强度、混凝土碳化、混凝土表面裂缝、钢筋强度及锈蚀、隧道衬砌拱顶厚度等.在检测结果基础上,对主洞衬砌和车站三联拱的承载能力进行了计算.通过多种力学模型讨论衬砌所承受的围岩压力,并依据比较结果,推荐泰沙基模型.计算结果表明衬砌结构承载能力满足现行有关规范要求.对衬砌存在的损伤和劣化进行了机理分析,并提出了有针对性的治理方法.结合地质勘查结果和衬砌结构使用寿命评估结果得出:哈尔滨7381工程经整治后可以用于地铁运营,其剩余使用寿命估算为80年.     

Dynamic responses and damage analyses of tunnel lining and errant large vehicle during collision

Collision accidents between errant vehicles and tunnels occur frequently, causing serious loss of life and property as well as the damage to the tunnel lining. Damage analysis of the tunnel lining under collision loads is still a lack of research at present. Based on dynamic finite element method, this study simulates and analyzes the interaction between errant large vehicles and tunnel lining structure and their dynamic response processes under various collision cases. It is noted that the lining structure mainly suffers tensile damage and its value increases with the increases of the collision angle and the vehicle speed. The larger the vehicle speed and the collision angle are, the bigger accelerations the passengers experience. A series of in-situ damage detections and sampling tests of the tunnel lining in a real collision accident that occurred in the Panlong Tunnel on Jinghu Highway in China in 2009 strongly approve the numerical simulation results. This study provides technical supports to the optimal design and operations management of tunnels.     

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。     

浅埋黄土隧道衬砌结构受力分析

通过对三十里铺隧道的现场测试,研究浅埋黄土隧道一衬和围岩接触应力、锚杆轴力、喷射混凝土表面应变、二衬中钢筋应力和浇注混凝土应变随时间变化规律及分布特征。结果表明,围岩释放应力最大值在7～10 d,位置在拱腰处;锚杆轴力稳定时间为30 d左右,且在空间上出现压应力区;喷射混凝土表面应变较大且常出现跳跃性变化;二衬钢筋应力初期为拉应力;边墙处的稳定时间为6～8 d后,拱顶处30 d后仍然递减;二衬混凝土应变由初期的拉应变向压应变变化。隧道衬砌的受力分析结果为支护系统的优化提供依据,对同类工程的设计提供借鉴。     

浅埋黄土隧道衬砌结构受力分析

 通过对三十里铺隧道的现场测试,研究浅埋黄土隧道一衬和围岩接触应力、锚杆轴力、喷射混凝土表面应变、二衬中钢筋应力和浇注混凝土应变随时间变化规律及分布特征。结果表明,围岩释放应力最大值在7～10 d,位置在拱腰处;锚杆轴力稳定时间为30 d左右,且在空间上出现压应力区;喷射混凝土表面应变较大且常出现跳跃性变化;二衬钢筋应力初期为拉应力;边墙处的稳定时间为6～8 d后,拱顶处30 d后仍然递减;二衬混凝土应变由初期的拉应变向压应变变化。隧道衬砌的受力分析结果为支护系统的优化提供依据,对同类工程的设计提供借鉴。     

基于FDEM的隧道衬砌裂缝开裂过程数值分析

采用杂交有限元–离散元法(FDEM),与日本等比尺浅埋隧道衬砌试验结果进行了对比分析。数值模型较好地再现了试验中衬砌结构性裂缝的初裂、增扩直至破坏的全过程。其次,建立荷载结构模型,针对影响衬砌开裂的3个主要荷载因素,即局部偏压、背后空洞和拱顶松弛地压,分别研究了这些压力不同作用位置、作用范围、作用大小下的裂缝扩展过程、分布规律。为用非连续方法研究衬砌裂缝开裂过程提供了借鉴,同时也为隧道衬砌裂缝病害的防治与加固修复打下了基础。