排水管堵塞引起的高铁隧道结构变形与渗流场特征模拟试验研究

基于3D打印技术构建了高铁隧道结构及排水系统设施精细模型,提出了切实可行的隧道堵管模拟方法及模拟装置,依托典型病害案例开展了堵管病害相似模型模拟试验,探讨了在不同堵管条件、不同地层水头下隧道渗流场(隧道排水量、结构外水压力)及结构位移量的变化规律特征。研究结果表明:随堵塞程度加深,隧道排水量呈现先慢后快型下降趋势,具体为排水管堵塞率为50%前隧道排水量下降幅度较小,而堵塞率达50%后隧道排水量骤减直至不排水;底部结构隆起位移存在"隧底>内轨>外轨"的量值关系,且随堵塞程度加深隆起位移呈现先慢后快型增长趋势;受排水减少影响,堵管后结构外水压力逐步由"隧底最大,拱顶、拱腰次之,墙脚最小"的扇贝型分布转为"静水压"型分布;至全堵条件下地层水头40 m时试验位移结果与现场病害特征吻合良好,验证了上述模拟方法的可行性与有效性。研究成果以期为富水隧道堵管防治及类似病害评价提供借鉴与指导作用。     

Chemical injection application at tunnel service shaft to prevent ground settlement induced by groundwater drainage: A case study

Chemical injections are used in a variety of applications in civil and mining engineering, including ground stabilization, support anchoring, strata sealing, reduction and diversion of groundwater flow and water ingress, and creation of a load-bearing ring during tunneling. Historically, injection application without pressure was first employed by the Romans. Polyurethane injections have been used in coal mines to stabilize roofs and to reduce problems regarding water ingress in shafts and tunnels. This paper focuses on chemical injection, which was employed to prevent ground settlement induced by groundwater drainage from the shaft. As a result of the drainage of 4.5 l/s groundwater from the Shaft 4, which was sunk for service at Guzelyali station of Izmir Metro Project, the groundwater level dropped 4 m from the original level, and ground settlement reached 98 mm, while the inner tunnel vertical convergence was 23 mm. This can be explained with the closure of pore volumes in the overburden. Ground settlement was stopped and groundwater level approached its original level after chemical injection.     

铁路隧道初期支护极限位移的意义及确定

阐述了隧道支护系统极限位移的意义,系统地介绍了初期支护极限位移的确定方法。采用连续体模型,按铁路隧道衬砌标准设计采用的断面形式和材料参数,对各级围岩中不同埋深条件下铁路隧道初期支护极限位移进行计算模拟,并对计算结果进行统计处理,与允许位移进行比较,单、双线断面相对位移分开,拱顶下沉、拱脚水平位移和墙脚水平位移设不同判据,采用修订前规范所列的埋深档次,确定档次范围值,最后综合确定出一套适于当今铁路隧道位移判别的极限位移数据。     

高速铁路路基沉降高聚物注浆修复后动力性能及长期耐久性的试验研究

高速铁路路基的过大沉降影响轨道结构耐久性和列车运行安全,有必要及时通过抬升路基水平恢复轨道线路的垂向平整性。尝试通过在路基表层和轨道混凝土底座之间进行非水反应高分子聚合物填充注浆的方法实现轨道结构的整体均匀抬升。通过大型物理模型试验测试分析了抬升后轨道-路基的整体动力学性能及长期耐久性。通过定点循环激振试验对比分析了路基抬升前后的轨道整体刚度的变化规律,发现抬升后整体刚度相比抬升前略有减小,但对轨道-路基体系自振频率的影响有限;模拟列车运行的大周次循环加载测试了抬升后路基的动力累积沉降和动刚度变化过程,结果表明抬升后路基在列车长期荷载作用下具有较好的动力稳定性。     

浅埋铁路隧道下穿高速公路施工沉降研究

简要的介绍了防止浅埋铁路隧道施工沉降的重要性以及导致浅埋铁路隧道施工沉降的主要因素,并提出了控制浅埋铁路隧道施工沉降的有效措施,以期在确保铁路正常通行的前提下保证高速公路的行车安全。     

厦门海底隧道结构防排水原则研究

 海底隧道不同于陆地隧道，水压高，水源充足，又无天然出口，海底隧道的渗水问题远比陆地隧道严重得多，处理起来也困难得多。海底隧道结构防排水系统的合理性和可靠性是海底隧道成功的关键，也是控制运营费用的主要部分，海底隧道结构防排水原则和标准的确定又是设计合理防排水系统的基础。在分析国外已建成海底隧道防排水设计的基础上，提出确定海底隧道防排水原则的临界地下水位，并通过数值分析计算厦门海底隧道设置盲管排水系统后的排水量和衬砌背后水压，从运营经济性角度分析排导系统设置的可行性，提出厦门海底隧道应采用“以堵为主，限量排放”的防排水原则。在此基础上，提出厦门海底隧道合理的防排水体系，并在工程中得到应用。提出的研究方法也可为其他海底隧道结构防排水系统设计提供参考。     

Experimental study on the anti-clogging ability of siphon drainage and engineering application

The safety of the slope retaining wall along the expressway is often threatened by groundwater, and the clogged drainage holes, which seriously affects the safety and stability of the retaining wall. To solve the clogging issue of the drainage hole, in this research, model tests and theoretical analysis were carried out to demonstrate the existing of clogging problem of the siphon drainage, the results showed that the soil particle (d < 1 mm) can be carried out by siphon drainage with 4 mm pipe diameter, the anti-clogging ability of siphon drainage with 4 mm pipe diameter was clarified. And the siphon drainage was applied to the retaining wall along the Longli Expressway. The monitoring data of the groundwater level showed that the groundwater level after the arrangement of siphon drainage was significantly decreased. There was no indication of clogging for the siphon drainage within the four-month of operation. It proves the implementation of siphon drainage method can effectively reduce the groundwater level behind the retaining wall in the rich water area, and it is a long-term method to treat the leakage hazard of the retaining wall.     

铁路隧道仰拱施工控制

针对仰拱是隧道结构的主要组成部分之一,它是隧道结构的基础,结合太中银铁路兴旺峁隧道仰拱施工的实例,着重说明了铁路隧道仰拱施工的主要注意事项及相应的处理措施,从而确保该隧道仰拱施工质量。     

Effect of drainage conditions on porewater pressure distributions and lining stresses in drained tunnels

This study deals with the effect of drainage conditions on porewater pressure distributions and lining stresses in drained tunnels. Firstly, simple closed-form analytical solutions for the steady-state porewater pressure are re-derived within a common theoretical framework for two different boundary conditions (one for zero water pressure and the other for a constant total head) along the tunnel circumference by using the conformal mapping technique. The difference in porewater pressure distributions among the analytical solutions is investigated. The numerical simulation of a drained circular tunnel under the steady-state groundwater flow condition is made to investigate the effect of porewater pressure distributions on lining stresses. Secondly, the case study of the planned South Blue Line Extension subway tunnel under the steady-state groundwater flow condition is performed for four different drainage conditions (sealed, fully-drained with zero water pressure or a constant total head, and invert only-drained) along the tunnel circumference. The effects of different drainage conditions on porewater pressure distributions, flow nets, and lining stresses are investigated.     

Evaluation of drainage system around a lined pilot cavern for underground cryogenic LNG storage

A lined pilot cavern for underground cryogenic LNG (liquefied natural gas) storage was constructed in granite in Daejeon, Korea in 2003 and commissioned in 2004. As the hydrostatic pressure of groundwater and thermal stress due to the formation of ice lenses may damage the containment system, rock drainage around the pilot cavern is needed to maintain the stability of the containment system. Once the drainage works were completed, the level of groundwater around the pilot cavern was controlled using drainage holes to form an ice ring as a second barrier to prevent the leakage of LNG from the cavern. In order to establish the drainage system for the pilot cavern, 15 boreholes were drilled into the rock. Fractures in the rock mass around the pilot cavern were characterized to determine the most appropriate orientation for the drainage holes. The major joints acting as conduits for inflow water were designed for efficient drainage. After the 15 drainage holes were drilled and their efficiency tested during the dry season in April 2003, it was found that there was a problem with the inflow of water through the main joint along the right-hand wall of the cavern, indicating the system was less efficient on the right-hand side. Hence, three more boreholes were drilled in the correct direction on the right-hand wall of the cavern. A second drainage test was conducted during the rainy season in August. This showed some seepage into the bottom of the pilot cavern. In order to reduce this seepage, two more additional drainage holes were drilled and grouted below the concrete invert. Although the drainage system was very efficient, weak points in the system were found by testing and changes were made to the system to improve its efficiency.     

三台阶临时仰拱法在单线铁路隧道中的应用

以具体工程为例,介绍了三台阶临时仰拱法在单线铁路隧道中的应用,分别阐述了CRD法与三台阶临时抑拱法的优缺点,并对开挖方案进行了优化,实践证明采用三台阶临时仰拱法施工既可保证隧道安全又能提高施工工效。     

Combined freeze-sealing and New Tubular Roof construction methods for seaside urban tunnel in soft ground

Construction of seaside urban tunnels is significantly difficult due to the densely adjacent buildings and underground facilities in conjunction with unfavourable geological conditions. For this, this paper investigates the construction methods used for Gongbei Tunnel, which is a typical seaside tunnel connecting Hong Kong-Zhuhai-Macau Bridge in China. The construction methods and stability of the undercutting section will be focused. In the tunnel section of interest, dozens of thick steel tubes are jacked into the soft soil, and freeze-sealing method is applied to form a thick water-proofing wall. In this study, the combined freezing and New Tubular Roof (NTR) method are simulated by thermo-mechanical coupling analysis. The temperature field obtained in the freezing process indicates that the thickness of frozen wall grows approx. 2.0 m after 50 days of freezing. Besides, the stability of the surrounding ground and supporting structures in the bench-cutting stage are also investigated. Then the thawing process is simulated and associated suggestions for post-grouting to prevent excessive thawing settlement are proposed. The numerical results show that the tunnel is stable and the influence of tunnel excavation on adjacent buildings is within the permissible range. It also shows that the designed construction methods can be used to adequately meet safety and stability standards when adopting the proposed construction and supporting system.     

深层排水孔堵塞对富水岩质高边坡稳定性的影响

高边坡施工或运营期间常因多种因素作用导致排水孔堵塞,从而抬升地下水位,影响边坡稳定性和支护结构的安全。基于渗流折射定律,采用空气单元法模拟排水孔,开展了岩质高边坡渗流应力耦合分析,重点研究了排水孔不同堵塞工况下的坡后地下水位变化及支护结构力学响应。计算结果表明:排水孔堵塞对坡后地下水位影响显著,坡内位移整体变化不大,坡趾位置岩体变形最大;坡体锚杆轴力明显增加,最大增长幅度达到45%。对于布设深层排水孔的岩质高边坡,排水孔堵塞后边坡支护结构的位移变化明显,对支护结构的影响不容忽视,尤其体现在坡趾剪出口位置。此外,排水孔接近完全堵塞时,边坡安全系数显著降低。提出了以框架式格构和锚杆共同作为支护体系的高边坡处理措施,即下部边坡加强格构支护强度,上部边坡增加锚杆锚固长度。     

Deformation characteristics and safety assessment of a high-speed railway induced by undercutting metro tunnel excavation

Stratum deformation (settlement) is a challenging issue in tunnel engineering, especially when construction of metro tunnels has to undercut high-speed railway. For this purpose, we used the FLAC^3D software to analyze the stratum settlement characteristics of high-speed railway at different crossing angles intersected by metro tunnel, in terms of ground settlement trough, stratum slip line and irregularity of ballastless tracks. According to the evolution of the stratum settlement at different angle regions, an optimized angle is proposed for the actual project design. In order to reduce the influence of stratum settlement on the safety of high-speed railway, an approach of safety assessment is proposed for the shield engineering undercutting high-speed railway, as per Chinese specifications using numerical results and on-site conditions. A case study is conducted for the shield tunnel section crossing the Wuhan – Guangzhou High-speed Railway between the Guangzhou North Railway Station and the Huacheng Road Station, which represents the first metro tunnel project passing below a high-speed railway in China. A series of measures is taken to ensure the safe excavation of the shield tunnel and the operation of the high-speed railway. The results can provide a technical support for performing a safety evaluation between high-speed railways and metro tunnels.     

列车振动下隧道基底合理结构型式的研究

采用弹塑性二维非线性有限元法分析了隧道及周围环境在列车振动下的响应，分析中考虑了仰拱的不同结构形式、不同曲率、不同刚度、仰拱与边墙的不同联结方式。根据分析得到的仰拱中和仰拱下部围岩中的应力分布图，评价了仰拱对列车振动反应的影响，认为列车振动下隧道基底结构较为合理的结构形式和措施为：(1)采用矢跨比较大的仰拱；(2)采用较厚的隧底填充；(3)将仰拱、隧底填充和道床用同级混凝土浇灌成为一个整体结构；(4)采用各种排水措施排除隧底以下积水，避免长期振动下引起的岩土液化；(5)采用注浆和安设锚杆加固基底围岩，以提高其强度。     

Design and optimisation of laser scanning for tunnels geometry inspection

The use of terrestrial laser scanning technology in engineering surveys is gaining an increasing interest due to the very high spatial density of the acquired data. Recent improvements regarding the speed, accuracy, software algorithms and the fall in price have introduced a high potential for large scale applications of this technology in highly demanding engineering environments such as tunnels. Railway tunnels, in particular those of a long length, create challenges for surveyors due to their elongation to obtain satisfactory geometry of the scanned data. The purpose of this paper is to give an optimal solution for surveying tunnel geometry using laser scanning technology to reliably inspect railway tunnels and create “as-built” documentation.The proposed methodology provides optimisation of scanning parameters, scans registration, the georeferencing approach and the survey control network design. The maximal size of the scanner shifting along the tunnel alignment is primarily conditioned by factors including the incidence angle of the laser beam and the point density distribution. The authors introduce the so-called arbitrary georeferencing approach in long tunnel scanning that controls the point cloud geometric distortions to the required limits and contributes to time and material resources savings. Optimal design of the survey control network ensures the required positional accuracy and the reliability of the measurements, together with a cost effective approach to tunnels surveying.The proposed methodology is followed by the empirical results of the modelling and profiling of 12 tunnels in a single track railway. The lengths of these tunnels are from 60 m to 1260 m, with a total length of 3.5 km. Due to the specific geometry of the case study tunnels, the maximal favourable laser incidence angle is 78° with a distance of 13 m and consequently the optimal size of the scanner shifting along the tunnel alignment is 26 m. The survey control network is designed with the condition that the optimal reliability factors are within the required limits for engineering networks. A priori estimation of the control network positional uncertainty and a posteriori adjustment results shows that the achieved positional accuracy of the control points is approximately five times better than the requested absolute accuracy of the tunnel model: σ_m = 2 cm. On the largest tunnel example it is shown that the arbitrary georeferencing approach assures that the optimal registration error size is within the requested limits.     

高速铁路路基动力学研究进展

高速铁路是各个国家竞相发展的关键交通基础设施,对经济发展和社会进步都具有重要意义。高速铁路有别于传统铁路的最大特点是列车运行速度高,从而对铁路路基的振动和沉降等提出严苛的控制要求,突破传统岩土工程理论和技术范畴,高速铁路路基动力学已经成为铁道工程、岩土工程、结构动力学等多学科交叉的国际前沿和研究热点。文中总结国内外对高速铁路路基动力学的研究进展,重点阐述列车荷载作用下路基动力响应的理论分析模型、路基内部动应力分布特征和随着列车运行速度提高的放大效应、列车运行引起路基循环累积沉降分析方法及控制和修复技术等三个方面,并提出高速铁路路基动力学发展的展望。     

A two-dimensional experimental study of active progressive failure of deeply buried Qanat tunnels in sandy ground

As an ancient underground hydraulic engineering facility, the Qanat system has been used to draw groundwater from arid regions. A qanat is a horizontal tunnel with a slight incline that draws groundwater from a higher location and delivers it to lower agricultural land. During long-term water delivery, the qanat tunnel has experienced different degrees of aging and collapse, which may result in the significant ground settlement and even disasters. This paper developed a two-dimensional laboratory system to investigate the influence of progressive failure on the stability of deeply buried qanat tunnels. The developed system is fully instrumented with a particle image velocimetry (PIV) system and earth pressure and displacement monitoring. A special cylindrical membrane tube is designed and connected to an advanced pressure–volume controller to simulate the step-wise failure process of the tunnel. Three model tests were conducted on a dry sand considering the buried qanat tunnels at three different depths. Experimental results clearly show the progressive evolution of soil arching effect in the dry sand associated with the progressive failure of the tunnels. The failure of the Qanat ground starts from the vault and develops upwards, which is closely related to the evolution of stress contour at three consecutive stages. Ground surface settlement and volume loss corresponding to three burial depths were compared. A deeply buried qanat tunnel has a small effect on surface settlement. Earth pressure evolution on the 2D plane shows the load redistribution when the qanat collapses. The maximum arch and the initial point of the limit state correspond to a volume loss of 12.5 % and 50 %, respectively. For the collapse of the deep buried qanat tunnel, ground earth pressure evolution can be divided into a stress-increasing region, stress-decreasing region, and no redistribution region. Furthermore, a multi trap-door model considering soil expansion is proposed to describe the progressive failure behavior and its effects.     

非扰动开挖隧道模型的水压力试验研究

 隧道施工地下水问题困扰着隧道工程界多年,关于地下水压力对支护结构的影响认识不一致,为此需要从地下水作用机制研究出发,开展隧道衬砌水压力模型试验研究。模型隧道净空设计参考国内300～350 km/h高速铁路单线标准,模型试验的设计包括围岩模拟、试验流体、参数选择、试验工况、试验仪器选择等,试验工况包括：不同水头高度(1,2和4 m)和不同支护及排水条件(无支护全排和二衬不排水)等。通过在实际岩体中的小比例洞室模拟试验研究,对隧道开挖和支护引起的地下水渗流变化过程、地下水排放方式与水荷载之间的相关关系等取得较明确的定性认识,并以模型试验为基础开展数值模拟分析,为隧道水压力定量研究奠定试验基础。     

Construction of a large-section long pedestrian underpass using pipe jacking in muddy silty clay: A case study

This paper presents a case study of constructing a large-section long pedestrian underpass using pipe jacking method in Nanjing, China. The underpass, having a width of 7 m and a height of 4.3 m, was jacked 94.5 m in muddy silty clay under a busy roadway with 6.2 m overburden soil, meanwhile it traverses above the existed shield metro tunnels with just 4.5 m from the underpass bottom to tunnel vault. This paper introduced the design and construction schemes of this project in detail. A pre-construction three dimensional numerical simulation was conducted to investigate the responses of the roadway and metro tunnels to pipe jacking construction. Based on the simulation results, the field monitoring program was proposed, and the tunnels deformation and ground settlement were constantly monitored. The field performances of the metro tunnels and roadway were analyzed according to the monitoring data. In the jacking process, the micro-underbreak method was adopted. In order to decrease the tunnels uplift and ground settlement, the actual volume of soil conveyed out from soil chamber to ground surface was kept 95–98% of theoretical soil volume cut by cutter head. In general, this project is completed successfully without taking any additional time and money-consuming deformation control measures. The ground traffic and underneath metro runs well during the whole construction process.