Analysis of the interaction between bolt-reinforced rock and surface support in tunnels based on convergence-confinement method

To investigate the interaction of the bolt-reinforced rock and the surface support,an analytical model of the convergence-confinement type is proposed,considering the sequential installation of the fully grouted rockbolts and the surface support.The rock mass is assumed to be elastic-brittle-plastic material,obeying the linear Mohr-Coulomb criterion or the non-linear Hoek-Brown criterion.According to the strain states of the tunnel wall at bolt and surface support installation and the relative magnitude between the bolt length and the plastic depth during the whole process,six cases are categorized upon solving the problem.Each case is divided into three stages due to the different effects of the active rockbolts and the passive surface support.The fictitious pressure is introduced to quantify the threedimensional(3D)effect of the tunnel face,and thus,the actual physical location along the tunnel axis of the analytical section can be considered.By using the bolt-rock strain compatibility and the rocksurface support displacement compatibility conditions,the solutions of longitudinal tunnel displacement and the reaction pressure of surface support along the tunnel axis are obtained.The proposed analytical solutions are validated by a series of 3D numerical simulations.Extensive parametric studies are conducted to examine the effect of the typical parameters of rockbolts and surface support on the tunnel displacement and the reaction pressure of the surface support under different rock conditions.The results show that the rockbolts are more effective in controlling the tunnel displacement than the surface support,which should be installed as soon as possible with a suitable length.For tunnels excavated in weak rocks or with restricted displacement control requirements,the surface support should also be installed or closed timely with a certain stiffness.The proposed method provides a convenient alternative approach for the optimization of rockbolts and surface support at the preliminary stage of tunnel design.

Trend analysis and comparison of basic parameters for tunnel blast design models

One of the most important factors influencing on a tunnel blast efficiency is the proper design of blasting pattern. Among blasting parameters, blasthole diameter and tunnel face area are more significant so that any change in these parameters could finally affect on specific charge and specific drilling. There are mainly two groups of methods for tunnel blast design categorized based on the parallel cuts and angular cuts. In this research, a software for tunnel blast design was developed to analyze the effect and sensitiveness of blasthole diameter and the tunnel face area on blasting results in different blast design models. Using the software, it is quickly possible to determine specific charge, specific drilling and number of blastholes for each blast design model. The relations between both of blasthole diameters and the tunnel face area with the above parameters in different blast design models were then investigated to yield a set of equations with the highest correlations to compare the methods. The results showed that angular method requires more blasthole numbers than parallel method in similar condition(blasthole diameter and tunnel face area). Moreover, the specific charge values yielded by the two methods are approximately the same and very close together.

Design and Wind Tunnel Study of a Top-mounted Diverterless Inlet

Combined with a UAV of the shape like Global Hawk, a new inlet is advanced to obtain high performance in both Radar Cross Section(RCS) and aerodynamic drag. Efforts are made to achieve this goal such as adopting a top-mounted inlet configuration, utilizing the diverterless technique and putting forward a new shape of entrance. A design method is brought forward and verified by wind tunnel tests. Results indicate: (1) Despite the negative effect of the front fuselage and the absence of the conventional boundary diverter, the performance of the top-mounted diverterless inlet advanced here(Ma:0.50-0.70, α:-4°-6°,σ>0.975) is equivalent to that of conventional S shaped inlet with diverter; (2) The integration of the inlet with the fuselage is realized by the utilization of a special inlet section and the diverterless technique, which disposes the whole inlet in the shield of the head of UAV, improving the drag characteristics and the stealthy performance of the aircraft; (3) The bump which is equal to the local boundary layer thickness in height can divert the boundary layer effectively. As a result, no obvious low total pressure zone is found at the outlet of the inlet; (4) According to the experimental results, negative angle of attack is favorable to the total pressure recovery and positive angle of attack is favorable to the total pressure distortion, while yaw brings bad effects on both; (5) The design of cowl lip is of great importance to the inlet performance at yaw, therefore, further improvement of the inlet performance will rely on the lip shapes of the cowl chosen.

Geotechnical investigations and remediation design for failure of tunnel portal section： a case study in northern Turkey

Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and anthropogenic impacts are generally reported as the most important triggering factors in the region. Following the portal slope excavations in the entrance section of Cankurtaran tunnel, located in the region, where the highly weathered andesitic tuff crops out, a circular toe failure occurred. The main target of the present study is to investigate the causes and occurrence mechanism of this failure and to determine the feasible remedial measures against it using finite element method(FEM) in four stages. These stages are slope stability analyses for pre-and postexcavation cases, and remediation design assessments for slope and tunnel. The results of the FEM-SSR analyses indicated that the insufficient initial support design and weathering of the andesitic tuffs are the main factors that caused the portal failure. After installing a rock retaining wall with jet grout columns and reinforced slope benching applications, the factor of safety increased from 0.83 to 2.80. In addition toslope stability evaluation, the Rock Mass Rating(RMR), Rock Mass Quality(Q) and New Austrian Tunneling Method(NATM) systems were also utilized as empirical methods to characterize the tunnel ground and to determine the tunnel support design. The performance of the suggested empirical support design, induced stress distributions and deformations were analyzed by means of numerical modelling. Finally, it was concluded that the recommended stabilization technique was essential for the dynamic long-term stability and prevents the effects of failure. Additionally, the FEM method gives useful and reasonably reliable results in evaluating the stability of cut slopes and tunnels excavated both in continuous and discontinuous rock masses.

Discussion on the Designing Difficulties of Fenghoshan Tunnel on Qinghai-Tibet Railway

The major technical difficulties of Fenghuoshan Tunnel were caused by arctic alpine, high altitude and permafrost. Through analysis of the major technical problems of Fenghuoshan Tunnel, this paper explored the designing methods and ways of tunnels in arctic alpine climate, on high altitude and on permafrost regions, to offer reference for the projects of similar nature.

Research on the stability analysis and design of soil tunnel surrounding rock

The paper first analyzes the failure mechanism and mode of tunnel according to model experiments and mechanical calculation and then discusses the deficiency of taking the limit value of displacement around the tunnel and the size of the plastic zone of surrounding rock as the criterion of stability. So the writers put forward the idea that the safety factor of surrounding rock calculated through strength reduction FEM(finit element method) should be regarded as the criterion of stability,which has strict mechanical basis and unified standard and would not be influenced by other factors. The paper also studies the safety factors of tunnel surrounding rock (safety factors of shear and tension failure) and lining and some methods of designing and calculating tunnels. At last,the writers take the loess tunnel for instance and show the design and calculation results of two-lane railway tunnel.

Determination of horizontal and vertical design spectra based on ground motion records at Lali tunnel, Iran

Most acceleration diagrams show high levels of unpredictability, as a result, it is the best to avoid using diagrams of earthquake acceleration spect~＇a, even if the diagrams recorded at the site in question. In order to design earthquake resistant structures, we, instead, suggest constructing a design spectrum using a set of spectra that have common characteristics to the recorded acceleration diagrams at a particular site and smoothing the associated data. In this study, we conducted a time history analysis and determined a design spectrum for the region near the Lali tunnel in Southwestern Iran. We selected 13 specific ground motion records from the rock site to construct the design spectrum. To process the data, we first applied a base-line correction and then calculated the signal-to-noise ratio （]~SN） for each record. Next, we calculated the Fourier amplitude spectra of the acceleration pertaining to the signal window （1）, and the Fourier amplitude spectra of the associated noise （2）. After dividing each spectra by the square root of the selected window interval, they were divided by each other （1 divided by 2）, in order to obtain the ~SN ratio （filtering was also applied）. In addition, all data were normalized to the peak ground acceleration （PGA）. Next, the normalized vertical and horizontal responses and mean response spectrum （50%） and the mean plus-one standard deviation （84%） were calculated for all the selected ground motion records at 5% damping. Finally, the mean design spectrum and the mean plus-one standard deviation were plotted for the spectrums. The equation of the mean and the above-mean design spectrum at the Lali tunnel site are also provided, along with our observed conclusions.

基于总安全系数法的喷射混凝土支护承载能力的试验研究

为验证总安全系数法中喷层的荷载结构模型及其安全系数计算方法,研制大型隧道结构模型试验系统,采取结构试验的方法,开展毛洞、不同厚度喷层以及二次衬砌的加载破坏试验。通过围岩和细砂材料的三轴试验明确模型试验中各材料的物理与力学参数,模拟毛洞、不同厚度喷层以及二次衬砌的加载破坏全过程,依据破坏状态明确喷层与二次衬砌的设计承载能力,试验中监测围岩应力应变、喷层内外侧应变和喷层位移,结合监测结果分析喷层与二次衬砌在承载过程中的变形特征与受力特征,明晰喷层与二次衬砌的承载机制,并与总安全系数法理论计算结果进行对比分析。结果表明:1)在试验断面条件下喷层受力状态为小偏心受压,喷层与围岩之间的粘结能有效传递剪力,从而减少了喷层的弯矩,有利于充分发挥喷层的抗压强度,同厚度情况下喷层的设计承载力要高于二次衬砌;2)试验得到的厚度为2 cm和4 cm喷层的设计承载力比总安全系数法理论计算结果分别大27.0%和22.9%,表明总安全系数法的喷层承载力计算模型是合理的,并具有合适的安全性。

小转弯曲线隧道TBM选型与掘进姿态调控方法

小转弯隧道施工时全断面隧道掘进机(full-section tunnel boring machine,TBM)的选型设计和掘进姿态控制具有特殊性,目前还缺乏通用的理论依据和指导方法。针对此问题,首先,对传统类型TBM小转弯选型进行研究,结合已有项目数据和几何模拟,确定传统类型TBM能适应的最小转弯半径。然后,对双盾敞开式TBM的推进系统和导向系统进行针对性设计,通过分析双盾敞开式TBM推进系统结构和实际施工,提出转弯时双盾敞开式TBM推进油缸内外侧行程差值的理论计算方法和施工过程中的姿态调控方法。最后,得出如下结论:1)当隧道转弯半径小于200 m时,敞开式TBM适应难度较大,需要采用双盾敞开式TBM;2)结合抚宁抽水蓄能电站项目实际施工情况,提出的双盾敞开式TBM的理论计算方法和姿态调控方法确保了转弯段隧道的轴线偏差在要求范围内。

基准排放因子更新对隧道需风量的影响研究

为解决交通车辆持续更新导致的城市隧道内通风系统设计浪费和运营闲置,研究基准排放因子更新对隧道需风量的影响,并建立2种应对车辆更新的基准排放因子计算方法.首先,通过理论分析明确需风量计算式中随时间更新的关键参数为基准排放因子;随后,根据定量分析得到基准排放因子和纵坡-车速系数更新对需风量的影响;最后,结合国外理念和实际设计经验,提出2种考虑时间更新的基准排放因子计算方法.研究结果表明:我国道路隧道通风设计规范在制定基准排放因子时参考了世界道路协会(PIARC)通风报告,并分析得到了参考理由;与2000年相比,2021年的CO、NOx和PM基准排放限值分别降低了81.6%、76.7%和97.9%;建立了使用机动车污染物排放限值作为基准排放因子的最不利设计方法,计算出2018年各污染物基准排放因子(CO为0.0011 m^(3)/(辆·km),PM为0.4610 m^(2)/(辆·km)),相比于2014年《细则》分别降低84.3%和77.0%.建立并验证了基准排放因子计算方法,为城市道路隧道通风系统设计提供参考.

列车活塞风对寒区铁路隧道温度场的影响

研究目的:列车通过隧道会产生活塞风,活塞风会将寒区隧道洞外冷空气带入洞内,导致洞内温度场分布发生变化,若对这种影响认识不到位,会导致洞内抗防冻措施不合理造成冻害发生,影响隧道运营安全。鉴于此,采用理论分析和数值模拟等方法,分析列车活塞风对隧道洞内温度场的影响机制,研究列车活塞风对寒区特长铁路隧道洞内温度场的影响规律,为寒区隧道抗防冻设计提供技术支撑。研究结论:(1)冬季列车通过隧道后,活塞风会引起洞内温度场在短时间内显著变化,列车活塞风对洞内温度场持续影响时间较短,列车通过后,洞内温度场会逐渐恢复,特别是当列车频次较小时,基本可恢复到自然通风条件下状态;(2)行车频次导致洞内纵向负温长度增大或减小率均在1%左右;随着围岩温度的增大,隧道洞内纵向负温长度显著降低,且围岩温度越高,活塞风作用方向对洞内温度场影响越小;(3)考虑活塞风对寒区隧道防寒抗冻影响时,应重点考虑其对两侧水沟抗防冻的影响;由于局部衬砌会出现交替冻融现象,隧道结构设计时,应对衬砌耐久性做一定的考虑;(4)本研究成果可供寒区特长铁路隧道建设参考,特别是单向自然风条件下铁路隧道抗防冻设计。

湖底隧道工程排水与消防系统设计

为将隧道受水灾和火灾可能性降至最低,以湖底隧道工程为依托,针对隧道排水与消防系统设计要点进行总结分析,应用排水与消防系统,能及早准确地预警水情与火灾,并实现即时现场报警与远程报警。该系统有效提升了隧道防汛预警和识别火灾的精准度以及应急抢险的智能化水平,能更好地保障人民群众的生命财产安全,可供类似隧道工程参考。

高速槽道双体艇船型设计与阻力性能评估

[目的]槽道双体艇是一种中部贯通含有两个滑行片体的特殊滑行艇船型,中部槽道受到气旋抬升作用能使艇体脱离水面达到更高的航速,具有良好的快速性,同时在高速航行时能很快进入稳定状态。针对高速槽道双体艇的艇型参数化设计与阻力性能评估对于高性能船舶的船型开发与设计具有重要意义。[方法]采用clamped B样条曲线定义槽道双体艇的主要型线进行艇体船型参数化构型,并通过STAR-CCM+软件设置多船型方案对比,研究双体艇槽道尺寸和斜升角大小对艇体阻力性能的影响。[结果]得到比初始设计船型阻力降低17.3%的优选船型方案。[结论]与同尺度同排水量单体滑行艇对比,结果证明,在中高速工况下,本文所研究的高速槽道双体艇具有更加优良的航行性能。

Numerical analyses in the design of umbrella arch systems

Due to advances in numerical modelling, it is possible to capture complex support-ground interaction intwo dimensions and three dimensions for mechanical analysis of complex tunnel support systems,although such analysis may still be too complex for routine design calculations. One such system is theforepole element, installed within the umbrella arch temporary support system for tunnels, whichwarrants such support measures. A review of engineering literature illustrates that a lack of designstandards exists regarding the use of forepole elements. Therefore, when designing such support, designersmust employ complex numerical models combined with engineering judgement. With referenceto past developments by others and new investigations conducted by the authors on the Driskos tunnelin Greece and the Istanbul metro, this paper illustrates how advanced numerical modelling tools canfacilitate understanding of the influences of design parameters associated with the use of forepole elements.In addition, this paper highlights the complexity of the ground-support interaction whensimulated with two-dimensional （2D） finite element software using a homogenous reinforced region,and three-dimensional （3D） finite difference software using structural elements. This paper further illustratessequential optimisation of two design parameters （spacing and overlap） using numericalmodelling. With regard to capturing system behaviour in the region between forepoles for the purpose ofdimensioning spacing, this paper employs three distinctive advanced numerical models： particle codes,continuous finite element models with joint set and Voronoi blocks. Finally, to capture the behaviour/failure ahead of the tunnel face （overlap parameter）, 2D axisymmetric models are employed. Finally,conclusions of 2D and 3D numerical assessment on the Driskos tunnel are drawn. The data enriched casestudy is examined to determine an optimum design, based on the proposed optimisation of designparameters, of forepole elements related to the site-specific considerations. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

国道G228线汕头湾跨海隧道总体设计方案研究

汕头湾跨海隧道作为国道G228汕头段控制性工程,总体设计难度大。为了科学、安全、经济地建设汕头湾跨海隧道,结合两岸城市规划、工程建设环境和环境敏感点等控制因素,采用工程类比、数值计算、模型分析等理论研究方法,对跨海隧道选址、接线、埋深、断面布置、通风及防灾救援等关键问题进行研究和专题论证,得出如下主要结论:1)跨海隧道选址及接线应以城市规划为基础,结合交通特性、路网结构、沿线用地等因素综合确定,是控制风险、降低投资和保障交通功能的关键;2)结合海床演变模型冲刷包络线,盾构段最小覆土不仅要满足掘进及运营期抗浮安全,还要尽量避免长距离穿越上软下硬地层;3)跨海段采用分段纵向+重点排烟的通风方案,解决长距离跨海隧道通风难题;4)盾构段采用人行滑梯或楼梯逃生的纵向疏散模式,明挖段采用横向疏散模式,可保障高地震烈度区跨海隧道的防灾疏散。

特急曲线水利隧洞针梁台车设计与施工

水利基础设施建设过程中,特急曲线水利隧洞具有弯多、弯急的特点。普通针梁台车在此类隧洞工程施工中,出现弯道碰壁、受压变形等诸多问题,传统施工装备与技术的适应性难题亟待解决。以金沙江向家坝灌区北总干渠一期工程望江岩隧洞衬砌施工为依托,在传统全圆针梁台车既有设计方法的基础上,开展加大单次衬砌长度、整体快速拆合、优化结构形式、改变脱模方式、实现高通用性等方面研究;研制特急曲线水利隧洞全圆针梁台车,创新台车不同状态下的施工工法,解决了台车在曲线处行走时会触碰隧洞壁,台车过特急曲线隧洞需重复拆卸及安装,衬砌完成后上、下侧模在受力状态下出现模板反向咬合等问题,有效推动了特急曲线隧洞施工装备设计方法革新。实际应用结果表明,所开发的特急曲线水利隧洞全圆针梁台车及其相关施工技术大幅度提高了特急曲线水利隧洞施工效率,降低了施工成本,保证了施工安全和工程质量。

铁路隧道绿色低碳建造技术工程实践与展望

为实现铁路隧道全生命周期向绿色低碳方向发展,以京张高铁清华园隧道、新八达岭隧道和八达岭长城站为背景,采用数据统计分析的方法研究铁路隧道建设和运营阶段的碳排放,从隧道线位和车站站位选择、建筑、结构、通风、照明等方面提出隧道减碳设计策略。研究结果表明,减碳设计策略主要包括增加碳汇和减少碳排放2大类。增加碳汇的措施有:1)采用隧道下穿方案可减少地表土地占用,增加地表绿化面积;2)隧道洞口可采用绿色格宾挡墙和绿色植被覆盖来增加碳汇能力。减少碳排放的措施有:1)合理选择隧道线位和车站站位,减少乘客交通接驳;2)车站采用群洞设计方案可减少土石方开挖和支护措施工程量;3)超大跨隧道采用围岩自承载的设计理念和方法可减少衬砌混凝土用量;4)地下车站采用无空调活塞通风系统、光源智能管理及光纤照明系统、电梯等大型设备智能管理系统等可减少运营阶段的能源消耗。最后,提出绿色结构物建造、全预制精巧化结构研发、设备智能管控技术、铁路带状光伏发电场、压缩空气储能电站等绿色建造技术。