Allowance of Lateral Breakthrough Error for Super Long Tunnels from 20km to 50km

Up to now there is no specification about the allowance of lateral breakthrough error for super long tunnel from 20 km to 50 km. On the basis of the design of GPS networks located outside and inside tunnel traverse network, we propose a method for calculating the influence value caused by control surveying errors. Through a lot of simulative calculations and combination with piercing practice of super tunnels in Wan Jiazai Project, Shanxi province, we present an allowance table of lateral breakthrough error for super long tunnels from 20 km to 50 km.

LONG AND DEEP DIVERSION TUNNELS OF 1^(ST) STAGE PROJECT IN WEST ROUTE OF SOUTH-NORTH WATER TRANSFER PROJECT

West Route of South-North Water Transfer Project,situated in southeastern Qinghai-Tibet Plateau,is a giant project,which will deliver 17 billion m3 of water from the main stream and tributaries upstream of the Yangtze River to the upper reaches of the Yellow River. It is to be constructed in 3 stages, of which the 1st stage project includes delivering 4 billion m3 of water by gravity from two tributaries of Yalong River and three tributaries of Dadu River. The project consists of 5 dams,7 tunnels and a channel in series,with the dam height of 63～123 m and water transfer length of 260.3 km,of which the tunnels measure 244.1 km. The special climatic,environmental and geologic conditions make the project much more complicated in construction,especially 3 tunnels with the length longer than 50 km each create challenges to the technical requirements of engineering survey,design and construction.

Predictive analysis of stress regime and possible squeezing deformation for super-long water conveyance tunnels in Pakistan

The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hoek–Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey's model can subsequently be employed to predict the areas' stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai–Tibet Plateau.Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH>-Sh> SVor SH> SV> Sh. The measured orientation of SHis NEE(N70.3°–89°E), and the regional orientation of SHfrom WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stresses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.

Practices on rockburst prevention and control in headrace tunnels of Jinping II hydropower station

Rockburst problems induced by high in-situ stresses were prominent during construction of the headrace tunnels of Jinping II hydropower station. The rockbursts occurred in various forms, and it is necessary to take pertinent measures for integrated prevention and control of rockbursts. In view of the rockburst characteristics during tunnel construction of Jinping II hydropower station, the engineering geological conditions were presented, and the features, mechanisms and forms of rockbursts observed during construction were analyzed in detail. A large number of scientific researches, experiments and applications were conducted. Multiple measures were adopted to prevent and control rockbursts, including the prediction and early warning measures, stress relief by blasting in advance, optimized blasting design and optimized tunnel support in the tunnel sections prone to strong rockbursts. The effectiveness of these prevention and control measures was evaluated. Experiences have been accumulated through a great number of helpful explorations and practices for rockburst prevention and control. A comprehensive rockburst prevention and control system has been gradually established.

Analysis of the Relationship between the Number of Traffic Accidents and the Traffic Flow &Section Location in Extra Long Tunnel

In order to study the influence of the traffic characteristics on traffic accidents in extra long tunnel, the main measurement indicators of traffic flow during the time of traffic accidents are matched with the accident information to form a data set of the number of traffic accidents and the hourly traffic flow of the accident. Vehicle ratio and the number of accidents are mainly used as the characteristic indicators of traffic flow. At the same time, the longitudinal distribution law of the average speed of traffic flow and the number of traffic accidents in the extra long tunnel is studied. Based on the superposition principle, the extra long tunnel is divided into 5 traffic safety zones. This paper analyzes the distribution of time, morphology, cause of accident, and other characteristics in different traffic safety zones, finding that the shape of traffic accidents in extra long tunnel is mainly rear-end collisions. Improper operation and illegal lane changes are the main causes of accidents.

A real-time prediction method for tunnel boring machine cutter-head torque using bidirectional long short-term memory networks optimized by multi-algorithm

Based on data from the Jilin Water Diversion Tunnels from the Songhua River(China),an improved and real-time prediction method optimized by multi-algorithm for tunnel boring machine(TBM)cutter-head torque is presented.Firstly,a function excluding invalid and abnormal data is established to distinguish TBM operating state,and a feature selection method based on the SelectKBest algorithm is proposed.Accordingly,ten features that are most closely related to the cutter-head torque are selected as input variables,which,in descending order of influence,include the sum of motor torque,cutter-head power,sum of motor power,sum of motor current,advance rate,cutter-head pressure,total thrust force,penetration rate,cutter-head rotational velocity,and field penetration index.Secondly,a real-time cutterhead torque prediction model’s structure is developed,based on the bidirectional long short-term memory(BLSTM)network integrating the dropout algorithm to prevent overfitting.Then,an algorithm to optimize hyperparameters of model based on Bayesian and cross-validation is proposed.Early stopping and checkpoint algorithms are integrated to optimize the training process.Finally,a BLSTMbased real-time cutter-head torque prediction model is developed,which fully utilizes the previous time-series tunneling information.The mean absolute percentage error(MAPE)of the model in the verification section is 7.3%,implying that the presented model is suitable for real-time cutter-head torque prediction.Furthermore,an incremental learning method based on the above base model is introduced to improve the adaptability of the model during the TBM tunneling.Comparison of the prediction performance between the base and incremental learning models in the same tunneling section shows that:(1)the MAPE of the predicted results of the BLSTM-based real-time cutter-head torque prediction model remains below 10%,and both the coefficient of determination(R^(2))and correlation coefficient(r)between measured and predicted values exceed 0.95;and(2)the incremental learning method is suitable for realtime cutter-head torque prediction and can effectively improve the prediction accuracy and generalization capacity of the model during the excavation process.

Benign Adjusting Effects of Long Tunnel on Environment and Slope Hazards:taking Erlang Mountain Tunnel as an example

The 21st century shall be a century of accelerated development of tunnel construction in China. But until now, what have been frequently stated in reports about influence of tunnels on environment are basically negative. In fact, this is not true. Tunnels, especially those extend across sensitive areas do exert some positive functions on improving environment and preventing local slope hazards. These positive effects, being new phenomena, are found and put forward by the authors after a series of careful observations have been carried out and in-depth analysis performed the first time. Meanwhile, it is a positive evaluation that the authors made upon tunnels. Many important phenomena and data are cited as evidence and their causative factors are analyzed in this paper as well.

Numerical simulation of rockburst disaster and control strategy of constant resistance and large deformation anchor cable in Gaoloushan tunnel

The Gaoloushan Tunnel in Longnan City,Gansu Province,China,frequently experiences rockburst disasters due to high in-situ stress.Managing rockburst in deep-buried tunnels remains a challenging issue.This paper employs RFPA(Rock Failure Process Analysis)software to establish a calculation model of constant resistance and large deformation(CRLD)anchorages and analyzes the effects of different support methods and pre-stress levels on rockburst.We simulate the process of tunnel rockburst disasters and find that ordinary anchor support incurs rockburst on the right arch waist and arch top,forming a V-shaped explosion pit.CRLD anchor support has several advantages in rockburst control,such as more uniform stress distribution in the surrounding rock,a uniform distribution of plastic zones,less noticeable damage to the tunnel,and effective control of the arch top displacement.The effectiveness of the CRLD anchor support under varying pre-stress conditions shows that a higher prestress results in a smaller plastic zone of the surrounding rock and arch top displacement and a lower number of acoustic emission signals,which better explains the excavation compensation effect.Moreover,adding long anchorages in the deep surrounding rock area can better control rockburst and reduce surrounding rock deformation.Based on these findings,we propose a comprehensive control system that combines long and short anchorages and provides the optimal scheme based on calculations.Therefore,by using high-prestress CRLD anchor support and the combination of long and short anchorages at critical positions,we can enhance the integrity of the surrounding rock,effectively absorb the energy released by the surrounding rock deformation,and reduce the incidence of rockburst disasters.

截至2023年底中国10km以上特长公路隧道统计与分析

在隧道行业相关单位的大力支持及既有统计数据的基础上,对截至2023年底中国已建成运营、正在建设、规划设计的共计74座长度10 km以上的特长公路隧道进行统计,其中,已建成运营特长公路隧道25座,正在建设特长公路隧道31座,规划设计特长公路隧道18座。从隧道长度、所在省份、公路等级、地理位置、技术标准、施工工法、设计与施工单位等方面,对中国已建成运营、正在建设、规划设计的长度10 km以上的特长公路隧道建设情况进行分析,其中:长度在10~14.9 km的隧道共62座,长度在15~19.9 km的隧道共10座,长度大于20 km的隧道共2座;隧道主要集中在中国西南部,约占63%,四川省最多,其次是云南省;高速公路隧道达65座,占比约为88%;山岭公路隧道68座,水下隧道6座;隧道技术标准以双向4车道为主;隧道施工工法以钻爆法为主,近些年出现了TBM+钻爆组合工法;隧道设计单位主要有31家;隧道施工单位主要有52家。

高地应力软岩隧道长期稳定性分析

研究目的:高地应力软岩具有明显的流变特性,流变过程中岩体参数随时间发生变化。本文结合梁王山隧道的设计施工方案,采用Cvisc模型对其施工过程及运营期间的围岩和支护的受力和变形情况进行分析,查明了隧道在施工阶段和长期运营阶段的应力、应变和变形特性以及隧道支护结构的内力与变形随时间发展规律。研究结论:(1)在软岩隧道工程施工中,施工时应对隧道初支拱脚处适当加固,控制拱脚变形;(2)不仅要保证施工期的安全,更需要关注隧道在后期运营过程中的长期稳定性;(3)需根据全寿命周期内的围岩流变稳定状态设计支护结构的刚度,从而确保隧道结构长期稳定;(4)本研究成果可为高地应力软岩隧道施工安全和长期稳定性研究提供参考。

CSAMT深埋长大隧道破碎岩体靶向勘察研究

铁路深埋长大隧道因其埋深大、里程长,同时伴随复杂多变的地质问题,致使地质勘察难以查明、查细,特别是对深埋长大隧道破碎岩体空间分布的精准定位一直是工程勘察中的难题。基于CSAMT三维正反演理论,研究建立了针对深埋长大隧道中破碎岩体靶向勘察模式,从而实现“点-线-面”的精准勘察。通过开展基于四面体网格的CSAMT三维正演和有限内存拟牛顿法的三维反演研究,以及二、三维模型分析对比,验证三维CSAMT在铁路隧道勘察中的优势。在滇西地区某深埋长大隧道TBM掘进工区开展三维“点-线-面”靶向勘察试验,结果表明该勘察体系可靠且精度高,精准探明了TBM卡机工区段前方的花岗岩蚀变带影响范围及其空间展布形态,确定了断层破碎带的影响范围及其空间展布形态,有效提高深埋长大隧道勘察精度。布置靶向测线从“点-线-面”进行三维CSAMT勘察这一思路,对深埋长大隧道的勘察工作提供一定的应用参考价值。

自动确定边角混合网独立闭合差的增量算法

为评定外业观测数据质量和发现粗差,提出了一种闭合差搜索的通用算法。首先,针对高速铁路隧道中的各类边角混合网,基于平差理论,计算由边角混合网中测站数、非测站数和观测数确定其独立闭合差的数目,给出最简闭合差构成原则,求出余弦和正弦闭合差,推导闭合差限差计算模型,建立由闭合差探测观测值粗差的方法;进而导出闭合差增量与测站递增产生的重叠观测点数之间的数学关系式,设计数据结构实现测站与结点间双向多对多的拓扑映射关系,并基于分治思想,提出队列-测站双循环的增量算法来自动搜索最简且独立的闭合差;最后,以西南某高速铁路隧道构建的边角混合网为例进行算法验证。结果表明:增量算法能够在混合网中自动确定100%数量的最简独立闭合差,对观测值中存在的粗差100%予以探测,验证了采用该算法搜索闭合差及检核粗差的有效性。

大跨度铁路桥附属构件对不同宽高比矩形断面涡振性能的影响

在已建成的大跨度鳊鱼洲长江大桥原设计宽高比为6.7∶1的四线铁路桥矩形箱型主梁断面的基础上,通过调整断面宽高比,设计宽高比为4∶1的二线铁路和宽高比为9∶1的六线铁路桥矩形箱梁断面。通过节段模型风洞试验,在0°,±3°和±5°风攻角的均匀来流下,对以上3种常用二线、四线和六线铁路桥矩形箱梁断面与对应相同宽高比纯矩形断面之间的涡振特性关系,以及铁路桥附属构件对不同宽高比矩形断面涡振性能的影响进行研究。结果表明:在宽高比分别为4∶1和6.7∶1的矩形断面上布置铁路桥附属构件能增大断面在负风攻角下的涡振振幅,在-5°风攻角下竖向涡振振幅增大率高达277.5%,但对正风攻角下的涡振响应起到一定的抑制作用,而在宽高比为9∶1的矩形断面布置六线铁路桥附属构件则能明显增大该断面在各风攻角下的涡振振幅,其扭转涡振振幅增大率均在48.3%以上;铁路桥附属构件对矩形断面涡振性能的降低作用随着断面宽高比的增大而提升,针对气动外形较钝的二线和四线铁路桥箱梁,可参考相似宽高比矩形断面涡振特性,并重点考察箱梁在负风攻角下的涡振响应,而针对宽高比较大的六线铁路桥箱梁,由于附属构件影响较大,参考相似宽高比矩形断面涡振特性的意义较小,均应详细研究其在各风攻角下的涡振性能。

特长水下公路盾构隧道结构防火保护策略及关键参数研究

特长水下公路盾构隧道普遍设置独立排烟道进行顶部集中排烟。现有隧道工程防火技术“护顶不护墙”,顶部设有排烟道时,顶部防火保护施加在烟道板上,而烟道层拱顶管片及车道层两侧管片不施加防火保护,存在安全隐患。根据隧道结构实际可能受到的火灾高温作用,结合管片、烟道板结构相对重要性,提出了新的车道层侧墙管片、烟道层拱顶管片、烟道板结构防火保护策略,即车道层所有结构表面采用RABT火灾升温曲线,烟道层所有结构表面采用基于CFD模拟的火灾升温曲线,耐火极限均不小于2.0h,管片耐火极限由管片混凝土表面及距表面25mm处温度判定,烟道板耐火极限由烟道板的极限弯曲变形量和极限弯曲变形速率判定。基于所提出的防火保护策略,开展数值模拟及耐火试验研究,确定了防火保护技术参数。结果表明:车道层侧墙管片防火保护层等效热阻应不小于0.10℃·m~2/W;烟道层拱顶管片防火保护层等效热阻在排烟口处不小于0.10℃·m~2/W,且随距排烟口距离的增大逐渐减小,距离排烟口16m处减小为零;隧道侧墙常用装饰材料搪瓷钢板在火灾过程中易发生变形而脱落;无防火保护烟道板耐火极限大于2.0h,掺加PP纤维、钢纤维可提升烟道板的耐火性能。

截至2023年底中国铁路隧道情况统计及2023年新开通重点项目隧道情况介绍

对截至2023年底中国铁路隧道、高速铁路隧道、特长铁路隧道情况进行统计。结果显示,截至2023年底,中国铁路营业里程达到15.9万km,其中,投入运营的铁路隧道18 573座,总长23 508 km;中国已投入运营的高速铁路总长超过4.5万km,共建成高速铁路隧道4 561座,总长7 735 km,其中,长度大于10 km的特长隧道115座,长约1 471 km;中国投入运营的特长铁路隧道共286座,长约3 869 km,其中,长度20 km以上特长铁路隧道13座,长约312 km。最后,对2023年新开通的重点项目贵南铁路隧道、成兰铁路成都至川主寺段隧道的概况及特点进行介绍,并总结其技术经验;同时对广汕铁路隧道、金甬铁路隧道、南崇铁路留村大直径盾构隧道、和邢铁路隧道的技术应用进行总结。贵南铁路通过空间选线、创新岩溶处理手段,以及加强运营期间的排水措施,有效降低了岩溶发育地区高速铁路运营的安全风险;成兰铁路设计充分贯彻“减灾选线”的理念,大规模减小了运营期间的安全风险,另外创新了隧道通过活动断裂带的处理技术。随着铁路建设向西部地区转移,隧道建设将面临埋深更大、地应力更高、地质构造更加复杂、高海拔地区缺氧等系列建设问题,仍需要各位同仁共同攻坚克难,不断创新隧道修建技术。

大坡道长大隧道及隧道群环境下高速列车车内外压力波特性的实车试验研究

高速列车通过25‰单面坡隧道时,形成压力波和大气压两者耦合下的车内外压力变化特征,因此,有必要研究在隧道大气压持续变化下的高速列车通过大坡道隧道时的气动载荷和车内压力舒适性问题。采用实车试验的方法,获取动车组通过西成高铁西安北—汉中线路的列车车内外压力测试数据。研究结果表明:1)列车下坡通过25‰特长隧道时车外压力波动受隧道压力波与大气压的共同作用,整体呈上升的变化趋势;2)单面坡上坡和单面坡下坡隧道的长度由1541.2 m增大至8399.2 m时,列车车内外最大压力峰值越靠近隧道出口,单面坡隧道长度越长,列车车内外压力峰值越大;3)随着大坡道隧道长度的增大,列车头车和尾车的整车气密效率在不断减小,列车车内Δp/1 s、Δp/3 s、Δp/10 s和Δp/60 s在不断增大,相应的车内压力舒适性环境更恶劣,当列车通过长大坡道隧道群时,车内压力舒适性环境和列车车体的气密性能更差;4)与压力保护阀逻辑控制相比,压力保护阀全程关闭时列车车内压力和不同时间间隔下的最大压力变化量要更小,车内压力舒适性环境更优。

高原高铁特长和超长隧道单列车通过时空气阻力变化规律研究

为研究列车通过高原高铁隧道时隧道长度、坡型、坡度、海拔和列车速度对列车平均空气阻力、最大空气阻力以及隧道平均空气阻力因子、最大空气阻力因子4个空气阻力指标的影响规律,基于一维可压缩非定常不等熵流动模型特征线模拟隧道压力波,将列车空气阻力分解为头尾车端部的压差阻力、车厢摩擦阻力、全列车压差阻力和列车周围空气重力沿列车运行方向的分量阻力(简称空气重力分量阻力),建立反映坡度的单面坡隧道空气阻力计算模型。研究结果表明:1)单列车通过有坡度隧道时,空气阻力变化规律与车外压力波和空气重力分量阻力有关,受到压缩波和膨胀波的作用增大或减小;单列车通过不同隧道长度的单面上坡/下坡、人字坡和平直隧道时,存在基于平均空气阻力的最不利坡型和临界隧道长度。单列车通过长10 km的单面上坡隧道时平均空气阻力最大,为47.05 kN。2)单列车通过单面上坡隧道时,平均空气阻力和最大空气阻力随着坡度和列车速度的增大而增大,随着海拔的升高而减小。3)通过对平均空气阻力与列车速度拟合得出,列车通过单面上坡、下坡隧道时,平均空气阻力分别与列车速度的1.92次方和2.14次方成正比。

大型抽水蓄能电站长直型隧洞风尘迁移规律研究

抽水蓄能电站地下洞室群施工存在通风难度大、风尘迁移变化规律无显著特征等难题,采用DPM气固两相流模型,针对地下洞室群中不同坡度的长直型隧洞进行数值试验研究,重点揭示了典型隧洞在不同施工条件下的风尘迁移规律及小粒径沉降粉尘分布特征。研究表明:不同区域粉尘质量浓度随风机风速的增大呈下降趋势,当风速增至21 m/s时开始升高;掌子面附近区域粉尘质量浓度随供风距离的增大呈上升趋势,当供风距离大于25 m时,风机风速不再满足隧洞内通风要求;掌子面附近区域粉尘质量浓度随隧洞坡度的增大呈显著上升趋势,通风管附近出现明显的粉尘空白带;小粒径沉降粉尘分布特征由通风管位置决定,沉降粉尘颗粒最多处位于通风管出口与掌子面之间,粒径分布较广,呈正态分布规律,在通风管出口正后方处急剧下降,并沿隧洞出口方向数量逐渐减少,平均粒径逐渐减小;流出洞外的粉尘颗粒平均粒径偏小。本研究可为抽水蓄能电站地下洞室群整体施工设计提供参考。