Effect of burial depth of a new tunnel on the seismic response of an existing tunnel

Burial depth is a crucial factor affecting the forces and deformation of tunnels during earthquakes.One key issue is a lack of understanding of the effect of a change in the buried depth of a single-side tunnel on the seismic response of a double-tunnel system.In this study,shaking table tests were designed and performed based on a tunnel under construction in Dalian,China.Numerical models were established using the equivalent linear method combined with ABAQUS finite element software to analyze the seismic response of the interacting system.The results showed that the amplification coefficient of the soil acceleration did not change evidently with the burial depth of the new tunnel but decreased as the seismic amplitude increased.In addition,the existing tunnel acceleration,earth pressure,and internal force were hardly affected by the change in the burial depth;for the new tunnel,the acceleration and internal force decreased as the burial depth increased,while the earth pressure increased.This shows that the earth pressure distribution in a double-tunnel system is relatively complex and mainly concentrated on the arch spandrel and arch springing of the relative area.Overall,when the horizontal clearance between the center of the two tunnels was more than twice the sum of the radius of the outer edges of the two tunnels,the change in the burial depth of the new tunnel had little effect on the existing one,and the tunnel structure was deemed safe.These results provide a preliminary understanding and reference for the seismic performance of a double-tunnel system.

Evaluation of new Austrian tunnelling method applied to Bolu tunnel’s weak rocks

Since the development of the new Austrian tunnelling method(NATM)in the 1960s,this technique has been applied successfully in many tunnels.However,opinions of NATM principles emerged till 2000,i.e.NATM is not a tunnelling method,but an approach covering all general principles of tunnelling.To investigate the general principles of the NATM,this study focused on tunnelling practises in the Bolu tunnel,and evaluated the conditions under which the NATM practises could be effective.The Bolu tunnel project was designed following the NATM principles.It is evident that practises adopted in this tunnel are important with respect to the NATM.In addition,it shows that the solutions to the problems encountered in this tunnel are consistent with the NATM principles.Finally,the study determines the ground types of the NATM principles and proposes associated updates.

New technologies for high-risk tunnel construction in GuiyangGuangzhou high-speed railway

Based on the construction of high risk tunnels in Guiguang-Guangzhou high-speed railway, several new technologies were developed for high-risk tunnel con- struction. First, an integrated advanced geological predic- tion was developed for tunneling in karst area. Then, a new system of ventilation by involving the dedusting technol- ogy was proposed and used in the field, which received a good air quality. Finally, a method to minimize the dis- tance between the working face and the invert installation was proposed by optimizing the invert installation and adopting the micro bench method. Applying the method to the project obtained an excellent result. The achievement obtained for this study would be able to provide a valuable reference to similar projects in the future.

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.

Estimation of convergence of a high-speed railway tunnel in weak rocks using an adaptive neuro-fuzzy inference system(ANFIS) approach

Estimation of tunnel diameter convergence is a very important issue for tunneling construction,especially when the new Austrian tunneling method（NATM） is adopted.For this purpose,a systematic convergence measurement is usually implemented to adjust the design during the whole construction,and consequently deadly hazards can be prevented.In this study,a new fuzzy model capable of predicting the diameter convergences of a high-speed railway tunnel was developed on the basis of adaptive neuro-fuzzy inference system（ANFIS） approach.The proposed model used more than 1 000 datasets collected from two different tunnels,i.e.Daguan tunnel No.2 and Yaojia tunnel No.1,which are part of a tunnel located in Hunan Province,China.Six Takagi-Sugeno fuzzy inference systems were constructed by using subtractive clustering method.The data obtained from Daguan tunnel No.2 were used for model training,while the data from Yaojia tunnel No.1 were employed to evaluate the performance of the model.The input parameters include surrounding rock masses（SRM） rating index,ground engineering conditions（GEC） rating index,tunnel overburden（H）,rock density（？）,distance between monitoring station and working face（D）,and elapsed time（T）.The model’s performance was assessed by the variance account for（VAF）,root mean square error（RMSE）,mean absolute percentage error（MAPE） as well as the coefficient of determination（R2） between measured and predicted data as recommended by many researchers.The results showed excellent prediction accuracy and it was suggested that the proposed model can be used to estimate the tunnel convergence and convergence velocity.

Conception and Exploration of Using Data as a Service in Tunnel Construction with the NATM

The New Austrian Tunneling Method （NATM） has been widely used in the construction of mountain tun- nels, urban metro lines, underground storage tanks, underground power houses, mining roadways, and so on, The variation patterns of advance geological prediction data, stress-strain data of supporting struc- tures, and deformation data of the surrounding rock are vitally important in assessing the rationality and reliability of construction schemes, and provide essential information to ensure the safety and scheduling of tunnel construction, However, as the quantity of these data increases significantly, the uncertainty and discreteness of the mass data make it extremely difficult to produce a reasonable con- struction scheme; they also reduce the forecast accuracy of accidents and dangerous situations, creating huge challenges in tunnel construction safety, In order to solve this problem, a novel data service system is proposed that uses data-association technology and the NATM, with the support of a big data environ- ment, This system can integrate data resources from distributed monitoring sensors during the construc- tion process, and then identify associations and build relations among data resources under the same construction conditions, These data associations and relations are then stored in a data pool, With the development and supplementation of the data pool, similar relations can then he used under similar con- ditions, in order to provide data references for construction schematic designs and resource allocation, The proposed data service system also provides valuable guidance for the construction of similar projects.

Excavation of Inlet Tunnels at Geheyan Power Station

The Geheyan Power Station on the Qingjiang river has four inlet tunnels, on the right bank, with its excavation diameter of 11.3 m to 12.5 m, after lining diameter of 9.5 m, axis to axis spacing of 24 m. The thickness of the pillar between tunnels should usually be more than two times of tunnel diameter to ensure the stability of surrounding rock during excavation. In this paper, the excavation methods of tunnels with the pillar thickness as small as the tunnel diameter, such as smooth surface blasting, shotcrete support protection, are emphatically discussed.

Kerr-Newman-Kasuya双荷黑洞隧穿辐射的改进新研究

本文首先通过坐标变换得到了新的Kerr-Newman-Kasuya双荷黑洞解形式。然后运用Euler-Lagrange变分原理,在一般坐标系下对Kerr-Newman-Kasuya双荷黑洞的类时和类光测地线方程作了新的统一推导,并利用Parikh-Wilczek建议的半经典隧穿方法,对有质量带电粒子在Kerr-Newman-Kasuya双荷黑洞视界附近的隧穿辐射作了新的研究,通过计算得到其隧穿几率。研究表明Kerr-Newman-Kasuya双荷黑洞这一类转动黑洞的隧穿辐射可以在一般坐标系下进行分析。

利用已建隧道剩余空间安装管道方案探究

某工程利用已建隧道剩余空间安装D1219 mm管道,已建隧道内已安装有一条D1016 mm管道,剩余空间有限、狭小、隧道内管道安装作业十分困难,考虑到已建隧道设计之初按照安装两条管道进行断面设计。本着节约投资、节省工期、充分利用已有管道资源的原则,开展了受限剩余空间内安装已建管道方案设计。该方案在隧道进口外部完成管道运布管、对口、组焊、无损检测和防腐补口等工作,在隧道出口外部设置管道牵引系统将管道牵引就位,实现已建隧道内管道安装。该工程利用已建隧道剩余空间,在隧道外部完成管道焊接组装,通过管道发送系统完成管道就位安装,不仅节省了新建隧道的问题,而且缩短了工程工期,为今后在已建隧道内新增管道敷设提供了参考。

考虑隧道掘进过程的新建隧道下穿既有隧道力学响应研究

为有效评估新建隧道下穿施工对既有隧道的影响,确保既有隧道运营安全,将既有隧道简化为放置在Pasternak地基模型上的Euler-Bernoulli梁,基于两阶段分析法提出新建隧道下穿施工引起既有隧道力学响应的计算方法。通过与现场监测和既有方法的结果进行对比,验证了本文方法的准确性。研究结果表明:当新建隧道开挖面位于既有隧道中点时,既有隧道差异沉降达到最大值,转角曲线关于既有隧道中心线对称;在新建隧道掘进过程中,既有隧道的最大正弯矩和最大负弯矩分别出现在既有隧道长度的2/5和3/5位置附近,最大负剪力出现在既有隧道中点处;当新建隧道开挖面到达既有隧道长度的1/4和3/4位置时既有隧道产生最大正剪力;随着隧道轴线夹角和相对弯曲刚度增大,既有隧道的内力显著增大;增大隧道竖向净距有利于控制既有隧道的力学响应。本文方法考虑了新建隧道掘进过程和新建隧道与既有隧道的不同相对位置,可为类似穿越工程风险防控提供理论依据。

公路隧道场景下的新能源汽车火灾风险评价方法研究

为有效评价公路隧道场景下的新能源汽车火灾风险,解决目前公路隧道火灾评价存在的指标考虑不足、权重确定困难、评价等级界定不清的问题。根据安全学原理,结合新能源汽车火灾致因,从“人-机-环-管”4个方面构建了公路隧道新能源汽车火灾风险评价指标体系。利用决策模型和欧式距离函数,将层次分析法(AHP)主观权重和熵权法客观权重利用组合赋权的方法有效结合,得到更为合理的组合权重。最后利用组合赋权-物元可拓模型对南京定淮门隧道新能源汽车火灾风险进行评价,所得级别变量特征值为1.646,确定该隧道风险等级结果为Ⅱ级,与工程实际相符合,验证了该方法的合理性与可靠性。

新建隧道上跨既有运营隧道施工要点

随着各城市地铁建设的快速发展,交叠隧道越来越多。以往的研究成果多从理论分析、数值模拟以及室内实验等方向展开。广州地铁5号线东延段庙~夏区间工程,新建盾构隧道上跨既有运营13号线,竖向最小间距1.27 m。针对该工况,从出土量控制、掘进参数、注浆参数、盾构姿态4个方面提出了施工控制要点。经与第三方自动化监测数据对比,本案例中采取的施工措施有效。

城市隧道下穿既有建筑的影响模式分析

城市中心城区建构筑物密集,新建城市地下隧道下穿既有建筑物的情况增多,为确保既有建构筑物的安全,需对新旧结构之间的相互影响模式进行分析。文中依托某城市新建隧道工程,初步判定施工对周边既有建筑的影响模式,并根据有限元分析软件,按照国家现行相关行业规范及标准,分析新建隧道工程施工过程及运营状态对既有建构筑物的影响程度,包括既有建筑基础的沉降、沉降差、地表变形三个方面。结果表明,采取合理的工程措施后,新建隧道工程对既有建构筑物的影响较小,且不影响既有建构筑物的正常使用,整体风险可控。

夏秋绿茶的杀青工艺及加工设备研究

本项目基于对贵州省夏秋茶的前期研究基础,通过结合先进的加工工艺和高效智能的加工设备可以生产出数量可观的优质绿茶。这种绿茶具有丰富的内含物,耐泡、鲜爽醇厚、香气高雅、汤色亮绿且安全可靠。通过这一项目,可以解决贵州省茶产业能效不足、茶农收入不高等问题。

基于新意法理念的隧道施工方法研究

随着我国隧道建设重心的逐步西移,所涉及的工程地质条件和地应力情况愈发复杂,运用传统隧道施工方法存在诸多问题,如难以克服大变形问题、无法在施工过程中精准预测隧道变形特征等。新意法理念为这些问题的解决提供了新的思路。为推广新意法施工设计理念,系统性论述了新意法的基本原理及其设计施工相关流程,并在此基础上分析与传统工法相比其优势所在,为相关工作人员提供参考与指导。

新能源车混入影响下的公路隧道运营通风设计折减系数研究

为进一步降低隧道运营期能耗,基于国家统计数据及高速公路沿线数据,从时空维度对数据进行分析,并使用多元线性回归对高速公路沿线新能源车混入度数据进行拟合。得到以下结论:1)近年来我国新能源车保有量占比呈高速增长态势,经济发达地区的新能源车保有量占比较高,新能源车混入度总体呈现从新能源车保有量占比高水平地区到低水平地区逐渐递减的趋势;2)新能源车混入度与时间和距离中心城市的里程存在明显的线性关系,与时间成正相关性,与里程成负相关性;3)根据新能源车混入度给出新能源车辆混入影响下的公路隧道运营通风设计交通量折减系数计算公式,能通过时间和空间信息预测隧道的交通量折减系数,为隧道设计阶段和运营阶段需风量的折减提供依据。

分层地基中隧道开挖对土体沉降及衬砌内力影响

由于地质条件的多样性,一些隧道常常修建在上下层土体性质差异较大的复杂地层中。多层地基中新建隧道引起的地层变形及结构内力比在均质地层中更加复杂。文章通过系列数值模拟,研究分析上下土层不同模量比和不同厚度条件下,新建隧道开挖引起的土体位移场及隧道衬砌附加应力。研究发现:随着上下层土体模量比的增加,隧道顶部的沉降逐渐减小,地层中土体变形影响范围逐渐增大,说明上硬下软地层中隧道施工对既有结构影响范围会相对增大。在拖拽作用和刚度变化的相互作用下,隧道表面沉降并非随着刚度比单调变化。衬砌上内力随着上层土体的模量增大分布变得均匀;相同模量比条件下,衬砌轴力随着软弱层深度的增大而增大。因此,在上软下硬地基中隧道施工时,尤其是软弱层埋深较大的情况,衬砌产生局部破坏的风险增高。

新建隧道施工对既有桥梁安全影响研究

为评判新建隧道施工过程中既有桥梁结构安全性能,利用有限元软件,基于地层结构法,建立三维实体仿真模型,解析新建隧道施工过程中,周边围岩及既有桥梁桩基变形规律。研究表明:既有桥梁桩基横向位移和竖向位移随着隧道施工步序开展逐渐增加,通道开挖完成为最不利工况,桩基顺桥向位移随着隧道施工步序开展呈上下来回波动规律,施工过程中,尚需加强关注各工序之间结构的变形和受力。隧道施工过程中,周边围岩及既有桥梁桩基最大水平位移和竖向位移均小于控制指标。研究成果可供此类项目安全评估参考。

既有桥梁下新建隧道安全性能评估

随着地铁和其他轨道交通工程的不断发展,新建隧道和既有邻近建筑物相互影响下的结构安全评估成为关注热点。本文基于桥梁外观检测开展既有桥梁技术状况评定,利用有限元数值模拟分析,开展新建隧道基坑开挖和桩基入侵相互影响下的结构安全评估。研究表明:既有桥梁桩基水平位移受基坑开挖影响较竖向位移敏感。最大水平变位和竖向变位均发生在桩顶位置。当桩基埋深>15 m后,随着埋深的增加,水平位移减小幅度降低。当埋深>20 m后,桩基竖向位移基本不受开挖影响。桩基入侵后新建隧道仰拱位置承载力安全系数最小,接近2.51。隧道基坑开挖和桩基入侵相互影响后,结构安全性能满足要求。

分层倾斜岩土大断面隧道新型让压支护结构支护效果:以兰州白塔山隧道为例

为解决分层岩土地层隧道中出现的应力及变形分布不协调的问题,提出了一种针对分层岩土地层的新型支护结构,并构建了常规支护结构和新型让压支护结构的数值计算模型,对两种支护结构的支护效果进行了对比研究。结果表明:不同地层中围岩压力变化均表现为快速增长-缓慢增长-趋于稳定3个变化阶段,最终围压和变形分布均呈现出“黄土侧大,岩石侧小”的分布形态;新型让压支护结构减弱了围岩位移分布向黄土侧偏移的效果,上部导坑的围岩竖向位移和水平位移也均小于常规支护结构;新型让压支护结构拱架受力和变形整体小于常规支护结构,且降低了两侧导坑的变形差异,而缓冲让压结构的设置使分层岩土界面处支护结构受力和变形减小,实现了缓冲让压支护效果。总体上,新型让压支护结构在分层岩土地层隧道中具有良好的支护效果。