A series solution for surface motion amplification due to underground twin tunnels:incident SV waves

A series solution of displacement response of the ground surface in the presence of underground twin tunnels subjected to excitation of incident plane SV waves is derived by using Fourier-Bessel series expansion method.The numerical parametric study shows that underground twin tunnels significantly amplify the nearby surface ground motion.It is suggested that the effect of subways on ground motion should be considered when the subways are planned and designed.

Safe range analysis of clear distance of twin shallow tunnels based on limit analysis and reliability theory

A method of analyzing the stability of twin shallow tunnels was presented using both limit analysis with nonlinear failure criterion and reliability theory.In the condition of nonlinear failure criterion,the critical clear distancesof twin shallow tunnels were obtained by analyzing the change of surrounding pressure.A reliability model was established based on limit state equation,and the failure probability was solved by virtue of Monte Carlo method.Safety factor and corresponding clear distance of different safety levels were obtained by introducing a target reliability index.The scope of clear distance for different safety levels is described,which can be used as a supplement and improvement to the design codes of tunnels.

Interaction of Twin Circular Shallow Tunnels in Soils—Parametric Study

In big and crowded cities with limited urban areas, it is sometimes necessary to build twin tunnels to overcome transportation problems. In a city like Riyadh in Saudi Arabia, tunneling becomes very essential to solve effectively traffic conjunctions and associated problems. The city started to construct big tunneling projects and it is expected in the near future to start building twin tunnels. If the design and construction process of twin tunnels are not understood and considered, damage to the tunnel lining or excessive ground surface settlement may take place. In this study, the interaction between adjacent tunnels excavated through soils in Saudi Arabia has been investigated using FE analysis and the range of the encountered soil properties. The investigation considered the effect of spacing between the twin tunnels and ground conditions on tunnel behavior. The analysis focused on the effect of constructing twin tunnels on ground surface settlement, contact pressure between lining and ground, and change in tunnel diameter. Based on the results obtained, it was observed that as the compressibility ratio, c, and spacing between tunnels decreased, the interaction effect between tunnels increased. For compressibility ratio of 0.01, the excavation of the new tunnel caused an increase in the lining deformation of the old one in the range of 0.1% to 0.3%. Furthermore, the excavation of the new tunnel leads to an increase in the contact pressure at the crown of the old one by 7% - 9%. At the spring line level, the excavation of the new tunnel had almost no effect on the far side of the old one. On the other hand, and for low compressibility ratio, the new tunnel excavation significantly affected contact pressure at the near side of the old one. For an expected tunnel life of 100 years, the results show an increase in the normalized contact pressure at the crown of the old tunnel due to the excavation of the new one in the range of 2% - 7% for compressibility ratio ranging between 0.01 - 0.1, respectively.

Energy analysis of stability of twin shallow tunnels based on nonlinear failure criterion

Based on nonlinear Mohr-Coulomb failure criterion, the analytical solutions of stability number and supporting force on twin shallow tunnels were derived using upper bound theorem of limit analysis. The optimized solutions were obtained by the technique of sequential quadratic programming. When nonlinear coefficient equals 1 and internal friction angle equals 0, the nonlinear Mohr-Coulomb failure criterion degenerates into linear failure criterion. The calculated results of stability number in this work were compared with previous results, and the agreement verifies the effectiveness of the present method. Under the condition of nonlinear Mohr-Coulomb failure criterion, the results show that the supporting force on twin shallow tunnels obviously increases when the nonlinear coefficient, burial depth, ground load or pore water pressure coefficients increase. When the clear distance is 0.5to 1.0 times the diameter of tunnel, the supporting force of twin shallow tunnels reaches its maximum value, which means that the tunnels are the easiest to collapse. While the clear distance increases to 3.5 times the diameter of tunnel, the calculation for twin shallow tunnels can be carried out by the method for independent single shallow tunnel. Therefore, 3.5 times the diameter of tunnel serves as a critical value to determine whether twin shallow tunnels influence each other. In designing twin shallow tunnels,appropriate clear distance value must be selected according to its change rules and actual topographic conditions, meanwhile, the influences of nonlinear failure criterion of soil materials and pore water must be completely considered. During the excavation process, supporting system should be intensified at the positions of larger burial depth or ground load to avoid collapses.

Numerical analysis of surface subsidence in asymmetric parallel highway tunnels

Tunnelling related hazards are very common in the Himalayan terrain and a number of such instances have been reported. Several twin tunnels are being planned for transportation purposes which will require good understanding for prediction of tunnel deformation and surface settlement during the engineering life of the structure. The deformational behaviour, design of sequential excavation and support of any jointed rock mass are challenging during underground construction. We have raised several commonly assumed issues while performing stability analysis of underground opening at shallow depth. For this purpose, Kainchi-mod Nerchowck twin tunnels(Himachal Pradesh, India) are taken for in-depth analysis of the stability of two asymmetric tunnels to address the influence of topography, twin tunnel dimension and geometry. The host rock encountered during excavation is composed mainly of moderately to highly jointed grey sandstone, maroon sandstone and siltstones. In contrast to equidimensional tunnels where the maximum subsidence is observed vertically above the centreline of the tunnel, the result from the present study shows shifting of the maximum subsidence away from the tunnel centreline. The maximum subsidence of 0.99 mm is observed at 4.54 m left to the escape tunnel centreline whereas the maximum subsidence of 3.14 mm is observed at 8.89 m right to the main tunnel centreline. This shifting clearly indicates the influence of undulating topography and inequidimensional noncircular tunnel.

Catastrophe stability analysis for shallow tunnels considering settlement

Limit analysis of the stability of geomechanical projects is one of the most difficult problems.This work investigates the influences of different parameters in NL failure strength on possible collapsing block shapes of single and twin shallow tunnels with considering the effects of surface settlement.Upper bound solutions derived by functional catastrophe theory are used for describing the distinct characteristics of falling blocks of different parts in twin tunnels.Furthermore the analytical solutions of minimum supporting pressures in shallow tunnels are obtained by the help of the variational principle.Lastly,the comparisons are made both in collapsed mechanism and stability factor with different methods.According to the numerical results in this work,the influences of different parameters on the size of collapsing block are presented in the tables and the limit supporting loads are illustrated in the form graphs that account for the surface settlement.

Three-dimensional hydro-mechanical coupling numerical simulation of shield-driven cross-river twin tunnels:A case study

With the rapid development of urban underground space,the construction of shield-driven cross-river twin tunnels is increasing,and the complex hydro-mechanical coupling effects and twin-tunnel interactions bring huge construction risks to such projects,which have attracted more and more attention.This study aims to understand the excavation effects induced by shield driving of cross-river twin tunnels through numerical simulation.A refined three-dimensional numerical model based on the fully coupled hydro-mechanical theory is established.The model considers the main components of the slurry pressure balance shield(SPBS)machine,including support force,jacking thrust,grouting pressure,shield-rock interaction and lining-grouting interaction,as well as the detailed construction process.The purpose is to examine the excavation effects during construction,including rock deformation around tunnels,the change in pore pressure,and the response of the lining.The results show the influence range of twin-tunnel excavation on rock deformation and pore pressure,as well as the modes of lining response.In addition,this study also systematically investigates the effects of water level fluctuation and burial depth on twin-tunnel excavation.The results indicate that the increase of water level or burial depth will enhance the excavation effects and strengthen the twin-tunnel interactions.These results provide useful insights for estimating the construction impact range and degree of twin tunnels,and serve as basic references for the design of cross-river twin tunnels.

World’s first implementation of close-fit pipe jacking of twin tunnels for construction of subway station--Innovation in equipment and construction technology

1 Project overview The Shasan station of Phase II of Shenzhen’s urban rail transit Line 12 is situated in Bao’an District,Shenzhen.It comprises a two-level underground island platform station,measuring 212 m in length,and 22.6 m in width,with an overburden thickness of about 7.0 m.Fig.1 illustrates the presence of a large underground reinforced concrete stormwater culvert,measuring 11.5 m by 3.6 m,traversing the station’s center.

煤矿智能快速掘进关键技术研究现状及展望

针对煤矿巷道掘进智能化建设情况,探讨了现阶段分别以连采机、掘锚一体机、全断面掘进系统、掘锚机为核心的四大类智能快速掘进成套装备发展现状,分析了四大类智能快掘装备与地质条件适用性,提出了实现煤矿智能化掘进需要解决的关键技术的问题,探讨了以信息传输与智能分析技术、智能感知技术、精确定位导航技术,自主定型定向截割技术、掘进机远程自主截割控制技术以及多级多工序智能协同控制技术为基础的智能化掘进实现途径;基于复杂地质条件下煤矿巷道掘进亟待解决的关键问题,提出了以掘进作业功能需求、掘进工艺要求为依据的系统化分析、模块化设计、功能优化组合的设计方法;研究了以虚控实、虚实结合的多级数字孪生构架,基于掘进巷道设备、环境、地质构造多维信息再现实现掘进机远程控制;提出了单机智能化、系统协同化、井下智控与地面远程监控相协同的控制方法。开发了新型的无重复碾压柔性超前支护技术、截割部多级伸缩截割技术、智能锚固机组多钻机并行作业等技术,研制了具有掘、支、锚、运、探多工序并行作业的新型快速掘进作业联合机组,提出了掘进机器人、超前支护机器人、锚固机器人、辅助运输机器人组柔性并行作业技术;提出了基于数据驱动的多机多工序协同控制行为规划决策方法。提出构建完整的煤矿井下跨系统全时空信息数字感知体系,构建集井下现场生产状态、掘进巷道空间信息、掘进装备状态、风险信息等多参量、多尺度、全时空特性的数据感知智能化监控平台,实现虚拟系统与实际掘进系统实时通信,通过数据驱动规划分析实现智能化、少人化掘进。

隧道施工引发粉土地面沉降模拟与分析

为研究黄泛区粉土地层内开挖双线地铁隧道对地上及其周边地面沉降的影响,以某双线地铁隧道开挖工程为例,考虑地下水、隧道间距对地面沉降的影响,采用流固耦合数值方法和理论分析方法对隧道施工引起的地面沉降规律进行分析。将数值模拟数据与Peck公式进行反演计算,并考虑隧道间隔和埋深的影响提出修正Peck公式,再结合叠加原理建立适用于双线隧道开挖引起地面沉降的修正叠加公式。结果表明:隧道开挖扰动地层将引起超静孔隙水压力现象;数值模拟与理论计算得到隧道间隔为4 m时,地面沉降曲线呈现“V”型,隧道间隔为8 m、12 m时,则沉降曲线呈现“U”形;粉土内开挖双线地铁隧道,地面容易受到扰动且沉降量大,随着隧道间距的增加,隧道上方土体沉降量逐渐减小;基于修正Peck公式计算结果与数值模拟结果基本一致,相对误差在3%左右,表明该公式具有很好的实用性。研究可为粉土地区隧道及地下工程建设提供理论依据和技术支撑。

钻爆法隧道下穿既有双连拱隧道施工技术研究

钻爆法隧道穿越新建既有双连拱隧道结构,下穿隧道为大跨度隧道,高度大、埋深较深,且在穿越既有隧道时,不能影响其安全运营和造成结构破坏,施工难度大、风险高。采用有限元软件Midas GTS NX对钻爆法隧道下穿既有隧道的变形和受力情况进行数值模拟计算,并研究了下穿施工前对上方隧道间地层采用大管棚和锚杆联合加固产生的效果。研究表明:未加固时,施工侧隧道结构的沉降要大于另一侧,呈现出“一峰二谷”变形形状,既有隧道上下部极易发生结构破坏。采用大管棚及锚杆联合加固,有效地转移了应力集中现象,降低了结构破坏风险,并且既有隧道沉降量仅为前者变化量的1/1.83,在控制标准以内。

分体箱梁中央隔涡板涡激振动抑制机理研究

借助风洞试验和计算流体力学对分体钢箱梁的涡激振动性能及中央隔涡板的抑振效果与机理开展研究,对比不同形式(水平隔涡板、一道竖向隔涡板、两道竖向隔涡板)和尺寸中央隔涡板的抑振效果,并根据流迹与速度云图对不同形式中央隔涡板的抑振机理进行分析。结果表明:开槽顶部水平隔涡板能够阻碍开槽处的气体对流,降低开槽内部及断面周围气流速度,增加旋涡移动和脱落难度,从而在一定程度上抑制涡激振动,抑振效果随隔涡板宽度增大而增加;开槽内部竖向隔涡板能够将旋涡稳定在隔板分隔出的几个小区域内,避免产生稳定的旋涡脱落,进而有效抑制涡激振动,设置两道半高竖向隔涡板比设置一道全高竖向隔涡板效果更好,但需对两板间距进行优化。

大跨度双幅非对称平行主梁涡激振动干扰效应研究

在双幅式桥梁的建设中,公路与铁路同层并排布置的大跨双幅非对称主梁属于较特殊的设计。由于公路桥与铁路桥的动力特性不一致、主梁尾流特性差异较大以及非对称双梁间存在特殊且显著的气动干扰,使得非对称双幅主梁的涡激振动特性更为复杂。为系统探究干扰效应对主梁涡振性能的影响,以一座大跨度公铁两用双幅桥为研究背景,开展了双幅主梁涡激振动风洞试验与流固耦合数值模拟,其中公路梁为Π型叠合梁,铁路梁为流线型箱梁。研究结果表明:公路梁位于迎风侧时出现了较大幅值的竖弯和扭转振动,且风速区间与结构振动频率具有典型涡振“锁定”特征,而位于背风侧时,振动现象基本消失;铁路梁位于迎风侧时未见明显振动现象,而位于背风侧时,试验观察到了大幅振动,且振幅具有迅速上升又迅速下落的特点,无明显“锁定”区间。数值流场表明,公路位于不同位置处(迎、背风侧)时,主梁附近涡结构的尺度与分布均有明显不同。当位于迎风侧时,下桥面腔内大尺度漩涡的存在以及涡结构的周期性变化是位于迎风侧时产生涡振的主要原因;当位于背风侧时,受干扰效应影响,下桥面腔内漩涡尺度减小,升力振荡频率改变,涡振锁定现象消失。铁路附近流场及压力分布表明:当位于迎风侧时,主梁附近流场稳定,自激升力近似为直流力;当位于背风侧时,受公路尾流的干扰,铁路表面存在较大面积的负压区,公路尾流的脉动导致了铁路气动升力的振荡,因而产生了大幅振动。研究了双幅非对称平行主梁间气动干扰效应对涡振性能的影响,揭示了涡振及气动干扰机理,为类似桥梁的工程设计提供了参考依据。

煤矿掘进机系统数字孪生技术研究

针对煤矿巷道掘进作业中,地质结构复杂、现场环境恶劣、掘进设备智能化程度低、安全事故频发等问题,提出了一种数字孪生解决方案。通过融合物联网、互联网、数字孪生和虚拟现实等技术,以PLC为硬件核心、MQTT协议和EMQX服务为基础、建立参数矩阵映射规则和故障原因分析表,实现了掘进作业数据采集与处理、设备与孪生模型间的数据映射、数据存储、作业过程仿真、远程遥控、智能故障检测与预警等功能,提升了煤矿掘进作业过程的数字化、智能化水平。研究结果表明,该方案在煤矿掘进作业过程中具备较强的可行性、可靠性和实用性,具有推广应用价值。

基于BIM技术深度策划的隧道掘进智能控制技术研究

为解决传统隧道铣挖法存在的截割作业工作环境恶劣、安全风险高、成隧质量差等问题,提出一种基于BIM和数字孪生技术深度策划的隧道掘进智能控制开挖方法。首先,通过地面综合物理探测构建隧道三维地质模型,导入隧道结构参数、设备模型、测量控制构件要素,生成基于BIM虚拟隧道掌子面场景;其次,运用BIM和数字孪生技术深度规划掘进机截割作业时截割部运动路径与轨迹,设计自动截割作业控制程序,并进行施工模拟碰撞,以提高模拟运算的准确性。结果表明,该方法解决了隧道铣挖法智能化、自动化施工水平低的问题,实现离机遥控操作自动截割作业;利用局域网和传感技术,解决高粉尘、低照度环境下掘进机截割部运动跟踪定位的难题,实现“人-机-环”全面感知;通过感知系统精确定位,跟踪测量掘进机和截割部的位姿,实现对掘进机的远程监测与控制;通过测控与传感器、计算机技术,能够精确地控制截割头位置,完成掘进断面截割自动成形;通过控制系统精确地控制,截割部运动控制精度达到±20 mm,从而有效提高隧道成形质量。

资阳市纵二路隧道内爆炸易损性问题研究

隧道作为重要的交通基础设施,其在内部爆炸荷载作用下的动力响应特性与易损性问题的研究具有重要的工程意义。针对四川省资阳市临空经济区纵二路双洞隧道,开展了内爆作用下的易损性问题研究。基于Hypermesh前处理软件建立了双洞隧道有限元数值模型,确定隧道内爆后损伤指标并对计算结果进行分析,采用非参数方法绘制双洞隧道易损性曲线。结果表明:炸药当量在0~1000 kg范围内,隧道损伤程度主要是轻度破坏;1000~2000 kg范围内,隧道内爆后出现中度破坏;2000~8000 kg范围内,隧道内爆损伤以重度损伤为主;一旦炸药当量>8000 kg,隧道损伤达到完全破坏。此外,当炸药当量≯8000 kg时,双洞隧道完全破坏的概率<25%。

双幅钢箱梁竖弯涡振气动力演变特性

双幅钢箱梁桥是工程实践中一种常用的大跨度连续梁桥型式,但并列双箱复杂的旋涡脱落和交互作用可能引发显著的涡激振动现象,影响结构的疲劳性能和行车舒适性。本文以某六边形双幅钢箱连续梁桥为工程背景,对大比例节段模型开展了测振、测压风洞试验,对比了双幅钢箱梁在不同间距下竖弯涡振全过程(涡振前、上升区、振幅极值点、下降区及涡振结束)的分布气动力演变特点,提出了有效控制双幅钢箱梁桥涡振的气动措施。研究表明,双幅钢箱梁桥涡振锁定区间长、振幅大,+3°为最不利攻角,涡激力的倍频效应与间距和双幅箱梁涡振的振幅均有关。在小间距及低风速时,上、下游梁背风侧的分布气动力对涡激振动起到增强作用;在大间距或较小间距且高风速时,开槽附近上表面和下游梁斜腹板位置的分布气动力对涡激力起主要增强作用,也是双幅钢箱梁产生大幅涡激振动的诱因。提出了槽间裙板与两端风嘴组合的综合气动控制措施,通过切断槽间涡的传播途径从而降低桥面处分布气动力对涡激力的贡献,该措施可有效减弱双幅钢箱梁桥的竖弯涡振。

基于能量法的双线下穿既有隧道沉降研究

针对双线隧道穿越施工造成的复杂影响问题,基于能量方法,提出了考虑地层损失率差异的双线下穿开挖作用下既有隧道沉降的计算方法。基于经典的Peck和Mair理论,在计算新建隧道开挖引起的地层位移时,引入Hunt双线开挖沉降修正系数,考虑双线隧道先后穿越引起的地层损失率差异性所造成的影响;基于Rayleigh-Ritz法和弹性地基梁理论,写出系统各部分功能关系式,建立系统总势能方程;利用变分法求解总控制方程,得到考虑地层损失率差异的双线隧道下穿引起既有隧道沉降的理论解析,并将理论计算结果与已有文献报道的工程实测沉降数据进行对比验证;以双线隧道下穿既有隧道为例,对双线中心间距、新建隧道直径以及新旧隧道净距展开参数分析。结果表明:理论计算结果与实测数据整体趋势一致,二者吻合较好,验证了所提方法的可行性;新建隧道先后下穿引起的地层损失率差异对既有隧道的沉降有显著影响;随着新建双线中心间距和新旧隧道净距的增大,既有隧道的沉降量随之减小;随着新建隧道直径的增大,既有隧道的沉降量随之增加,且第二次下穿施工产生的沉降影响会越发明显。研究成果可快速且合理评估既有隧道受新建隧道穿越施工影响时的纵向变形响应,对类似的双线隧道工程起到一定的理论支持和指导意义。

双洞隧道地铁运行引起的软土地基振动及孔压研究

建立双洞隧道的三维有限差分模型,通过车轨耦合计算得到地铁运行中隔振器的力时程,以集中力的形式施加到地铁轨道对应的节点上,分析探讨了软土地基中振动加速度和超静孔隙水压力的变化规律及影响范围等。结果表明:左侧隧道和右侧隧道振动及孔隙水压力的变化基本一致,在地铁的一次相向运行过程中,软土地基的地表竖向振动加速度在两隧道中心处出现最大值,在距隧道中心轴约25 m处存在地表振动加速度放大现象,在距隧道中心轴150 m外,地表加速度峰峰值衰减至2 gal以下。软土地基中的超静孔隙水压力随着远离隧道而快速减小,在距隧道中心轴80 m外,超静孔隙水压力便衰减至100 Pa以下。白天地铁运行过程中,超静孔隙水压力出现较平稳的振荡,晚间地铁停运后,超静孔隙水压力出现一定程度下降,且随着地铁的反复运行下降幅度减小。

基于数字孪生的铁路隧道智能运维关键技术与实现方法研究

在工程建设行业转型升级的趋势下,针对铁路隧道工程运维过程中存在的管控效率低、健康状态评价解释性差、运维决策过程复杂等难题,提出基于数字孪生的铁路隧道智能运维关键技术与实现方法。构建以数字孪生为驱动核心的铁路隧道智能运维整体框架,梳理隧道运维数据流转与应用的层级,明确数字孪生在系统框架中的主体功能和核心价值,并针对物理实体与虚拟模型信息映射机制和智能运维关键技术开展研究。首先,通过总结归纳提出铁路隧道运维数据分类体系与信息的存储和表达方法,揭示隧道智能运维中动态感知数据与数字孪生数据的映射机制;然后,总结分析隧道智能运维亟待解决的关键技术,包括状态智能感知、数据智能分析、运维辅助决策;最后,在系统框架、融合机制和关键技术的基础上,提出隧道智能运维的实现路径,并通过研发铁路隧道智能运维平台验证技术框架的可靠性和实用性,也验证数字孪生技术在提高隧道运维管理效率和智能化程度方面的可行性。