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.

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.

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.

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。

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。

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。

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。

间距对公铁双幅主梁气动特性影响的试验研究

为研究间距对非对称公铁双幅主梁气动特性的影响,以某大跨度公铁双幅斜拉桥主梁断面为背景进行节段模型风洞试验,在间距L/Br=0.2~2.0范围内,测试了2种不同来流方向下双幅主梁的气动特性,分析非对称双幅主梁气动力系数、表面风压分布并推断主梁周围绕流特征,明确间距对非对称公铁双幅主梁气动干扰规律的影响规律。结果表明:无论风向角α=0°或α=180°,上游主梁气动力系数、表面风压分布和绕流方式受间距影响程度相对较小,与单幅主梁气动特性和绕流方式相似;但下游主梁气动特性受间距影响较大,且完全不同于单幅主梁,间隙处的绕流形式随间距的增大而发生变化,下游主梁气动力系数、平均风压系数曲线和脉动风压曲线也表现出完全不同的规律;且间距越大,下游主梁气动特性和绕流方式越接近于单幅主梁。公路主梁的流线性相比于铁路主梁更强,这种气动外形差异导致2种来流方向下非对称双幅主梁气动特性和绕流形式不同,间距在L/Br=0.2~2.0范围内,气动干扰对其影响规律也完全不同。如α=0°时,双主梁上表面始终为“单一钝体流态”;但α=180°时,双主梁上表面属于“剪切层附着流态”,间距不同,上游公路主梁尾流附着于下游铁路主梁的位置不同,据此可再细分为2种不同的绕流方式。研究成果可为同类型非对称双幅桥梁间隙距离设计提供参考。

软土地层双线隧道地表沉降计算公式修正

由于双线隧道存在复杂的耦合作用,盾构施工引起的地表沉降规律极为复杂,所以准确计算地表沉降较为困难。基于Peck公式和Chapman修正参数,考虑先行隧道的施工影响和双线隧道的相对位置关系,通过参数的经验量化,建立双线隧道地表沉降的计算公式。此外,依托苏州市轨道交通S1号线工程,讨论公式在不同土层中的适用性及参数取值范围,在此基础上采用PLAXIS 3D有限元软件对双线隧道盾构施工进行了数值模拟。结果表明:在软土地层中进行盾构施工,应用所建修正公式计算得到的地表沉降值与数值模拟和现场实测结果均较为吻合。所建修正公式考虑了双线隧道的位置信息,可以定量反映隧道埋深和双线隧道间距对地表沉降的影响。研究成果可为软土地区双线隧道盾构施工沉降计算提供参考。

基于数字孪生的地铁隧道智能监测系统建设探讨

地铁隧道是城市轨道交通重要的组成部分,由于地质环境复杂,其挖掘与运营成本高、安全隐患大。为实现地铁隧道科学养护和智能化运营管理,迫切需要全息全生命周期的智能化监测系统做支撑。以数字孪生技术为基础,探讨了地铁隧道智能监测系统建设的关键技术、系统架构和主要建设内容,提出了将数字孪生、智能算法调度引擎、激光雷达与视频融合技术相结合的建设思路,对指导隧道智能监测系统建设具有一定的参考价值。