Numerical simulation of dynamic response of operating metro tunnel induced by ground explosion

To evaluate the effects of possible ground explosion on a shallow-buried metro tunnel, this paper attempts to analyze the dynamic responses of the operating metro tunnel in soft soil, using a widely applied explicit dynamic nonlinear finite element software ANSYS/LS-DYNA. The blast induced wave propagation in the soil and the tunnel, and the von Mises effective stress and acceleration of the tunnel lining were presented, and the safety of the tunnel lining was evaluated based on the failure criterion. Besides, the parametric study of the soil was also carried out. The numerical results indicate that the upper part of the tunnel lining cross-section with directions ranging from 0° to 22.5° and horizontal distances 0 to 7 m away from the explosive center are the vulnerable areas, and the metro tunnel might be safe when tunnel depth is more than 7 m and TNT charge on the ground is no more than 500 kg, and the selection of soil parameters should be paid more attentions to conduct a more precise analysis.

Experimental Study of Tunnel Fire with Natural Ventilation

The 1/15 reduced-scale experiments using Froude scaling were designed to study the effect on the smoke control efficiency for subway tunnel fires with natural ventilation mode.The propane gas fires with heat release rate 11.48 kW was used,which corresponds to the heat release rate 10 MW in the full-scale tunnel.The temperature distributions under the ceiling were measured by K-type thermocouples to investigate smoke movement,and the velocity of smoke in shafts was measured by hot-wire anemometer to obtain the smoke extract amount of ventilation shafts.The results show that the smoke temperature under the ceiling varies with the longitudinal different distance from fire source.The results also show that the smoke temperature distributions and the smoke control efficiency in tunnel vary with the space between ventilation shafts and vary with the area and the height of ventilation shaft.

Strata consolidation subsidence induced by metro tunneling in saturated soft clay strata

To choose the optimum construction method of metro tunneling, we conducted research with numerical simulation on strata consolidation subsidence by dewatering, dynamic dewatering, and non-dewatering construction method, taking the integrated effects of fluid-solid coupling and tunneling mechanics into account. We obtained the curved surfaces of ground surface subsidence and strata consolidation subsidence. The results show that the quantity of ground surface subsidence is 31 mm for the non-dewatering method, 39 mm for the dynamic dewatering method, and 105 mm for the dewatering method. Their ratio is 1：1.3：3.4; and the percentages of strata consolidation subsidence to whole ground surface subsidence of each construction method is 27% （no-dewatering）, 50% （dynamic dewatering）, and 79% （dewatering）. It is obvious that the non-dewatering construction method is the most effective method to control the strata consolidation subsidence induced by metro tunneling in saturated soft clay strata, and it has been successfully applied to the construction of the Shenzben metro line 1.

Tunnelling performance prediction of cantilever boring machine in sedimentary hard-rock tunnel using deep belief network

Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in the field of underground space engineering.This paper presented a case study of tunnelling performance prediction method of CBM in sedimentary hard-rock tunnel of Karst landform type by using tunneling data and surrounding rock parameters.The uniaxial compressive strength(UCS),rock integrity factor(Kv),basic quality index([BQ]),rock quality index RQD,brazilian tensile strength(BTS) and brittleness index(BI) were introduced to construct a performance prediction database based on the hard-rock tunnel of Guiyang Metro Line 1 and Line 3,and then established the performance prediction model of cantilever boring machine.Then the deep belief network(DBN) was introduced into the performance prediction model,and the reliability of performance prediction model was verified by combining with engineering data.The study showed that the influence degree of surrounding rock parameters on the tunneling performance of the cantilever boring machine is UCS > [BQ] > BTS >RQD > Kv > BI.The performance prediction model shows that the instantaneous cutting rate(ICR) has a good correlation with the surrounding rock parameters,and the predicting model accuracy is related to the reliability of construction data.The prediction of limestone and dolomite sections of Line 3 based on the DBN performance prediction model shows that the measured ICR and predicted ICR is consistent and the built performance prediction model is reliable.The research results have theoretical reference significance for the applicability analysis and mechanical selection of cantilever boring machine for hard rock tunnel.

Mechanical responses of underground carriageway structures due to construction of metro tunnels beneath the existing structure:A case study

To understand the mechanical response pattern of the existing structure and ground due to the construction of metro tunnels underneath,the finite difference method is adopted to study the torsional deformation and stress variation of the existing structure and the effect of underground carriageway structures on the surface subsidence.The curves of the maximum differential subsidence,torsion angle,and distortion of the cross-section of the existing structure show two peaks in succession during traversing of two metro tunnels beneath it.The torsion angle of the existing structure changes when the two tunnels traverse beneath it in opposite directions.The first traversing of the shield tunnel mainly induces the magnitude variation in torsional deformation of the existing structure,but the second traversing of the subsurface tunnel may cause a dynamic change in the magnitude and form of torsional deformation in the existing structure.The shielding effect can reduce the surface subsidence caused by metro tunnel excavation to a certain extent,and the development trend of subsidence becomes slower as the excavation continues.

地铁区间隧道消防应急照明与疏散指示系统设计研究

由于地铁区间隧道较长、空间狭小和出入口少,因此一旦发生火灾事故,乘客紧急疏散将非常困难。为了提高地铁区间隧道消防疏散的合理性、有效性和快速性,首先,简单介绍了地铁区间隧道消防应急照明和疏散指示系统的系统设计流程,其次,根据不同区间长度提出两种合理、可靠的系统设置方案,最后,依据规范详细分析了系统选择、系统灯具、系统配电、应急照明集中电源和配电箱、系统控制。同时,推导出相关合理合规的具体数据,并总结了其设计经验,以期为类似项目的设计提供参考。

Influence of extreme shallow jacked box tunnelling on underlying metro tunnels:A case study

The application of jacked box tunnelling for underground passages has grown rapidly in recent years in China.In this study,the design of an extreme shallow jacked box tunnel traversing the underlying metro tunnels was introduced.An innovative additional soil filling above the ground surface was carried out to overcome the overlying-soil-carrying effect of the extreme shallow jacked box tunnelling.The structural safety of metro tunnels during the jacking process was analyzed through in-situ monitoring.It indicated that the overlying-soil-carrying effect was successfully alleviated.The metro tunnels generally showed horizontal displacement towards the receiving shaft,uplift and horizontal stretch during the jacking process.The stop of jacking machine in front of obstacles generally contributed to the decrease of horizontal displacement,uplift and horizontal stretch of metro tunnels.The largest horizontal displacement(1.3–1.6 mm),uplift(1.5 mm)and horizontal convergence(1.6–1.8 mm)generally occurred when the reception of jacking machine was completed,and they all met the requirement of 2 mm for this project.The design and construction of this shallow jacked box tunnel project could provide references for future similar projects.

地铁区间隧道顶部热烟气温度分布

通过调查统计重庆地铁6号线区间隧道的断面形式,引入隧道断面形状系数ζ,建立断面形状系数ζ<1的模型实验台。采用模型实验与FDS模拟相结合的方法,探讨地铁隧道采用纵向排烟系统时,不同热释放速率及排烟速度的条件下区间隧道内烟气温度纵向分布特征。研究结果表明:Kurioka模型适用于断面形状系数ζ≥1的地铁区间隧道,对于断面形状系数ζ<1的地铁区间隧道,需要对Kurioka模型进行修正。对于断面形状系数ζ≥1的地铁区间隧道,顶棚上游烟气温度纵向分布服从指数衰减规律。然而,对于断面形状系数ζ<1的地铁区间隧道,顶棚上游烟气温度虽然也服从指数衰减规律,但需要进行模型修正。修正值Kζ与断面形状系数ζ之间满足线性关系,顶棚上游烟气温度沿纵向衰减速度,随隧道断面形状系数的增大而增大。

地铁区间隧道火灾烟气分区控制试验研究

地铁区间隧道内对乘客生命威胁最大的是火灾烟气,因此防灾的关键在于烟气控制。车头和车尾火灾时采取纵向通风能使人烟分离,但对于列车中部着火时下风侧乘客将不可避免地在烟气笼罩的环境中。提出了火灾烟气纵向分区控制模式,即利用防烟隔板将隧道划分成行驶区和疏散通道2个防烟分区,采取适当通风阻止烟气侵入疏散通道,保障人员疏散过程与烟气分离。通过1∶5隧道模型中烟气分区控制试验结果的比较分析,证实采取不同通风方式均可使疏散通道保持较高压力,使气流由疏散通道流向行驶区,以阻止火灾烟气侵入疏散通道内,但不同通风方式在高温控制及烟气控制效果上存在差异,其中以疏散通道正压送风及行驶区单侧排烟相结合的通风方式综合控制效果最好。

地铁车站及隧道全尺寸火灾实验研究(1)-实验设计

全尺寸火灾实验是对地铁系统的火灾安全性最有效的检测手段。为了研究地铁车站和隧道火灾烟气扩散和控制规律,及检测地铁防灾系统联动的有效性,在地铁内开展了全尺寸火灾实验研究。本文首先对全尺寸的实验设计进行了报道,设计提出了一套切实可行的实验系统和方案,包括火源系统、测量系统及实验测试的指标参数和实验步骤。并已利用该系统在国内多个城市地铁开展了全尺寸火灾实验。在后续文章中将集中报道在不同城市地铁内不同排烟模式情况下的实验结果。

地铁区间隧道的烟气逆流长度与临界风速

采用因次分析方法推导了地铁区间隧道火灾烟气逆流长度的无因次表达式;以重庆地铁6号线为例,开展了区间隧道形状的调查,选择了9种不同断面形式的区间隧道,采用FDS5.5模拟计算了隧道火灾烟气运动状况,进而提出了烟气逆流长度和临界风速的预测模型,并进一步建立了几何比例尺为1∶10的地铁区间隧道模型实验台来开展小尺寸试验研究.结果表明:文中提出的烟气逆流长度和临界风速的预测模型的模拟结果与小尺寸试验结果吻合较好;相比于文中提出的临界风速预测模型的预测结果,现有的预测模型预测的临界风速偏小.

关于地铁列车火灾人员疏散问题的几点讨论

针对地铁车站火灾人员疏散时间计算方法的问题,比较研究国内现行《地铁设计规范》(GB50157—2003)和美国专门针对有轨交通系统的NFPA130标准的异同,其结果说明:国内设计规范关于人员疏散时间的计算方法存在不足;对区间隧道内列车着火的情况进行分析讨论,指出对列车在区间隧道内着火,且还能继续运行的情况,着火列车的运行速度对火势的发展以及人员疏散时间的影响是不可忽视的。

地铁车站及隧道全尺寸火灾实验研究(3)——车站隧道火灾

为了研究烟气在地铁车站隧道内的蔓延特征,及在车站隧道通风排烟系统、区间隧道通风排烟系统及车站公共区通风排烟系统联合排烟情况下烟气控制效果,在一地铁车站隧道内开展了全尺寸火灾实验。实验研究了车站隧道顶部横向排烟作用下的烟气扩散规律,及烟气的温度变化,分析了屏蔽门开关状态下烟气与空气的卷吸混合特性,及区间风机的气流组织对通风排烟的影响。实验结果对于地铁车站隧道火灾防排烟设计提供了数据支持。

地铁车站及隧道全尺寸火灾实验研究(2)——区间隧道火灾

为了研究强制通风情况下地铁区间隧道火灾时的烟气扩散规律,在一实际地铁区间隧道内开展了全尺寸火灾实验。实验改变火源功率,在区间隧道通风排烟系统启动状态下,研究了区间烟气纵向蔓延速度、烟气竖直温度分布和水平温度变化,分析了烟气火焰倾斜角,顶棚烟气温升的纵向指数变化特征。实验结果对于地铁区间隧道火灾烟流控制及防排烟设计提供了数据支持。

基于无线传感器网络(WSN)的城市轨道交通隧道火灾定位研究

地铁隧道距离长、半密闭,火灾定位难度大。利用无线传感器网络(WSN)及Amorphous定位算法,结合开发的载有无线摄像头和相关传感器的可移动平台,实现了对地铁车站及隧道火灾的快速、准确定位,并可返回现场相关情况及参数。

火源尺寸对地铁隧道火灾临界风速的影响

以地铁区间隧道为研究对象,考虑有无列车两种情况,采用火灾动力学模拟软件FDS 5.5.3对不同火源尺寸条件下控制地铁隧道火灾烟气不向上游蔓延的临界风速进行数值模拟。结果表明:火源功率一定时,有无列车情况下火源高度、长度及宽度均对临界风速产生影响。无列车时,临界风速随着火源高度、长度、宽度的增加逐渐减小;有列车时,临界风速随着火源高度、宽度的增加先增大后减小,随着火源长度的增大而递减。

地铁区间隧道火灾自然排烟的数值分析

针对地铁区间隧道火灾的自然排烟,采用FDS(fire dynamics simulator)软件,数值模拟通风竖井的长宽比、埋深和开口形式对自然排烟效果的影响。模拟结果表明:当通风竖井的长宽比在1.25～2.5时,其自然排烟效果明显好于其长宽比为5时的自然排烟效果;当通风竖井的埋深在5～15 m时,对自然排烟的影响不明显;采用直通风竖井的自然排烟效果优于采用渐扩通风竖井的自然排烟效果。

地铁隧道火灾联动功能联调方法探讨

主控系统(即综合监控系统)实现了中央调度指挥的一体化、信息共享化和决策支持半自动化。介绍了主控系统的联动功能,以及在隧道火灾情况下主控系统的联动方式。根据隧道火灾疏散原则和环控工艺,对基于主控系统的隧道火灾模式的联调方法和步骤等进行了探讨,并对主控系统的发展方向提出了自己的看法。

分布式光纤测温系统监测地铁火灾的试验研究

介绍了分布式光纤温度测量原理,详细描述了分布式光纤测温系统的主要组成结构和各模块的功能特点。通过设置不同高度的火源位置以及不同的火源功率,在模拟地铁区间隧道中开展全尺寸火灾试验,研究分布式光纤测温系统在地铁区间隧道内发生火灾时的温度响应性能,测量隧道拱顶处最高温度分布,并根据温度变化情况来讨论火灾发生的规模和火灾探测器的报警阈值。研究发现,在隧道内纵向风速较大时,火焰及烟气会发生倾斜,导致分布式感温火灾探测器报警位置发生变化。最后,对分布式光纤测温系统中感温光纤在地铁区间隧道内敷设高度进行了讨论。

地铁长区间事故通风模拟分析

论述可有效分析地铁空气环境的软件SES(Subway Environmental Simulation),对其中的火源模型进行详细介绍。利用该软件,对北京地铁7号线达官营站—广安门站内区间火灾工况下的不同通风方案进行模拟分析。通过计算结果可知:开启着火区间两端车站隧道风机以及在区间渡线位置增加射流风机,均不能保证区间的风速要求;在本区间内设置中间风井并开启区间风机及着火区间两端车站风机后,着火区间风速为2.6 m/s,可满足规范要求。