坑道内挡板对化爆冲击波消减作用的数值模拟

在现代高技术战争条件下,精确制导武器在坑道入口附近爆炸,从而破坏防护门结构而使冲击波进入坑道成为可能。在坑道壁面的约束下,坑道内冲击波压力将衰减得很慢,且持续时间增加得很多。采用ANSYS／LA-DYNA动力有限元分析软件对常规武器在坑道内发生爆炸的工况进行了数值模拟,得出了坑道中冲击波峰值压力的衰减规律;提出了采用挡板对坑道中的冲击波进行消减的措施;进而研究了挡板的数量等参数对冲击波消减的规律。     

坑道内爆炸冲击波传播规律的研究

摘 要：炸药在坑道内爆炸将产生沿坑道传播的空气冲击波，冲击波与坑道壁相互作用，使得坑道内冲击波的传播规律明显不同于自由大气中冲击波的传播规律。使用有限元计算软件LS-DYNA对已有的坑道试验进行了数值模拟，通过数值模拟结果与试验结果数据比较，验证了有限元计算中所使用的计算模型和参数取值的合理性。利用数值模拟的计算结果，使用量纲分析理论，拟合了距离爆炸中心点一定距离处爆炸冲击波超压峰值的计算公式，并与试验结果进行对比，分析了该公式的适用性，为坑道中爆炸冲击波的传播规律研究提供了参考。
     

坑道口部内爆炸情况下扩散室中冲击波的数值分析

扩散室是一类重要的防护工程坑道口部消波措施,其结构形式和几何尺寸对消波效果影响显著.为使其消波效率最大化同时具有较高性价比,对化爆荷载作用下坑道中不同特征尺寸扩散室的消波规律进行探讨,提出了数值分析的计算方案,并取得了理想的消波模拟效果.在此基础上与试验进行比较,对模拟结果展开分析,验证了计算结果的准确性和计算方法的可行性.计算给出了扩散室中冲击波瞬变位置取值的表达式,并指出费效比合理的扩散室长径比为3,为扩散室在防护工程坑道结构设计中的应用提供了技术参考.     

坑道口部内爆炸冲击波传播速度规律的数值分析

准确计算坑道口部内爆炸条件下冲击波传播速度的变化,是确定坑道内主动消波设备时间响应指标的关键.为此,基于AutoDyn进行5种不同工况的坑道内爆炸计算.采用量纲分析构建了冲击波传播速度的工程模型,通过对数值计算结果的拟合确定了模型的系数.与坑道化爆实验的实测值进行分析比较表明,所拟合的坑道内冲击波传播速度的经验模型最大误差为15％,作为一种工程方法而言具有较强适用性.     

装药位置及形状对某坑道中冲击波压力的影响研究

为了弄清装药位置及形状对某坑道中冲击波压力传播规律的影响,基于Hopkinson比例定律,用LS-DYNA动力有限元软件较为系统地研究了不同装药位置及形状情况下,长坑道中冲击波峰值压力的传播规律.计算结果与其他经验方法的预测结果进行了比较.研究表明,整体上看,柱状装药的压力较大;在爆炸近区,装药位置及形状对预测结果的影响显著.随着传播距离的增加,这种影响越来越小.研究方法和数据可供类似工程问题参考.     

爆炸冲击波在坑道内传播规律研究

为了给坑道防护工程防爆炸空气冲击波的设计与研究提供一定的参考依据,收集整理了国内外常用的计算坑道口外爆炸产生的坑道内爆炸空气冲击波传播参数的计算方法,对其进行了比较和分析后给出了能够较好描述冲击波传播规律的计算方法。采用ANSYS AUTODYN有限元软件对某坑道比例模型试验进行了数值模拟,将模拟结果与坑道模型试验数据进行了比较,说明采用ANSYS AUTODYN有限元软件进行爆炸冲击波问题的数值模拟是可行的。     

坑道内冲击波冲量传播规律的试验研究

为获得坑道中冲击波冲量的传播规律,共进行了20次坑口外装药比例模型爆炸试验.模型坑道为等截面钢筋混凝土直墙圆拱结构,截面积为0.67m2,TNT炸药的装药量范围为1000g～4600g.用压力传感器记录了坑道中的冲击波波形,分析了实测的冲击波波形和冲击波冲量的传播规律,由实测数据拟合出了装药在坑口外爆炸情况下,冲击波冲量沿着等截面直坑道传播的工程经验模型.算例分析表明,该文提出的冲击波冲量工程经验模型具有一定的应用价值.     

坑道口部内爆炸冲击波传播速度规律的数值分析

准确计算坑道口部内爆炸条件下冲击波传播速度的变化,是确定坑道内主动消波设备时间响应指标的关键。为此,基于AutoDyn进行5种不同工况的坑道内爆炸计算。采用量纲分析构建了冲击波传播速度的工程模型,通过对数值计算结果的拟合确定了模型的系数。与坑道化爆实验的实测值进行分析比较表明,所拟合的坑道内冲击波传播速度的经验模型最大误差为15%,作为一种工程方法而言具有较强适用性。     

坑道口部内爆炸冲击波传播速度规律的数值分析

准确计算坑道口部内爆炸条件下冲击波传播速度的变化,是确定坑道内主动消波设备时间响应指标的关键。为此,基于AutoDyn进行5种不同工况的坑道内爆炸计算。采用量纲分析构建了冲击波传播速度的工程模型,通过对数值计算结果的拟合确定了模型的系数。与坑道化爆实验的实测值进行分析比较表明,所拟合的坑道内冲击波传播速度的经验模型最大误差为15%,作为一种工程方法而言具有较强适用性。     

冲击波负压对防护门反弹效应的影响分析

本文对冲击波负压作用下防护门的反弹效应进行了研究,采用合理的荷载假定形式,推导了考虑负压影响的防护门反弹力的精确解析公式,评价了负压对防护门反弹效应的影响规律：即随着比例爆距的增大,负压峰值相对于正压峰值逐渐增大,反弹增大效应也较明显,但这样一个响应可能仅对比较小的超压值才出现,由于正压、负压峰值都较小,防护门刚度较大,故增大的反弹力不足以对防护门造成破坏,设计中可以不考虑负压的影响。     

强震区黏滑断层隧道刚柔相济抗减震技术模型试验研究

为研究强震区黏滑断层隧道刚柔相济抗减震技术,依托都汶高速龙溪隧道F8黏滑断层段,开展了静力断层黏滑错动试验和大型三方向六自由度强震震动试验,通过对试验数据的分析,主要研究了上下盘隧道结构的纵向应变、接触压力和内力。试验结果表明:施设减震缝后,沿纵向隧道结构纵向应变及接触压力增加倍数由剧烈变化变为较均匀变化;采用结构加强抵抗断层黏滑错动和强震震动对隧道结构的影响,效果有限;通过施设减震缝抵抗断层黏滑错动和强震震动的影响,效果明显,隧道结构纵向应变抗减震效果97%以上,接触压力抗减震效果86%以上,安全系数最小值增加5倍以上;强震区黏滑断层隧道采用刚柔相济抗减震措施进行设防,可大幅提高隧道结构的安全性,安全系数最小值增加8倍以上。研究成果可为强震区黏滑断层隧道抗减震设防设计提供参考。     

爆炸荷载作用下地铁隧道的冲击反应研究

随着地铁的大规模兴建,地铁隧道的抗爆防护研究成为一个迫切需要解决的问题。针对南京地铁区间隧道的实际工程地质条件,建立了地铁隧道的冲击反应计算模型和各种材料的模型,采用流固耦合算法, 对10kgTNT炸药作用下地铁隧道的冲击反应进行了全面研究。研究结果表明,隧道衬砌的速度和加速度变化与超压有关,随着距爆心距离的增大,爆炸冲击波对衬砌结构的影响逐渐减弱,而且在爆炸的初始时刻,隧道衬砌处于受拉状态,随着时间的推移,超压峰值逐渐衰减,隧道衬砌则由受拉状态变为受压状态,并逐渐趋于稳定,从而为地铁隧道的抗爆防护和应急预案的制定提供了依据。     

基于小波、小波包两种方法的爆破振动信号对比分析

在小波、小波包的理论基础上,结合某市城市建设中基岩爆破中振动监测数据,采用这两种方法对同一爆破振动信号在信号去噪、对细节信号的处理、信号的分解与重构方面将两种方法的应用和效果进行了对比。分析表明,采用小波包技术研究爆破地震波信号比小波分析技术有更强的灵活性,能更加完整地反映爆破振动信号的特征。     

爆炸荷载作用下坑道结构振动响应及影响因素分析

根据爆炸荷载条件下的模型坑道试验,运用LS-DYNA显式动力分析软件,对试验中典型坑道段在顶爆和侧爆作用下的动力响应进行了数值模拟计算,研究了模型坑道结构在爆炸荷载下的最大振动加速度分布特征,并与试验结果进行了对比验证。结果表明,计算结果和实测结果基本吻合,能够真实反映爆炸荷载下坑道结构的振动响应。最后对不同单个影响坑道振动的截面形状参数进行了一系列数值计算,分析了在相同爆炸荷载下单个特定参数对坑道振动影响规律。     

常规武器坑道口部爆炸效应的试验与数值模拟分析

通过现场试验和LS-DYNA有限元数值模拟方法研究了不同装药长径比对坑道内空气冲击波超压的影响.数值模拟计算结果与试验数据表明,常规武器战斗部装药长径比的增加引起了坑道内部空气冲击波超压明显增大,破坏能力得到增强.该结论为坑道防护设计提供了较好的参考依据.     

On the basically single-type excitation source of resonance in the wind tunnel and in the hydroturbine channel of a hydraulic power plant

We have investigated the spectra of pressure pulsations in the near field of the open working section of the wind tunnel with a vortex flow behind the tunnel blower formed like the flow behind the hydroturbine of a hydraulic power plant. We have made a comparison between the measurement data for pressure pulsations and the air stream velocity in tunnels of the above type and in tunnels in which a large-scale vortex structure behind the blower is not formed. It has been established that the large-scale vortex formation in the incompressible medium behind the blade system in the wind tunnel is a source of narrow-band acoustic radiation capable of exciting resonance self-oscillations in the tunnel channel.     

Dynamic response analysis of a building structure subjected to ground shock from a tunnel explosion

Dynamic responses of a multi-storey building without or with a sliding base-isolation device to ground shock induced by an in-tunnel explosion are numerically analyzed in this paper. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation, is also considered in the analysis. Different modeling methods, such as the eight-node iso-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition and the multi-storey building with or without the sliding base-isolation device. In numerical calculations, a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated in the study. The final conclusions based on the numerical results will provide some guidance in engineering practice.     

Ground movement and tunnel stability when tunneling in sandy ground

Abstract

Tunneling may cause ground movements and damage to adjacent buildings and overlying facilities. In this study, the failure mechanism and ground movement behavior around tunnels embedded in sandy soil below the water table were investigated in a series of model tunnel tests in a centrifuge. The magnitudes and extents of the surface settlement troughs for the cases of various ground loss for tunnels buried at various depths are provided. A new failure mechanism is proposed and validated by comparison with the test results. The proposed mechanism enables accurate prediction of two of the key quantities in the design of linings for tunnels embedded in sandy soils, namely the minimum supporting pressure needed to retain tunnel stability and the vertical soil pressure acting on the tunnel crown.     

Key Techniques for the Construction of High-Speed Railway Large-Section Loess Tunnels

The successful completion of the Zhengzhou–Xi’an high-speed railway project has greatly improved the construction level of China’s large-section loess tunnels, and has resulted in significant progress being made in both design theory and construction technology. This paper systematically summarizes the technical characteristics and main problems of the large-section loess tunnels on China’s high-speed railway, including classification of the surrounding rock, design of the supporting structure, surface settlement and cracking control, and safe and rapid construction methods. On this basis, the key construction techniques of loess tunnels with large sections for high-speed railway are expounded from the aspects of design and construction. The research results show that the classification of loess strata surrounding large tunnels should be based on the geological age of the loess, and be determined by combining the plastic index and the water content. In addition, the influence of the buried depth should be considered. During tunnel excavation disturbance, if the tensile stress exceeds the soil tensile or shear strength, the surface part of the sliding trend plane can be damaged, and visible cracks can form. The pressure of the surrounding rock of a large-section loess tunnel should be calculated according to the buried depth, using the corresponding formula. A three-bench seven-step excavation method of construction was used as the core technology system to ensure the safe and rapid construction of a large-section loess tunnel, following a field test to optimize the construction parameters and determine the engineering measures to stabilize the tunnel face. The conclusions and methods presented here are of great significance in revealing the strata and supporting mechanics of large-section loess tunnels, and in optimizing the supporting structure design and the technical parameters for construction.     

基坑上跨开挖诱发既有盾构隧道隆起变形研究EI北大核心CSCD

基坑上跨开挖将会引起既有盾构隧道隆起变形,危及既有盾构隧道的服役性能。目前基坑开挖引起的盾构隧道隆起变形的解析方法,通常将盾构隧道简化为埋置于弹性地基上的连续长梁,忽略了环间接头影响。针对前人研究的不足,提出带环间接头的盾构隧道计算模型,通过非线性Pasternak地基模型来考虑地基土变形的非线性特征,通过两阶段分析法,推导得到基坑上跨开挖作用下盾构隧道隆起位移和张开量简化解答。通过MINDLIN解计算基坑开挖引起的作用于盾构隧道上的附加荷载;建立基坑卸载下盾构隧道的隆起变形微分方程。利用有限差分法求解出基坑开挖引起的邻近盾构隧道隆起变形和内力分布。收集了三个工程实测数据,并将所提方法和实测数据、既有理论方法进行对比,验证所提方法的适用性。