缩比地下化学爆炸气体泄漏规律研究

针对气体通过均匀多孔介质、非均匀多孔介质和贯通裂缝泄漏三种机制,研究地下爆炸缩比实验气体泄漏时间和份额的规律.结果显示,对于相同介质中的缩比化学爆炸实验,气体泄漏时间与药量的三分之二次方成正比,不同药量实验的最终泄漏份额基本一致.实验室缩比化学爆炸实验气体泄漏时间关系的监测结果与理论分析基本一致.     

浅埋三舱管廊甲烷爆炸的地面响应规律

地下综合管廊可燃性气体爆炸事故时有发生,给地面人员的生命和财产造成了巨大损失。依托重庆市某地下综合管廊试点工程,基于物质点法,采用点火增长模型模拟浅埋管廊泄漏甲烷气体爆炸冲击管廊本体结构和围岩的过程,研究爆炸作用下地面压强与位移的响应特性。研究发现:泄爆作用下管廊及围岩会出现因接触面反射和折射产生的次生应力波,管廊横向方向次生波振幅随距起爆点水平距离的增大而增大,而管廊纵向方向产生的次生波振幅较小,且随距离增大变化较小;爆炸作用造成整体地面沉降,但在起爆点中心附近地面隆起,这种隆起由管廊本体结构破裂,气体直接冲击岩土体形成的剧烈隆起和管廊整体震动形成的轻微隆起两部分组成。     

地下强爆炸辐射流体动力学过程的二维数值模拟

为评估强爆炸的毁伤效应,利用流固耦合界面处理方法,考虑辐射输运引起的能量沉积过程,建立同时求解辐射流体力学方程和流体弹塑性方程的二维耦合计算方法,给出地下强爆炸时,爆室内辐射波传播、辐射能量沉积到岩土表层、岩土表层膨胀、冲击波在岩土介质中传播、爆室内高压压缩爆室壁、爆室壁振荡增大的完整物理过程.     

地下管廊在燃气爆炸作用下的动力响应分析

在燃气通过地下管廊输送过程中,若燃气泄漏进入管廊内部并引起爆炸将会产生严重的后果。以平潭综合试验区环岛路管线工程为背景,借助LS-DYNA非线性动力分析有限元软件,基于流固耦合和ALE多物质算法,建立地下空间燃气爆炸数值计算模型,探讨管廊内燃气爆炸过程中爆炸冲击波对管廊结构的影响。数值计算结果表明:在爆炸过程中,超压峰值从爆源中心转移到波阵面上,导致爆源附近压力低于波阵面压力,爆源附近形成负压区;爆炸荷载作用下,燃气仓内距离爆源最近的内墙上的测点超压值最大,在t=7.8ms时达到最大值为18.65MPa,且在t=10ms左右时,位移和速度达到最大值,分别为10.47mm、3.303m/s;气体爆炸后,管廊燃气仓内墙正负压振荡时间持续较长,振动现象最为明显,最易发生破坏。     

高压氢气输运装置物理爆炸状态场特征及灾害效应研究

 由于输运装置突然失效而引发的高压氢气喷射,能够在流场中造成超压和足以引发爆炸的扩散。运用数值计算方法,建立可用于计算的物理和数学模型对发生泄漏后有、无障碍物两种情况下的外部流场进行分析,可得到外部流场中的气体泄漏压力和浓度的分布等值线图。从计算结果可以得出氢气发生爆炸事故后的危险区域,障碍物对氢气的喷射泄漏以及爆炸所产生的影响,从而可为预防和处理氢气爆炸事故提供参考依据。     

顶爆和拱腰侧爆同时作用下锚固洞室的动态响应

基于相似模型试验,采用显式非线性动力分析程序LS-DYNA3D研究了地下锚固洞室在拱顶和拱腰侧两处集中装药爆源同时爆炸作用下应力波传播规律、裂纹形成机理以及洞壁围岩位移分布特征。通过对比分析顶爆试验和计算模型的压应力时程曲线,发现模拟与试验结果吻合,且符合应力波的传播规律,表明数值模拟结果可靠。爆源爆炸后,应力波以圆形向周围岩体传播,两应力波相遇处压应力强度明显大于周围岩体;当应力波传到自由面时,会反射形成拉伸波,在地表下方和洞室上方发生“层裂”现象,在拱顶和拱腰侧爆源中间沿洞室径向有裂纹延伸,由于拉伸波的叠加,在爆源下方出现“八”字形的锥形裂纹面。锚杆能够起到加固岩体的作用,锚固洞室比毛洞裂纹分布少,毛洞迎爆侧裂纹主要为横向裂纹,而锚固洞室则为径向劈裂和横向裂纹。两爆源中点洞室径向处的洞壁围岩位移峰值最大,极易产生破坏。     

地下爆炸空腔压力和温度历程数值模拟

将气体的渗透、气体与空腔壁的辐射换热、气体与周围介质的热传导三种因素相结合,建立地下爆炸空腔稳定后气体温度和压力变化的数学模型,编制一维球对称有限体积数值模拟程序.用该程序对美国内华达试验场冲积土介质中一次地下核爆炸空腔温度和压力历程进行数值模拟,并对压力监测结果进行分析.     

循环爆炸作用下地下洞室的动态响应及损伤累积

为研究循环爆炸对地下洞室的影响,基于相似模型试验,采用通用有限元软件ABAQUS对比研究了洞室拱顶高水平单次爆炸和低水平10次循环爆炸作用下地下洞室围岩的应力波衰减规律、损伤累积规律及洞壁位移和环向应变分布特征。结果表明:循环爆炸中,洞室围岩的应力波衰减速度随着爆炸次数的增加先减小后增大。单次爆炸中,洞壁环向峰值应变从拱顶至直墙脚由拉应变转为压应变;循环爆炸中,随着爆炸次数的增加,拱顶环向峰值应变由压应变转为拉应变。爆炸荷载总水平相同时,低水平循环爆炸中洞室围岩的损伤面积和程度比高水平单次爆炸大。循环爆炸中,围岩的损伤累积呈现不可逆的逐级增加趋势,且累积损伤和爆炸次数之间呈明显的非线性关系。     

煤矿巷道瓦斯爆炸冲击波与高温气流的关系

 为了给瓦斯爆炸后煤尘二次爆炸的深入研究提供理论依据,应用计算流体力学方法,对煤矿巷道内瓦斯爆炸的瞬态流场进行了数值模拟,得到了冲击波与高温气流流动的时空关系,并借助实验对数值方法进行了验证。研究表明：在瓦斯爆炸后的一定时间内,近场区域和远场的部分区域极有可能引发煤尘二次爆炸。给出了可能发生煤尘二次爆炸的区域随瓦斯区长度的函数关系式,以及远场中峰值温度和峰值超压到达时间的间隔随轴向距离和瓦斯区长度的分布特性。     

一种基于形状的红外图像泄漏气体检测方法

针对工业生产中泄漏气体导致的爆炸和火灾问题, 提出一种基于形状和SVM分类的红外图像泄漏气体检测方法。采用泄漏气体和干扰物红外图像样本的形状特征训练SVM分类器, 通过对红外图像序列采用基于背景差分的运动检测得到候选目标区域, 再对候选目标区域提取其形状特征, 最后使用SVM分类器进行判别, 从而得到最终的检测结果。使用乙烯气体泄漏仿真数据进行实验, 检测率最高可达98%, 结果表明, 采用该方法可以有效检测泄漏气体, 相比其他方法, 极大地减少了干扰物造成的误检。     

不同方式地下爆炸地震耦合效应的数值模拟

通过一种Euler与Lagrange相结合的有限差分法,开展地下爆炸地震耦合效应的数值模拟.比较花岗岩介质中填实和空腔两种爆炸方式在地震耦合效应方面的差异,进一步分析初始空腔大小在填实以及空腔爆炸地震效应中的作用以及空腔爆炸解耦因子随频率的变化特性.计算结果表明,花岗岩介质中完全空腔解耦因子能达到50~60倍.     

Radial oscillation and translational motion of a gas bubble in a micro-cavity

According to classical nucleation theory, a gas nucleus can grow into a cavitation bubble when the ambient pressure is negative. Here, the growth process of a gas nucleus in a micro-cavity was simplified to two “events”, and the full confinement effect of the surrounding medium of the cavity was considered by including the bulk modulus in the equation of state. The Rayleigh–Plesset-like equation of the cavitation bubble in the cavity was derived to model the radial oscillation and translational motion of the cavitation bubble in the local acoustic field. The numerical results show that the nucleation time of the cavitation bubble is sensitive to the initial position of the gas nucleus. The cavity size affects the duration of the radial oscillation of the cavitation bubble, where the duration is shorter for smaller cavities. The equilibrium radius of a cavitation bubble grown from a gas nucleus increases with increasing size of the cavity. There are two possible types of translational motion: reciprocal motion around the center of the cavity and motion toward the cavity wall. The growth process of gas nuclei into cavitation bubbles is also dependent on the compressibility of the surrounding medium and the magnitude of the negative pressure. Therefore, gas nuclei in a liquid cavity can be excited by acoustic waves to form cavitation bubbles, and the translational motion of the cavitation bubbles can be easily observed owing to the confining influence of the medium outside the cavity.     

Artificial radionuclides in oils from the underground nuclear test site (Perm region,Russia)

The results of radionuclide determination in oil samples from the Gezh oil deposit (Perm region, Russia) where five underground nuclear explosions took place are presented. High³H and¹⁴C concentrations were found in oil from the wells were the explosions were made as well as from distant wells. This contradicts the assumption that the holes after the explosion are hermetic and the radionuclide leakage is negligible.     

Statistics of discrete photodetection of resonance fluorescence in the Mollow sidebands

A method is proposed for generating conditional single-photon states with a high degree of purity in a single-mode cavity by successive discrete photodetection. The cavity is pumped by resonance fluorescence emission from a source atom driven by a classical field. The cavity is tuned to a Mollow sideband. A relation between detector parameters is found that makes it possible to interpret the detection of a probe atom in the excited state as unambiguous evidence that a pure single-photon state has been prepared in the cavity. An expression is derived for the prior probability of such an event, and dependence of the one-photon state population of the cavity field on detuning, relaxation rate, and time is examined.     

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena

Gas-induced geodynamic phenomena can occur during underground mining operations if the porous structure of the rock is filled with gas at high pressure. In such cases, the original compact rock structure disintegrates into grains of small dimensions, which are then transported along the mine working space. Such geodynamic events, particularly outbursts of gas and rock, pose a danger both to the life of miners and to the functioning of the mine infrastructure. These incidents are rare in copper ore mining, but they have recently begun to occur, and have not yet been fully investigated. To ensure the safety of mining operations, it is necessary to determine parameters of the rock–gas system for which the energy of the gas will be smaller than the work required to disintegrate and transport the rock. Such a comparison is referred to as an energy balance and serves as a starting point for all engineering analyses. During mining operations, the equilibrium of the rock–gas system is disturbed, and the rapid destruction of the rock is initiated together with sudden decompression of the gas contained in its porous structure. The disintegrated rock is then transported along the mine working space in a stream of released gas. Estimation of the energy of the gas requires investigation of the type of thermodynamic transformation involved in the process. In this case, adiabatic transformation would mean that the gas, cooled in the course of decompression, remains at a temperature significantly lower than that of the surrounding rocks throughout the process. However, if we assume that the transformation is isothermal, then the cooled gas will heat up to the original temperature of the rock in a very short time (<1 s). Because the quantity of energy in the case of isothermal transformation is almost three times as high as in the adiabatic case, obtaining the correct energy balance for gas-induced geodynamic phenomena requires detailed analysis of this question. For this purpose, a unique experimental study was carried out to determine the time required for heat exchange in conditions of very rapid flows of gas around rock grains of different sizes. Numerical simulations reproducing the experiments were also designed. The results of the experiment and the simulation were in good agreement, indicating a very fast rate of heat exchange. Taking account of the parameters of the experiment, the thermodynamic transformation may be considered to be close to isothermal.     

Relaxation behavior of laser-polarized (129)Xe gas: size dependency and wall effect of the T(1) relaxation time in glass and gelatin bulbs

Size dependency of the relaxation time T(1) was measured for laser-polarized (129)Xe gas encapsulated in different sized cavities made by glass bulbs or gelatin capsules. The use of laser-polarized gas enhances the sensitivity a great deal, making it possible to measure the longer (129)Xe relaxation time in quite a short time. The size dependency is analyzed on the basis of the kinetic theory of gases and a relationship is derived in which the relaxation rate is connected with the square inverse of the diameter of the cavity. Such an analysis provides a novel parameter which denotes the wall effect on the relaxation rate when a gas molecule collides with the surface once in a second. The relaxation time of (129)Xe gas is also dependent on the material which forms the cavity. This dependency is large and the relaxation study using polarized (129)Xe gas is expected to offer important information about the state of the matter of the cavity wall.     

The applications of single crystals

The word ‘crystal’ comes from a Greek word meaning clear ice which was also applied to rock crystal (clear, transparent quartz). It was not until about the 17th century that the word was extended to other naturally occurring, transparent minerals which showed a regularity of outward form. It was appreciated at this time that this regularity resulted from an inner symmetry of atomic arrangement and it has since been realized that almost all solid materials are, to some extent at least, crystalline although this is often not apparent from their outward appearance. Indeed most materials of practical importance are polycrystalline-they consist of an aggregate of randomly-arranged small crystals-although single crystals have been used for special purposes for some considerable time, e.g. the crystals of calcite that are used to make Nicol prisms, and the crystals of galena (lead sulphide) that were used in early ‘crystal’ wireless receivers. But in recent years increasing use has been made of single crystals for a wide variety of purposes and the demand for single crystals of particular materials is such that large quantities of single crystals of materials such as ethylene diamine tartrate or terphenyl are now grown artificially by one of several techniques now available for the growing of single crystals.