Numerical study on the fracturing mechanism of shock wave interactions between two adjacent blast holes in deep rock blasting

With the application of electronic detonators, millisecond blasting is regarded as a signifi cant promising approach to improve the rock fragmentation in deep rock blasting. Thus, it is necessary to investigate the fracturing mechanisms of short-delay blasting. In this work, a rectangle model with two circle boreholes is modeled as a particles assembly based on the discrete element method to simulate the shock wave interactions induced by millisecond blasting. The rectangle model has a size of 12 × 6 m (L × W) and two blast holes have the same diameter of 12 cm. The shock waves are simplifi ed as time-varying forces applied at the particles of walls of the two boreholes. Among a series of numerical tests in this study, the spacing between two adjacent boreholes and delay time of millisecond blasting are considered as two primary variables, and the decoupling charge with a coeffi cient of 1.5 is taken into account in each case. The results show that stress superposition is not a key factor for improving rock fragmentation (tensile stress interactions rather than compressive stress superposition could aff ect the generation of cracks), whereas collision actions from isolated particles or particles with weakened constraints play a crucial role in creating the fracture network. The delay time has an infl uence on causing cracks in rock blasting, however, whether it works heavily depends on the distance between the two holes.

Experimental Investigation on Shock Wave Characteristics of Aluminized Explosives in Air Blast

To investigate the shock wave characteristics of RDX-based aluminized explosives,air blast tests were conducted for measuring the parameters of 10 kg aluminized explosives which contained 0-40% aluminum.The results showed that with the increasing of aluminum content,the overpressures and impulses increase at first and then decrease within 7 m or 5 m,which reached the maximum when aluminum content was 20% or 30%.Power exponential formulas are used to fit the shock wave parameters vs scaled distance,where an equal weight of TNT is used to calculate the scaled distance.The overpressures of HL0 and TNT in tested locations not only conform to the similar law,but also conform to the same attenuation law after gaining the scaled distances of equal TNT mass.The pre-exponential factors of overpressure and impulse,kp and kI,decrease along with the increasing of Al content and keep the same pace as the calculated PCJ）.The attenuation coefficients a_P and aIincrease at first and decrease later with the increasing of aluminum content,and they reached the maximal values with30% Al containing,which keeps the same pace as the calculated QV.

Velocities and Displacements of Shrapnel and a Shock Wave during Blast

It is important to minimize the destruction of defense works when blasted. In our opinion, information in the available literature is very deficient. We now present our research results on better and simpler formulas for calculating the velocities and displacements of shrapnel and a shock wave; these formulas are indispensable for understanding the destruction of blast. Formulas now available in China are too complicated. In this paper, we derive Equation （ 13 ） as the formula for calculating the velocity of shrapnel and Equation （ 18 ） as that for calculating the velocity of a shock wave. We used the test data of Denver Research Institute, as reported in Reference 4, as numerical example and found that our Equations （13） and （18） give calculated results that agree well with their test data in two respects： （ 1 ） both test data and our calculations show that at first a shock wave is ahead of shrapnel, then their displacements are equal, and finaUy shrapnel is ahead of the shock wave; （2） when the displacements of shrapnel and shock wave are equal, the time is 0. 34 s according to test data and 0. 31 s according to our calculations.

Physics-informed machine learning model for prediction of ground reflected wave peak overpressure

The accurate prediction of peak overpressure of explosion shockwaves is significant in fields such as explosion hazard assessment and structural protection, where explosion shockwaves serve as typical destructive elements. Aiming at the problem of insufficient accuracy of the existing physical models for predicting the peak overpressure of ground reflected waves, two physics-informed machine learning models are constructed. The results demonstrate that the machine learning models, which incorporate physical information by predicting the deviation between the physical model and actual values and adding a physical loss term in the loss function, can accurately predict both the training and out-oftraining dataset. Compared to existing physical models, the average relative error in the predicted training domain is reduced from 17.459%-48.588% to 2%, and the proportion of average relative error less than 20% increased from 0% to 59.4% to more than 99%. In addition, the relative average error outside the prediction training set range is reduced from 14.496%-29.389% to 5%, and the proportion of relative average error less than 20% increased from 0% to 71.39% to more than 99%. The inclusion of a physical loss term enforcing monotonicity in the loss function effectively improves the extrapolation performance of machine learning. The findings of this study provide valuable reference for explosion hazard assessment and anti-explosion structural design in various fields.

Attenuation Effect of Expansion Configuration and Acoustic Material on Propagation of Blast Waves in a Duct

With recent increase of cars, the noise problem has been caused by the exhaust sounds released from exhaust pipes, which consist of weak and pulsed shock waves called blast waves. To diminish the noise, a silencer is set up in front of the exhaust pipe. In the present study, reflectors were installed in the high-pressure section of the shock tube to generate blast waves, and three types of expansion region were investigated, combined with acoustic material of glass wool. The pressure decay was evaluated by transmission factor and reflection factor for the incident blast wave, together with pressure histories and high-speed Schlieren photography. As results, it was confirmed that the acoustic material greatly contributed to blast-wave attenuation: the one stage expansion model with glass wool recorded the highest decay of the peak over pressure for transmission, and other models with glass wool showed the second highest. The acoustic material also contributed to decay of reflected shock waves propagating toward an upstream duct.

环形复合内衬头盔冲击波防护性能研究

冲击波防护能力是单兵头盔的主要性能指标,对提高单兵战场生存能力具有重要意义。为了提高单兵头盔的冲击波防护性能,针对先进战斗头盔内衬的结构以及布置方式展开探索,提出环形聚脲-聚氨酯泡沫-海绵复合材料外沿内衬设计,并进行防护性能评估。通过激波管和实爆,针对有/无头盔以及装配不同结构及尺寸外沿内衬头盔的冲击波防护性能展开测试,对前额、颅顶及后脑3个重点区域位置表面的冲击波波形以及压力峰值进行对比分析。实验结果表明:佩戴头盔后冲击波主要通过头-头盔间隙以绕射的形式进入并作用于头部表面,间隙内冲击波聚集叠加反而可能会使压力增强,且由于叠加汇聚效应往往导致距离爆源较远的位点,容易形成局部高压区;环形聚脲-聚氨酯泡沫-海绵复合材料外沿内衬可以有效阻挡绕射波进入头盔内部、减弱绕射波叠加效应,各测点冲击波超压衰减率均可达40%以上;在所采用的入射冲击波(弱冲击波)条件下,冲击波作用过程中形成的间隙越小,防护效果越好;当聚脲-聚氨酯泡沫材料宽度为15 mm时外沿内衬与头模贴合程度最好且防护效果最优,外场爆炸实验结果显示,前额、颅顶和后脑位置超压衰减率分别可高达92.26%、88.82%和87.19%。

露天开采爆破空气冲击波安全影响及控制研究

为研究露天深孔台阶爆破空气冲击波对矿区周边环境安全的影响,通过理论计算与工程实践研究了平坦地形爆破、120 mm和150 mm两种孔径露天深空台阶爆破时爆破空气冲击波的安全距离及影响。结果表明,通过分析平坦地形下露天爆破冲击超压经验公式,得出TNT炸药当量为3698 kg时,不设防的非作业人员安全距离为910.1 m,掩体中的作业人员安全距离为225.8 m,高压线(塔)的安全距离为73.7 m。基于露天台阶深孔爆破空气冲击波安全距离R的计算结果,对于120 mm的台阶爆破炮孔,最大单孔装药量为124.9 kg,无掩体时,人的最小冲击波安全距离约149.9 m。炮孔孔径为150 mm时,最大单孔装药量为170.1 kg,人的最小冲击波安全距离约为166.2 m。

A Review of Current Researches on Blast Load Effects on Building Structures in China

The damages of building structures subjected to multifarious explosions cause huge losses of lives and property. It is the reason why the blast resistance and explosion protection of building structures become an important research topic in the civil engineering field all over the world. This paper provides an overview of the research work in China on blast loads effect on building structures. It includes modeling blast shock wave propagation and their effects, the dynamic responses of various building structures under blast loads and the measures to strengthen the building structures against blast loads. The paper also discusses the achievements and further work that needs be done for a better understanding of the blast loads' effects on building structures, and for deriving effective and economic techniques to design new or to strengthen existing structures.

Rock-breaking mechanism and experimental analysis of confined blasting of borehole surrounding rock

The rock-breaking mechanism and effect of confined blasting were analysed by blasting and impact dynamic mechanics, fluid dynamic mechanics, fracture mechanics as well as blasting experiment. The results showed that the fracturing of surrounding rock in confined blasting condition is the result of coaction of rock pre-cracking by shock wave and stress wave and the continuing expanding crackenhancement of confined medium, and the model of crack development of borehole surrounding rock in confined blasting condition was established. This study acquired the damage range of surrounding rock under the action of shock wave and stress wave, as well as the crack development characteristics of surrounding rock after the wedge-in confined medium into the crack space. Deep-hole confined blasting experiment on large rock showed that the high-efficient utilisation of in-hole explosive was achieved and the safety of rock blasting operation was ensured. Safe static rock-breaking under the action of high-efficient explosive blasting was achieved as well as the unification of super dynamic load of explosive blasting and static rock-breaking of water medium.

基于高压气体驱动的爆炸波模拟激波管冲击波衰减历程控制方法

基于高压气体驱动的爆炸波模拟激波管,一般采用驱动段、喉部、膨胀段的结构形式,可产生特征与爆炸波接近的模拟冲击波,是实验室中开展长正压作用时间爆炸毁伤效应研究的理想平台。通过调整激波管的变截面结构和驱动段形状,实现冲击波超压衰减历程的控制,是此类爆炸波模拟激波管设计面临的核心问题之一。基于实验室现有的爆炸波模拟激波管结构,建立了激波管内一维流动数值计算模型;参考统计学理论,提出了基于决定系数的激波管模拟冲击波与标准爆炸波相似度评价方法;进而以变截面激波管的流动特性为基础,研究了驱动段形状对冲击波衰减历程的影响机理。研究结果表明:采用距离喉部越远、截面直径越小的驱动段形状,以决定系数为量化标准、优化驱动段形状,控制稀疏波、压缩波在激波管内的运动过程,可以获得接近于爆炸波指数衰减特征的模拟冲击波。

激波管模拟产生近场爆炸冲击波

激波管可以在实验室环境下模拟爆炸产生冲击波,具有参数易于控制和测量手段准确多样等优势,在爆炸冲击效应的研究中被广泛应用。但与真实爆炸相比,尤其是近场爆炸,激波管产生的冲击波存在正压作用时间难以缩短、超压峰值难以提升的困难。通过对激波管运行理论和数值模拟分析发现:缩短正压作用时间的关键是让反射稀疏波尽快追上入射激波;提升超压峰值的关键是提高驱动气体的驱动能力。为此,设计了一种驱动段为锥形截面的激波管,使得反射稀疏波更快地追上入射激波,从而有效减小激波管设备长度并缩短正压作用时间;同时,采用正向爆轰驱动技术,利用化学能代替高压空气驱动提高驱动气体声速,在低爆轰初始压力下可以获得高的超压峰值。数值计算结果表明,在入射激波马赫数(MS=2.0)相同条件下,相对于等截面驱动方式,采用锥形截面驱动方式时,激波管长度可以减少近2/3,正压作用时间可以缩短近1/2。激波管实验结果表明,锥形截面驱动激波管产生的超压曲线满足近场爆炸冲击波形要求,并获得了超压峰值为64.7~813.4 kPa、正压作用时间为1.7~4.8 ms的爆炸冲击波波形。该研究可为近场爆炸冲击波致伤及装备防护效应评价实验提供参考。

长脉宽爆炸波与圆柱壳作用的波系演化与载荷分布特征

长脉宽爆炸波与结构作用的波传播及其载荷分布规律是大型爆炸防护设计与安全评估的重要基础。为了掌握长脉宽爆炸波与圆柱壳的相互作用机制及其作用下圆柱壳表面的载荷分布规律,开展了100 ms级冲击波圆柱绕流的激波管试验,并采用大涡模拟方法和高阶WENO-TCD(weighted essentially non-oscillatory-tuned centered difference)混合格式进一步对150 ms长脉宽冲击波与圆柱作用过程的波系演化与压力分布进行了数值分析。结果表明:数值仿真与压力实测结果吻合较好,长脉宽作用下圆柱壳载荷分布呈现出明显的角度和高度相关性,背面压力高于侧面甚至与迎爆面相当,具有不同于传统短脉宽冲击波传播中的压力衰减模式。流场的压力云纹和波系三维结构演化揭示了侧端面的突然扩张是压力初期震荡及相比于正面和背面压力更低的主要原因;系列绕射激波在壳体背面碰撞与反射,以及序列减速激波在135°相位附近的驻定与叠加作用,是引起背面压力呈现出载荷整体提升的主要机制。此外,背风面上尾涡结构的形成与演化过程受边界效应的影响是导致长脉宽圆柱壳载荷分布沿高度方向出现差异的关键因素。

深部岩体爆破冲击波能量分布特征

地应力对岩体爆炸应力与爆炸能量的分布有重要影响。针对深部岩体爆破冲击波能量分布,基于叠加原理,计算地应力和爆炸荷载双重作用下岩体爆炸应力分布,结合岩体破坏准则,得到了冲击波作用下深部岩体的破坏特征,分析不同工况下传递入深部岩体引起爆破扩腔、径向裂隙扩张及岩石弹性变形的冲击波能量占比,采用数值模拟方法探究了地应力对岩体爆破冲击波能量分布的影响。研究结果表明:岩体性质、炸药性能及地应力水平均会对深部岩体冲击波能量分布产生显著影响;高地应力环境下,硝铵炸药传递入硬岩(花岗岩)的冲击波总能量占比及有效能量的占比较于软岩(页岩)更小,与低性能炸药相比,采用高性能炸药爆破时传递入花岗岩的冲击波总能量占比及有效能量的占比更大;随地应力增大,用于爆腔膨胀的冲击波能量占比基本不变,用于裂隙扩张的冲击波能量占比近似呈线性减小,用于引起弹性变形的冲击波能量占比近似呈指数增长;高地应力环境下,传递入岩体的冲击波总能量占比虽然较大,但有效能量的占比较小;研究成果可为改善深部岩体爆破冲击波能量分布及提升岩体爆破效果提供参考。

爆炸冲击波下地应力对岩石裂纹扩展的影响

随着地下工程深度的增加,地应力对爆炸引起的断裂影响不容忽视。为了探讨地应力大小和方向对岩体爆破的影响,文章以花岗岩为研究对象,通过有限元程序LS-DYNA和颗粒流程序(Particle Flow Code,PFC)相结合的爆破模拟方法研究了爆炸冲击波下地应力对岩石裂纹扩展的影响。结果表明:双轴等压应力对岩石近场裂纹的影响较小,而对远场裂纹发育有较大的抑制作用;单轴应力条件下,与应力垂直方向的压缩效应得到增强,而拉伸效应受到抑制,应力垂直方向的裂纹数量远小于平行方向的。

爆炸冲击波作用后变形机翼模态数值模拟

为研究典型机翼在爆炸冲击波作用下的毁伤效应及其损伤后的结构动力学特性,基于有限元方法,研究了爆炸当量、爆炸方位及爆炸距离等对典型机翼损伤程度的影响,并分析了机翼结构变形程度与模态的关系。研究结果表明:冲击波强度和作用位置的变化对机翼结构的损伤及模态频率会产生不同程度的影响;随着冲击波强度的增加,机翼结构越早产生变形,对应的各阶模态频率下降越大,其中,二阶频率最大减少了15.02%;爆炸点位于机翼中心正上方时,机翼的变形最大;与无损伤机翼模态固有频率相比,爆炸冲击波作用在机翼中心位置时,各阶模态频率减小幅度最大,减少幅度为8.29%~15.02%。

海拔高度对化爆冲击波压力分布规律影响分析

海拔高度会引起空气密度及气压的变化,直接影响冲击波压力在空气介质中的传播分布规律。该项研究采用AUTODYN建立了0、1 000、2 000、3 000、4 500 m等5种海拔高度下爆炸冲击波压力传播规律的有限元数值仿真模型,开展了等效TNT当量为10、30、50 kg工况下的数值仿真分析,并对获取的冲击波压力分布规律进行了分析。分析结果表明:海拔高度对冲击波压力具有显著的影响作用,具体表现为在同一等效TNT当量下,随海拔高度的增加,冲击波超压峰值、比冲量都逐渐减小,峰值到达时刻随测点距离增大逐渐提前;并且随等效TNT当量的增加,爆炸冲击波压力峰值和比冲量都逐渐增大,峰值到达时间逐步提前。数值仿真结果与试验结果具有较高的吻合度,该项研究揭示了海拔高度对爆炸冲击波传播分布规律的影响作用,为实际工程测试提供了理论支撑。

天然气净化工厂泄爆冲击波影响计算探讨

随着对清洁能源要求的不断提高,净化工厂也有了很大的挑战。净化工厂设备比较紧密,人员结构比较复杂,一旦发生泄漏、爆炸事故,不仅会对设备造成不可逆的损失,而且可能会危及人员的生命。为了保证天然气净化工厂的安全建设及运行,对净化工厂泄漏爆破冲击波影响进行计算,本文通过PHAST软件对净化工厂区储罐天然气的泄漏、蒸汽云爆炸进行分析。结果表明,天然气储罐一旦发生泄漏、火灾、爆炸,其影响范围跟储藏量、内部压力、裂口尺寸、输气量等都有着直接的关系。研究结果能够为净化工厂泄漏爆炸的安全评估、制定火灾应急预案等提供参考,为天然气净化工厂的建设提供了重要理论依据。

爆炸驱动激波管冲击波压力参数研究

爆炸驱动激波管的作用是通过驱动段内的炸药爆炸产生冲击波,经扩张段的激波整形对目标物体进行平面波加载。为获得爆炸驱动激波管试验段内的冲击波超压环境,得到试验件的加载条件,通过数值模拟和量纲分析的方法,综合考虑装药质量、激波管结构尺寸、目标物体位置等参数的影响,建立冲击波压力峰值与上述参数之间的经验计算模型,并通过多种工况的考核试验对该模型的准确性进行了验证。结果表明:模型得到的计算值与试验值的平均相对偏差为10%,可满足工程应用的要求,且爆炸驱动激波管试验段内冲击波超压峰值主要与装药质量、爆心距、激波管直径及驱动段长度有关,其余参数的影响基本可以忽略。

爆炸冲击波和爆生气体的动态作用演化机制的实验与数值分析

在岩石爆破过程中,爆炸冲击波和爆生气体的波动机理尚不清楚。通过高速纹影系统和超压测试系统并结合AUTODYN数值模拟分析,对爆炸冲击波和爆生气体的波动机理开展研究。设计了不同炸药类型和装药结构下的5种药包,通过纹影照片直观地显示爆生产物的动态作用演化过程。对比分析5种情况下爆炸冲击波和爆生气体在流场中的波动变化,将数值模拟结果与纹影实验结果进行对比并反演了炸药内部爆轰波动过程。结果表明:爆炸冲击波与爆生气体一开始伴随扩展,并以起爆点为中心向外以球形传播。在传播过程中,爆炸冲击波与爆生气体逐渐分离,爆炸冲击波传播速度大于爆生气体的传播速度。在不同的装药结构情况下,爆炸冲击波和爆生气体的分离特征不同,分离的时间随药包外壳约束作用的增强而缩短。在不同的炸药类型情况下,爆炸冲击波和爆生气体的波动形态基本相同,但因炸药材料本身物理力学参数不同,所以爆炸冲击波和爆生气体传播过程中的速度和压力变化会有差异。当存在切口时,爆炸冲击波和爆生气体会优先从切口处向外传播,然后向其他方向进行绕流,切口方向的压力和速度都会变大,切口方向能量集中且管壁优先破坏,达到定向破坏的效果。数值模拟中爆炸冲击波和爆生气体的波动变化形态与纹影实验结果在形态上较为吻合。

爆炸冲击载荷下猪肺部的损伤特性

为了深入研究爆炸冲击波作用下生物体肺部的力学响应和损伤特性,首先建立了猪胸部有限元模型,借助新研制的PVDF(polyvinylidene fluoride)柔性冲击波压力传感器测试了激波管试验中动物的体表压力,验证了有限元模型的准确性。然后,使用已验证的模型开展了不同比例距离下猪肺部损伤特性研究,分析了在不同强度冲击波作用下肺部的损伤程度和损伤区域,并建立了胸肺部表皮压力峰值与肺损伤的关系。最后,通过开展爆炸试验,获得了不同比例距离下猪的肺部损伤情况和胸部表皮压力曲线,验证了所建立的胸肺部表皮压力峰值与肺损伤关系的正确性。