Effect of Blasting Stress Wave on Dynamic Crack Propagation

Stress waves affect the stress field at the crack tip and dominate the dynamic crack propagation.Therefore,evaluating the influence of blasting stress waves on the crack propagation behavior and the mechanical characteristics of crack propagation is of great significance for engineering blasting.In this study,ANSYS/LS-DYNA was used for blasting numerical simulation,in which the propagation characteristics of blasting stress waves and stress field distribution at the crack tip were closely observed.Moreover,ABAQUS was applied for simulating the crack propagation path and calculating dynamic stress intensity factors(DSIFs).The universal function was calculated by the fractalmethod.The results show that:the compressive wave causes the crack to close and the reflected tensile wave drives the crack to initiate and propagate,and failure mode is mainly tensile failure.The crack propagation velocity varies with time,which increases at first and then decreases,and the crack arrest occurs due to the attenuation of stress waves and dissipation of the blasting energy.In addition,crack arrest toughness is smaller than the crack initiation toughness,applied pressure waveforms(such as the peak pressure,duration,waveforms,wavelengths and loading rates)have a great influence on DSIFs.It is conducive to our deep understanding or the study of blasting stress waves dominated fracture,suggesting a broad reference for the further development of rock blasting in engineering practice.

Monitoring and analysis of shock wave in water for underwater drilling blasting

Taking the underwater reef blasting in Gulei sea channel of Xiamen Port as an example,the forming characteristic of shock wave in water for underwater drilling blasting is analyzed.By field monitoring,the pressure of shock wave in water for different distances is attained;the major parameters such as pressure amplitude and positive action time,and the propagation attenuation rule of shock wave in water are analyzed in this paper.The results can be helpful for engineering design and construction and environmental safety assessment.

Progressive fracture processes around tunnel triggered by blast disturbances under biaxial compression with different lateral pressure coefficients

To investigate the progressive fracture processes around a tunnel triggered by static stress and dynamic disturbance,experiments and numerical simulations were performed.The results show that the spatial distributions of acoustic emission(AE)events become very different as lateral pressure coefficients change.The combined effect of static stress and dynamic disturbance causes the damage around the tunnel,and initial stress conditions control the damage morphology.The blast disturbance cannot fundamentally change the damaged area but will deepen the extent of damage and accelerate the failure speed.The more significant the difference between the vertical and horizontal stresses is,the higher the impact on the tunnel by the dynamic disturbance is.The AE activity recovers to a relatively stable state within a short time after the blast and conforms to power-law characteristics.

A novel method for simulating nuclear explosion with chemical explosion to form an approximate plane wave: Field test and numerical simulation

A nuclear explosion in the rock mass medium can produce strong shock waves,seismic shocks,and other destructive effects,which can cause extreme damage to the underground protection infrastructures.With the increase in nuclear explosion power,underground protection engineering enabled by explosion-proof impact theory and technology ushered in a new challenge.This paper proposes to simulate nuclear explosion tests with on-site chemical explosion tests in the form of multi-hole explosions.First,the mechanism of using multi-hole simultaneous blasting to simulate a nuclear explosion to generate approximate plane waves was analyzed.The plane pressure curve at the vault of the underground protective tunnel under the action of the multi-hole simultaneous blasting was then obtained using the impact test in the rock mass at the site.According to the peak pressure at the vault plane,it was divided into three regions:the stress superposition region,the superposition region after surface reflection,and the approximate plane stress wave zone.A numerical simulation approach was developed using PFC and FLAC to study the peak particle velocity in the surrounding rock of the underground protective cave under the action of multi-hole blasting.The time-history curves of pressure and peak pressure partition obtained by the on-site multi-hole simultaneous blasting test and numerical simulation were compared and analyzed,to verify the correctness and rationality of the formation of an approximate plane wave in the simulated nuclear explosion.This comparison and analysis also provided a theoretical foundation and some research ideas for the ensuing study on the impact of a nuclear explosion.

The test research on partial relieving pressure for the entry in the deep mine under high stress and friable surrounding rock

Based on the geological condition of Zhangxiaolou deep mine in Xuzhou mining area, under 986 m in depth, 20.6-31.6 MPa in maximum horizontal principal stress, and friable and fractured surrounding rock, test researches on partial relieving pressure were completed for the entry with U-steel arched yielding support. The relieving pressure parameters, technology process and results of springing blasting by boreholes and excavating pockets in the two sides of entry were introduced. It is demonstrated that springing will not be shaped under the condition of single borehole arrangement after exploded, the arrangement by a group, it will make borehole bottom form springing in 0.6-0.8 m in diameter, that convergence of two sides and roof to floor have some increments by using springing blasting for reliving pressure. This kind of method for reliving pressure is not suitable to use in the deep mine, and that the convergence of two sides obviously declined by excavating pocket in two sides, it can be still used in the entry with metal support, while maintenance of entry in deep mines is difficult, and can not be supported by bolt or bolt with wire mesh.

Blast Pressure Mitigation by Surface Explosion Using Water in a Walled Container

Mitigation of blast pressure using water in a walled container was evaluated. A PETN （pentaerythritol tetranitrate） pellet of 1.4 g near the model wall was detonated on a steel plate. A water-filled container was placed between the explosive and the wall. The pressure histories at six points, which corresponded to Hopkinson scaled distance of from 3.6 m·kg^-1/3 to 21.7 m·kg^-1/3 were evaluated along with dependence of mitigation effects on the amount of water and the position of the container. The presence of the water and the wall mitigated the peak overpressure near the explosion points and the positive impulse along all points. The mitigation effect was equivalent to 20-30% reduction of explosive weight based on discussion of the equivalent ratio. The presence of the water along the wall （not very close to the explosive） also mitigated the blast pressure.

High Strain-Rate and Shock Response of Carbon SupercompositeTM

This study focuses on assessing the dynamic behaviors of carbon SupercompositeTM laminates when subjected to high strain-rates and air blast loads, using a shock tube for testing. The investigation aims to understand the response of these advanced materials under extreme conditions, which is crucial for applications in aerospace, military, and other high-performance industries. SupercompositeTM (CZE) prepreg, made up of a 3K plain weave carbon fabric with milled carbon fibers as interlaminar reinforcements impregnated with epoxy, is used to create SupercompositeTM (CZE) laminates. A woven carbon composite (CBE) laminate was also created using 3K plain weave Carbon/Epoxy (CBE) prepreg. Both types of laminates were designed and fabricated using the autoclave process. The dynamic behaviors of CZE and CBE laminate under transverse compression loads were evaluated using a modified Split Hopkinson Pressure Bar (SHPB). The study found that the 3D reinforcement with milled carbon fibers significantly affected the dynamic behavior of the CZE laminate. Stereo imaging videos, captured using two SHIMADZU high-speed video cameras in shock tube experiments, recorded the time history of back surface deflection. The plate specimens exhibited low deflections without any visible damage. The experimentally observed center point deflections of the CZE plates decayed sooner than those of the CBE laminates, indicating an improvement in damping due to the presence of 3D reinforced milled carbon fibers. This research shows that optimized utilization of milled carbon fibers as 3D reinforcement can withstand high stress in the thickness direction and higher energy absorption when subjected to impact and high strain-rate loading.

Pressure-impulse diagram with multiple failure modes of one-way reinforced concrete slab under blast loading using SDOF method

Two loosely coupled single degree of freedom (SDOF) systems were used to model the flexural and direct shear responses of one-way reinforced concrete slabs subjected to explosive loading. Blast test results show that the SDOF systems are accurate in predicting the failure mode of the slab under blast loads by incorporating the effects of the strain rate effect caused by rapid load application. Based on different damage criteria, pressure-impulse (P-I) diagrams of the two failure modes were analyzed with the SDOF systems. The effects of span length, concrete strength, and reinforcement ratio of the slab on the P-I diagram were also investigated. Results indicate that a slab tends to fail in direct shear mode when it is of a smaller span length and tends to fail in flexure mode when it is of a larger span length. With the increase of the concrete strength or reinforced ratio, both the flexure and shear capacity increase. Based on numerical results, a simplified method and a semi analytical equation for deriving the P-I diagram are proposed for different failure modes and damage levels.

Experimental study on expansion and cracking properties of static cracking agents in different assembly states

Rolled static cracking agent(RSCA)can solve the intractable problem of traditional bulk static cracking agent(BSCA)in engineering applications.This paper innovatively studies the rational water-cement ratio of BSCA and the immersion soaking time of RSCA under the condition of controlling temperature.Through the expansion and cracking performance experiments,the development characteristics of expansion pressure,the cracking effect of the single-hole specimen and the performance of hole spraying prevention under the action of BSCA and RSCA were compared and analyzed.The results show that:(1)The volume growth rate of static cracking agent decreases with the increase of water-cement ratio,and the fluidity increases with the increase of water-cement ratio.The rational water-cement ratio for BSCA application is 0.3,and the rational immersion time of RSCA is 2-2.5 min;(2)Under the bore diameters of 30,35,40 and 45 mm,the expansion pressure of BSCA with a water-cement ratio of 0.3 is 38.2,52.3,61.5 and 68 MPa,and the expansion pressure of RSCA immersed in water for 2.5 min is 43.5,58.8,69.5 and 75.1 MPa,respectively.Among them,the development speed of expansion pressure of BSCA is higher than that of RSCA,and the arrival time of the peak expansion pressure of RSCA is 1.7 times that of BSCA;(3)The crack initiation speed of single-hole specimen under the action of RSCA is 10.3%lower than that under the action of BSCA,but the cracking speed of the former is 72.6%higher than that of the latter;(4)The hole spraying occurs in BSCA under the bore diameter of 50,55 and 60 mm,while the hole spraying occurs in RSCA under the bore diameter of 60 mm.In terms of bore diameter,the hole spraying prevention of the RSCA is better than that of BSCA.The research results enrich the static blasting technology and provide data support and theoretical reference for field application.

Blast Pressure Measurements of an Underwater Detonation in the Sea

Blast pressure measurements of a controlled underwater explosion in the sea were carried out.An explosive of 25-kg trinitro-toluene(TNT)equivalent was detonated,and the blast pressures were recorded by eight diferent high-performance pressure sensors that work at the nonresonant high-voltage output in adverse underwater conditions.Recorded peak pressure values are used to establish a relationship in the well-known form of empirical underwater explosion(UNDEX)loading formula.Constants of the formula are redetermined by employing the least-squares method in two diferent forms for best ftting to the measured data.The newly determined constants are found to be only slightly diferent from the generally accepted ones.

Effects of ambient pressure on the severity of blast injury in rats

The effects of different ambient pressures of 53.99,61.33 and 96.60 kPa on theseverity of blast injury were observed in rats.It was found that when the incident shock wavewas 190.40 kPa in its peak pressure and 10 ms in its duration, both the mortality and the severityof lung injury were progressively increased along with the decrease of the ambient pressure.Themortality rate of the rats in the 6th hour after exposure was 0%,25% and 36.8% and the hem-orrhagic area on the lungs was 63.75+69.01,313.50+357.25 and 653.21+652.25 squaremilimeters when the ambient pressure was 96.60,61.33 and 53.99 kPa respectively.In addi-tion, the lung/body index was 0.93+0.21%,1.31+0.65% and 1.50+0.77% respectively.Itis believed that the decrease of the ambient pressure might decrease the tolerance of the rat to theimpact of blast waves to result in higher mortality and more extensive hemorrhage on the lungs.

A Method for Calculating Blast Pressure of Failed Lithium-Ion Cells with C-H-O Solvents

Blast pressure of C-H-O solvents on failed lithium-ion cells at the voltage range between 3.8 V and 4.18 V may be calculated by means of the simple semi-empirical equation, y = （Ia ＋ Jb）/（Ka ＋ Lb ＋ Me）, p is the initial density of solvent, Q is the chemical energy of explosion, v is the voltage. The values of a, b, c depend on C-H-O composition. Value of I, J, K, L, Mmay be estimated from the H20-CO2 arbitrary decomposition assumption. Blast pressure derived in this manner can provide preliminary protective estimation and it is compared with experiment results by adiabatic calorimeter.

3种现场混装炸药耦合装药炮孔壁峰值压力计算

炮孔壁峰值压力是产生炮孔周围应力场的源头,是造成孔壁附近岩石破坏的强动载荷。对于耦合装药,炮孔壁峰值压力是由爆轰波碰撞孔壁而生产的,通常这种碰撞是斜碰撞,并不是正碰撞。基于这样的物理事实,通过对现有耦合装药孔壁压力计算方法行了评述,并提出斜碰撞的炮孔壁峰值压力计算方法。结果表明,爆轰冲击理论计算结果接近实测值和数值模拟值;引入斜入射系数可计算爆轰波斜入射时孔壁压力,爆轰波碰撞在炸药与孔壁的分界面上,在不同的入射角度下,作用在孔壁的压力是不同的。孔壁压力与炸药特性、岩体特性、爆轰波曲率半径、爆轰波入射角等有关。

爆炸荷载下聚脲涂覆含局部缺陷油气管道的失效判定研究

通过埋地静爆试验,对经聚脲弹性体材料加固的含局部缺陷埋地油气管道抗爆性能及损伤评价进行研究,同时结合所得试验数据进行数值模拟,建立了浅埋爆炸荷载下聚脲弹性体材料加固含局部缺陷埋地油气管道损伤失效评估准则。结果表明:在折合距离为0.23 m/kg 1/3试验条件的浅埋爆炸荷载作用下,含局部缺陷普通管道与含局部缺陷聚脲管道迎爆面均发生了明显凹陷变形,含缺陷聚脲管道凹陷变形量较前者降低28.87%,且管道迎爆面及端部连接处易于遭受损伤;含局部缺陷普通管道迎爆面超压高于含局部缺陷聚脲管道且变形响应时间早于后者,表明聚脲材料可以有效降低爆炸冲击波压力峰值和推迟爆炸冲击波的作用时间。在进行爆炸荷载作用下管道的损伤失效判定时引入衡量管道横截面变形的截面临界椭圆度指标,最终建立了基于管道截面临界椭圆度的聚脲涂覆含局部缺陷埋地油气管道的超压-冲量损伤准则及判定公式。

高海拔环境下运动装药的爆炸冲击波特性

为了研究高海拔环境下运动装药的爆炸冲击波传播特性,利用AUTODYN有限元软件,研究了不同海拔高度及其解耦对应的低温条件和低压条件对运动装药爆炸冲击波超压场的影响规律;建立了预测低温环境和低压环境下运动装药爆炸冲击波超压的理论计算模型,并通过试验数据和数值模拟进行了对比验证。结果表明,该计算模型可以有效预测不同低温、低压以及低温和低压耦合的高海拔环境下运动装药的爆炸冲击波超压;海拔高度从0升至10000 m,冲击波超压峰值平均减小35.6%,冲击波作用范围增加62.0%;随着环境温度降低,冲击波超压峰值平均增加0.43%,冲击波作用范围减小11.9%;随着环境压力降低,冲击波超压峰值平均减小36.4%,冲击波作用范围增加83.5%;不同海拔高度下装药运动速度引起的冲击波超压增大系数变化规律与解耦对应的低压条件影响规律基本相似;高海拔环境对运动装药爆炸冲击波的作用范围及超压的影响主要取决于低压条件,低温条件的影响程度较小。

爆破振动作用下桥梁桩孔稳定性振动台试验研究

为了解爆破振动对邻近桥梁桩基成孔后桩孔稳定性的影响,以与山体爆破工程计划同时施工的某主跨280 m的斜拉桥为背景,设计、制作土箱和缩尺比1∶40桩孔模型开展振动台试验,研究桩孔孔壁的破坏特征、土体振动速度和动土压力的变化规律。结果表明:土体的振动速度峰值和动土压力峰值均随着爆破强度的增大而增大,在土体产生破坏后,土体的振动速度峰值和动土压力峰值均呈现出非线性增大趋势;爆破强度较小时土体的动土压力峰值曲线为U形,爆破强度较大时桩孔区域土体的动土压力峰值曲线为W形,桩孔中上部区域的动土压力峰值较大;山体爆破振动会使钢护筒底部与土体交界面以下桩孔的中上部区域出现破坏,应对山体爆破施工加强现场监测,桩孔附近的振动速度峰值不宜超过2 cm/s,以保障桩孔的稳定性。

高炉放散煤气治理技术

总结了高炉均压放散煤气和休风放散煤气治理技术的研究进展和应用情况。高炉均压放散煤气干法回收技术自2014年起逐步在京津冀地区率先获得推广应用至今,经过多次迭代更新,最终形成了“三级除尘+高效引射+智能控制”的引射法均压煤气干法全回收技术,该技术成熟可靠,已在国内多数高炉上获得成功应用。对于高炉休风放散煤气治理技术的研究仍处于发展阶段,当前的主流技术路线是利用现有煤气净化设施,通过在调压阀组区域并联引射器,对高炉休风末期、炉顶放散阀开启前的炉内低压煤气强制回收进入管网,可实现休风煤气全量回收,达到应收尽收,在休风结束时,高炉炉顶放散阀开启前,炉顶压力可降至0~1 kPa。但该技术仅适用于长期休风和短期休风,不适用于降料线休风和事故紧急休风。鉴于高炉休风过程的煤气回收操作是一项危险性作业,对休风放散煤气的治理还需在确保安全的前提下谨慎选择。选择技术方案时,需要综合考虑节能环保、投资、运行维护成本对高炉生产的影响以及系统是否能安全可靠运行等多方面的因素,采用性价比高的技术实现钢铁企业的长期绿色发展。

构造煤层顶板爆破跨界面致裂增透机制研究及应用

深部煤炭开采地质条件恶化,原生煤在多期构造运动作用下形成松软低渗高瓦斯构造煤层,煤层钻孔施工困难,爆破增透产生的裂隙不发育且易于重新压实。针对目前构造煤层顶板爆破致裂增透关键技术没有得到根本突破问题,构建试验模型进行煤层顶板爆破相似模拟试验和数值分析,监测跨界面应力波传播和宏观三维裂隙演化形态,再现了爆破应力波传播和煤岩体内部损伤破坏过程。研究表明:(1)构造煤层爆破损伤范围主要集中在爆破孔和煤层上下煤岩交界面附近煤体;构造煤顶板爆破产生跨界面致裂卸压裂纹,爆破损伤沿爆破孔向四周岩体扩展,最后蔓延到煤层底板,爆破孔位置和上部煤岩交界面以及煤层内部的损伤较为严重。(2)爆破应力波从构造煤层顶板传播到煤岩交界面时发生波的透射和反射,透射的压缩应力波破坏煤体;反射的拉伸应力波反作用于煤岩交界面区域岩体。(3)爆破累积损伤产生的跨界面交叉裂纹卸压,使顶板岩层裂隙和构造煤层裂隙贯通,有利于构造煤层的瓦斯垂向运移流动和卸压瓦斯抽采。现场应用表明,煤层顶板爆破瓦斯抽采纯量及其浓度快速上升,瓦斯抽采纯量从爆破前的0.07 m^(3)/min提高到1.73 m^(3)/min,体积分数从10.46%上升到68.50%,并且长时间维持在较高水平。研究成果可为深部构造煤层瓦斯高效抽采提供理论基础和技术支持。

松软煤层底板爆破致裂增透模拟试验研究及应用

针对松软煤层爆破增透钻孔施工困难,爆破增透产生的裂隙不发育且易于重新压实的问题,提出在底板岩层开展爆破作业,达到松软煤层增透进而增加瓦斯有效抽采时间的目的。为了监测跨界面应力波传播规律及煤层损伤状况,在实验室构建了物理模型并开展了煤层底板爆破相似模拟试验。同时使用数值模拟的研究方法对煤层底板爆破过程中煤、岩体内部的损伤及裂隙的演化过程进行补充。结果表明:松软煤层底板爆破裂纹沿爆破孔向四周岩体扩展,爆破孔位置和底板煤岩交界面以及煤层内部的破坏较为严重,产生跨界面损伤裂纹。爆炸应力波从松软煤层底板岩层传播到松软煤层时,岩体和松软煤体的交界面产生透射压缩应力波和反射拉伸应力波,透射波作用于松软煤体,使煤层裂隙增加;反射波反作用于岩体,在煤岩交界面形成交叉裂纹,使底板岩层裂隙和松软煤层裂隙贯通,有利于松软煤层的瓦斯垂向运移流动和卸压瓦斯抽采。潘一东煤矿现场应用表明,煤层底板爆破增透后瓦斯抽采纯量及其浓度快速上升,抽采纯量从0.06 m^(3)/min提高到1.46 m^(3)/min,增加了23.33倍;瓦斯浓度从爆破前的10.46%上升到45.50%左右,增加了3.34倍,并且长时间维持在较高水平。研究成果可为深部松软煤层瓦斯高效抽采提供理论基础和技术支持。

炮孔壁初始冲击压力直接测量试验研究

基于电测法构建出一套测试系统对孔壁压力进行直接测量,以获得现场岩石炮孔中的孔壁压力实测数据,根据灵敏度、抗冲击和抗干扰能力等参数,选择PVDF压电传感器作为压力测试系统的敏感元件;根据爆炸荷载的加载特性,选择并联25Ω碳膜电阻的电流模式作为系统的测试电路;最后根据带宽、采样率等参数选择示波器进行数据采集。将测试系统应用于高速公路边坡爆破开挖中,试验得到炮孔壁轴向距炸药0、0.1、0.2、0.3 m 4个位置的压力时程曲线,结果表明:在90/32的装药条件下,轴向距炸药0~0.3 m范围内,孔壁峰值压力范围为1 446~156 MPa;各测点的压力上升时间为6.1~1.5μs,距离炸药越近、压力上升时间越长;对试验值进行拟合,发现在轴向距炸药0~0.3 m范围内孔壁压力峰值呈幂函数递减。试验验证了孔壁压力直接测试系统的可靠性。