Observational results of electromagnetic radiation caused by explosion of small dimension rocks in field experiments

In order to probe the mechanism of the phenomena of seismic electromagnetic radiation (EMR), we have completed field experiment on EMR caused by explosiom of rocks. In the experiments, the data of medium low freguency (<5000 Hz) EMR caused by 26 explosion tests of small dimension rocks have been obtained. This paper shows some representative observational results of the field experiment. The observational results show that, nearly 20 points of the 26 explosive points, the EMR phenomena are recorded at various degrees in the related explosive processes. The EMR intensities decay with the distance from explosive origins and increase with the explosive energy. The EMR records have certain repeatability (under the same condition), complexity( multiple EMR effects caused by one explosion) and regional characteristics such as rock structure and observational direction etc.

Simulations of explosion-induced damage to underground rock chambers

A numerical approach is presented to study the explosion-induced pressure load on an underground rock chamber wall and its resultant damage to the rock chamber.Numerical simulations are carried out by using a modified version of the commercial software AUTODYN.Three different criteria,i.e.a peak particle velocity (PPV) criterion,an effective strain (ES) criterion,and a damage criterion,are employed to examine the explosion-induced damaged zones of the underground rock chamber.The results show that the charge chamber geometry,coupling condition and charge configuration affect significantly the dynamic pressure exerted on the rock chamber wall.Thus the chamber is damaged.An inaccurate approximation of pressure boundary ignoring the influences of these factors would result in an erroneous prediction of damaged area and damage intensity of the charge chamber.The PPV criterion yields the largest damaged zone while the ES criterion gives the smallest one.The presented numerical simulation method is superior in consideration of the chamber geometry,loading density,coupling condition and rock quality.The predicted damage intensity of rock mass can be categorized quantitatively by an isotropic damage scalar.Safe separation distance of adjacent chambers for a specific charge weight is also estimated.

AFFECTING PROCESS OF EXPLOSION IN ROCK MASS BY CYLINDRICAL CHARGE

The explosion effects and physical process in rock mass by cylindrical charges are discussed.The maximum explosion cavity radius and the coefficient of effective explosion work are found through mechanical model and numerical method.The dependance of explosion parameters on time is got.The results show that the maximum explosion cavity radius produced by cylindrical charge of ammonium trinitro-toluene No.2 explosive in limestone and diabase is 1.50 and 1.26 times respectively as much as that of blasthole;and the coefficient of effective explosion work is 0.71 and 0.54 respectively as much as that of the blasthole.

A model to determine hole spacing in the rock fracture process by non-explosive expansion material

The application of the non-explosive expansion material （NEEM） is widely used as the controlled fracture method in quarry min- ing, especially in hard rocks. The pressure of NEEM is an important parameter in causing rock fracture. An empirical model based on hole spacing was developed to determine the pressure of NEEM in the rock fracture process. Primarily, the empirical model was developed by the mathematical method, utilizing dimensional analysis. Then, the Phase2 code, which is based on the finite element method, was utilized to predict crack growth in rocks. The results of numerical analysis show slight deviations from the empirical model. Hence, the polynomial re- gression analysis was used to modify the model. Finally, the modified model shows a good agreement with the results gained from numerical modeling.

A laboratory method to simulate seismic waves induced by underground explosions

The seismic waves induced by underground explosions generate geological hazards affecting deep buried tunnels such as rockbursts and engineering-induced earthquakes. This issue is difficult to study through full-scale testing due to the expense and unpredictable danger. To solve this problem, the authors developed experimental apparatus and presented a laboratory method to simulate seismic waves induced by underground explosions. In this apparatus, a combined structure of a diffusive-shaped water capsule and a special-shaped oil capsule was designed. This structure can provide an applied confining stress and freely transmit the stress wave generated by external impact. Therefore, the coupled loading of in situ stress and seismic waves induced by underground explosions in the deep rock mass was simulated. The positive pressure time and peak value of the stress wave could be adjusted by changing the pulse-shaper and the initial impact energy. The obtained stress waves in the experiments correspond to that generated by 0.15-120 kt of TNT equivalent explosion at a scaled distance of 89.9-207.44 m/kt.

Impedance Matching Algorithm for Selection of Suitable Explosives for Any Rock Mass-A Case Study

Proper selection of the explosive is an important part of blast design.The judicious selection of explosives is governed by economic considerations and site/field conditions.The mine management desires to select an explosive that will give the lowest cost per unit of rock broken,while assuring that fragmentation,fragment size distribution,muck pile profile,muck pile diggability,displacement of the rock,onset of movement,face movement,burden relief rate,ground vibration and noise remains within control limits.Factors which influence the selection of an explosive include explosive cost,charge diameter,cost of drilling,fragmentation difficulties and fragment size requirement with loose muck pile condition,water conditions,atmospheric temperature,propagating ground,storage considerations,sensitivity considerations,explosive atmospheres and nearness of communities from mine.All these concerns can be handled effectively by using the impedance matching technology where explosive impedance is matched with rock impedance for optimal blast performance with due concern to productivity,economics and environment.This paper discusses a case study in limestone mines where rock impedance was determined by carrying out surface refraction test and a patented algorithm was used to estimate the explosives’properties i.e.VOD(velocity of detonation)and density of explosives required.

Dynamic responses of deep underground explosions based on improved Grigorian model

It is important to investigate the dynamic behaviors of deep rocks near explosion cavity to reveal the mechanisms of deformations and fractures. Some improvements are carried out for Grigorian model with focuses on the dilation effects and the relaxation effects of deep rocks, and the high pressure equations of states with Mie-Grüneisen form are also established. Numerical calculations of free field parameters for deep underground explosions are carried out based on the user subroutines which are compiled by means of the secondary development functions of LS-DYNA9703 D software. The histories of radial stress, radial velocity and radial displacement of rock particles are obtained, and the calculation results are compared with those of U.S. Hardhat nuclear test. It is indicated that the dynamic responses of free field for deep underground explosions are well simulated based on improved Grigorian model, and the calculation results are in good agreement with the data of U.S. Hardhat nuclear test. The peak values of particle velocities are consistent with those of test, but the waveform widths and the rising times are obviously greater than those without dilation effects. The attenuation rates of particle velocities are greater than the calculation results with classic plastic model, and they are consistent with the results of Hardhat nuclear test. The attenuation behaviors and the rising times of stress waves are well shown by introducing dilation effects and relaxation effects into the calculation model. Therefore, the defects of Grigorian model are avoided. It is also indicated that the initial stress has obvious influences on the waveforms of radial stress and the radial displacements of rock particles.

EFFECT OF ORIGINAL EXPLOSION STRESS WAVE ON PROPAGTION OF EXPL

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A new theory of rock-explosive matching based on the reasonable control of crushed zone

Rational rock-explosive matching is of great importance to enhancing explosive energy effective utilization and improving rock fragmentation effect.The traditionally emphasized method of acoustic impedance matching is not rational.Based on blasting breakage mechanism,a new theory of rock-explosive matching in drilling and blasting is proposed.The new approach chooses explosive parameters by reasonable control of the size of crushed zone under the condition of fully fragmentation between adjacent blast holes.This method can directly reflect the blasting fragmentation effect and energy effective utilization,which is easy to implement.Also,a modified model is developed,taken adjacent blast hole blasting loading into account.As a result,explosive parameters of different grades of rock are given in full coupling on-site mixed explosive charge for different project objectives.

冻结砂岩爆破破岩的能量耗散特性

为探究冻结岩体的冲击力学性能,并提出寒区爆破开挖工程中合理的爆破炸药单耗,针对寒区典型分布的砂岩,采用室内分离式霍普金森压杆试验与理论分析相结合的方法,开展了冻结砂岩冲击力学性能及爆破破岩能量耗散特性研究。结果表明:(1)冻结状态砂岩的动态抗压强度和动态弹性模量相比常温状态整体有所提升,而应变峰值整体有所下降。对比静载与动载试验结果,相同物理参数下,砂岩的抗压强度差距不大,而动态弹性模量明显高于静态弹性模量。(2)常温状态砂岩和冻结状态砂岩试件的耗散能量均随含水率的增大而逐渐减低,且冻结状态砂岩的耗散能量高于常温状态。相比常温状态,冻结砂岩在含水率为0、0.25ω、0.50ω、0.75ω、1.00ω时,其耗散能量增幅分别为21.6%、64.9%、80.3%、78.2%、83.3%。(3)相同含水率下,冻结状态砂岩的炸药单耗均高于常温状态,在含水率为0、0.25ω、0.50ω、0.75ω、1.00ω时,冻结状态砂岩爆破炸药单耗相比常温状态分别增加20.4%、61.3%、60.0%、55.6%、66.7%。(4)将常温与冻结状态砂岩爆破炸药单耗数值进行拟合,得到不同状态砂岩爆破破岩的单耗修正模型,可为寒区爆破工程提供参考。

不耦合装药下岩石爆破块体尺寸的分布特征

通过不同装药结构下立方体红砂岩小型爆破实验,分析了岩石的损伤程度和破坏模式,同时引入三参数极值分布函数量化岩石爆破块体尺寸分布特征。此外,根据岩样R1的爆破实验结果进行了有限元数值模型验证,基于验证的模型展开了岩石单孔爆破损伤破裂行为的模拟,讨论了径向、轴向不耦合系数和耦合介质对岩石破碎效果的影响。结果表明,三参数极值分布函数可以较好地表征岩石爆破后破碎块体尺寸分布特征,块体平均尺寸随着不耦合系数的减小呈线性降低趋势,且破碎块度趋于均匀。通过比较不同耦合介质装药时岩石内部的能量分布特征和破坏体积发现,水作为耦合介质时,爆炸能量的传递效率最高,其次分别是湿砂和干砂,空气的能量传递效率最低。结合等效波阻法计算的理论应力透射系数可以很好地反映不耦合装药时岩石的破碎程度。

考虑岩体破坏分区的岩石爆破爆炸荷载历程研究

针对岩石爆破爆炸荷载历程中未联合考虑岩石爆破动态过程和炮孔周围岩体破坏分区的不足,开展了考虑岩体破坏分区的岩石爆破爆炸荷载历程及其适用性研究。联合岩石爆破动态过程和岩体破坏分区的理论解,推导了考虑岩体破坏分区的岩石爆破爆炸荷载理论公式,比较了考虑岩体破坏分区的岩石爆破爆炸荷载历程与实测炮孔爆炸压力曲线,开展了单孔爆破现场试验和相应条件下3种爆炸荷载工况的数值模拟,并对爆破振动现场实测和数值模拟结果进行了对比。研究结果表明:考虑岩体破坏分区的爆炸荷载历程包括上升段和衰减段Ⅰ、Ⅱ、Ⅲ,上升段持续时间极短,衰减段持续时间较长且主要由填塞情况控制;考虑岩体破坏分区的爆炸荷载历程理论计算结果与实测炮孔爆炸压力曲线的变化趋势一致,验证了考虑岩体破坏分区的岩石爆破爆炸荷载理论公式的可靠性;考虑岩体破坏分区的爆炸荷载工况下,单孔爆破振动波形的数值模拟结果与现场实测结果的主要特征一致,该荷载工况下质点峰值振速计算结果与现场实测值偏差率最小,绝大部分在7%以内,表明了其应用于数值模拟的优越性;考虑岩体破坏分区的爆炸荷载可随岩石爆破系统条件的变化而动态调整,其可靠性好、适应性强、应用效果佳。

基于XGBoost模型岩体可爆性研究

岩体可爆性是衡量岩体爆破难易程度的一个重要指标,准确对岩体可爆性评价能够为合理爆破设计提供依据。选取岩石密度、单轴抗压强度、岩石抗拉强度、岩石脆性指数、动载强度和完整性系数等作为岩体可爆性数据集的指标,采用Z-Score方法标准化岩体可爆性数据集,消除量纲对模型预测影响,分别采用朴素贝叶斯、支持向量机和XGBoost模型进行岩体可爆性分级,结果表明:采用XGBoost模型能够准确评价岩体的可爆性,为岩体可爆性评价提供一种新的方法。

金属丝电爆炸的电流波形特征及其破岩效果研究

为研究不同电压下金属丝电爆炸的电流波形特征及破岩效果,基于高压脉冲放电系统开展了金属直丝在空气和红砂岩介质中的电爆炸试验研究。通过比较不同电压下金属丝在空气和岩石中电流波形异同,得到了金属丝在空气和岩石中电流峰值随电压变化的规律,结合金属丝电爆炸破碎红砂岩试验结果,进一步分析了红砂岩在不同高压脉冲载荷作用下的裂纹扩展模式与碎块分布特征。试验结果表明,空气和岩石中的金属丝电爆炸电流峰值与放电电压均呈线性增加关系,在岩石介质约束作用下,岩石中金属丝电爆炸电流峰值和震荡时间均低于空气介质;金属丝电爆炸产生的冲击波使岩石孔壁质点沿径向运动从而产生切向拉应力,形成了以金属丝为中心、径向裂纹为主导的裂纹扩展模式;放电电压对岩石的破碎效果具有显著影响,放电电压由40 kV增加至80 kV,主裂纹数量由一条增加至多条,岩石的破碎程度明显增加且碎块块度分布更加集中。试验成果为高压脉冲放电技术破碎岩石等固体材料的应用与研究提供参考。

抽水蓄能电站主机房底板精确控界切割技术研究

抽水蓄能电站主机房底板爆破开挖时,对其平整度及保留岩体完好度要求很高,传统爆破方法会带来底板开挖边界控制精度差、装药量大、保留岩石损伤严重及环境危害大等问题。为克服上述缺点,提出沿主机房底板水平钻凿炮孔并侧向预切槽,沿切槽多点双向设置聚能装药进行岩石控界爆破的方法。首先采用数值模拟正交分析方法对工业炸药装填的聚能装药参数进行了优化,然后根据优化结果制作了聚能切割装置并在实地进行了试验。试验结果表明,当炮孔中双向聚能射流控界切割装置的平均线装药密度为150 g/m、孔距0.5 m时,爆破后就可以在炮孔间岩体产生精确的贯穿性裂纹。相较于传统爆破方法,该控界切割爆破方法在保证切割面精确的同时,大幅度地减少了装药量,降低了保留岩体的损伤程度和对周围环境的影响。

Rock fragmentation control in opencast blasting

The blasting operation plays a pivotal role in the overall economics of opencast mines.The blasting subsystem affects all the other associated sub-systems,i.e.loading,transport,crushing and milling operations.Fragmentation control through effective blast design and its effect on productivity are the challenging tasks for practicing blasting engineer due to inadequate knowledge of actual explosive energy released in the borehole,varying initiation practice in blast design and its effect on explosive energy release characteristic.This paper describes the result of a systematic study on the impact of blast design parameters on rock fragmentation at three mines in India.The mines use draglines and shoveledumper combination for removal of overburden.Despite its pivotal role in controlling the overall economics of a mining operation,the expected blasting performance is often judged almost exclusively on the basis of poorly defined parameters such as powder factor and is often qualitative which results in very subjective assessment of blasting performance.Such an approach is very poor substitutes for accurate assessment of explosive and blasting performance.Ninety one blasts were conducted with varying blast designs and charging patterns,and their impacts on the rock fragmentation were documented.A high-speed camera was deployed to record the detonation sequences of the blasts.The efficiency of the loading machines was also correlated with the mean fragment size obtained from the fragmentation analyses.

岩石钻孔爆破能量调控理论与应用技术研究进展

岩石钻孔爆破过程涉及复杂的温度—流体—应力—化学(T—H—M—C)耦合过程的相互作用,其实质是炸药能量释放、传输与转化过程,研究爆破能量调控理论与技术对于提高炸药能量利用率、降低有害效应具有重要意义。聚焦炸药非理想爆轰模型、炸药与岩石的相互作用机制、爆破能量传输模型、爆破能量分配规律等方面,系统梳理了岩石钻孔爆破中炸药能量释放、传输与转化机理方面的研究进展。研究表明:炸药爆破破岩的能量利用率依赖于整个爆轰波的压力分布,炸药非理想爆轰时有相当一部分能量在波后稀疏波内释放;传统的波阻抗匹配理论对爆破破岩过程的描述过于简化,并不能合理地描述炸药和岩石之间的能量传输过程;可以从炸药能量的释放过程和传输转化两个环节实现对爆破能量的调控,主要有基于性能可调炸药的爆破能量调控技术、基于电子雷管精确延时的爆破能量调控技术、基于起爆位置和起爆方式的爆破能量调控技术、基于装药结构优化的爆破能量调控技术等。在上述分析的基础上,总结了岩石钻孔爆破能量调控理论与应用技术的发展现状及存在的主要问题,并探讨了该技术的研究发展趋势。

最优化岩石爆破的理论及方法探索

阐述了最优化岩石爆破的理论和方法。提出了爆区岩石最佳破碎原理、最优炸药单耗原理、能量平衡分配原理、可碎能带分布原理、单孔爆破最佳破碎原理和面能比中值化原理。依据这些原理提出了爆破设计和爆破块度预测的方法,从而实现岩石爆破最优化的目标。

水下钻孔CO_(2)气爆和乳化炸药爆破对比分析

水下爆破作业中飞石、毒气、振动等爆破共生物严重影响水下环境安全,为完成水下炸礁爆破施工任务和不破坏水下生态环境的要求。通过长期的施工经验的思考和总结,提出了水下钻孔CO_(2)气爆代替乳化炸药爆破的施工技术方案。文章通过对比水下破岩CO_(2)气爆与乳化炸药爆破,分析在相同作用效果下,CO_(2)使用量,水击波和地震波数据,以及对鱼类的影响。总结了CO_(2)在水下膨胀破岩作业中的工艺、技术及施工方法,计算出钻孔爆破孔距、排距等相关参数。