Adjustment mechanism of blasting dynamic-static action in the water decoupling charge

Water decoupling charge blasting excels in rock breaking,relying on its uniform pressure transmission and low energy dissipation.The water decoupling coefficients can adjust the contributions of the stress wave and quasi-static pressure.However,the quantitative relationship between the two contributions is unclear,and it is difficult to provide reasonable theoretical support for the design of water decoupling blasting.In this study,a theoretical model of blasting fracturing partitioning is established.The mechanical mechanism and determination method of the optimal decoupling coefficient are obtained.The reliability is verified through model experiments and a field test.The results show that with the increasing of decoupling coefficient,the rock breaking ability of blasting dynamic action decreases,while quasi-static action increases and then decreases.The ability of quasi-static action to wedge into cracks changes due to the spatial adjustment of the blast hole and crushed zone.The quasi-static action plays a leading role in the fracturing range,determining an optimal decoupling coefficient.The optimal water decoupling coefficient is not a fixed value,which can be obtained by the proposed theoretical model.Compared with the theoretical results,the maximum error in the model experiment results is 8.03%,and the error in the field test result is 3.04%.

Implications of fine water mist environment on the post-detonation processes of a PE4 explosive charge in a semi-confined blast chamber

The effects of a fine water mist environment in a semi-confined blast chamber on the chemical and thermodynamic processes following detonation of a 20 g PE4 explosive charge have been investigated.The effects were quantified by the analysis of pressure profiles recorded where several parameters including arrival time of the shock at the sensors, peak overpressures, specific impulse of the positive phase, period of the negative phase and the specific impulse of the multiple reflections were quantified.The effect of the fine water mist on the arrival time, peak pressures and the specific impulse of the positive phase agrees with previous findings in literature. In this paper, the focus is on the implications of the fine water mist on the negative phase and the impulse of multiple pressure reflections. The period of the negative phase was found to have increased by 40% and with higher negative peak pressure in the mist condition compared to the atmospheric condition. The activities of the multiple pressure reflections were found to have decreased considerably, both in number and in amplitude leading to lower impulses(by about 60%) for the water mist conditions.

Roof pre-blasting to prevent support crushing and water inrush accidents

Support crushing and water inrush when mining under an unconsolidated confined aquifer in the Qidong Coal Mine was prevented by roof pre-blasting. The mechanism and applicable conditions for this method have been studied. The results show that when an overburden structure that may cause support crushing and a water inrush accident exists the weakening of the primary key stratum, which thereby reduces its weighting step, roof pre-blasting is both feasible and effective. If the position of the primary key stratum can be moved upward to exceed 10 times the mining height the possibility of support crushing and water inrush disaster caused by key stratum compound breakage will be lowered. The overburden structure of the number 7121 working face was considered during the design of a technical proposal involving roof pre-blasting. After comprehensively analyzing the applicability of roof pre-blasting the resulting design prevented support crushing and water inrush disasters from happening at the number 7121 working face and laid a solid foundation for mining safely.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

STRESS AND ENERGY TRANSFER OF WATER COUPLING BLASTING

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Cooling Water Flow Rate Calculation for Hearth of Large Blast Furnaces

The cooling water flow rate for hearth of large blast furnaces was calculated by simulation. The results show that the cooling water flow rate shall be above 4 200m3/ h for hearth of large blast furnaces; to meet requirements of the increasing smelting intensity and to ensure the safety at the end of the first campaign,the designed maximum cooling water flow rate should be 5 900m3/ h; according to the flow distribution stability and the calculated resistance loss,hearth cooling stave pipes with the specification of 76 mm × 6 mm shall be adopted to assure the flow velocity in pipes of hearth cooling stave in the range of 1. 9- 2. 3 m / s.

黑河连接洞开挖爆破对黑河引水洞稳定性的影响

鉴于施工支洞与主隧洞交叉段复杂的受力状态及稳定性问题日益引起关注,提出了兼顾考虑现场位差爆破时炸药段位的群孔爆破简化方法,拟定相应的隧洞开挖爆破动力荷载,采用三维动力有限元分析方法,研究了黑河连接洞与黑河引水隧洞交叉施工过程中,连接洞开挖爆破振动对已建引水洞围岩稳定及衬砌结构安全性的影响。结果表明,黑河引水洞衬砌各关键点振动速度随着与爆破荷载距离减小而逐渐增大,最大振速主要发生在交叉口往交叉角为锐角方向17m范围内,衬砌振速在0.733~9.76cm/s之间;爆破的衰减速度较快,在进行爆破时,应考虑爆破点位置以减少多余的处理措施。根据规范要求,仅有1个监测点最大振速略高于最低标准,且超出时间很短,可认为实施八期爆破施工满足要求。

水耦合爆破破岩的数值模拟研究

水耦合爆破因其节能、高效等优势在工程爆破中具有广阔的应用前景。利用数值模拟水耦合爆破破岩过程及最终破坏特征,与空气耦合爆破对比表明,水介质加快了岩体裂纹扩展速度,提高了岩体的破碎程度与范围;岩体中的初始裂纹与爆源交叉时,水增强了初始裂纹对破坏的导向作用;岩体中的初始裂纹与爆源无交叉时,闭合裂纹使爆炸破坏作用向弱面集中,水增强了闭合裂纹周围的岩体破碎效果。

淤泥-岩石地层爆破临近给水管道振动特征

盾构机通过淤泥-岩石地层时,可以在地面钻孔预先爆破破碎岩石,但是淤泥-岩石地层爆破产生的振动威胁爆区周围供水管道的安全。通过对爆破振动进行现场测试和数值模拟,首先验证爆破现场材料的物理和力学参数,然后研究了爆区附近供水管道的动态响应。得出如下结论:在管道轴向上,节点峰值速度(PPV)随着距爆炸源水平距离的增加而减小;在管道正上方地表沿管道轴向,节点峰值速度也随着距爆炸源水平距离的增加而减小;管道上节点峰值速度与管道上方地面的节点峰值速度之间存在函数关系。管道内壁最大PPV是最小PPV的3.97倍,管道内壁90°处的节点峰值速度最高,管道外壁最大PPV是最小PPV的1.03倍,管道外壁150°处的节点峰值速度最高,每个节点的PPV彼此不同,给水管道内壁PPV大于外壁,内壁PPV变化较大,但外壁PPV相对接近。单元的最大峰值有效应力是单元的最小峰值有效应力的4.06倍,在管道外壁240°~270°处单元的峰值有效应力最高。本研究的结论可以为确定爆区周围供水管道的安全性提供参考。

富水矿岩区域爆破参数优化数值模拟研究

为改善某露天矿山富水矿岩区域水孔爆破效果,通过理论分析和现场试验进行了岩屑填塞料的研究,并结合数值模拟分析了径向水不耦合装药系数、填塞长度、延期起爆对爆破效果的影响。结果表明:随着岩屑粒径的增加,填塞结构的抗剪强度也随之增加,填塞的作用也得到增强;填塞结构以<5 mm与≥5 mm粒径岩屑颗粒配比为3∶7时填塞作用最为显著;在径向水不耦合装药系数K d为1.33时,能够取得理想的爆破效果节约炸药成本;延期起爆能够提供更多的自由面有利于降低岩体破碎的块度。

单天线功率受限的自适应调制V-BLAST系统

提出了一种在单天线峰值瞬时功率和总平均功率都受限条件下的改进注水法和离散调制的比特、功率分配方法,并应用于自适应调制V-BLAST系统。如果由注水法得到的分配结果中某发射天线的瞬时功率高于峰值功率限制,就修正该天线的分配比特数和功率使之满足限制要求,剩余的功率再由注水法分配到其他天线上。仿真结果表明,提出的算法很好地满足了目标要求,而且单天线功率受限使比特率有所下降。

硬岩地层中盾构机下部爆破脱困技术应用

广州地铁22号线某区间掘进过程中刀具损坏且检查不及时,导致开挖直径过小,盾壳被岩体包裹无法继续向前掘进,额外增加推力依然无法脱困。常规脱困方案是从开挖范围上半部爆破松动地层,因工程顶部硬岩稳定地层较薄,爆破上部容易导致上部地层塌方,故选择向下半部爆破,相对上半部爆破施工及技术难度更大。以对土仓侧壁切割开口的方式提供爆破临空面,分层采用水压爆破步进,直至爆破完下半圈岩体。解决了全断面中风化花岗岩盾构卡壳问题,盾体成功脱困恢复掘进。

“三硬”薄煤层沿空留巷围岩破坏特征及控制技术研究

为解决薄煤层沿空留巷应力条件复杂、留巷难度大以及巷道围岩长时稳定性的难题,以陕西汇森煤业凉水井煤矿4301工作面为研究对象,采用理论分析、数值模拟、工程实践等方法,对浅埋“三硬”薄煤层沿空留巷围岩破坏特征及控制对策进行研究,分析巷旁支护体结构参数对于巷道稳定性的影响。结果表明:给顶板提供充足的支护强度以及合适的可缩量,是巷旁充填体整体稳定的前提;高水充填材料单轴加压下的力学行为可分为“均匀压密、弹性变形、动态失稳、劣化破坏”4个阶段;在充填体宽度增加过程中,最大应力表现为先增后减再增的趋势,在充填体1.6 m宽时出现稳定承载应力核;理论计算的切顶最佳高度为10.7 m。工程实践表明,工作面后方60 m范围无大变形和明显应力集中,围岩整体控制效果良好、结构稳定,留巷效果达到设计要求。

露天煤矿富水深孔爆破间隔器研发与应用

为解决露天矿开采中,遇到的富水炮孔无法安装空气间隔器进行间隔装药爆破的问题,在分析空气间隔器适用性和结构的基础上,研发了一种水孔专用间隔器,用于减少乳化炸药使用量。通过地面实验与现场检验的方式研究了水孔间隔器的膨胀效果、对乳化炸药的支撑作用,以及对爆破效果的影响。结果表明:该水孔间隔器应用于富水深孔爆破中,爆破后爆堆情况、大块率和铲装后根底均与周边非间隔装药爆破情况相当,实现了降本增效。

露天含水炮孔爆破优化及应用研究现状

针对我国露天矿生产规模持续扩大,许多露天矿已经转入了深凹露天开采阶段,炮孔含水的情况经常出现,给传统露天爆破施工的装药及填塞增加了难度,导致爆炸能量利用率低,爆破破岩效果差。为了解近些年专家、学者对露天矿含水炮孔爆破工艺的研究现状,分别从排水工艺、装药结构、孔网参数及炮孔填塞几个方面着手,总结了优化爆破效果的有效措施,并讨论了水介质与炸药耦合增能破岩作用机理,指出利用水介质增能破岩、实现水雾降尘是未来含水炮孔的爆破施工的一个重要发展方向。

水下钻孔爆破水不耦合装药的减振效应研究

为了研究水不耦合装药爆破在水下爆破中的减振效应,以减少对邻近建筑物等被保护对象的危害,分别采用理论推导和现场试验方法,研究了水不耦合装药爆破振动的衰减规律。在理论推导中,根据牛顿第三定律、介质连续条件和波的动量守恒定律,通过计算波阻抗比,分别推导了水不耦合装药爆破和耦合装药爆破两种情况下,炸药爆炸冲击波在水体和岩体之间反射、透射之后的质点振动速度,得出水不耦合装药爆破爆炸冲击波传入岩体内的质点振动速度衰减率。计算结果表明,水不耦合装药爆破炸药爆炸冲击波经水体传入岩体后,岩体质点振动速度仅为炸药质点振动速度的3.8%;与耦合装药爆破相比,岩石质点振动速度减少93.10%。现场实验结果表明,综合采取水不耦合装药、逐孔起爆、精确限定单孔装药量和一次起爆最大装药量,以及其他减震措施,基于实测的爆破振动数据,动态优化调整爆破参数,减少了爆破振动和水中冲击波对被保护物的危害,保障了爆破质量和工程进度。无论是理论推导还是现场试验,均表明水不耦合装药爆破在水下爆破中具有明显的减振作用,计算得出的质点振动速度衰减率具有理论指导意义,而在现场试验获得的实际效果,为水下爆破工程的振动控制,提供了实践经验和借鉴,并形成了一套水下钻孔水不耦合装药爆破技术施工工艺。

深水条件下水深对炸药性能影响研究

在深水条件下进行水下爆破时,由于装药时间较长,炸药将受到高水压的影响,并且浸泡时间较长,只有当炸药性能达到技术要求时,才能保证爆破效果。结合三峡—葛洲坝两坝间莲沱段航道整治工程,炸礁时发现原乳化炸药成分抵抗深水压力能力较弱,在40 m水深施工时殉爆距离较小,猛度不足。实验室通过采用深水测定法,调整静水表面压力模拟深水条件,对水胶炸药、化学敏化炸药、玻璃微球敏化炸药和珍珠岩敏化炸药的性能变化进行实验,探寻不同水深条件下炸药性能随浸水时间的变化关系和不同浸水时间条件下炸药性能随水深的变化关系。经过实验结果对比,研究表明:当水深为0~20 m时玻璃微球敏化炸药、化学敏化炸药、珍珠岩敏化炸药、水胶炸药的性能下降均较小,这四种炸药都满足工程需求;当水深为20~40 m时推荐使用玻璃微球敏化炸药与珍珠岩敏化炸药;当水深为40~50 m时推荐使用玻璃微球敏化炸药,玻璃微球敏化炸药在高压与长时间浸水条件下,炸药性能下降程度均较小,适用于深水条件下水下钻孔爆破施工。

金属矿规模化开采爆破污染物与爆破质量协同控制技术研究

金属矿地下规模化开采爆破量大,释放高浓度CO和粉尘等污染物的炮烟对矿山生产安全带来不利影响。加大通风量和喷雾等常规炮烟治理措施效率低、通风时间长,严重影响生产效率。针对井下爆破质量与污染物协同控制的生产要求,以某铁矿采场为试验点,通过多组现场试验和Fluent模拟相结合的方法研究水炮泥布置方式对爆破块度和炮烟中CO浓度的影响,得出了水炮泥的协同控制布置方法。试验表明:①采用1卷水炮泥—炮塞—炸药的布置方式,炮烟污染物浓度减少20%~30%,同时爆破块度集中在6~10 cm,与未使用水炮泥的爆破质量基本相同;②炮孔底部增设1卷水炮泥连接炸药布置,CO浓度峰值降低35%左右,污染物控制效果较1卷水炮泥提升较小,但爆破岩块集中在10~12 cm,爆破质量明显降低;③水炮泥数量的增加能有效提升污染物控制效果,缩短通风时间,但水炮泥同时吸收炸药爆轰带来的冲击力,减少矿岩体受压,使爆破块度增大,影响爆破质量。

隧道周边孔切缝药包水间隔装药聚能爆破试验

勐省隧道Ⅳ级围岩掘进采用孔底连续装药爆破开挖,存在明显的超欠挖现象。为保证一次爆破成型,减少爆破对围岩和支护结构的扰动,在勐省隧道周边孔应用切缝药包水间隔装药聚能爆破技术,并开展现场试验。试验结果表明,相较于传统光面爆破,水间隔装药聚能爆破技术不仅有效控制了超欠挖,形成了平整轮廓线,且周边孔单孔药量降低了25%,孔距增加了100~300 mm,周边孔半孔率大于70%,节约了混凝土初喷量,避免了欠挖补炮,降低了对围岩的频繁爆破扰动。

露天矿含水间隔装药的爆破抑尘效果研究

钻爆工序在整个露天矿生产环节中产生的粉尘量比重最大,为了从源头降低爆破作业产生的粉尘量,通过研究爆破粉尘的产生机理及粉尘的粒径分布和逸散规律,并结合含水条件下炮孔应力变化理论,探讨水间隔爆破的抑尘效果。以某露天矿为背景,合理地建立试验及监测方案,设置4个不同装药结构的爆区,爆破后监测不同时间、不同中心距离下的粉尘浓度变化,根据污染点源扩散方程分析数据,对比含水、无水情况下及含水条件下不同装药结构的抑尘效果。结果表明,含有间隔水柱的炮孔爆区产生的粉尘浓度比干炮孔爆区平均降低了约50%,其中水柱位于炮孔顶部和底部时,降尘效果最为明显,粉尘强度约为干炮孔的57%。