Theoretical and numerical simulation investigation of deep hole dispersed charge cut blasting

Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways.With the advent of digital electronic detonators and the need for increased production efciency,the traditional blasting design is no longer suitable for deep hole blasting.In this paper,a disperse charge cut blasting method was proposed to address the issues of low excavation depth and high block rate in deep hole undercut blasting.First,a blasting model was used to illustrate the mechanism of the deep hole dispersive charge cut blasting process.Then,continuous charge and dispersed charge blasting models were developed using the smooth particle hydrodynamics-fnite element method(SPHFEM).The cutting parameters were determined theoretically,and the cutting efciency was introduced to evaluate the cutting efect.The blasting efects of the two charging models were analyzed utilizing the evolution law of rock damage,the number of rock particles thrown,and the cutting efciency.The results show that using a dispersed charge improves the cutting efciency by about 20%and the rock breakage for the deep hole cut blasting compared to the traditional continuous charge.In addition,important parameters such as cutting hole spacing,cutting hole depth and upper charge proportion also have a signifcant impact on the cutting efect.Finally,the deep hole dispersed charge cut blasting technology is combined with the digital electronic detonator through the feld engineering practice.It provides a reference for the subsequent deep hole cutting blasting and the use of electronic detonators in rock roadways.

ESTIMAING AMOUNT OF EXPLOSIVE FOR FRACTURE PLANE CONTROL BLASTING WITH NOTCHED BOREHOLES

With the development of fracture mechanics,the fracture plane control blasting with notched borcholes hascome into being.This technique is used to create a satisfactory presplit along the contour of an excavation inrock.However,the amount of explosive loaded in each hol usually is determined by trial and error.Because ofthis,two approaches estimating the amount of explosive for the blasting technique are suggested.

Numerical simulation of parallel hole cut blasting with uncharged holes

The cavity formation and propagation process of stress wave from parallel hole cut blasting was simulated with ANSYS/LS-DYNA 3D nonlinear dynamic finite element software. The distribution of element plastic strain, node velocity, node time-acceleration history and the blasting cartridge volume ratio during the process were analyzed. It was found that the detonation of charged holes would cause the interaction of stress wave with the wall of uncharged holes. Initial rock cracking and displacement to neighboring uncharged holes become the main mechanism of cavity formation in early stage.2008 University of Science and Technology Beijing. All rights reserved.

Modified scaled distance regression analysis approach for prediction of blast-induced ground vibration in multi-hole blasting

The blast-induced ground vibration prediction using scaled distance regression analysis is one of the most popular methods employed by engineers for many decades. It uses the maximum charge per delay and distance of monitoring as the major factors for predicting the peak particle velocity(PPV). It is established that the PPV is caused by the maximum charge per delay which varies with the distance of monitoring and site geology. While conducting a production blasting, the waves induced by blasting of different holes interfere destructively with each other, which may result in higher PPV than the predicted value with scaled distance regression analysis. This phenomenon of interference/superimposition of waves is not considered while using scaled distance regression analysis. In this paper, an attempt has been made to compare the predicted values of blast-induced ground vibration using multi-hole trial blasting with single-hole blasting in an opencast coal mine under the same geological condition. Further,the modified prediction equation for the multi-hole trial blasting was obtained using single-hole regression analysis. The error between predicted and actual values of multi-hole blast-induced ground vibration was found to be reduced by 8.5%.

Influence of delay interval on blasting efficiency of parallel hole cuts with an empty hole

Time interval of short delay ignition is an important factor to affect theefficiency of blasting cuts. The motion process of rock pieces in the cut cavity is analyzed, amechanical model to calculate the delay time of parallel hole cuts is presented for tunnel blasting,and a theoretical method to determine the volume ratio (the clearage rate) of the rock pieceswithin the cut cavity at different moments is proposed for the blasting cut with an empty hole.Numerical analysis results show that the optimal delay interval is proportional to the boreholedepth. The suggested results are of practical value to the optimal design of the delay interval inmillisecond blasting related to the parallel hole cuts with an empty hole.

Research on the control technology of medium-length hole blasting fragmentation in underground mine

The scalloped medium-length hole blasting mining method used in Dahongshan Copper Mine accounted for more than 61%of the total amount of mining,but the large boulder yield restricted the intensity of ore supply for mines,and the average boulder yield was as high as 22.7%.In order to develop the mine production efficiency,the circular medium-length hole blasting technology was proposed and field tests were carried out.The test results showed that circular medium-length hole blasting mining can reduce the average boulder yield to 10.3%.Compared with the traditional scalloped medium-length hole blasting mining,the average boulder yield was decreased by 12.4%.The daily yield of ore for the panel on duty was increased by 152.29 t,and the growth rate was 51.1%.The new technology can reduce the time for the handling of boulder and the consumption of explosives and detonators for recrushing,and increase the efficiency of mining while reduce the mining cost,which has received good blasting effects.

炮孔间距对偏心不耦合装药贯通裂纹扩展的影响

为研究光面爆破中偏心不耦合装药炮孔间距对贯通裂纹扩展的影响,利用同心不耦合装药的孔壁压力计算公式并结合应力波叠加原理,推导偏心不耦合装药的炮孔间距计算方法。基于求得的炮孔间距范围,计算3种岩石介质在不同炮孔间距条件下贯通裂纹的扩展位置,并选择砂岩材料进行数值模拟。结果表明:偏心不耦合装药爆破中,贯通裂纹主要集中于偏心侧;抗拉强度大的岩石,贯通裂纹偏离炮孔连心线的程度也较大。砂岩的炮孔间距为60 cm时,贯通裂纹扩展方向与炮孔连心线重合,连心线下方出现裂纹比较集中的贯通区域;炮孔间距的增大导致贯通裂纹远离炮孔连心线,从而造成欠挖。偏心不耦合装药爆破后,偏心侧岩石的损伤明显大于非偏心侧。

周边眼偏位空孔爆破设计优化研究与应用

依据已有研究对空孔效应和设置空孔时裂纹扩展规律进行探讨,发现空孔有利于裂纹贯通,对提升爆破效果有一定帮助,但也发现传统的直线型空孔布置会导致裂纹偏向,即在空孔附近转向、偏离原发展路径,影响原设计开挖轮廓。若设置偏位空孔,则可充分利用空孔效应及导向作用以提高开挖质量。对于偏位空孔在爆破中的效应,采用数值模拟研究了不同炮孔间距、空孔偏位角下的裂纹扩展规律和炮孔间贯通情况,探讨了最优偏位角度设计,并根据模拟结果对现场爆破方案进行优化,研究实际应用效果。研究结果表明:偏位空孔对爆生裂纹具有较直线空孔更明显的导向作用,主要表现在爆生裂纹尖端向空孔本身发展或被空孔裂纹引导偏向、最终主裂纹与空孔连通或在空孔范围之外主裂纹相贯通,更利于炮孔主裂纹扩展与贯通;通过提取模拟结果并测量裂纹范围,对于孔间距在60 cm及以下时,适用于周边眼爆破设计的最优偏位角为15°,在此情况下炮孔连线方向形成了与孔心连线相平行的裂纹,能显著提升贯通效果;对于优化后的福厦铁路某隧道爆破施工方案,通过振速监测及超欠挖断面扫描分析,发现周边眼起爆引起的爆破振速降低了超过50%,超欠挖值也由平均25 cm降低至15 cm以内,整体应用效果良好。该项研究可为隧道爆破减振及超欠挖控制研究提供一定参考。

中凯矿业大直径深孔爆破落矿装药结构优化研究

装药结构对厚大矿体大直径深孔爆破落矿效果具有重要影响。中凯矿业帮中矿区现行装药结构(空气间隔长度比例24.2%)存在爆破后冲破坏作用严重的问题,造成后一排炮孔堵塞、坍塌甚至报废,严重影响生产效率;而盲目增大空气间隔长度比例则存在爆破大块率增加的风险。以矿山实际的炸药和岩石参数为基础,采用数值模拟软件LSDYNA开展大直径深孔爆破落矿装药结构优化研究。选择常用空气间隔器作为间隔材料,以空气间隔长度比例为研究对象设计了12种装药结构方案进行数值模拟,得到了装药结构与爆破后冲作用、大块率、自由面质点振动峰值速度以及峰值有效应力等评价指标之间的关系。结果表明:自由面质点振动峰值速度以及峰值有效应力随空气间隔长度比例增加逐渐下降;当空气间隔长度比例小于等于30.5%时后冲作用明显,后排炮孔可能出现塌孔现象,当空气间隔长度比例大于等于45.3%时,存在大块率增加的风险,最优装药结构的空气间隔长度比例为44.2%。现场深孔爆破落矿试验表明,优化的装药结构爆破后大块率为7.1%且爆破后冲作用得到有效控制。

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。

综采面坚硬顶板超深孔预裂爆破远场解危控制技术

工程实践表明,顶板事故在煤矿各类事故中占首要位置,已严重制约了我国现代化矿井安全高效开采。为了实现煤矿综采面坚硬顶板的安全治理,亟需形成综采面坚硬顶板超深孔预裂爆破远场解危控制技术以有效解决因工作面大空间坚硬顶板垮落而影响安全生产的重大难题。基于此,通过自主创新和联合攻关,面向深部矿井坚硬顶板,开展了综采面坚硬顶板超深孔预裂爆破远场解危技术研究;研发了高威力三级煤矿许用水胶炸药、填塞材料等技术与装备,形成了成熟的深孔爆破工艺,突破了厚硬顶板爆破中煤矿许用炸药威力与安全度的矛盾,解决了超深孔爆破中炸药可靠起爆等技术瓶颈问题;通过构建大空间采场覆岩-支架-围岩系统力学模型,揭示了采场大小周期来压及强矿压作用机理,提出了大空间采场厚硬覆岩多层位精准定位爆破弱化控制原理和基于爆破损伤的综采工作面厚硬顶板深孔爆破参数设计方法,形成了综采工作面厚硬顶板超前深孔卸压控制技术。研究成果在全国近百个综采面进行工程应用,未发生一起顶板事故,避免了综采面厚硬顶板发生压架、形成飓风、矿震等重大安全事故的风险,保障了综采面的安全高效生产,为综采面坚硬顶板远场解危的设计提供了理论依据并为现场施工提供了指导作用。

高应力扇形中深孔采场边帮控制爆破参数优化

针对扇形孔采场爆破边帮控制问题,提出了一种将靠近边帮的扇形炮孔施工成垂直平行孔用以控制边帮的构想。首先,通过理论计算得到4组平行炮孔不耦合系数与炮孔间距匹配下的模型参数,使用LS-DYNA对4组参数进行数值模拟;然后,通过对比分析4组模型在无地应力作用和不同方向地应力作用时的爆破裂纹扩展情况,获得最优参数;最后基于优化参数开展工业试验。结果表明:高地应力会促进最大应力方向爆破裂纹扩展;4种模型中,不耦合系数为1.65,炮孔间距为1.1 m时开挖区域破岩效果最为合理;在试验采场开展工业试验,使用优化后的爆破参数进行爆破,采场回采后边帮平整,稳定性较好,验证了研究结论的正确性。

大直径空孔对掏槽爆破效果的影响机理研究

针对大红山铜矿巷道掘进爆破出现炮孔利用率低、单次循环进尺低、现场半孔率低、超欠挖严重及轮廓面不平整等问题,通过数值模拟软件LS-DYNA,构建三、四、五、六个大直径空孔四种掏槽爆破模型,对四种大直径空孔数量条件下的掏槽爆破成腔效果进行数值模拟研究,为后续掏槽布孔设计提供指导。研究表明:大直径空孔对岩体爆破损伤有导向作用,六个大直径空孔诱导形成的爆腔面积最大,约0.1321 m^(2),比五个大直径空孔的爆腔面积增长了8.55%,比四个大直径空孔的爆腔面积增长了2%,比三个大直径空孔的爆腔面积增长了8.01%;大直径空孔的阻隔作用明显,空孔的存在可以使得爆破振动峰值下降51.63%,有效应力峰值下降67.24%。

宽孔距爆破模型试验及近场动力学计算研究

针对宽孔距爆破破岩技术中炮孔密集系数合理取值的问题,在总结国内外宽孔距爆破破岩机理的基础上,开展了炮孔密集系数为1.7、2.5、3.5、4.5的有机玻璃板室内爆破试验,并基于常规态型近场动力学原理,开发了爆破计算模块,对宽孔距爆破破岩中裂纹扩展过程、介质位移响应规律进行了研究。结果表明:临空面一侧的径向裂纹受到临空面反射拉伸应力波的作用,表现出向临空面拐角分叉的特征,并逐渐向临空面扩展,最后形成主裂纹组成漏斗形状。在最小抵抗线固定不变条件下,随着炮孔密集系数的增加,应力降低区逐渐增大,同排炮孔间的径向贯通裂隙消失,过大的炮孔密集系数也进一步造成前后排孔间贯通裂纹消失,最后导致单孔爆破的情况发生。位移计算结果进一步证实了上述规律,并且当炮孔密集系数较小时,前排炮孔留下的岩埂刚好被后排炮孔爆破破碎,随着炮孔密集系数的增大,后排孔爆破对前排炮孔所留下的岩埂破碎作用效果逐渐降低。建议实际工程中根据岩体力学性质、地质条件以及爆破目的适当调整密集系数来降低炸药单耗与大块率。

延期时间对逐孔预裂爆破振动衰减规律的影响

为了获得逐孔预裂爆破的最优延期时间,基于Ansys/LS−Dyna有限元软件,结合现场实验研究了不同延期时间下逐孔预裂爆破的振动衰减规律,为实际工程应用提供了理论依据。结果表明:与齐发起爆相比,逐孔起爆可以有效地降低质点峰值振动速度(PPV),特别是预裂沟附近区域;随着延期时间的增大,萨道夫斯基公式的K值逐渐减小,而α值变化不大,当延期时间大于0.6T(T为单孔爆破振动持续时间)时,K与α的值趋于稳定,接近于单孔爆破;校正系数β与延期时间成反比,最优延期时间应为0.6T~1.0T;逐孔预裂成缝后对主爆区的减振率大于齐发预裂爆破。

台阶单孔爆破振动预测模型研究

爆破振动具有随机性,振动波的强度和频率具有非平稳性,为了构建能够真实反映爆破振动波形特性的台阶单孔爆破振动预测模型,通过调制白噪声的过程确定模型的频率函数,用角频率的时变性来描述振动波形频率的非平稳性;通过对强度包络函数的筛选,选取Gamma函数来描述爆破振动波形强度的非平稳性;用高通滤波处理提高了预测模型在低频段的模拟精度.以预测模型与现场实测波形的时程频率一致为约束条件,阻尼比与不规则指数呈线性关系,确定模型的频率参数(η,ξ,γ),以现场实测波形累计能量为约束条件,确定模型的强度参数(I0,α,β),模型输出波形的峰值振速、主频分别与现场实测波形特征的较好吻合,证明了所构建预测模型的正确性和有效性.

露天台阶爆破设计智能化的探索

基于经验的传统露天台阶爆破设计已不能满足爆破精细化和矿山数字化发展要求,根据新提出单孔破碎负担区拟柱体破碎理论构建了适应精确延时逐孔起爆条件的台阶爆破智能设计系统。该系统将人工智能手段与台阶爆破设计原理结合,实现了三维自动布孔、爆破参数智能选取、逐孔校核药量和爆破地震、飞石及爆堆预测等技术目标,解决了数字矿山中精细爆破设计的核心问题。最后,将该系统应用于西安频山石灰石矿的台阶爆破设计中,有效提高了爆破设计的智能化水平,降低了爆破作业成本、改善了爆破效果,显著提升了矿山的经济和社会效益。

基于CE-YOLOv8的炮孔识别方法

为了实现工程爆破中炸药的自动装填,现针对炮孔检测这一前置任务进行研究。由于实际工程中存在炮孔形状各异、碎石多、检测背景复杂等问题,导致检测过程中易出现遗漏和误判,因此,基于YOLOv8进行了改进,并提出了一种更高效的炮孔检测方法CE-YOLOv8。首先,将骨干网络中的C2f模块替换成C2f_DCN模块,增加了网络的空间变形适应性,从而能更准确地提取到炮孔特征,提高炮孔的检测精度。其次,在YOLOv8特征提取网络中加入改进C-CBAM注意力机制,对CBAM注意力机制的输入特征进行分组,并增加一个并行分支实现多尺度特征处理,最后通过跨空间学习模块将信息进行融合,提升模型的感受野和表征能力。最后,引入了E-IOU作为评估锚定框相互关系的计算方法,克服了传统IOU在梯度传递方面的缺陷,加快了网络的收敛。实验结果表明:改进后的模型对炮孔具有较好的识别效果,其中平均检测精度提升至98.6%,精确度和召回率分别达到95.7%和96.1%。改进的方法在爆破工程中识别炮孔从而实现智能化炸药装填具有较广泛的应用前景。

深孔轴向多段间隔装药孔壁冲击压力分布

为确定地下垂直长深孔爆破时合理的空气间隔长度,基于爆轰波理论,分析了多段间隔装药爆破条件下孔壁冲击压力随间隔长度变化的内在分布规律函数;依据Mises准则,得出了不同岩性时合理的间隔长度参考值,并通过数值模拟和现场爆破试验进行了验证。结果表明,空气间隔段孔壁冲击压力沿炮孔轴线从两端向中间骤降,但在中点周围略微增大,压力曲线呈两端大、中间小、中点周围略微凸起的“W”形对称分布。

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。