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.

Application of Directional Broken Control Blasting in Cutting

Based on experiments in lab, this paper analyzes the mechanism of directional broken controlled blasting and applies the technology to the cutting by utilizing its characteristic. The model cutting experiment and the practical application result show that the cutting blasting technology is an effective way.

CONTROLLED BLASTING RESEARCH FOR SHAPEN CUTTING OF STRUCTURAL DECORATION STONE

This paper analyses the fragmenting principle of static blasting agent (SBA) and the action of its cutting fragmentation. Using SBA for sterming material proved very useful and advantageous. Here we analyse in detail the cutting action of pre- stress and stress wave in pre-stressing force blasting.

A new method of cut-blasting for vertical shaft excavation and its experimental study

Based on cutting principle and technology development of vertical blasthole cutby stage and deck in vertical shaft excavation, combined with the merits of middle spacecharging and toe space charging, the reinforced cutting effect of central large-diameterblasthole and the method of cutting blast by stage and deck toe space charging for thevertical large-diameter blastholes was put forward and analyzed theoretically.This new cutblasting method is provided with the advantages of high blasthole using ratio, big cavitybulk, low rate of chunk, even lumpiness, and relatively high energy using ratio.The parameterchoices and practical effects of this cutting method were discussed after in situexperiment.It shows that the decked delay time of 75～100 ms is applicable.

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.

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.

Damage evolution and fragmentation behavior of pyramid cut blasting under uniaxial compression

Pyramid cut blasting is an essential form of inclined hole cut blasting,but the in-situ stress effect of pyramid cut blasting is rarely studied.Based on the research background of pyramid cut blasting in a deep rock mass,the size,volume,and fragment size distribution of the blasting cavity before and after uniaxial compression were analysed by a model test.Otherwise,the damage and effective stress of the pyramid cut blasting were analysed with LS-DYNA numerical simulation.The results show that the damage and fragmentation of pyramid cut blasting are not only affected by blasting stress wave and blasting gas,but also affected by uniaxial compression.Under the influence of uniaxial compression,the blasting stress wave and blasting gas are more likely to damage the rock mass parallel to the uniaxial compression direction near the connecting line of blasting hole,and make the volume of cavity larger and the fragment rate lower.Additionally,uniaxial compression has a prominent influence during the middle and late stages of blasting.

Cutting parameter optimization for one-step shaft excavation technique based on parallel cutting method

The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters（such as the hole spacing L and the empty hole diameter D） and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η1 and η2 that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η1 and η2 can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress.

Blasting technologies of vibration damping in subway tunnel passing under upper buildings closely

Reducing the blasting vibration is important for blasting excavation in subway tunnel construction.Taking the 3rd bid section of Line 3 of Qingdao subway project as an example,the distance between tunnel vault and ground is 5 ~ 8 m.In order to insure the safety of the upper buildings,technologies of parallel cut with large diameter empty hole,one-time initiation and delay by parts,and multiple shallow holes were adopted in the project.The results showed that the maximum value of vertical vibration was limited in the criterion allowance,and the upper buildings were not damaged.Besides,problems were solved that the number of nonel detonator was difficult to meet the requirements of excavating a large cross-section tunnel by blasting,multiple cross-section could’t be initiated simultaneously,and construction efficiency was low,which ensure the construction safety and schedule.

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%。

赵官矿切顶卸压沿空留巷爆破参数研究

以赵官矿2707W工作面为工程背景,对切顶卸压沿空留巷爆破参数进行研究。结合现场工程地质条件,选用双向聚能拉伸爆破技术对试验段顶板进行预裂。综合运用理论分析计算、现场爆破试验等手段,得到了合理的爆破参数:爆破钻孔深度8.0 m,切顶角度10°,炮孔间距600 mm,装药结构为5+4+3。通过现场钻孔窥视和矿压监测等手段验证了切顶爆破效果良好,在丰富切顶卸压沿空留巷爆破技术理论的同时,也为类似工况提供一定的工程借鉴意义。

复杂岩性隧道超前切割爆破方法研究

针对复杂岩性隧道传统爆破开挖效果差的问题,基于传统光面爆破与预裂爆破的研究,在隧道周边局部存在软弱围岩情况下,将软弱围岩区周边孔的爆破提前至掏槽孔爆破之后进行,提出一种超前切割控制爆破方法。建立了准三维模型,使用流固耦合(ALE)算法和ANSYS/Ls-dyna有限元分析软件,对超前切割爆破方法与传统预裂、光面爆破方法进行了数值模拟对比研究,结果表明:相较于光面爆破与预裂爆破,对超前切割爆破在隧道轮廓周边损伤深度分别降低了6.85%与10.08%。结合仿真结果设计了现场爆破试验方案,并开展了光面爆破及超前切割爆破方法的现场对比试验,爆破结果表明:采用超前切割的爆破方法后,隧道的轮廓面成型效果好且软弱围岩区无掉块、坍塌情况,同时超欠挖得到有效控制。对爆破后的断面进行三维断面扫描数据及统计结果表明:相较于效果较好的光面爆破,超前切割爆破的最大超挖降低了35.98%、平均超挖降低了25.60%,混凝土消耗数量降低了26.3%,其平整度标准差提高了24.29%。该方法经过现场实践验证,在降低超挖的同时还可以减弱复杂岩性区内的爆破损伤,提升隧道保留围岩平整度。

金属矿山硬岩巷道分阶段掏槽爆破数值模拟研究

针对地下金属矿山深部硬岩强度高,掏槽难度大,掘进效率低下的问题,以首钢杏山地下铁矿巷道掘进项目为背景,基于数码电子雷管精准逐孔起爆,提出针对直眼桶形掏槽爆破的掏槽区孔内分段与孔间、孔内延时相结合的分阶段爆破方案。采用数值模拟以及现场试验方式,在现场原传统方案的基础上,对掏槽区炮孔进行孔内分段、孔间以及孔内微差起爆的分阶段起爆设置。通过LS-DYNA数值模拟软件建立掏槽区三维模型,设置了原传统方案和3种分阶段方案进行模拟计算,对比分析了原传统爆破方案和分阶段方案在掏槽区的有效应力峰值演化情况。数值模拟结果表明:采用孔间短延时分阶段爆破方案能够改变有效应力峰值波动形态,与原传统方案相比,掏槽区沿炮孔方向岩体的有效应力峰值状态提升40%~57%,炮孔底部0~30 cm半径岩体有效应力峰值状态提升幅度在84%~92%。在数值模拟结果的基础上,开展了现场试验验证,现场试验表明:在矿石点位掘进中,采用孔间短延时微差起爆能够改善碎石挤死的现象,采用孔内短延时微差起爆能够提高抛掷能力,改善上段炮孔爆破后产生碎石的抛掷效果,避免影响后续炮孔爆破,在硬岩爆破中二者结合可以明显改善爆破效果,掏槽进尺提高28%;在岩石点位掘进中,采用孔间短延时,孔内长延时设置能获得良好的掘进效果。

岩巷掏槽爆破掘进数据库建立及参数优化研究

掏槽爆破掘进参数是岩巷钻爆法施工的关键参数,优化爆破掘进参数是确保钻爆法高效率施工的重要途径之一。依据1980—2022年共200个代表性爆破掘进案例,利用统计学方法分析了爆破参数在普氏系数和断面面积2个岩巷特征参数维度下的变化特征,通过构建爆破掘进案例数据库研究了岩巷掏槽爆破客观规律。结果表明:随着普氏系数增加,岩石极限抗压强度增大,为保证爆破效果,可适当增加炮孔长度和炸药单耗,同时也会略微增加单循环进尺,但岩石自身高应力导致的夹制作用会降低炮孔利用率;通常设置空孔为掏槽爆破提供新的自由面,通过应力波反射拉伸使得靠近自由面的岩体破坏区域更大,硬岩巷道更适合直孔掏槽爆破。在较大断面岩巷的掏槽爆破掘进过程中,岩石夹制作用较小,较小的炸药单耗可以达到良好的爆破效果,从而促进了单循环进尺和炮孔利用率的提高;由于大断面面积对岩石爆破的限制作用减弱,无需过分增加炮孔数量和装药量,相反适当减缓炮孔数量的增长速率也能够达到良好的爆破效果。上述分析可以为爆破参数优化、岩巷高效施工提供参考。

复式楔形掏槽在大断面隧道掘进中的应用研究

掏槽孔爆破效果对整个断面的爆破质量有着重要影响,为解决大断面隧道掘进困难,炮孔利用率低的问题,采用基于ANSYS/LS-DYNA的流固耦合算法对比研究单楔形掏槽与复式楔形掏槽的内部有效应力与损伤破坏范围,与现场实际爆破效果印证解释了复式楔形掏槽爆破效果优于单楔形掏槽的原因。研究结果表明:单楔形掏槽应力峰值出现在孔底处,随孔底至堵塞段应力峰值缓慢降低,堵塞段到掌子面应力峰值骤降。复式楔形掏槽应力峰值则出现在一级掏槽孔底位置,且其数值大小高于单楔形掏槽应力峰值。选取两种掏槽模型的损伤区域截面发现,两者的破碎面积接近,但单楔形掏槽模型的堵塞段至掌子面区域的岩石未能破碎贯通,复式楔形掏槽模型整个槽腔完全贯通。根据数值模拟结果改进了某公路隧道爆破方案并进行了现场试验,复式楔形掏槽能更好地解决大断面隧道爆破炮孔利用率低以及爆后大块多的问题。研究结果可为相关隧道掏槽孔布设方案提供选择和参考。

高地应力巷道掏槽爆破的应力演化与损伤破裂研究

近年来,矿产资源的开采状态由露天转地下,由浅部转深部,在深部岩体的钻爆法施工中,地应力对爆破效果有显著影响。有关掏槽爆破机理和应用的研究主要是针对浅部地层中的巷道爆破施工,没有考虑地应力对爆破效果的作用。采用一种考虑爆破荷载下粉碎区能量耗散的改进型连续-非连续单元法(Continuum-Discontinuum Element Method,CDEM),基于二维平面应变模型,分别研究了普通直眼掏槽爆破和大空孔直眼掏槽爆破在不同地应力条件下的应力演化过程和破裂损伤特征。数值模拟结果表明,大空孔的存在增强了爆炸应力波的反射拉伸作用,削弱了地应力对爆炸裂纹扩展的抑制作用,促进了爆炸主裂纹的扩展,增加了掏槽爆破的分形损伤和损伤面积,提高了掏槽爆破的岩体破碎程度。双向等压地应力对爆炸裂纹的扩展有抑制作用,对径向爆炸裂纹的扩展尤为显著。较大的地应力削弱了孔间爆炸应力波的相互作用,相邻炮孔对爆炸主裂纹扩展的导向效应减弱。随着地应力的增加,爆炸裂纹的分形维数和分形损伤整体上呈逐渐减小的趋势,但是大空孔直眼掏槽爆破的裂隙区分形损伤和损伤面积均显著大于普通直眼掏槽爆破的裂隙区分形损伤和损伤面积。说明在高地应力环境下,大空孔直眼掏槽爆破依然能够显著增加岩石破碎程度和破碎范围,提高爆破效果和破碎效率。

切割井中深孔孔内分段爆破一次成井数值模拟

为分析中深孔孔内分段爆破一次成井的爆破效果,采用ANSYS/LS-DYNA有限元数值模拟软件,对孔内分段装药和不分段装药2种不同装药结构下中深孔爆破切割井处应力变化、损伤区域进行模拟计算研究。结果表明:孔内分段装药爆破时切割井中部两侧应力更集中,炸药爆炸产生的应力波更多的作用于炮孔顶部岩石处,使其受到的应力更大;分段装药时炮孔下层炸药首先起爆为上层炸药爆炸创造了良好的自由面,炸药爆炸产生的能量更多作用于岩石两侧及顶部,导致其损伤区域高度更高,模型底部产生的裂纹较密集,并且模型外侧边界处裂纹衍生的数量以及裂纹宽度和长度明显较高,证明孔内分段装药对切割井爆破一次成井具有更优的效果。最后,应用此方案在矿山现场成功施工1条高度为13.2 m、断面为2.1 m×2.2 m的切割天井,表明该方案具有较好的工程意义和推广价值。

角柱形垂直掏槽爆破参数研究

针对角柱形掏槽孔网参数确定问题,依据前人研究,总结推导了岩体爆破作用下粉碎区半径Rp和裂隙区半径Rf的计算模型,量化了爆炸应力波和爆生气体对岩体破碎的影响,并根据Rp和Rf的结果结合碎胀空间效应构建了角柱形掏槽孔网参数的计算模型。结合现场实际情况,可得爆炸应力波产生的粉碎区半径R1=50 mm,裂隙区半径R2=550 mm,爆生气体二次破碎产生的粉碎区半径l c=16 mm,裂隙区半径l g=420 mm;从而得到Rp=66 mm、Rf=970 mm结合碎胀空间效应,可知装药孔和空孔距离L和装药孔间距L_(1)满足66 mm<L<L_(1)<160 mm,依据现场实际取L=0.1 m、L_(1)=0.15 m;对该掏槽方案建立数值模型进行计算,模拟结果表明裂隙区裂纹平均长度为1069.4 mm,与Rf=970 mm相比误差为99.7 mm,粉碎区槽腔破碎的平均长度为67.1 mm,与Rp=66 mm相比误差仅为1.1 mm,再对该掏槽方案进行多次现场巷道掘进试验,试验结果表明炮孔利用率可由原先的80%提高至93%以上,验证了模型的有效性。

深孔聚能预裂爆破切顶卸压机理与应用

为解决悬顶导致的煤柱及邻近巷道高应力和大变形问题,结合工作面顶板地质条件,提出深孔聚能预裂爆破切顶卸压专项方案,采用数值模拟及现场试验对卸压效果开展综合研究。研究结果表明,煤层顶板在切顶后垂直应力减幅为21.62%,预裂切顶措施可显著降低煤柱及邻近巷道围岩应力水平。试验发现,炮孔内轴向贯穿裂缝明显,可实现采空区顶板及时垮落。顶底板在切顶后累计位移量减幅达59.27%,巷道两帮及顶底板移近变形得到有效控制,煤柱垂直应力增量显著降低。实践证明,采用深孔聚能预裂爆破切顶卸压效果显著,可大幅提高作业效率,为类似矿压防治工程提供借鉴。

不同堵塞条件下硬岩隧道直眼掏槽破岩效果数值模拟研究

为研究不同堵塞材料及堵塞长度对硬岩隧道直眼掏槽爆破效果的影响,依托工程实例,采用ANSYS/LS一DYNA仿真模拟软件建立三维数值模型,对5种不同堵塞条件展开研究。根据数值模型计算结果,对掏槽区域爆破裂纹拓展情况进行了定性分析,对典型部位的岩石受力情况进行了定量分析。结果表明:1)自由面岩石主要受拉应力作用产生裂纹,炮孔堵塞使得爆炸荷载整体作用时间延长,致使自由面上裂纹更加密集;2)位于炸药和堵塞材料之间空气段附近的围岩,先受爆炸应力波作用岩石被压碎,后受力在拉压应力之间多次转化,致使裂纹被放大,结合爆生气体发挥的“气楔”作用,使得裂纹几乎贯穿模型截面;3)炮孔堵塞后炸药段周围岩石受到的爆生气体作用应力值显著提升,比不堵塞时的炸药段周围岩石峰值应力高出1.31~2.34倍,炮孔堵塞使得爆生气体持续稳定发挥作用时的压应力值提高3.70~4.70倍;4)以黏土和水作为堵塞材料时,堵塞长度为40cm的直眼掏槽破岩效果优于堵塞长度为60cm的效果。研究成果可为优化硬岩隧道直眼掏槽爆破参数提供理论基础。