Finite element analysis for blasting law of jointed rock mass

On the basis of Mises strength theory,rock models are built including vertical,horizontal and diagonal joints to simulate jointed rock mass under blasting load by using FEM. The dynamic procedures of jointed rock mass under blasting are quantified and the effective stress-time curves of typical elements are compared to analyze the barrier of joints to the stress wave. The blasting law was studied according to the process of computer simulation and the effect of blasting,and some suggestions were given for solving the problems of overbreak and underbreak.

Incidence Law and Disease Symptom of Rice Blast and Its Control Technique

The article systematically summarizes the pathogen, incidence law and disease symptom of rice blast, and raises the integrated control technique for the disease, which will provide the certain theoretical basis for the control of the disease, being benefit for the actual production of rice in field.

Analysis of predictor equations for determining the blast-induced vibration in rock blasting

The paper proposes a new empirical correlation designed to complement the‘‘site laws"currently used to evaluate the attenuation in the rock masses of vibrations induced by rock blasting.The formula contains a deformed exponential known as the K-exponential,which seems to well represent a large number of both natural and artificial phenomena ranging from astrophysics to quantum mechanics,with some extension in the field of economics and finance.Experimental validation of the formula was performed via the analysis of vibration data covering a number of case studies,which differed in terms of both operation and rock type.A total of 12 experimental cases were analysed and the proposed formulation exhibited a good performance in 11 of them.In particular,the proposed law,which was built using blast test data,produced very good approximations of the points representing the vibration measurements and would thus be useful in organising production blasts.However,the developed formula was found to work less well when a correlation obtained for a given site was applied to another presenting similar types of rocks and operations,and thus should not be employed in the absence of measurements from test data.

Comparison of dominant frequency attenuation of blasting vibration for different charge structures

Dominant frequency attenuation is a significant concern for frequency-based criteria of blasting vibration control.It is necessary to develop a concise and practical prediction equation describing dominant frequency attenuation.In this paper,a prediction equation of dominant frequency that accounts for primary parameters influencing the dominant frequency was proposed based on theoretical and dimensional analyses.Three blasting experiments were carried out in the Chiwan parking lot for collecting blasting vibration data used to conduct regression analysis of the proposed prediction equation.The fitting equations were further adopted to compare the reliability of three different types of dominant frequencies in the proposed equation and to explore the effects of different charge structures on the dominant frequency attenuation.The apparent frequency proved to be more reliable to express the attenuation law of the dominant frequency.The reliability and superiority of the proposed equation employing the apparent frequency were verified by comparison with the other five prediction equations.The smaller blasthole diameter or decoupling ratio leads to the higher initial value and corresponding faster attenuation of the dominant frequency.The blasthole diameter has a greater influence on the dominant frequency attenuation than the decoupling ratio does.Among the charge structures applied in the experiments,the charge structure with decoupling ratio of 1.5 and blasthole diameter of 48 mm results in the greatest initial value and corresponding fastest attenuation of the dominant frequency.

The scaling laws of cabin structures subjected to internal blast loading:Experimental and numerical studies

This paper presents a combination of experimental and numerical investigations on the dynamic response of scaling cabin structures under internal blast loading.The purpose of this study is to modify the similar relationship between the scaled-down model and the prototype of the cabin structures under internal blast loading.According to the Hopkinson’s scaling law,three sets of cabin structure models with different scaling factors combined with different explosive masses were designed for the experimental study.The dynamic deformation process of the models was recorded by a three-dimensional digital imaging correlation(DIC)method and a 3D scanning technology was used to reconstruct the deformation modes of the specimen.In addition,a finite element model was developed for the modification of the scaling law.The experimental results showed that the final deflection-to-thickness ratio was increased with the increase of the model size despite of the similar trend of their deformation processes.The reason for this inconsistency was discussed based on the traditional scaling law and a modified formula considering of the effects of size and strain-rate was provided.

Exponential decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast

To investigate decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast,a new exponential decay(ED)law was proposed.The results show that the micro-fracture activity decay law after multistage stress loading and blasting disturbance conforms to the ED model,in which the sum of A and n represents the number of initial micro-fracture events,and n represents the level of background micro-fracture events.The ED model can describe the number of initial micro-fracture events with a deviation less than 10%.The ED model outperforms the traditional aftershock models in describing the micro-fracture event decay law in the three cases considered.The ED model can provide a reference for selecting the blasting interval in mines,which is of great significance to maintain the stability of the surrounding rock and ensure safe production in metal mines.

STRESS AND ENERGY TRANSFER OF WATER COUPLING BLASTING

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浅埋隧道爆破施工近接建筑结构动力响应规律

为了研究上覆建筑物在浅埋隧道爆破施工时的动力响应规律,该文以福州某城市隧道为工程背景,采用现场监测和Ansys/LS-DYNA模拟相结合的方法对上覆建筑群结构响应进行分析。监测结果表明:建筑结构在竖直方向上受爆破影响最为明显且具有高程放大效应,最大振速值为2.45 cm/s;各向振速随爆心距的增大而逐渐减小并趋于稳定,在爆心距较小时衰减较快;竖向振动主频更接近于建筑结构自身频率,主要分布在25~35 Hz区间。数值模拟结果与监测结果相吻合,进一步分析得到:同一测点在Ⅲ~Ⅴ级围岩下最大峰值振速分别为2.29 cm/s、2.51 cm/s和2.79cm/s,地表建筑物振动响应随围岩等级提高而增强;建筑物柱体和板等结构的力学响应与振速变化密切相关,建筑物保护要充分考虑爆破在建筑物中引起的各方向振速。

初始环境压力对RDX基温压炸药冲击波超压和温度的影响

为分析初始环境压力对温压炸药的冲击波超压峰值和温度的影响,在2.6 m^(3)的爆炸罐内开展不同初始环境下不同质量温压炸药的内爆试验,研究初始环境压力对温压炸药冲击波超压峰值与温度的影响.试验结果显示,初始环境压力对冲击波的影响明显,在海拔5 km处产生的冲击波超压峰值衰减率最大.借助Sachs比定律量纲一参数和Hopkins-Brown公式,构建了一个将平原数据推广至不同海拔高度的冲击波入射超压关联模型.进一步分析表明,在相同初始压力下,爆炸温度峰值与炸药量成正比,且随初始压力降低而下降,大药量炸药温度峰值下降程度大于小药量.这些发现对评估温压炸药在高海拔或低气压地区爆炸威力和温度效应评估有着一定的参考价值.

超深竖井爆破掘进围岩损伤规律数值模拟研究

为了分析爆破荷载作用下超深竖井围岩损伤演化规律,基于三山岛金矿西岭副井爆破施工实践,采用数值模拟的方法,基于ANSYS/LS-DYNA重启动技术,根据爆破设计方案,利用等效爆炸荷载方法,分别对四种地应力(15 MPa、30 MPa、45 MPa和60 MPa)和四种侧压系数(1.0、1.25、1.5和2.0)条件下超深竖井爆破掘进围岩损伤进行数值计算;分析竖井围岩损伤效应,研究地应力与侧压系数对竖井围岩损伤范围的影响。数值计算结果表明:随着地应力的增大,损伤区域受到明显抑制作用,地应力从15 MPa增加到60 MPa,损伤区域的半径从5.75 m减小到3.4 m;随着侧压系数的增大,爆破损伤区域体现出各向异性,损伤区域向较大地应力方向集中。研究成果为控制竖井围岩爆破损伤提供理论基础。

会宝岭铁矿爆破振动危害控制研究

随着国民对美好生活的向往,矿山需要更加重视爆破振动给人和建(构)筑物造成的不良影响。基于会宝岭铁矿爆破振动实测数据,利用萨道夫斯基经验公式研究矿山爆破振动衰减规律,分析爆破振动安全距离,确定不同中段开采的允许最大段药量,为矿山的安全开采提供理论依据和指导意见。结果表明:距离工作面1197.21 m之外的房屋建筑不存在爆破振动安全问题,而矿区内保护对象一般离爆源400~500 m,若要达到0.2 cm/s的爆破振动速度,允许最大段药量需控制在200 kg左右。

基于FSWT算法的某露天矿山边坡爆破振动传播规律研究

为掌握露天矿山边坡在复杂条件下爆破振动信号的传播规律,以尖山磷矿边坡测得爆破振动数据为研究对象,采用频率切片小波变换技术(frequency slice wavelet transform,FSWT)、Hilbert−Huang变换(HHT)算法分析爆心距、边坡高程放大效应对振动波能量分布及传播规律的影响。结果表明:爆破振动波在传播距离较近时,能量上升而后会随着时间推移减小,且能量分布不密集;振动波在传播距离较远时,能量上升速度缓慢并且分布相对较集中。边坡底部振动能量主要集中在93.75~125 Hz高频率段且含有大量高频能量,顶部振动能量主要集中在0~46.87 Hz低频率段且含有大量低频能量。1972平台三号机在0~46.87 Hz频率段能量占比平均为69.45%,而一和二号机分别为51.37%、42.55%,前者相较于后两者分别提高18.08、26.9百分点。四号机爆心距比三号机更远,其低频能量大于三号机,但三号机在0~46.87 Hz频率段的能量平均占比相较于四号机提高24.32百分点,高程效应相较于爆心距的影响要更为明显,顶部相对底部高频能量表现为高程衰减效应,顶部相对底部低频能量表现为高程放大效应。

爆破振动对龙首矿露天转地下安全顶柱稳定性影响研究

为了探索爆破振动影响下龙首矿露天转地下开采安全顶柱的稳定性演化规律,结合矿区现状建立了对应的三维数值模型,通过计算获取了安全顶柱最危险截面位置,随后以最上部中段开采为例构建了最危险截面位置的二维数值计算模型。根据爆破参数和等效弹性边界的计算,得到掏槽眼、辅助眼和周边眼传递到开挖轮廓面上的爆破荷载峰值。将爆破荷载等效到开挖面后,开展了针对安全顶柱稳定性的数值计算。结果表明:每段延期爆破都产生了位移和振速峰值,且距离爆破位置最近的安全顶柱内监测点位移最大;以爆破作业位置为中心,振动速度向四周岩体球形扩散。根据爆破振速与岩石损伤判据,安全顶柱总体处于无损伤或轻微损伤状态。此外,最大主应力低于岩体抗拉强度,安全顶柱未形成明显地拉裂破坏塑性区。总体上来说,安全顶柱的设计厚度能够满足露天转地下开采需要。然而与数值模型相比,实际地质条件更为复杂,随着开采继续,仍需观察和监测安全顶柱的变化,从而确保其稳定性。

掏槽孔爆破作用下隧道掌子面应力传播与衰减规律研究

为明晰掏槽孔爆破作用下隧道掌子面应力传播与衰减规律,借助爆破试验分析隧道掌子面在掏槽孔爆破作用下水平方向、竖向和斜向的振动速度变化规律,同时采用ANSYS/LS-DYNA模拟掏槽孔爆破作用下隧道围岩同一截面内应力传播特点。研究结果表明:隧道掌子面边缘测点振动速度大于距爆源近测点振动速度,最小爆源距测点振动速度大于中间位置测点振动速度;隧道掌子面的拱顶和拱肩位置振动速度较大,上部测点振动速度大于下部测点;隧道掌子面应力主要集中在水平方向和竖向,纵向应力较小,水平方向和竖向应力变化时刻主要集中在0~5 ms,水平方向应力传播范围更广;隧道掌子面炮孔下方测点应力大于同爆源距上方测点。相关结论可为类似隧道动力响应分析提供参考。

地铁隧道下穿既有老旧建筑物的爆破振动传播规律

[目的]国内外对于地铁隧道下穿既有老旧建筑物爆破施工的研究较少。此类工程采用爆破开挖时,可能会影响临近建筑物的安全,需要掌握爆破振动的传播规律,并分析爆破振动对周围建筑物的影响。[方法]以重庆市轨道交通10号线二期工程的南坪站—南滨路站区间隧道爆破施工为案例,在隧道爆破开挖过程中对爆破振动进行了监测。通过爆破振动仪得到了爆破振动监测数据,并使用萨道夫斯基公式对实际的爆破振动监测数据进行回归分析,得到了爆破振动的传播衰减规律,讨论了振动速度、最大段装药量、爆心距等各因素对爆破振动的影响。[结果及结论]3个测振方向的爆破振动速度同爆心距、装药量的回归拟合结果中,计算数据与监测数据的相关性系数均大于0.800。爆心距从0增至40 m时,最大段装药量的增幅较小。爆心距为40~80 m时,最大段装药量的增幅明显增大。垂直于隧道底板方向随爆心距增加的变化幅度最大,应重点关注该方向爆破振动安全控制速度为1.0 cm/s时的最大段装药量取值。

采矿爆破振动主频率在岩溶区衰减规律现场试验研究

为减小岩溶区采矿爆破施工中振动产生的地表塌陷灾害影响,文章根据岩溶区矿山爆破振动现场实测数据,采用傅里叶变换及回归分析方法,对比分析塌陷区与非塌陷区爆破振动主频率的衰减规律,以讨论岩土体性质、震中距及爆破药量对爆破振动主频率特性的影响。结果表明:岩土体性质对爆破振动主频率存在较大影响,表现为结构愈松散、孔隙度愈大、密实度愈小,其爆破振动主频率和振动能量衰减得愈快;同一次爆破中,在塌陷区外及塌陷回填区内,所获得的振动主频率随其震中距的增加而呈减小趋势,而在塌陷区内,并非严格衰减,出现波动现象,略有上升趋势;在塌陷区与非塌陷区,爆破振动主频率随着震中距和药量的增加而减小;在同一振动荷载作用下,爆破振动主频率在塌陷区的衰减速度明显大于非塌陷区,且爆破药量在塌陷区内对爆破振动主频率衰减速度的影响更大。

关于一维双曲方程组解的爆破机制探讨

从守恒律出发,以一维Burgers方程为例,详细叙述一维守恒律激波的形成,随后从方程解的显式表达式上结合特征线来具体分析解的爆破机制,最后给出两类守恒律方程解的爆破问题的证明.

截面短长轴比对椭圆钢管混凝土柱抗爆性能影响

目的 研究椭圆钢管混凝土柱抗爆性能,分析截面短长轴比对其抗爆性能的影响。方法 利用LS-DYNA有限元软件建立TNT炸药-空气-椭圆钢管混凝土柱-刚性地面整体三维实体有限元模型,分别从短轴和长轴两个方向进行起爆设置,探究椭圆钢管混凝土柱受爆炸荷载作用后冲击波传递特性。结果 与双向刚度相同的柱子相比,椭圆钢管混凝土柱抗爆冲击波反射、衍射作用更为复杂;椭圆钢管混凝土柱沿长轴迎爆的抗爆性能明显优于沿短轴方向;绘制短长轴比-柱中侧向位移曲线,根据短轴方向与长轴方向抗爆性能差异,提出了设计宜采用的短长轴比为0.6~1.0;沿短轴向施加爆炸荷载时,短长轴比设计值不应小于0.4。结论 得出了不同短长轴比下构件破坏形态,进一步提出了采用短长轴比0.4~0.6内的椭圆钢管混凝土柱时,应采取加固措施。

裂隙岩体精细化数值模型构建与爆破模拟

裂隙岩体爆破数值模拟过程中,裂隙分布模型的真实性,是影响数值模拟结果的关键因素之一,现有节理裂隙构建方法难以实现三维分布上的复杂表征或是实现操作过于繁杂。为探索在LS-DYNA软件中构建三维分布上真实、复杂表征的节理裂隙模型简单可行的操作方法,通过MATLAB软件对爆破数值模型K文件进行解析重组,按照节理裂隙三维分布规律进行勾勒并赋予节理裂隙材料本构,构建出符合节理裂隙分布规律的节理岩体三维精细化数值模型。以某露天石灰石矿山为实例,开展节理裂隙三维分布规律统计分析并在台阶爆破数值模型中进行还原,基于裂隙岩体精细化数值模型,开展露天台阶爆破数值模拟试验和现场爆破试验对比研究。结果表明:采用解析重组方法构建的数值节理模型与实际节理裂隙的误差小于13%;节理裂隙面使岩体内的损伤分布规律发生了变化,与完整岩体相比,损伤范围增加了12.04%,粒径处于0~100 mm的占比降低了8.11%;爆破模拟得到的损伤结果与现场破碎效果接近,统计粒径在0~100 mm之间的碎块的占比,误差为4.16%。解析重组法构建三维节理裂隙,可行、操作简便,数值模拟结果接近实际。

隧道内部爆破振动传播规律与降振技术研究

目前隧道施工普遍应用矿山法,爆破振动对隧道内围岩、支护结构的影响及其灾害控制一直是热点问题。为研究爆破振动在隧道内部的传播规律,以某软弱围岩隧道为工程背景,分别对错距三台阶齐爆和分爆的振动信号进行现场监测。采用萨道夫斯基公式非线性回归、Fourier变换方法对测试数据进行分析和研究。结果表明:对于隧道同一断面,拱顶具有振动速度大、振动主频高、衰减速度慢的特点;三台阶间采用100 ms延时爆破时,可以实现爆破能量在时空分布上的离散,振动叠加效应明显减弱。设计单孔爆破试验,掏槽区域中间设置试验孔,试验孔与整个爆破网络的延期设置为100 ms获取单孔振动波形,基于线性叠加原理,计算不同延期时间下掏槽爆破合成振动波形来优选微差延期时间。结果表明:孔间延期时间在4~7 ms时,掏槽爆破引起的峰值振速急剧下降,干扰降振的效果明显,延时超过7 ms后,峰值振速无显著差异;掏槽孔延期时间取7 ms时减振效果最佳,将最佳延期时间应用于现场爆破,取得了良好的降振效果。