岩体的初始损伤对爆破效果的影响研究

根据损伤力学理论，提出了含初始损伤岩体动态损伤本构模型。结合Grady根据破碎能量守则给出的脆性材料动态平均块度尺寸公式，将初始损伤变量引入计算模型，并充分考虑爆炸应力波对岩体的破碎作用和在爆生气体膨胀及渗流压力作用下岩块之间的相互挤压碰撞作用，得出了爆破后的平均块度计算式，同时进行了试验验证。计算和试验结果表明，岩体的初始损伤对爆破效果的影响是非常显著的，但是可以通过改变爆破设计参数控制并利用初始损伤以改善爆破效果。同时还得出了一些有益的结论，对指导工程实践具有一定参考价值。     

爆破漏斗岩石破碎块度实验与仿真

为研究单自由面岩石爆破破坏范围变化以及破碎块度分布规律，首先采用光学折射Snell定律研究爆炸应力波在单自由面的反射规律，进而确定爆破漏斗底半径；然后结合白马铁矿现场爆破漏斗实验，分析不同药包埋深和药包质量条件下爆破漏斗几何特征和岩石破碎块度大小；并采用连续-非连续单元法(CDEM)模拟爆破漏斗形态和岩石破碎块度。研究结果表明：单位药包质量下的爆破漏斗体积以药包比值质量的幂函数型增大，并随药包比值埋深的增加呈现先增加后减小的规律，在比值埋深值为1.01时存在极大值点；爆破漏斗岩石破碎块度随药包质量的增加而减小，随药包埋深的增加而增大，破碎岩块的平均粒径以药包质量的-19/30次方减小，以药包埋深的1.42次方增大。最后，采用验证过的数值模拟方法，再现了三峡工程下岸溪料场宽孔距小抵抗线爆破设计破岩效果，为实际工程岩石爆破块度分析和预报提供参考。     

最小抵抗线对岩石破碎块度影响的能量分析

运用分形理论对台阶爆破块度分布规律进行描述,将断裂力学理论与块度分布规律结合推导了台阶爆破岩石破碎能计算方法.基于相似理论浇筑台阶模型并进行爆破试验,研究不同最小抵抗线条件下台阶爆破岩石块度分布规律、岩石破碎能变化规律,试验结果表明:岩块分形维数随最小抵抗线增大呈线性降低,并且分形维数越小,块度评价指标K80、K越大,...     

深孔台阶抛掷爆破岩石破碎及抛掷机理

为了分析提高抛掷爆破效果,揭示深孔台阶抛掷爆破岩石破碎及抛掷机理具有重要意义。分析了露天矿岩石抛掷爆破采用深孔柱状装药时岩石的破碎抛掷过程和受力特性,通过理论分析和公式推导,揭示了应力波和爆生气体对岩石破碎和抛掷的作用机理。研究结果表明,冲击波作用于炮孔壁周围形成径向裂隙和环向裂隙,爆生气体促使裂缝扩展,并形成破碎块度,剩余爆生气体能量促使破碎岩块沿最小抵抗线方向抛掷。     

冲击荷载下类煤岩组合体能量耗散与破碎特性分析

利用分离式霍普金森压杆(SHPB)对类煤、岩单体及组合体试件进行冲击压缩试验,分析了试件能量耗散与破碎块度特征,通过对组合体煤、岩两组分碎块分别筛分,得到了各自的平均破碎块度,并依据单体试件平均破碎块度及破碎耗能密度与入射能之间的关系,获得了两种组分的破碎耗能密度,探究了两者吸能特性。结果表明:结合面的存在使得应力脉冲在组合体试件与压杆间传播做功过程更复杂,试件耗散能变化与煤单体接近,而小于波阻抗较大的岩单体。煤组分由于受到岩组分变形抑制作用而能量集聚程度更高,破碎耗能密度与破碎程度大于同等冲击强度下的煤单体,破碎过程岩组分的能量转移亦加剧了煤组分的破碎程度;相反,岩组分破碎耗能密度与破碎程度相比岩单体则偏小。复合煤岩体能量集聚程度更高,发生动力灾害所需的能量更低,在对复合煤岩巷道冲击地压和瓦斯突出动力灾害机理认识上及采取防治措施时应注意此特性。     

基于原生节理统计和爆破裂纹模拟的堆石料块度分布预测

 水电工程堆石料爆破级配要求高、块度预测难,以岩体原生节理统计和爆破裂纹模拟为切入点,采用现场调查、室内试验、数值仿真和工程检验等方式,开展堆石料爆破块度分布研究,尝试建立一套堆石料爆破块度预测方法。通过现场调查,绘制研究区域的天然节理分布网络图,建立基于原生节理统计的三维节理岩体模型;通过SHPB试验装置获取岩石在冲击荷载作用下的动力学参数,利用Ansys/Ls-Dyna模拟了爆破裂纹的扩展范围;综合原生节理调查信息和爆破裂纹模拟成果,建立调查区域爆后三维节理岩体模型;利用ANSYS输出模型所有岩块的线–面–体数据并编制Matlab块度计算程序,采用基于爆破岩块第5条最长边的块度预测指标,得到调查岩体的预测级配曲线。工程应用表明,综合考虑原生节理和爆破次生裂纹联合切割作用的堆石料级配预测方法基本符合工程实际,且基于爆破岩块第5条最长边指标的级配预测结果要优于等体积球直径指标的级配预测结果,其在江咀料场级配预测中的整体误差为5.5%。研究可为类似工程的堆石料爆破开采提供可借鉴的级配预测手段。     

节理特性对应力波传播及爆破效果的影响规律研究

建立节理岩体一维分析模型并进行量纲分析,探讨节理特性对应力波传播规律的影响。单节理时,应力波通过节理后出现了明显的延时和振幅衰减,但主频无明显变化;多节理时,随着节理间距及节理数量的增加,透射应力波幅值均有所降低,且节理岩体等效波速随着节理数量的增加而线性减小。采用连续–非连续单元方法(CDEM),探讨节理强度、节理刚度、节理刚度/强度、节理间距、节理倾角等参数对爆破效果的影响规律,并通过平均破碎尺寸、极限破碎尺寸、大块率、系统破裂度及等效损伤因子等指标进行综合评价。计算结果表明:爆破效果随着节理强度(刚度)的降低而逐渐变差,当节理的强度(刚度)达到岩块强度的1/1 000后,更低的节理强度(刚度)对爆破效果的影响不大;当节理强度和刚度取为岩块的1/1 000时,节理间距越密集,爆破效果越差,但节理倾角对爆破效果的影响不大。节理岩体中爆破时,爆破能量被圈闭在炮孔与附近的节理面之间,导致炮孔附近区域过于破碎,而远离炮孔的区域破碎较少;因此,爆区内节理的发育程度与爆破效果之间存在负相关关系。     

孔内双点起爆条件下的爆炸能量传输与破岩效果分析

爆破破岩过程中,起爆方式对爆炸能量传输和破岩效果有着重要影响。从理论上证明两相向传播的爆轰波的碰撞聚能效应,分析孔内双点起爆条件下的爆炸能量传输特征。采用张拉–压剪统计损伤模型计算不同起爆方式下的岩石爆破破碎范围,并结合台阶爆破现场试验对比不同起爆方式下的爆破块度分布规律。结果表明,孔内双点起爆时两束相向传播的爆轰波在炮孔中部发生正碰撞,碰撞点附近的压力大于两冲击波的强度之和,局部破岩能力显著增强。双点起爆条件下炮孔附近岩体的张拉破坏区和压剪破坏区体积均大于常规的孔底、孔口、中间起爆,当改变孔内双点起爆的起爆点位置时,压剪破坏区域体积变化不大,而张拉破坏区域体积有明显的改变。可以通过合理设计起爆点的位置和数量,利用爆轰波、冲击波的碰撞来调整炸药爆炸能量的空间分布,从而显著提高局部爆破破岩能力,以满足不同的工程要求。     

矿山岩石的爆破破碎及爆破飞石问题

矿山岩石的爆破破碎及爆破飞石问题汪一佛（中国建材研究院）中图分类号ＴＤ２３５１前言岩石爆破破碎技术，随着科学技术的发展，破岩方法也日益增多。本文仅介绍有发展前途的方法及矿山爆破飞石造成原因及其预防设施。２国外有发展前途的爆破破碎新方法２．１微波爆破岩...     

深孔爆破成井技术数值仿真分析

深孔爆破成井过程是复杂的物理、化学作用过程，深入分析这一作用过程原理可以为实践提供理论依据。本文利用 ANSYS/LS-DYNA 程序对柱状装药爆破情况下的矿岩内部作用的物理过程进行了数值模拟，进而得到爆破应力波的传播情况、衰减规律以及各区域岩石破碎成因。     

Dynamic fragmentation of microwave irradiated rock

The microwave-assisted rock fragmentation has been proven to be a promising approach in reducing cutting tools wear and improving efficiency in rock crushing and excavation.Thus,understanding the influence of damage induced by microwave irradiation on rock fragmentation is necessary.In this context,cylindrical Fangshan granite(FG)specimens were exposed to microwave irradiation at a power of 6 kW for different durations up to 4.5 min.The damages of the specimens induced by irradiation were quantified by using both X-ray micro-CT scanning and ultrasonic wave measurement.The CT value and Pwave velocity decreased with increase of irradiation duration.The irradiated specimens were then tested using a split Hopkinson pressure bar(SHPB)system to simulate rock fragmentation.A momentum-trap technique was utilized to ensure single-pulse loading on the specimen in SHPB tests,enabling valid fragment size distribution(FSD)analysis.The dependence of dynamic uniaxial compressive strength(UCS)on the irradiation duration and loading rate was revealed.The dynamic UCS increased with increase of loading rate while decreased with increase of irradiation duration.Using the sieve analysis,three fragmentation types were proposed based on FSD,which were dictated by both loading rate and irradiation duration.In addition,an average fragment size was proposed to quantify FSD.The results showed that the average fragment size decreased with increase of loading rate.A loading rate range was identified,where a dramatic reduction of the average fragment size occurred.The dependence of fragmentation on the irradiation duration and loading rate was also discussed.     

Numerical modelling of block size effects and influence of joint properties in multiply jointed rock

Two-dimensional numerical experiments are conducted for investigating the effects of block size and joint properties on the behaviour of multiply jointed rock. The paper explains how the size of the individual blocks controls both the shear strength of the assembly (rock mass) and its deformational characteristics. A closely, jointed rock mass, in which block rotations occur, exhibits a lower stiffness but a higher strength than a rock mass with widely spaced joints. These numerical results are similar to those from reported physical model tests on jointed slabs of a rock model material. The paper shows how parametric studies on a single joint using the Barton-Bandis (BB) formulation are useful for providing information about the response of a jointed rock mass.     

Numerical modelling of block size effects and influence of joint properties in multiply jointed rock

Two-dimensional numerical experiments are conducted for investigating the effects of block size and joint properties on the behaviour of multiply jointed rock. The paper explains how the size of the individual blocks controls both the shear strength of the assembly (rock mass) and its deformational characteristics. A closely jointed rock mass, in which block rotations occur, exhibits a lower stiffness but a higher strength than a roch mass with widely spacedjoints. These numerical results are similar to those from reported physical model tests on jointed slabs of a rock model material. The paper shows how parametric studies on a single joint using the Barton-Bandis (BB) formulation are useful for providing information about the response of a jointed rock mass.     

Prediction of strength and deformability of an interlocked blocky rock mass using UDEC

The accurate prediction of strength and deformability characteristics of rock mass is a challenging issue.In practice,properties of a rock mass are often estimated from available empirical relationships based on the uniaxial compressive strength(UCS).However,UCS does not always give a good indication of in situ rock mass strength and deformability.The aim of this paper is to present a methodology to predict the strength and deformability of a jointed rock mass using UDEC(universal distinct element code).In the study,the rock mass is modelled as an assemblage of deformable blocks that can yield as an intact material and/or slide along predefined joints within the rock mass.A range of numerical simulations of uniaxial and triaxial tests was conducted on rock mass samples in order to predict the equivalent mechanical properties for the rock mass under different loading directions.Finally,results are compared with the deformability parameters obtained by analytical methods.     

Numerical modelling of the effects of joint spacing on rock fragmentation by TBM cutters

The influence of joint spacing on tunnel boring machine (TBM) penetration performance has been extensively observed at TBM site. However, the mechanism of rock mass fragmentation as function of the joint spacing has been scarcely studied. In this study, the rock indentation by a single TBM cutter is simulated by using the discrete element method (DEM), and the rock fragmentation process is highlighted. A series of two-dimensional numerical modelling with different joint spacing in a rock mass have been performed to explore the effect of joint spacing on rock fragmentation by a TBM cutter. Results show that the joint spacing can significantly influence the crack initiation and propagation, as well as the fragmentation pattern, and can hence affect the penetration rate of the TBM. Two crack initiation and propagation modes are found to fragment the rock mass due to the variation of joint spacing. The simulation results are analyzed and compared with in situ measurements.     

柱状节理岩体宏观等效弹性模量尺寸效应研究

以金沙江白鹤滩水电站工程为背景,结合相关的岩石力学试验方法,建立了柱状节理岩体三维离散元模型,对柱状节理岩体进行了三轴压缩试验数值模拟。数值试验研究了六棱柱形柱状节理岩体柱体直径变化、四棱柱形柱状节理岩体柱体边长、节理错距变化对其等效弹性模量的影响。为研究随机柱状节理岩体柱体尺寸对岩体等效弹性模量的影响,提出柱体大对角线长尺寸控制方案,并研究了柱体大对角线长变化对岩体等效弹性模量的影响。通过与现场试验的对比研究,结果表明：随机柱体尺寸控制方案可靠;柱体尺寸的变化对与柱体垂直方向的等效弹性模量影响较大,是主要影响因素;四棱柱形柱状节理岩体错距变化主要对与错距平行的岩体等效弹性模量产生影响,对其它两个方向的等效弹性模量的影响较弱,是次要影响因素。研究结果为工程实践中等效力学参数的确定提供了相关参考。     

广东岭澳核电站爆破开挖岩体损伤特征研究

为控制爆炸荷载作用下岩体的损伤范围,在岭澳核电站二期工程现场进行了爆前、爆后岩体声波测试,得到岩体的损伤范围。以此为基础,根据爆炸荷载作用下岩体损伤发展规律,基于概率形式定义损伤变量,利用有限元程序LS-DYNA和有限差分程序FLAC3D相结合的方法,对现场基岩爆破产生的岩体损伤范围进行数值模拟,并与现场岩体声波实验结果进行比较,确定爆炸荷载作用下岩体损伤门槛值Dcri=0.2,由此得到了岩体损伤范围随装药量的变化规律。结论认为,在柱状装药情况下,岩体损伤范围随装药量的增大而增大;爆炸荷载作用下的岩体损伤区深度小于损伤区半径,二者比例约为1∶3。     

掘进机刀盘滚刀间距对北山花岗岩破岩效率的影响实验研究

掘进机(TBM)开挖隧道过程中,其刀盘上滚刀间距设计的合适与否关系着破岩效率的高低。由于岩石非均匀、非连续、各项异性的特性,使用数值模拟方法研究滚刀破岩过程存在局限性。现场掘进实验主要是针对特定的掘进机做出机械运行参数优化,无法研究不同刀间距对破岩的影响。全尺寸滚刀破岩实验可以人为调整刀间距,且实验中采用大体积岩石可以避免尺寸效应的影响,因此受到了广泛的关注。采用北京工业大学自制的机械破岩试验平台,安装17英寸(432 mm)盘形滚刀,选取尺寸为1000 mm×1000 mm×600 mm的北山完整花岗岩试样,进行了5组刀间距的线性切割试验。实验中采集滚刀三向力,分层收集岩片且对其进行称重。对不同刀间距作用下的平均法向力、平均滚动力和比能进行了分析研究。当贯入度较小时,刀间距对平均法向力和平均滚动力的影响都不明显,随着贯入度的增加,刀间距对平均法向力和平均滚动力的影响增加。对于所有的刀间距而言,增加贯入度会产生更多的岩片,但并不一定会提高破岩效率,对于北山花岗岩而言,当刀间距与贯入度的比值为30左右时,比能值最低,此时破岩效率最高。