Numerical Simulation of Independent Advance of Ore Breaking in the Non-pillar Sublevel Caving Method

The mechanism of stress generation and propagation by detonation loading in five separate independent ad-vance of ore breaking patterns is discussed in the paper. An elastic numerical model was developed using AN-SYS/LS-DYNA 3D Nonlinear Dynamic Finite Element Software. In this package ANSYS is the preprocessor and LS-DYNA is the postprocessor. Numerical models in the paper to actual were 1:10 and the element mesh was dissected in scanning mode utilizing the symmetry characteristics of the numerical model. Five different advance rates were stud-ied. Parameters,such as the time required to maximum stress,the action time of the available stress,the maximum ve-locity of the nodes,the stress penetration time,the magnitude of the stress peak and the time duration for high stress were numerically simulated. The 2.2 m advance appeared optimum from an analysis of the simulation results. The re-sults from numerical simulation have been validated by tests with physical models.

Failure of hanging roofs in sublevel caving by shock collision and stress superposition

Hanging roofs or high hang-ups.a common problem in sublevel caving mining,usually result in a large ore loss and undermine mining safety.This paper analyzed the formation of a hanging roof and showed that increased confining pressure and reduced free surface were its main characteristics.In order to break down a hanging roof,a new method based on shock wave collision and stress superposition was developed.In this method,two blastholes containing multi-primer at different positions are simultaneously initiated at first.By doing this,a new free surface and a swell room can be created.After these holes are fired,a long delay time is given to the next blasthole so that the fragments from the first twohole blasting have enough time to fall down.This new method was applied to three hanging roofs in one production area,and all of them were successfully broken down.Field inspection indicated that almost no damage was caused in the nearby drifts/tunnels due to the new method.In addition,the far field vibrations were found to be smaller than the maximum vibrations induced by some other blasts.

Statistic constitutive equation of top-coal damage for fully mechanized coal face with sublevel caving

Under the action of abutment pressure in front of fully mechanized coal face with sublevel caving(CFSC),top-coal over CFSC deformed.In the process of whole de- formation of top-coal,it changed from continuum elastic mass to non-continuum plastic mass contained fissures,become a loose body.According to its bearing characteristics and mechanical properties,top-coal mass can be divided into four deformation zones along the winning direction of CFSC,i.e.initial stress zone,elastic zone,plastic zone and loose zone.Top-coal in plastic zone located in the post-peak zone of the stress-strain curve for top-coal.With equivalent strain principle of damage mechanics and mathemati- cal theory of statistic,combining the movement law of top-coal,set up a constitutive equa- tion with damage statistics for top-coal in different position in CFSC.The equation illus- trated the mathematical relationship among top-coal bearing capacity,horizontal confining pressure along the winning direction of CFSC and mechanical properties of top-coal mate- rial.The conclusions not only provide a basis for numerical computer simulations on damage deformation and failure mechanism for top-coal,but also further promote the ap- plication of damage mechanics in CFSC.

STUDY ON THE BROKEN-ORE DRAWING DATA MANAGEMENT SYSTEM OF SUBLEVEL CAVING

In order to realize the modernized miningmanagementi the authors. based on the practice of a specified mine, developed the application software of the broken ore drawing data management system for sublevel caving through the study on FOXBASE computer language. This paper elabo-rates the overall conception of this system , indicates the main task which should he completed in this system and introduces its module structure and main functions.

Arrangement of anchor reinforcement in roadway for fully mechanized sublevel caving

Bolting of mining roadway for fully mechanized sublevel caving has been practised successfully in Hebi mining area.It provides a new method for roadway support and settles the problem of support difficulty radically for sublevel caving in Hebi mining area.Where anchor reinforcement holds an important station in roadway support.This article brings forward the arrangement project of anchor based on theoretic analysis.Compared with arranged in the middle of the entry, anchor arranged in the vertex of the entry can reduces the length of anchor,shortens the anchor installation time,and heightens the reliability of anchor installation.

Optimal location of terminal line in sublevel caving face with suspend-shift support in thinner thick-seam

According to the geological and mining technical conditions of No.18128 sub- level caving face with suspend-shift support,the first working face of the working area,the distribution laws of abutment pressure were studied by jointly employing FIAC^(3D) numerical simulations and field tests.With the full consideration of these laws and the service time- limit of the mining district,the optimal location of the terminal mining line,should be 60 m away from the W4-B8 track dip,which was 20 m shorter than the 80 m distance deter- mined according to traditional experiences.The retained coal safety pillar for the protect- ing of dips,already proved by the industrial practice,can not only improve the rate of coal recovery and satisfy the subsequent service requirement for the following working faces, but also decrease the maintaining expenditure and thus increase profits.

STUDY ON PRODUCTION SYSTEM OPERATION REGULARITY OF FULLY MECHANIZED SUBLEVEL CAVING MINING AND SEQUENTIAL OPERATION

According to a lot of practical data in Liujialiang Mine and reliability theory and result of computer simulation, operation regularity of fully mechanized sublevel caving mining production system in the condition of gently inclined complicated geological structure and production shortcomings are found out and reliability of system and output of the working face are predicted finally.

有限回采空间内贫矿资源无底柱分段崩落法低贫损开采方案研究

做好无底柱分段崩落法的贫损控制对于矿山经济效益及环境保护具有重要意义,但当矿床开采条件复杂、矿石品位较低时,矿石贫损控制难度将会大幅增加,在此条件下如何做好矿石贫损控制一直是崩落法开采方向的重要关注点。金川龙首矿西二采区无底柱分段崩落法采场仅可布置4个分段,回采空间十分有限,不利于矿石的贫损控制,加之西二采区矿石品位较低但经济价值较高,因此在开采过程中需要严格控制矿石贫损。针对西二采区的复杂开采条件及贫损控制需求,提出了一种“首采分段总量控制出矿、中间分段低贫化出矿、最末分段低贫化出矿+辅助进路回收残留矿石”的组合式低贫损回采方案。以西二采区为工程背景,设计并制作了一种高仿真度的物理放矿模型并对该方案展开了试验研究。结果表明:即便是在暂时不考虑回收最末分段残留矿石的情况下,该方案可使西二采区崩落法采场的矿石回收率达到75.6%,而废石混入率仅为6.0%,在确保矿石回收率的基础上显著降低了矿石贫化。该方案在现场应用后,实际的矿石回收指标与试验结果基本接近,表明该方案在西二采区有限回采空间内实现了贫矿资源低成本、高质量回收的总体目标。

基于Aegis的无底柱分段崩落法中深孔爆破过程模拟与应用

无底柱分段崩落法因其回采效率高、结构简单、安全性高等优势被广泛应用于地下金属矿开采,其落矿方式常采用中深孔爆破。针对传统无底柱分段崩落法中深孔爆破设计过程繁琐、模拟效果不够直观等问题,开展了基于爆破设计与分析软件Aegis的中深孔爆破过程模拟与应用研究。首先介绍了该软件的模块构成和功能,并梳理和总结了模拟分析流程;其次研究了利用模型边界限制爆破空间以及利用爆炸能量的交错状态校验孔网参数的两项关键技术;最后基于该软件对某地下矿山无底柱分段崩落法中深孔爆破进行了数值模拟。研究结果表明:单排炮孔内爆炸能量集中且充盈了整个爆腔,连续耦合的装药结构以及0.3 kg/t的炸药单耗设计较为合理;临排炮孔间爆腔壁呈相切的状态,可能存在排间能量不足以完全破碎岩体的情况,2.2 m的炮孔排距稍大;预测的多条进路爆破块度质量分布结果均出现大块占比偏高的情况,与现场的工程实践结果一致,并以其中一次爆破后的爆堆照片为例进行说明,其大块率达到了18.03%。结合Aegis软件的模拟结果,分析炮孔排距偏大可能是导致大块率偏高的主要原因。此外还对实验分段的6个开采进路进行了12次爆破试验并加以模拟验证,得到了基本一致的爆破块度质量占比结果,有效佐证了该软件的现场应用效能。

程潮铁矿崩落法开采对上覆岩体变形的影响研究

针对程潮铁矿开展工程地质调查,采用离散元分析软件UDEC建立其二维地质剖面模型,在假设其上部水平矿房未开采的条件下,模拟了程潮铁矿无底柱分段崩落法开采-480m、-500m相邻分段的过程,研究单一分段及相邻分段开采导致的围岩“冒落带、导水裂隙带”的分布规律及范围,探索程潮铁矿单分段矿房开采时其上覆岩体形成的导水裂隙带高度范围y随采长x的变化函数,分析无底柱分段崩落法不同分段矿房开采对于上覆岩体变形及影响机理,为类似开采技术条件矿山安全生产提供参考。

浅孔诱导落矿小分段空场采矿法在某金矿的应用

针对某金矿矿岩节理裂隙发育、矿体稳固性差、采准工程掘进与支护困难、回采安全性差等问题,在局部矿体破碎区域开展了浅孔诱导落矿小分段空场采矿法试验研究,利用矿岩本身的力学特性和受人为工程控制的崩落应力场来崩落破碎矿石。详细介绍了该方法的采场结构参数,采切工程布置、拉底切割和落矿等工艺。现场应用表明:采用该方法开采,采场生产能力达127 t/d,采矿损失率为9.2%,矿石贫化率为14.6%,取得了较好的效果,对于该类矿体的安全高效回采具有一定的借鉴意义。

基于正交试验法的爆破参数优化

为了降低矿石的大块率和贫化率,通过正交试验,利用极差分析方式,研究孔深、边孔角、扇形孔排面倾角三个水平因素对矿石的大块率和贫化率试验指标的影响。经实践证明利用正交试验对爆破参数进行优化,有效改善了地下爆破效果,提高了生产效率,对于大块率和贫化率指标,扇形孔排面倾角是影响最显著的因素。以某金属矿为例,通过优化最终得到最优爆破参数为孔深16m,边孔角55°,扇形孔排面倾角90°,对地下矿山进一步控制大块率和贫化率具有一定的参考意义。

龙岩市非煤矿山顶板事故分析与管理措施

顶板事故在非煤地下矿山事故中占比最多,顶板管理是非煤地下矿山安全管理的重点和难点。统计分析龙岩市2008—2023年共15a的顶板事故情况,总结非煤矿山顶板事故的特点。研究得出,矿井爆破工艺技术水平低及在大暴露空间下进行作业是顶板事故原因。提出改善措施,将中深孔爆破分段崩落采矿法代替空场法,但受到矿石价格影响,该方法成本高,当前可行性低;通过推广应用凿岩台车、撬毛台车等机械工具,严格控制井下采掘作业空间宽度和高度等措施,加强顶板管理,努力实现顶板零事故。

黑山铁矿井下采场切割与回采过渡期损失贫化控制方法

针对黑山铁矿无底柱分段崩落法开采切割与回采过度期矿石损失贫化大的问题,分析了该时期盲区块产生及矿石损失贫化大的原因,认为下水平切割边壁对上水平布孔阻隔作用,生产中单方面考虑切割槽空间补偿作用而增大自由空间,忽略了切割边壁对上水平的后续影响,是造成扇形自由面失效形成盲区块的主要原因。由于大块主要聚集在放出体顶部,随着放矿的进行,大块提前到达眉线,不得不组织下一次爆破,导致二次矿量损失;同时,大块的存在导致其上部覆盖层小块废石沿着块体间空隙先到达出矿口,造成矿石贫化率较大。从消除盲区块与控制矿石损失贫化角度入手,根据上下水平切巷投影情况,明确了每种情况下的过渡关系,并根据上下两水平切割巷位置关系,提出了合理优化切割巷布孔参数及有效消除盲区块的矿石损失与贫化控制方法。通过现场实践,黑山铁矿井下采矿切割与回采过渡期矿石贫化率与损失率分别降低26.2%与29.3%,同时为类似条件矿山生产提供了借鉴。

Rational cutting height for large cutting height fully mechanized top-coal caving

Large cutting height fully mechanized top-coal caving is a new mining method that improves recovery ratio and single-pass production. It also allows safe and efficient mining. A rational cutting height is one key parameter of this technique. Numerical simulation and a granular-media model experiment were used to analyze the effect of cutting height on the rock pressure of a fully mechanized top-coal caving work face. The recovery ratio was also studied. As the cutting height increases the top-coal thickness is reduced. Changing the ratio of cutting to drawing height intensifies the face pressure and the top-coal shattering. A maximum cutting height exists under a given set of conditions due to issues with surrounding rock-mass control. An increase in cutting height makes the top-coal cave better and the recovery ratio when drawing top-coal is then improved. A method of adjusting the face rock pressure is presented. Changing the cutting to drawing height ratio is the technique used to control face rock pressure. The recovery ratio when cutting coal exceeds that when caving top-coal so the face recovery ratio may be improved by over sizing the cutting height and increasing the top-coal drawing ratio. An optimum ratio of cutting to drawing height exists that maximizes the face recovery ratio. A rational cutting height is determined by comprehensively considering the surrounding rock-mass control and the recovery ratio. At the same time increasing the cutting height can improve single pass mining during fully mechanized top-coal caving.

限制性空间内无底柱分段崩落法组合式放矿方案及实验研究

以金川龙首矿西二区上部中段由下向分层胶结充填法转无底柱分段崩落法开采为例,研究了限制性空间内无底柱分段崩落法采场各分段的矿石回采和回收特点,构建了一种以分段为放矿控制单元的组合式放矿方案:第一、二分段采用总量控制方式出矿以确保顶板安全冒落形成覆盖层;第三分段采用低贫化方式出矿以避免无效贫化,实现矿石的高质量回收;第四分段采用正常回采进路低贫化放矿+辅助回收进路截止品位放矿以实现矿石的充分、有效回收。设计并开展了3种不同放矿方案的物理实验,结果表明,本文设计的组合式放矿方案在限制性空间实现崩落法安全高效开采和损失贫化控制方面具有显著优势,可使矿山整体开采经济效益处于较优水平,为后期工程实践提供科学的理论和技术指导。

水平分段综放开采顶煤放出体理论计算模型

水平分段综放开采是急倾斜特厚煤层的主要开采方法之一。水平分段综放开采工作面相对较短,导致顶、底板边壁对放煤规律的影响较大。基于BBR理论,采用Bergmark-Roos (B-R)模型分析了存在倾斜边壁影响时的顶煤运移规律及放出体形态变化机理;建立了水平分段综放开采受顶、底板侧边壁影响的放出体理论计算模型,推导了包含轴倾角参数的放出体边界方程;通过颗粒流离散元数值分析得出了轴倾角参数与边界条件的定量关系,采用物理相似实验数据对理论模型进行了验证,提出了不同煤层倾角范围内的合理分段高度及放煤方式优化建议。研究结果表明:倾斜边壁的存在使得散体顶煤受到更大的横向应力,从而改变了顶煤颗粒运移加速度的方向;近边壁处放煤口两侧散体顶煤递补潜力的差异,导致其运移加速度的大小不同;顶煤加速度大小和方向的改变导致放出体轴线方向偏离重力方向。受倾斜边壁影响,放出体形态在轴线两侧呈现非对称性,与近底板侧相比,近顶板侧放出体受边界影响的程度更大;放出体轴倾角β随着煤层倾角的增大呈线性增大关系。随着不放煤段长度的增大,近顶、底板侧放出体的轴倾角均逐渐趋近于90°。物理模拟试验结果验证了理论模型的准确性;采用“底板单轮、中部多轮”、端头逆序放煤方式可有效利用放出体形态特征,减少近顶、底板侧残煤损失。

复杂开采条件下低品位镍矿安全高效回采方案研究

在龙首矿西二采区上部中段采矿方法由胶结充填法转为无底柱分段崩落法时,矿山面临着覆盖层形成及矿石损失贫化控制等一系列技术难题。首先提出了大体积胶结充填体诱导冒落覆盖层形成方案,分析得出胶结充填体具有较好的可冒性;然后对胶结充填体破碎后的块度分布规律进行了研究,结果表明胶结充填体在破碎过程中不会产生大量粉状物,因此不会造成矿石提前贫化;最后针对崩落法采场仅有的4个回采分段提出一种组合式放矿方案,并对该方案在矿石贫损控制方面的有效性进行了试验验证。将各项研究成果应用于现场生产实践,成功诱导顶板胶结充填体冒落形成覆盖层,在获得良好矿石贫损指标的基础上,使采场产能提升30%,采矿成本降低28%,在复杂开采条件下实现了低品位矿石的安全高效、低贫损及低成本开采。