Evaluation of the effect of geometrical parameters on stope probability of failure in the open stoping method using numerical modeling

Stress-induced failure is among the most common causes of instability in Canadian deep underground mines.Open stoping is the most widely practiced underground excavation method in these mines,and creates large stopes which are subjected to stress-induced failure.The probability of failure(POF)depends on many factors,of which the geometry of an open stope is especially important.In this study,a methodology is proposed to assess the effect of stope geometrical parameters on the POF,using numerical modelling.Different ranges for each input parameter are defined according to previous surveys on open stope geometry in a number of Canadian underground mines.A Monte-Carlo simulation technique is combined with the finite difference code FLAC3D,to generate model realizations containing stopes with different geometrical features.The probability of failure(POF)for different categories of stope geometry,is calculated by considering two modes of failure;relaxation-related gravity driven(tensile)failure and rock mass brittle failure.The individual and interactive effects of stope geometrical parameters on the POF,are analyzed using a general multi-level factorial design.Finally,mathematical optimization techniques are employed to estimate the most stable stope conditions,by determining the optimal ranges for each stope’s geometrical parameter.

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 advance 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 l：10 and the element mesh was dissected in scanning mode utilizing the symmetry characteristics of the numerical model. Five different advance rates were studied. Parameters, such as the time required to maximum stress, the action time of the available stress, the maximum velocity 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 results from numerical simulation have been validated by tests with physical models.

Evaluation of the use of sublevel open stoping in the mining of moderately dipping medium-thick orebodies

The flow of blasted ore during mining of moderately dipping medium-thick orebodies is a challenge.Selecting a suitable mining system for such ore bodies is difficult.This paper proposes a diamond layout sublevel open stoping system using fan blastholes with backfilling to mine such orebodies.To evaluate the performance of system the relationships between ore recovery and stope footwall dip angle,footwall surface roughness,drawpoint spacing and production blast ring burden were investigated.An ore recovery data set from 81 laboratory physical model experiments was established from combinations of the listed factors.Various modules in a back propagation neural network structure were compared,and an optimal network structure identified.An ore recovery backpropagation neural network(BPNN)forecast model was developed.Using the model and sensitivity analysis of the factors affecting the proposed open stope mining system,the significance of each factor on ore recovery was studied.The study results were applied to a case study at the Shandong Gold Group Jiaojia Gold Mine.The results showed that the application of a BPNN and sensitivity analysis models for ore recovery prediction in the proposed mining system and field experimental results confirm that the suggested mining method is feasible.

Safety analysis of Sormeh underground mine to improve sublevel stoping stability

In underground mines,sublevel stoping is used among a variety of different methods for mining an orebody,which creates large underground openings.In this case,the stability of these openings is affected by a number of factors,including the geometrical characteristics of the rock and mining-induced stresses.In this study,a sensitivity analysis was conducted with the numerical,squat pillar,and Mathews stability methods using the Taguchi technique to properly understand the influence of geometric parameters and stress on stope stability according to Sormeh underground mine data.The results show a full factorial analysis is more reliable since stope stability is a complex process.Furthermore,the numerical results indicate that overburden stress has the most impact on stope stability,followed by stope height.However,the results obtained with Mathews and squat pillar methods show that stope height has the greatest impact,followed by overburden stress and span.It appears that these methods overestimate the impact of stope height.Therefore,it is highly recommended that Mathews and squat pillar methods should not be used in high stope that is divided with several sill pillars.Nonetheless,Mathews method cannot accurately predict how the sill pillar impacts the stope stability.In addition,numerical analysis shows that all geometric parameters affect the roof safety factor,whereas the sill pillar has no significant influence on the safety factor of the hanging wall,which is primarily determined by the stope height–span ratio.

复杂应力环境下胶结充填采矿法进路开采顺序优化

针对复杂应力环境下胶结充填采矿法进路开采顺序合理性问题,以金川二矿区为例,借助数值仿真软件构建三维数值模型,对不同进路开采顺序下应力场、位移场及塑性破坏区进行分析;在此基础上,采用组合赋权与模糊综合评价相结合的方法对进路开采顺序优化,并开展现场工业试验。结果表明:不同走向进路开采顺序和进路开采空间顺序均对开采区域最大主应力、最大拉应力、垂直位移、塑性破坏区以及临近下一采场最大主应力、垂直位移有一定程度影响;采用下盘至上盘、先开采垂直矿体走向进路的开采顺序时,采场整体开采安全性高,且现场试验效果良好。研究结果可为复杂应力环境下胶结充填采矿法进路开采顺序设计与优化提供理论依据。

软破矿岩条件下胶结充填法转分段崩落法研究及应用

金川集团龙首矿西二采区上部中段充填采场发生失稳事故后,采矿方法由下向分层进路式胶结充填法转为无底柱分段崩落法时,面临着软破矿岩条件下覆盖层形成和采场稳定性问题。采用数值计算和现场试验等方法,对这2个关键技术问题进行了研究。数值模拟结果表明,随着崩落法首采分段回采工作的进行,采场复合顶板经历了破坏裂纹萌生、零星散块冒落、拱形批量冒落和柱塞状整体冒落等阶段,当首采分段回采结束时,顶板复合岩层冒落能够为崩落法采场提供足够厚度的覆盖层,且在崩落法采动地压下软破矿岩采场能够保持稳定。现场工业试验表明,在崩落法采场首采分段采用“阶梯式退采均匀扩展采空区+总量控制出矿”的技术方案,能够安全、高效地形成覆盖层,并通过增补“钢拱架+钢筋网+锚杆”的技术方案,解决在崩落法采动地压下维持破碎矿岩采场稳定性的问题,为无底柱分段崩落法在西二采区的扩大应用奠定了技术基础。

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。

白音诺尔铅锌矿下向中深孔分段空场采矿法稳定性分析

针对内蒙古白音诺尔铅锌矿采用下向中深孔分段空场采矿法存在的顶板暴露面积大、采空区高度高、回采过程中需在采空区上部作业的安全风险,采用采空区稳定性分析理论及数值模拟等方法,探究顶板安全厚度及采场稳定性。研究结果表明:当采场跨度为5~30 m时,采空区顶板安全厚度为4~15 m;根据Mathews稳定图及数值模拟分析结果,白音诺尔铅锌矿采场较为稳定,阶段高度50 m,分段高度13 m的采场结构参数及回采顺序较为合理。研究可为相似矿山安全生产提供一定参考。

红岭铅锌矿采场结构参数优化研究

为确定红岭铅锌矿分段凿岩阶段空场嗣后充填采矿法的合理采场结构参数,采用数值模拟的方式对顶板厚度分别为3 m、5 m、7 m和10 m,采场长度分别为20 m、30 m、40 m和60 m的16种工况进行了研究,对比了顶板厚度为3 m情况下各工况的应力、位移和塑性区分布。结果表明:红岭铅锌矿分段凿岩阶段空场嗣后充填采矿法采场顶板厚度3 m,采场长度35 m时,采场稳定性较好。

缓倾斜极厚矿体高阶段采场开采顺序优化

为了平衡缓倾斜极厚矿体高阶段采场的产能与安全,以某铁矿阶段空场嗣后充填采矿法为背景,进行开采顺序优化研究。首先,基于间柱承压理论,得出间柱宽度合理值为14.2~47.2 m。根据采场结构参数,设计间柱宽度分别为15 m、30 m、45 m,即隔一采一、隔二采一、隔三采一,并采用FLAC^(3D)建立矿体模型,对比分析各方案顶板沉降以及间柱稳定性。最后,在数值模拟基础上,综合考虑安全与产能的影响因素,构建基于层次分析与模糊综合评判法的开采顺序判断矩阵,计算得出3种方案的综合隶属度分别为0.86、0.79、0.80,确定间柱宽度15 m(隔一采一)为最优方案。工业试验结果表明,该方案在实现最大化生产能力的同时,可保持采场相对稳定。

充填体下高分段中深孔采场一次成槽技术研究与应用

目的:下向高分段中深孔充填采矿法,作为一种新型采矿技术,主要适用于岩体质量一般至极差的矿体或深部高应力环境中的坚硬矿体开采。其关键技术在于如何快速构建切割槽,为爆破创造自由面和补偿空间。本研究旨在研发一种安全、高效的成槽技术,以提高深部厚大破碎矿体的开采效率。方法:本文提出了“分次成井+单次侧向爆破”的切割槽形成方法。为验证该技术方案的可行性,以三山岛金矿为工程依托矿山,结合数值模拟、理论计算方法,开展了现场工业试验。结果:研究表明,在深部矿岩不稳固且采用充填体构筑人工假顶的情况下,该方法能安全、高效地构建切割槽。结论:该方法不仅显著提升了凿岩爆破的安全性和效率,同时减少了爆破扰动,具有良好的爆破效果和广泛的适应性,为类似矿山切割槽的形成提供了重要借鉴。

分段采矿法采场稳定性分析

研究了分段充填采矿法的动力学原理。针对右江河地区铁矿的开采条件,设计了4种分段开采方案,利用有限元分析软件ANSYS模拟分析了覆岩及副井在分段采矿时的移动及破坏过程。结果表明:在定配比充填体情况下,4种开采方案副井和覆岩都是安全的。

无底柱分段崩落法采场稳定性分析

无底柱分段崩落法是国内外地下矿山广泛采用的采矿方法。长期以来由于受凿岩、装药以及出矿设备的制约,国内矿山大多采用小结构参数的无底柱分段崩落法,所产生的地压问题十分严重,开采效率低。近年来无底柱分段崩落法朝着增大采场结构参数的方向发展,不但有利于改善采场稳定性,同时还降低了生产成本。因此,开展采场稳定性分析有利于实现安全、高效开采。采用三维有限元方法对10 m×10 m、15 m×15 m、15 m×20 m共3种不同结构参数的崩落法采场进行了数值模拟,对进路开挖与矿石回采两个不同过程的巷道顶板竖直位移、主应力进行分析。数值计算结果表明:进路开挖时15 m×20 m与10 m×10 m的结构参数相比较,巷道顶板的竖直位移降低了20.1%,最小主应力下降了约18.8%;开采过程中顶板的竖直位移、主应力值都比进路开挖时小,采场地压得到改善;进路开挖与矿石回采过程巷道顶板的竖直位移和主应力值都随着结构参数的增大而降低。因此,大结构参数能更好地改善采场地压,增强采场稳定性,采用大结构参数的无底柱分段崩落法是安全可行的。

无底柱分段崩落法采场结构参数优化研究

分析了目前崩落法结构参数优化的常用方法及存在问题,采用随机介质放矿理论建立了进路间距优化的数学模型,并推导出崩矿步距的理论计算公式;为了评价结构参数的综合经济技术指标,给出了采场结构参数与采出率和贫化率之间的计算公式;最后,将所提出的方法在矿山进行了实际应用,并与传统的采场结构参数优化方法进行了对比。对比结果表明,所提出的优化方法与实际基本相符。

大冶铁矿缓倾斜挂帮矿开采方法的研究

根据大冶铁矿采用无底柱分段崩落法开采的情况 ,就其挂帮矿倾角缓、一端与露天坑相连的赋存特性 ,提出采用联合开采的方法 :挂帮矿的主体部分采用改进型分段空场法 ,靠近露天坑部分采用无底柱分段崩落法开采。使矿山现行的无底柱分段崩落法作业习惯、管理操作经验和原有的机械设备能得到充分利用 ,提高了矿石回收率 ,增强了生产的安全性。

某锡矿缓倾斜中厚矿体的分段空场嗣后充填采矿法

华南某锡矿体由于倾角缓厚度大,构造变形复杂,矿石无法借助自重实现搬运,且顶板暴露面积大,无轨设备无法进入采场作业;同时采空区面积大,若均采用胶结充填则成本过大。针对以上问题,在采用分段空场嗣后充填采矿法的基础上,对采场中的参数进行结构优化,交替布置矿房与矿柱时,对第一步骤回采的矿柱尽量设计较小的尺寸,嗣后进行胶结充填,同时对第二步骤回采的矿房尽量设计较大的尺寸,嗣后进行非胶结充填,从而解决了矿石无法实现自重搬运、顶板管理困难以及胶结充填成本过大等问题。实践证明:改进后的方案使矿山综合生产能力提高112%,矿石贫化率降低0.5%,每年的充填费用减少540万元,提高了综合生产能力,增强了作业效率,实现了矿体开采安全、高效、经济的技术目标。

分段凿岩阶段矿房法在金岭铁矿的应用

分段凿岩阶段矿房法是金岭铁矿的一种典型回采方法,为了适应不断变化的外界条件,在全矿几代工程技术人员的共同努力下,该采矿法已由最初的低分段发展为后来的高分段,不但为矿山节约了生产成本,还提高了采矿强度、劳动生产率以及作业安全性等矿山技术经济指标。同时也拓宽了阶段矿房法的标准设计方案,具有实践与理论的双重价值。

基于PFC数值模拟的无底柱采场结构参数优化研究

结合大冶铁矿东采车间工程条件，设计了几种无底柱采场结构参数，并运用PFC数值模拟软件，对多个采场结构方案进行模拟分析，根据各方案的矿石回收指标和现场实施的难易程度，推荐采用分段高度12m、进路间距15m、崩矿步距2．0-2．5m的最优采场结构参数组合。同时研究了放矿过程中不同阶段颗粒间接触力的变化规律，详细分析了数值模拟结果回收率偏高和贫化率偏低的原因。

大冶铁矿充填法采场结构参数校核与建议

结合大冶铁矿矿床开采技术条件,对东采-180m水平空场嗣后胶结充填采矿法的采场结构参数进行了校核计算和模拟分析。首先采用力学模型法,将采场顶板简化为简支梁,计算顶板的最大跨度以确定采场结构参数范围,并对矿柱的强度进行计算。其次采用FLAC软件进行数值模拟分析,采用"隔一采一"的开采顺序对矿房和矿柱进行分步开挖,通过对应力分布规律、塑性区和位移变化规律的分析,求解安全系数,并综合开采效率和安全系数等因素,提出了大冶铁矿充填法采场结构参数范围建议。

分段空场法分区回采在芨岭铁矿的应用

甘肃金昌铁业集团公司芨岭铁矿矿体属倾斜中厚矿体。矿山主体采矿方法为分段空场法,分段高度为10 m,采用中深孔爆破回采。多年来矿石回收率一直徘徊在50%左右,贫化率高达29%左右。研究表明,分段空场法在该矿应用时存在下盘废石开挖量大、放矿时下盘矿石残留损失大、顶柱无法回收等一系列问题。针对上述主要问题,采用了分段空场法分区回采工艺。实践表明,分段空场法分区回采可使矿石回采率由50%左右提高到68%～71%,贫化率由29%降低到17%～20%,因而经济效益显著。该工艺可给类似矿山提供借鉴。