矿柱及围岩对采空区破坏影响的数值模拟研究

顶板冒落、巷道底鼓和矿柱破坏是采矿过程中的重要岩石力学问题．开展采空区稳定性方面的研究,对保证矿山持续发展和人民生命财产安全有非常重要的意义．运用岩石破裂过程分析软件RFPA^ZD,采用不同的顶板、底板和矿柱岩性对采空区的破坏过程进行了数值模拟研究．模拟结果再现了采空区从变形到破坏的全过程．结果表明,不同的顶板、底板和矿柱岩性对采空区的破坏过程影响很大．从整个采空区的破坏过程来看,依不同的岩性对比,采空区有不同的破坏特点,微破裂均首先在软弱处产生,并由此扩展以至顶底板和矿柱破坏．     

碎柱破坏过程及其声发射规律的数值模拟

运用一个岩石破裂过程分析ＲＦＰＡ＾２Ｄ系统,对矿柱的破坏过程进行了数值模拟研究,矿柱被看成是非均匀脆性岩石材料。模拟结果再现了矿柱从变形到破坏的全过程及其声发射规律。结果表明,劈裂是矿柱破坏的主要形式,并首先在矿柱表面出现,然后再形成由表及里的破裂扩展直至矿柱最后产生剪切破坏。     

矿柱弹塑性破裂过程数值模拟研究

本文采用 REPFPA分析软件 ,对矿柱的弹塑性破裂过程进行了数值模拟研究。矿柱被看成是非均匀弹塑性材料。分析结果再现了矿柱从微破裂产生到宏观裂纹形成、最后产生失稳破坏的全过程 ,并研究了统计平均强度与极限承载力的关系。结果表明 ,剪切破坏是矿柱弹塑性破坏的主要形式     

矿柱弹塑性破裂过程数值模拟研究

本文采用REPFPA分析软件，对矿柱的弹塑性破裂过程进行了数值模拟研究。矿柱被看成是非均匀弹塑性材料。分析结果再现了矿柱从微破裂产生到宏观裂纹形成、最后产生失稳破坏的全过程，并研究了统计平均强度与极限承载力的关系。结果表明，剪切破坏是矿柱弹塑性破坏的主要形式。     

矿柱及围岩非均质性对采空区破坏过程的影响

顶板冒落、巷道底鼓和矿柱破坏是采矿过程中的重要岩石力学问题.开展采空区稳定性方面的研究,对保证矿山持续发展和人民生命财产安全有非常重要的意义.运用岩石破裂过程分析RFPA2D系统,依据不同的矿柱和围岩非均质性对采空区的破坏过程进行了数值模拟研究.模拟结果再现了采空区从变形到破坏的全过程.结果表明,不同的矿柱和围岩非均质性对采空区的破坏过程影响很大.     

芒特艾萨矿1100矿体矿柱破裂机理

多年来,芒特艾萨矿1100矿体中的横向矿柱破裂一直是个问题,过去总认为破裂是由过高应力造成的。测量表明矿柱应力并不很高,而且,应力监测表明,只要矿柱成为孤立矿柱,应力实际上降低。较低的矿柱应力是矿柱细长的结果.传统的破坏准则不能预测矿柱破裂的开始,而张应变破坏准则成功地预测了破裂的范围和方向。而且还能解释为什么矿柱的破裂随总应力的减少而加剧。使用三种不同的试验技术试验了芒特艾萨矿的岩石,得出的临界张应变值相接近,在确定矿柱破裂机理后,本文提出了一些防止破裂的措施。     

红透山铜矿采场矿柱破裂过程的数值模拟

基于对红透山铜矿采场矿柱破坏形式的现场调研,发现高应力下矿柱破坏形式主要为剥落、劈裂破坏、剪切破坏3种形式。为研究其采场矿柱破坏的力学机制,依据红透山矿采场的实际情况及矿岩分布模式,将红透山矿矿柱分为3种矿岩组合模型。以此为基础,应用基于有限元的数值分析方法,对3种矿岩组合矿柱模型的破裂模式进行了模拟分析。数值计算结果表明：I型矿柱均为矿石,其破坏形式为X型剪切破坏;II型矿柱为矿岩组合,其破坏形式主要为矿柱上部围岩发生破坏,而在矿柱下部矿体仅仅产生一些裂纹;Ⅲ型矿柱为上下围岩中间夹矿,裂纹先在上下2层围岩中产生,继而向中间矿石扩展,直至最后裂纹贯通,矿柱失稳。该数值分析结果可为类似矿山矿柱的设计提供一定的参考依据。     

基于应变能平衡的条带矿柱破裂宽度及其影响因素

条带法回采矿床时,矿柱破裂区宽度是采场稳定性设计的主要依据之一。引入弹性应变能平衡原理,视条带矿层中储存的应变能由体变弹性能、形变弹性能及顶板弯曲弹性能组成,根据开采前后弹性能平衡关系导出矿柱破裂区宽度的计算模型。运用矿柱破裂区宽度计算模型对上横山矿床矿体中的2个矿柱破裂区宽度进行计算,计算结果和相似模拟试验对比分析,得到矿柱破裂区宽度的计算结果分别为10.06 m和12.42 m,与相似模拟试验结果吻合较好。分析了矿柱破裂区宽度计算模型中各参数对矿柱破裂区的影响,矿柱破裂区宽度与矿层高度、矿体埋深及上覆岩层容重成正相关,与矿体抗压强度、泊松比成反相关;增加开采条带宽度,矿柱破裂区宽度先增大后减小。研究结果可为水平及缓倾斜条带矿柱稳定性设计提供一定的理论指导。     

矿柱偏心承载特性与失稳破坏机制研究

荷载重心与矿柱截面形心不重合的偏心承载普遍存在于地下开采工程之中。为揭示矿柱偏心压缩承载特性与失稳破坏力学机制,采用一种模拟偏心压缩的试验装置,开展了5组不同偏心距条件下矿柱轴向压缩试验,得到了偏心压缩时矿柱抗压强度及失稳破坏特征。利用MV-XG280相机监测了加载过程中矿柱表面的散斑图像,结合数字图像相关方法分析了偏心距为1/6矿柱宽度时,其表面位移场与应变场演化过程,研究结果表明：(1)矿柱的抗压强度和弹性模量随偏心距增加呈降低趋势,偏心距越大矿柱越容易达到强度极限而破坏,与均匀压缩相比,偏心荷载作用大大降低了其承载能力;(2)偏心荷载下矿柱的破坏特征为小偏心受压破坏和大偏心受拉破坏。偏心压缩使矿柱受力和力矩的共同作用,表现出偏心距越大整体弯曲变形程度越严重。(3)偏心距为矿柱宽度的1/6时,位移场及应变场反映了试件变形破裂的演化过程,随着荷载的增加,位移场最大位移区域进一步集中,应变场出现明显的局部化带,形成最终导致矿柱破坏的宏观裂隙。     

高应力破裂矿柱阶梯式诱导崩落法回采实践

铜坑矿以采富留贫的方式对92~#矿体进行回采,在高地压应力、多次开采扰动和空区冒落的影响下,预留的大量不规则矿柱大多呈破裂、不完整状态。矿柱群Ⅱ采区是高应力破裂矿柱的典型代表,由于多分层采准工程同时施工,严重削弱了矿柱的完整性,诱发区域性地压活动,大部分采准工程被破坏。针对矿柱群Ⅱ采区采准工程遭地压破坏的情况,通过对地压监测数据、各区域破坏类型进行系统分析,运用原地碎裂爆破技术,对高应力矿柱进行泄压,改善矿柱内部的应力环境,布置阶梯式出矿底部结构,大面积拉底,诱导顶部矿体垮落,实现破裂矿柱诱导崩落,矿石回收率达75%,贫化率为19.5%,取得了良好的开采效果。     

Pillar failure by axial splitting in brittle rocks

An analytical approximate elastic model is presented of the pillar failure mechanism in the case of multiple underground openings in brittle rocks by parallel equidistant vertical splitting cracks forming slabs, which are assumed to buckle. The failure region is considered to be elliptical in shape with the major axis growing as failure proceeds parallel to the minimum applied principal stress. A modified solution for the potential energy loss due to the presence of an elliptical hole in an infinite elastic space was derived in order to account for multiple openings. This solution, which yields the failure initiation stress and the crack spacing, was achieved by inserting configuration correction factors estimated by considering certain limiting conditions. In order to obtain simple approximate formulae and after considering the blast damage effect, equivalent effective circular holes are assumed for the case of square openings and elliptical holes for the case of rectangular openings. Next, the stable mode of pillar failure was formulated based on the observation that the weak inclusion of the axially split rock mass reduces the stresses for some distance inside the pillar. The stable model was obtained first by computing the elastic stresses outside the failure zone using a circular approximation and then applying a stability criterion based on Huber's classical fracture hypothesis. Comparison of the theoretical results with field data concerning a bauxite mine using room and pillar have indicated reasonable agreement. Furthermore, the scale effect exhibited by the strength and the axial splitting crack spacing was predicted sufficiently well by the above model.     

Seismic imaging of rock mass responses to excavation

Three case studies are presented which illustrate rock mass characterization using a combination of tomographic images of spatial variation in seismic p-wave velocity with induced seismicity. In the controlled case of a tunnel excavation, known stress changes and fracturing were successfully mapped using velocity images and the location of induced seismicity. Within a stabilizing pillar in a deep South African gold mine, an active-source velocity image resolved the location of stress concentrations ahead of the mining face, and fracturing around the stope. Velocity images of pre-existing, seismically active faults were also computed by simultaneously inverting the induced seismicity data for velocity structure and hypocentral location. The resulting velocity image was interpreted in terms of the expected deformation and seismic potential along the faults. The potential role of velocity imaging and induced seismicity in validating geomechanical models is discussed, along with a possible strategy for incorporating the technique into an integrated geomechanical investigation of induced seismicity.     

金属矿山阶段嗣后充填采场空区破坏机理

依据和睦山铁矿现场实测资料,证明金属矿山阶段嗣后采场围岩破坏具有明显的间歇性和突发性;对其破坏机理进行了数值模拟分析。结果表明：采场顶部围岩产生卸压圈,受拉伸作用,卸压圈内岩体自重应力通过应力拱传递到矿柱上,导致矿柱应力集中出现剪切滑移破坏;其变形破坏程度受顶板、矿柱围岩稳定性以及二次开采扰动的影响。基于普氏拱理论,以矿柱为研究对象,建立了阶段嗣后采场失稳演化模型,得到了矿柱破坏方式和采场失稳演化过程：矿柱稳定阶段、矿柱大形变阶段、部分矿柱失效以及矿柱整体失效。     

煤柱诱发冲击地压的微震事件分布特征与力学机理

通过建立下保护层中残留孤岛煤柱的结构力学模型,应用力学原理分析了残留煤柱及被保护层煤体中的应力状态,得到煤柱诱发冲击地压具有2种机理：① 在煤柱外围的强剪切区内岩层受剪断裂诱发冲击地压;② 煤体本身破裂所致.这一过程在煤柱区附近表现为微震事件在煤柱区前方50 m开始“停滞”不前,应力出现分区性.研究了煤柱失稳破裂过程中微震事件能量统计曲线与失稳破裂过程的对应关系,得到了煤柱的失稳破裂是由微破裂到局部失稳、由渐变到突变的过程.现场采用深孔爆破和大孔径钻孔对煤柱进行卸压后,微震事件沿工作面倾向方向的分布呈均匀形态,且能量较小,证明了卸压效果十分明显.     

内部填充型矩形开口矿柱承载特性研究

为研究部分充填置换高强度充填材料对矩形开口矿柱力学承载特性的影响。采用中机电子万能试验机和DS5型声发射信号采集系统,对不同开口宽度的矿柱试样开展了单轴载荷作用下破坏全过程的力学承载特性试验,在破坏过程中采用快速相机进行监测和记录,总结了充填高强度充填材料填充矩形开口矿柱的力学承载特性和破坏机理。结果表明：无充填矿柱试样(Ore Pillar Bearing, OPB)和充填矿柱试样(Ore Pillar-Filling Bearing, OPFB)模型试样变形破坏分为孔隙压密阶段、弹性变形阶段、屈服阶段和峰后破坏阶段,与AE振铃计数演化特征同步响应;OPB模型试样b值曲线缓慢下降,而OPFB模型试样b值曲线呈平缓趋势,高强度充填材料能有效改善脆性材料的应变软化现象,且对破坏后残余强度的提升影响最大;OPB和OPFB模型试样抗压强度及弹性模量随着掘充宽度的增加而减小,OPB模型试样由劈裂破坏面转向剪切破坏面,呈现延性向脆性破坏转变,OPFB模型试样呈现出延性破坏。研究可为矿柱的回收和稳定提供科学依据。     

破碎围岩条件下预留矿柱开采对充填体稳定性的影响

为研究预留矿柱开采对其上部充填体稳定性的影响,结合某金矿矿岩赋存条件,采用考虑封闭系数的矿柱开采经验公式,提出开采尺寸为180 m×15 m×20 m（走向长度×高度×宽度）的矿柱开采方案。利用MAP3D软件对590~605 m水平间矿柱开采进行数值分析,结果表明：在一般原岩应力情况下,矿柱完全开采后上部充填体仍保持稳定;在较差原岩应力情况下,矿柱完全开采后上部充填体受压作用明显,可能发生失稳破坏。应用极限平衡方程对矿柱开采经验公式进行修正,提出通过减小采场跨度及加强支护的方式,降低对充填体单轴抗压强度的要求,能保证预留矿柱的安全回采和上部充填体的稳定。研究结果可为其他类似矿山提供设计思路。     

Development of failure acceleration and critical rate during cleaning operations around pillars

Conclusions 1. Examination of the problem of a pillar undergoing softening during creep of the enclosing rock suggests the possibility of the manifestation of failure acceleration and a critical rate of expansion of the working or pillar reduction.2. The critical rate corresponds to attainment of the maximum load by an element located on the boundary of the stability region.3. The range of variation in parameters in which a critical rate exists and varies from zero to infinity in the problem under consideration is small. Although a reduction in rate of face advancement contributes to stable deformation on the whole, therefore, it would hardly be possible to control the failure process in the range of existence of the critical rate due to statistical scatter in the properties of enclosing rocks and pillar. It would be interesting to investigate the range of existence of the critical rate for other problems and working conditions.4. A rational means of preventing dynamic phenomena in pillars consists in converting the central portion to a state corresponding to residual strength beforehand (for example, by camouflet blasting or the injection of a liquid).5. The general conclusions obtained concerning conditions favorable to the appearance of acceleration and critical rate permit a natural extension to problems involving induced seismicity.The authors express appreciation to the Russian Fund for Fundamental Research for their support of this study (Grant 94-05-16447).Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemyh, No. 4, pp. 25–42, July–August, 1995.