研究论文 正式出版 版本 2 Vol 9 (3) : 298-304 2018
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旺格维利采矿法矿柱合理尺寸数值模拟
Numerical Simulation of the Reasonable Sizeof the Pillarwith Wongawilli Mining Method
: 2018 - 05 - 16
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摘要&关键词
摘要:摘 要:为回收瓦厂坪铝土矿边角矿体并提高矿井资源回收率,本文基于简支梁、固定梁及两区约束理论,结合FLAC3D数值模拟软件,对瓦厂坪铝土矿采用旺格维利采矿法回收边角矿体时刀间矿柱的合理尺寸进行模拟分析,得出刀间矿柱随采硐数目增加所受垂直应力和塑性区的变化规律。结果表明:较合理的刀间矿柱尺寸为1.0m,1.0m刀间矿柱能够保护当前回采采硐,且靠近工作面的三到四对刀间矿柱部分发生塑性破坏,能起到临时支撑顶板作用。
关键词:关键词:铝土矿;旺格维利采矿法;矿柱宽度;塑性破坏
Abstract & Keywords
Abstract: AbstractBackground, aim, and scope Bauxite is a water-based alumina, the composition of the variable natural multi-mineral mixture, is the most important ore to extract aluminum. Wagang Ping bauxite for the first time in the industry to adopt long-walled fully mechanized mining technology, resulting in some corner of the mine is difficult to arrange the regular mining face for mining. Therefore, the FLAC3D numerical simulation software is used to recover the marginal ore body of the mine by using the Wanggevili mining method. And the purpose is to provide the basis for the mining work of the mine.Materials and methods In this paper, based on the theory of simply supported beam, fixed beam and two-zone constraint theory, combined with numerical simulation method, the size of the inter-pillar pillars with different widths is calculated when the Wagangping bauxite is recovered by Wanggevili mining method Perform a simulation analysis. The results show that the vertical stress and plastic zone change with the increase of the number of mining caves.Results The results show that when the interlayer pillar is 0.5m, the whole plastic shear failure occurs in the mining process of the sixth mining cave, and the pillar is completely broken and can not play the role of protecting the current mining cave And temporary support roof role. When the size of the pillar is 1.0m, the local pressure is still lower than that of the original rock, and the plastic shear and tensile Destruction, and even through the entire pillar, the basic loss of support capacity. And then the two pairs of knife between the pillars of plastic shear damage, but still has a certain ability to support, played a role in protecting the current mining cave and temporary support roof; and set aside 1.5m knife between the pillars, from the mining of the fifth As the number of mining caves increases, the vertical stress of the pillars continues to be maintained at higher stress. After the mining, the pillars are always in the elastic steady state, and the supporting capacity is kept. The roof can not collapse in time, Easy to cause a large area of roof, leaving security risks.DiscussionAccording to the three schemes proposed in this paper, it is a reliable technical means to determine the reasonable size of the castle of the Wanggevili mining method by numerical simulation method, which has a certain guiding effect on the exploitation of the marginal ore body. ConclusionAccording to the structure of the "simply supported beam" and the "fixed beam" structure, the width of the mine is 5m. According to the formula of the small pillar protection pillar, the width of the fault is 19m. According to the constraint theory of the two zones, The theoretical width is 0.91 m. Based on the actual conditions of the Baoshanping bauxite, the numerical simulation method is used to analyze the two schemes of 0.5m, 1.0m and 1.5m. The calculation results show that the scheme of 1.0m is the most reasonable, To ensure that the knife pillars to play a temporary role in supporting the roof, and will not cause a large area of the roof so as to leave a security risk. Recommendations and perspectivesAs the longwall mining residual pillars and irregular blocks and other ore bodies are increasing, the corner ore body recycling problem has become a urgent problem to be solved. This paper has some reference significance for improving the recovery rate of mine resources and optimizing the reasonable width of the pillars.
Keywords: Key words:bauxite;Wongawilli mining method;pillar width;plastic failure
旺格维利采矿法是澳大利亚采矿专家在美国肋条式采矿法的基础上研究出的一种新型房柱式短壁采煤法(任满翊,2004)。以机械化程度高、设备使用量少、生产系统简单、采出率高,可实现采掘统一、工作面布置灵活等特点成为短壁开采中较先进的回采方法(樊克恭等,2016)。我国神东矿区引进该开采方法,先后应用于神东矿区大海则煤矿、大柳塔煤矿和康家滩煤矿(白士邦等,2006)。经过多年的试验和改进,目前旺采技术已经日趋完善。由于铝土矿硬度及其他岩石力学参数与煤相近,故旺格维利式采矿法同样适用于铝土矿。
刀间矿柱是相邻采硐间留设的起临时支撑顶板和辅助连续采矿机工作的小矿柱(彭海兵,2009),该类矿柱宽度根据地质情况一般为0.5~2m,长度一般为连续采矿机机身的长度11m,矿柱宽度越大,支撑能力越强,但采出率也越低。为保证矿段开采过程中的人员、设备安全和增加资源的回收率,必须对旺采刀间矿柱的宽度和塑性破坏情况进行研究。周茂普等(周茂普,2007)对大柳塔煤矿2-2煤层12607旺格维利采区哈拉沟20107L旺格维利工作面矿压显现进行了研究,总结出浅埋煤层工作面矿压显现特点和顶板垮落规律。解兴智等(2011)运用FLAC3D数值模拟软件和现场观测手段,分析了东圪堵煤矿1601连续采煤机短壁工作面,优化了刀间煤柱合理宽度、采区隔离煤柱合理宽度,并对短壁机械化开采两种煤柱留设对比分析。
本文以瓦厂坪矿边角矿体为研究对象,运用简支梁、固定梁理论(李石林等,2014),两区约束理论(韩斌等,2004)等对旺格维利式采矿法刀间矿柱尺寸进行计算。结合数值模拟分析不同宽度刀间矿柱受力和塑性破坏情况(王红胜等,2014),为合理矿柱留设尺寸提供依据。
1   计算模型与计算参数
1.1   工程背景
瓦厂坪铝土矿是中电投贵州遵义产业发展有限公司务川铝矿分公司建设的两个一百万吨铝矿山之一,是黔东北发现的大型铝土矿之一。矿体属大型规模,单层矿体,走向长3300m,最大宽度2850m。由于该矿首次在行业内采用走向长壁综采工艺,导致一些边角矿段很难布置正规综采工作面进行回采。
根据该矿地质条件和边角矿段的特点,采用两翼集中布置和单翼集中布置的旺格维利采矿法。论文研究的边角矿体位于1102工作面切眼至井田边界线范围内,含单一矿层,平均厚度2.2 m。矿体倾角较缓,平均倾角12°,地质构造简单。矿层顶板以泥质灰岩、泥岩为主,伪顶0.7 m,直接顶2.5m,中等稳定。矿层底板为铝土质泥岩,其中伪底1.5m,直接底7.0m,比较稳定。
F2逆断层将边角矿体分为I区、II区两部分,本文研究I区面积12065㎡,估算储量59677t,埋深212~235m,平均埋深221m。如图1所示。


图1   瓦厂坪铝土矿边角矿体区域划分图
Fig. 1 Division map of boundary rebody-pillar
1.2   理论计算
旺格维利采矿法保护矿柱的留设与传统房柱式开采不同,矿柱的留设有其自身的特点,矿柱主要包括区段隔离矿柱、工作面巷道护巷矿柱、支巷口矿柱、刀间矿柱等,鉴于矿柱所起的作用不同,对矿柱尺寸和支撑能力要求也完全不同。
(1)矿房宽度
按“简支梁”理论中岩梁因最大拉应力超过其抗拉强度而破坏的极限跨距为:
(1)
式中,—梁的厚度;—许用正应力;—岩梁承受载荷;
按“简支梁”理论中岩梁因最大拉应力超过其抗拉强度而破坏的极限跨距为:
(2)
比较上述两种计算结果,得到短壁开采矿房宽度极限跨距为6.23m,考虑到安全性原则以及矿井实际条件,最终确定矿房宽度为5m。
(2)断层保护矿柱宽度
由于在边角矿体中有一条逆断层F2,所以在断层和开采区域留设一定宽度的矿柱,起着隔离断层和保护回采工作巷道的作用。根据彭文庆提出在断层倾角小于时保护矿柱合理宽度留设的计算公式:
(3)
式中,—基本稳定点离工作面的距离,可取40~60m;—内摩擦角;—强度比值系数,砂岩为1,砂质页岩为0.7,泥岩为0.5;—岩石的实际厚度;—断层倾角;
代入瓦厂坪相关数据,得到,根据瓦厂坪铝土矿地质条件及其它类似矿井相关设计,断层保护矿柱为19m可满足要求。
(3)刀间矿柱宽度
刀间矿柱宽度的计算首先要确定矿柱所受载荷:
=0.21MPa (4)
式中,—安全系数,取1.5;—载荷集中系数,取1.6;—顶板均布载荷,KN;
刀间矿柱属于无核区条形矿柱,根据两区约束理论,其宽度为:
(5)
式中,—上覆岩层平均容重,25KN/m;—矿柱长度,11m;—上覆岩层厚度,m;
根据上述计算,刀间矿柱理论宽度为0.91m。数值模拟中选取0.5m、1m、1.5m三种方案,通过数值模拟结果确定最终刀间矿柱尺寸。
2   数值模型及结果分析
数值计算模型的建立对于计算的可靠性有着很大的影响,由于FLAC3D自身建模功能的不足以及SURFER、Midas-GTS、ANSYS在三维建模和划分网格上的优越性能,本文使用AutoCAD、SURFER、Midas-GTS、ANSYS进行辅助三维建模(王猛等,2016)。研究区域为铝土矿边角矿体,涉及到的模拟材料均为岩石,故选择摩尔库伦本构模型为数值模拟本构关系。模型设计为230m×170m×282m,共152463个节点和869412个单元,如图2所示。


图2   FLAC3D数值模型图
Fig. 2 Numerical model diagram of FLAC3D
边界条件的确定应力求与现场实际情况吻合,考虑到模型边界效应,将模型X、Y方向的边界面与Z方向底面均固定,即模型X方向两个边界不允许发生X方向位移,Y方向两个边界不允许发生Y方向位移,底面不允许发生Z方向位移。由于数值模型较为准确建立了地表形态,故垂直方向应力由模型各岩层重力生成;由于矿层埋深较浅,侧压系数=1,故水平应力值与边界单元垂直应力值相等,工作面布置方式如图3所示。


图3   旺格维利式回采模型切面图
Fig. 3 Sectional drawing of Wongawilli mining method
2.1   数值模拟参数的确定
因本模型采用Mohr Coulomb本构模型,所需的岩石物理力学参数包括:密度、剪切模量、体积模量、抗拉强度、内聚力、内摩擦角等6个。经过实地钻孔、探槽取样,在实验室测得各岩石样本的物理力学参数。考虑到岩层的尺寸效应、节裂隙发育及风化等问题,实验室测得的参数不能直接应用于数值模拟计算中,因此需要将各个参数进行不同程度的修正,本文应用王永秀等(2003)提出的均匀正交设计方法对岩层参数进行修正,修正后的各岩层物理力学参数见表1。
表1   各岩层物理力学参数Tab. 1 Physical and mechanical parameters of the rock
2.2   模型计算结果分析
由数值模型可知,矿井第一条支巷长71.5m,当留设刀间矿柱为0.5m、1.0m、1.5m时,可分别布置11对、10对和9对采硐。模型分别模拟矿井采用旺格维利式短壁采矿工艺回采第一对至最后一对采硐的情况。为更直观的观察留设不同宽度刀间矿柱的应力和破坏情况,在各方案第五、六采硐间的矿柱上设置监测点,得出各方案监测点处垂直应力随开采深度的变化,结果如图4所示。同时对开采各采硐时刀间矿柱塑性区变化情况进行模拟,结果如图5所示。


图5   开挖第六对采硐时塑性区分布
Fig.5 Distribution of plastic zone in sixth mining excavation
 
(a)0.5 m刀间矿柱
(a)0.5 m knife pillar
(b)1.0 m刀间矿柱
(b)1.0 m knife pillar
(c)1.5 m刀间矿柱
(c)1.5 m knife pillar
根据不同宽度刀间矿柱第五采硐处矿柱垂直应力分布规律图可知:在开挖采硐数为0时,模型原岩应力值为4.12MPa;三种矿柱留设方案在开挖第一到第五对采硐时,刀间矿柱垂直应力分布均呈逐步上升趋势,三者增幅相差不大;在开挖至第五对采硐时,0.5m和1.0m刀间矿柱所受垂直应力达到峰值,分别为6.50MPa和6.82MPa,最大垂直应力分别达到原岩应力的1.58、1.66倍。随着开挖至第六对采硐,0.5m、1.0m刀间矿柱留设方案的矿柱垂直应力出现明显下降,分别达到3.50MPa、5.90MPa,降幅为46%和13%。而留设1.5m刀间矿柱方案在回采第六采硐时垂直应力无明显变化,基本与开采第五采硐时持平。
结合塑性区破坏图可以得出结论:当刀间矿柱为0.5m时,矿柱在第六采硐回采过程中发生全塑性剪切破坏,矿柱随采随碎,完全失去承载能力,不能起到保护当前回采采硐和临时支撑顶板作用。刀间矿柱尺寸为1.0m时,回采第六采硐也发生局部卸压情况,其垂直应力仍比原岩应力大,此时前三对刀间矿柱大部分发生塑性剪切和拉伸破坏,甚至贯通整个矿柱,基本失去支承能力。而后两对刀间矿柱部分发生塑性剪切破坏,但仍具有一定支撑能力,起到了保护当前回采采硐及临时支撑顶板作用;而留设1.5m刀间矿柱,从回采第五对采硐开始,随着开采采硐数量的增加,矿柱的垂直应力仍持续保持在较高的应力情况,说明回采之后,矿柱始终处于弹性稳定状态,持续保留支撑能力,顶板不能及时垮落,易造成大面积悬顶,留下安全隐患。因此可以确定刀间矿柱合理宽度为1.0m。
3   结论
(1)根据“简支梁”结构和“固定梁”结构确定矿房宽度为5m;根据较小倾角断层保护矿柱留设公式确定断层保护矿柱宽度为19m;根据两区约束理论确定刀间矿柱理论宽度为0.91m。
(2)根据瓦厂坪铝土矿的实际条件及刀间矿柱理论宽度0.91m,运用数值模拟方法对0.5m、1.0m、1.5m三种方案进行比较分析,计算结果表明:1.0m刀间矿柱的留设方案是最合理的,能保证刀间矿柱起到临时支撑顶板的作用,且不会造成大面积悬顶从而留下安全隐患。
(3)由于长壁开采后残留矿柱和不规则块段等矿体日益增多,边角矿体回收问题已成为亟待解决的紧要问题。本文对于提高矿井资源回收率及优化刀间矿柱合理宽度有一定的借鉴意义。
致谢
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稿件与作者信息
王 猛1,2,齐特1*,秦洪岩1,邱占伟1
WANG Meng1,2,QI Te1*,QIU Zhan-wei1,QIN Hongyan1
基金项目:国家自然科学基金项目(51174109,51074086)
Foundation Item : National Natural Science Foundation of China (51174109,51074086)
出版历史
出版时间: 2018年5月16日 (版本2
参考文献列表中查看
地球环境学报
Journal of Earth Environment