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黄金科学技术, 2021, 29(2): 218-225 doi: 10.11872/j.issn.1005-2518.2021.02.119

采选技术与矿山管理

充填体室内单轴压缩试验声发射指标特性分析

卢蓉,1,2,3, 马凤山,1,2, 赵杰3, 郭捷1,2, 顾金钟4, 黄业强4

1.中国科学院地质与地球物理研究所,中国科学院页岩气与地质工程重点实验室,北京 100029

2.中国科学院地球科学研究院,北京 100029

3.山东黄金集团有限公司深井开采实验室,山东 莱州 261400

4.金川集团有限公司,甘肃 金昌 737100

Analysis of Acoustic Emission Index Characteristics for Indoor Uniaxial Com-pression Test of Backfill

LU Rong,1,2,3, MA Fengshan,1,2, ZHAO Jie3, GUO Jie1,2, GU Jinzhong4, HUANG Yeqiang4

1.Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China

2.Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China

3.Deep Mining Laboratory of Shandong Gold Group Co. ,Ltd. ,Laizhou 261400,Shandong,China

4.Jinchuan Group Co. ,Ltd. ,Jinchang 737100,Gansu,China

通讯作者: 马凤山(1964-),男,河北吴桥人,研究员,博士生导师,从事地质工程与地质灾害研究工作。fsma@mail.iggcas.ac.cn

收稿日期: 2020-07-06   修回日期: 2020-11-18   网络出版日期: 2021-05-28

基金资助: 国家自然科学基金面上项目“深部矿山胶结充填体与围岩接触带力学行为及变形机理研究”.  42072305
国家自然科学基金重点项目“海底采矿对地质环境的胁迫影响与致灾机理”.  41831293
国家自然科学基金面上项目“金属矿山地下采动引起的竖井变形破坏机理研究”.  41772341

Received: 2020-07-06   Revised: 2020-11-18   Online: 2021-05-28

作者简介 About authors

卢蓉(1988-),女,甘肃金昌人,博士后,从事工程地质与岩土工程研究工作lurongwowo@163.com , E-mail:lurongwowo@163.com

摘要

随着浅部矿产资源开采殆尽,采矿活动逐渐转向深部。充填法开采作为现阶段维持矿山稳定的最有效方法,在国内外各大矿山得到了广泛应用。随着充填法的不断完善,充填体的力学行为特点引起了广泛关注。以充填体力学行为为研究对象,通过室内岩石力学试验并结合声发射监测手段,对不同倾角的预制裂隙影响下,强度在35 MPa以内的充填体试块变形破坏行为进行分析。本次共开展了5组单裂隙压缩试验,裂隙倾角分别为0°、30°、45°、60°和90°。试验结果表明:90°竖直裂隙的充填体试块脆性特点明显,而塑性程度较其他裂隙试块低;裂隙倾角对充填体变形影响很大,预制裂隙倾角较小的充填体试块整体发生拉张型破坏,而预制裂隙倾角较大的充填体试块整体呈拉剪型破坏。

关键词: 充填体 ; 单轴压缩 ; 声发射 ; 信号拾取 ; 拉张型破坏 ; 拉剪型破坏

Abstract

As the shallow mineral resources exhausted,deep mining is the general trend for global mining engineering. Backfill method is widely used in metal mining engineering which control the mine stability. With the improvement of the method,the mechanical behavior of backfill is attracted extensive attention. This article analyzed backfill mechanical behavior based on the experimental test.Combined uniaxial compression tests with acoustic emission monitoring,backfill samples with pre-existing crack were tested.Five groups backfill samples were tested and all samples with strength within 35 MPa. Five groups sample with dips of 0°,30°,45°,60°,and 90°,represented five fractures distribution.The results show that backfill sample with 90°-dip fracture demonstrated more obvious brittleness and less plasticity than other samples.Acoustic emission signals could represent fractures initiation and development of backfill samples.Acoustic emission locations have their characteristics in five groups backfill samples. Initially,acoustic emission of backfill sample with 0°-dip fracture located near the pre-existing fracture,and then develop to the other parts of sample.While for backfill samples with other four dips fractures,acoustic emission mainly concentrated near the pre-existing fractures from initial stage to failure.For acoustic emission monitoring,some parameters could demonstrate the me-chanism of fractures propagation.In this article,three parameters were analyzed,they are AF,RA,and lg(AF/RA),respectively. AF represented the tensile fracture propagation,RA represented the shear fracture propagation,and lg(AF/RA) could reveal the overall fracture development.The process of backfill compression is divided into eight stages,namely crack closure,line elastic deformation,micro-crack initiation,stable micro-crack growth,micro-crack coalescence,unstable micro-crack growth,macro-crack coalescence,and failure. Finally,the results show that the dip of pre-existing crack has large influence to backfill deformation and failure according to these three parameter analysis. AE value of the backfill sample with 0°-dip fracture is high in whole deformation process,and RA value remains low and waves in small range. The change of AE and RA value showes shear and rupture in particles is not obvious,and initialed and developed fractures are major tensile.Based on this parameters changed,other four samples parameters values were analyzed,and backfill samples with 30°-dip and 45°-dip fracture are similar to backfill sample with 0°-dip fracture,and backfill samples with 60°-dip and 90°-dip fracture are different.Finally the research come to a conclusion that samples with small dips of pre-existing crack failed by tensile cracks,and samples with large dips of pre-existing crack failed by tensile-shear cracks.

Keywords: backfill ; uniaxial compression ; acoustic emission ; signal pick-up ; tensile crack ; tensile-shear crack

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本文引用格式

卢蓉, 马凤山, 赵杰, 郭捷, 顾金钟, 黄业强. 充填体室内单轴压缩试验声发射指标特性分析[J]. 黄金科学技术, 2021, 29(2): 218-225 doi:10.11872/j.issn.1005-2518.2021.02.119

LU Rong, MA Fengshan, ZHAO Jie, GUO Jie, GU Jinzhong, HUANG Yeqiang. Analysis of Acoustic Emission Index Characteristics for Indoor Uniaxial Com-pression Test of Backfill[J]. Gold Science and Technology, 2021, 29(2): 218-225 doi:10.11872/j.issn.1005-2518.2021.02.119

矿体开采工程中,矿体开挖不可避免地破坏了原岩应力平衡,使得采空区围岩应力重新分布,产生局部应力集中和地压问题,进而导致采矿顶板冒落和矿柱失稳等。近年来,随着无轨化机械设备的广泛应用,充填开采技术得到了快速发展。当前我国充填采矿工艺基本趋于成熟,甘肃金川镍矿的尾砂胶结充填、凡口铅锌矿全尾砂高浓度胶结充填和招远金矿的全尾砂高水速凝固化胶结充填均取得了成功。

随着矿山充填采矿法的应用比重逐步提高,充填体力学特性也得到了广泛关注。很多学者针对不同矿山的充填体进行单轴压缩、三轴压缩和剪切抗拉等试验,对充填体相关的岩石力学参数进行判断(邓代强等,2007a2007b刘志祥等,2006李庶林等,1997Ercikdi et al.,2009Wu et al.,2014)。考虑到充填体材料对充填体力学性质的影响,Cui et al.(2015)通过理论分析与数值模拟等方法分析了THMC多场作用下充填体早期强度的变化规律。曹帅等(2015)Fall et al.(2007)考虑到充填过程的差异对充填体力学性能的影响并开展了试验分析,对不同填充次数的胶结充填体进行了单轴压缩试验,定义了强度折减系数,对充填体的强度进行实用性的修正。徐文彬等(2014)宋卫东等(2016)在侧限压缩条件下初步探讨了充填体和岩柱的相互作用,指出充填体对岩柱破坏具有较好的限制作用。除了对充填体进行室内试验和理论分析之外,大量的数值模拟与统计学分析方法也应用到充填体的力学研究中(谢文兵等,2004)。宋玉普(2002)史晓鹏(2015)利用回归计算等方法分析了安庆铜矿的爆破震动对充填体的影响,并提出了控制爆破技术。

充填体属于类岩石材料,对于充填体的力学性能已有较多研究(宋玉普,2002陈升平等,2003李强等,2008),部分学者还对充填体受外荷载出现损伤破裂进行了相关试验(吴政,1995彭向和等,2000Wang et al.,2015)。Sheng et al.(2017)对含裂隙脆性岩体试块进行了力学试验,发现裂隙起裂扩展甚至偏离的现象。Mohsen et al.(2012)利用ISRM建议的方法对岩石材料进行了裂纹扩展压缩试验及声发射监测分析。张波等(2012)分析了单轴压缩下含交叉裂隙混凝土材料试块的力学性能,比较了不同裂隙夹角条件下试块的力学强度。

本文以充填体力学行为为研究对象,通过室内声发射试验监测,分析含不同倾角预制裂隙的充填体试块的变形破坏情况,研究裂隙分布对充填体破坏过程的影响。

1 矿山充填体概况

经过多年开采,多数金属矿山已经形成了体积较大的充填体。在矿山开采工程中,充填体逐渐成为一种大尺度、人工构筑的地下受力结构,除了自身的重力外,还需要承担上下盘、顶底板传递来的应力,因而易产生破坏(图1)。通过分析,矿山胶结充填体中普遍采用的材料为棒磨砂、戈壁砂和水泥等。所形成的充填体基本强度为5~35 MPa。

图1

图1   充填体破坏现象

Fig.1   Failure phenomenon of backfill


2 室内试验介绍

在室内对充填体试块进行单轴压缩试验,并配以声发射监测。根据充填体特点选定棒磨砂作为骨料,以水泥作为胶结剂。试验样品尺寸设计为150 mm×200 mm×100 mm,利用岩石力学试验机对试样进行单轴加载,分别在样品两侧的顶部和底部设置声发射传感器。试验中制备了不同配比的充填体试样,共进行20组样品的试验,分析不同强度充填体的力学及声发射特性。在矿山开采过程中,部分特殊关键部位会通过提高局部充填体强度来增加其支护效果,因此本次分析强度较高的充填体样品,完整试样是以水泥、砂和水按照5∶5∶2的质量配比进行混合,经固结硬化制成的。对试样进行预制裂隙的切割,最终形成不同倾角的裂隙,如图2所示,裂隙倾角分别设置为0°、30°、45°、60°和90°。

图2

图2   不同预制裂隙倾角下充填体试块破坏情况

Fig.2   Failure condition of backfill samples under different prefabricated crack inclination angles


充填体试块单轴压缩强度结果如图3所示。由图3可知,充填体强度范围集中在20~35 MPa之间,这是根据国内外各大矿山充填体强度范围(一般在数兆帕到数十兆帕之间不等,部分特殊位置充填体强度会加强)进行确定的。根据强度等级划分,本次试验中充填体强度在实际工程中属于强度较高的充填体,将试验中充填体强度作为研究区充填体强度的上限进行极限分析。由图3可知,5种倾角裂隙分布对岩体试样的强度影响明显。其中,90°竖直裂隙的充填体试块应力曲线在后期基本呈现为直线下降趋势,在应力下降过程中,几乎没有产生应变,整体应变量相较其他裂隙样品的应变量小很多,其应力—应变曲线的峰后特点与矿山脆性围压相似,并且在试验过程中虽未发生崩块破坏现象,但破坏的突发性较为明显,故相较于其他裂隙样品,该充填体试块脆性特性明显。其他裂隙倾角对充填体试块的塑性影响程度较小。

图3

图3   充填体试样应力—应变曲线

Fig.3   Stress-strain curves of backfill samples


3 试块单轴压缩声发射信号分析

3.1 单裂隙声发射定位分析

图4图5均为充填体试块单轴压缩过程中声发射监测定位结果,其中图4为初始阶段的声发射定位,图5为破坏阶段的声发射定位。

图4

图4   含不同预制裂隙倾角的充填体变形过程中声发射监测初始定位图

Fig.4   Initial location of AE signals of the backfill bodies with different prefabricated fracture inclination angles


图5

图5   含不同预制裂隙倾角的充填体变形过程中声发射监测破坏时定位图

Fig.5   Failure location of AE signals of the backfill bodies with different prefabricated fracture inclination angles


声发射定位图显示起始的声发射信号都集中在预制裂隙附近。从预制裂隙附近开始微裂隙起裂扩展,最终分布在试样的整体范围内。同时,不同预制裂隙倾角对于微裂隙的扩展有明显影响,对于含0°裂隙的充填体试块,声发射扩展至试块边界区域,而其他倾角裂隙的声发射事件在预制裂隙区域集中较多,边界处较少。

3.2 单裂隙声发射信号拾取

在岩体单轴压缩试验过程中进行的声发射监测,声发射信号参数AF、RA和lg(AF/RA)是反映岩石破坏特征及差异性的重要参数。

通过大量的试验分析可知,在岩石损伤破坏的过程中拉伸型裂隙产生时声发射信号AF值较高,而声发射信号RA值较低。与之相反的是,剪切型裂隙产生时声发射信号AF值较低,而声发射信号RA值较高。AF和RA参数分别用于判断试样的拉裂隙、剪裂隙的产生和分布情况,但试样中拉裂隙和剪裂隙在一定情况下同时发生,并对试样产生破坏,仅通过AF和RA参数不能够反映试样的变形破坏程度。因此引入一个更为综合的判断指标lg(AF/RA),由于拉伸型裂隙的lg(AF/RA)值比剪切型裂隙的lg(AF/RA)值高,因此引入lg(AF/RA)指标可以较全面地对岩体裂隙发育进行评价,通过lg(AF/RA)指标与AF和RA共同分析岩体变形破坏模式(陈炳瑞等,2020)。

根据大量试验分析结果,通过声发射监测信号将岩体及类岩石材料试块的破坏划分为8个阶段,分别为裂隙闭合阶段、线弹性阶段、微裂隙起裂阶段、微裂隙稳定扩展阶段、微裂隙贯通阶段、微裂隙不稳定扩展阶段、宏观裂隙贯通阶段和最后的破坏阶段。通过声发射监测信号的对应分析,基本能够判断各阶段充填体试块的裂隙发展特点。

图6(a)是含0°裂隙充填体试块的声发射参数变化图。由图6(a)可知,AF值在整体试块变形破坏的过程中保持高值并且波动剧烈,而RA值则较低,仅在微裂隙起裂阶段前后出现突然增大,说明含0°裂隙充填体试样整体破坏过程中颗粒间的剪切错动不明显,整体裂隙以拉张型裂隙为主,剪切裂隙发育有限,整体破坏呈拉张破坏。与含0°裂隙试块相比,含30°裂隙充填体试块整体的RA值突增阶段位于试块产生破坏的后期,并伴随着AF值与lg(AF/RA)值的减小,说明后期阶段剪裂隙有发育,但整体破坏仍然以拉张型破坏为主[图6(b)]。含45°裂隙充填体试块整体的参数分布与含0°裂隙试块较为相似,但RA值没有出现大的波动,说明仅有小部分的颗粒出现剪切作用,但并未形成剪切裂隙,充填体试块呈现拉张型破坏,几乎没有发育剪切裂隙[图6(c)]。

图6

图6   含不同预制裂隙倾角的充填体变形过程中声发射监测AF、RA和lg(AF/RA)参数变化

Fig.6   AF,RA,lg(AF/RA) curves of backfill bodies with different prefabricated fracture inclination angles


与上述3个倾角裂隙分布的试块相比,含60°和90°裂隙的充填体试块最大的特点就是RA值增大并持续在较大的范围内波动,说明剪切错动剧烈,如图6(d)和图6(e)所示。60°裂隙分布的充填体试块前期的剪切特点并不明显,当岩体进入微裂隙扩展阶段时,AF值和RA值均增大,说明该阶段拉张型裂隙和剪切型裂隙共同发育,试块整体呈拉剪破坏。虽然90°裂隙充填体试块的整体破坏也呈现出拉剪破坏,但裂纹扩展的演化是不同的,体现在前期试块内部的微裂隙闭合阶段,颗粒间的剪切活动非常剧烈,持续至微裂隙起裂阶段后,RA值出现突降,并在一段时间内保持低值,说明在微裂隙扩展阶段以拉张裂隙发育为主,到后期才又重新出现拉剪共同作用的现象。

4 结论

(1)充填体试块单轴压缩强度集中在20~35 MPa之间,裂隙倾角对岩体试样的强度影响明显,含90°裂隙的充填体试块表现出明显的脆性特点。

(2)大部分充填体试块微裂隙起始阶段声发射事件集中分布于预制裂隙附近,只有含0°裂隙的充填体试块声发射事件扩展至试块边界区域。

(3)预制裂隙倾角较小(0°,30°,45°)的充填体试块整体发生拉张型破坏,而预制裂隙倾角较大(60°,90°)的充填体试块整体破坏呈拉剪型。

http://www.goldsci.ac.cn/article/2021/1005-2518/1005-2518-2021-29-2-218.shtml

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