受载煤体电磁辐射动态非线性特征

为了研究受载煤岩变形破裂过程中电磁辐射动态非线性特征,对不同力学性质的煤样进行了不同加载速率的单轴压缩实验和分级加载实验,发现受载煤体电磁辐射由煤的力学性质、应力水平及加载速率共同决定,煤的强度越高、加载速率或应力水平越大,电磁辐射非线性特征越明显.依据煤的力学性质,受载煤体在变形破裂过程中其破坏前兆信号可以划分为3种类型.应用时变多重分形理论分析了电磁辐射时间序列,结果表明煤岩破裂失稳之前多重分形参数Δαm随载荷的增加呈增大趋势,在破坏后期Δαm有一定程度降低.裂纹扩展越激烈,煤岩内部损伤程度越高,Δfm越小.Δαm,Δfm的动态变化可以用来评价煤岩变形破裂过程及破坏阶段.     

煤岩破坏表面电位特征规律研究

研究了煤岩在单轴压缩、拉伸、三点弯曲等不同破坏方式下的表面电位特征和规律,初步探讨了煤岩破坏表面电位机理.结果表明,煤岩在受载破坏时能够产生表面电位,并且表面电位与载荷具有较好的一致性,二者之间的相关系数在0.6～0.9以上,可达到高度相关;表面电位信号一般随载荷的增加而增强,随载荷的降低而减弱.试样上不同电极处测得的表面电位信号强度是不完全相同的,是随载荷及煤样的破坏状态的变化而变化的.根据表面电位与栽荷之间的相关关系,可以用表面电位信号来反映煤岩受栽破坏的状态.     

预制裂纹岩板破坏电位与电磁辐射特征的实验研究

为了研究预制裂纹岩板破坏电位和电磁辐射变化规律,对不同裂纹倾角花岗岩板进行了不同加载速率单轴压缩实验.结果表明:预制裂纹岩板电位和电磁辐射随载荷的变化而变化,破坏前出现电磁辐射能量峰值和一定的电位峰值,电位和电磁辐射能量增量与变化率一般会出现突变;电位变化幅度及其破坏前均值与距离主破裂的位置有关;预制裂纹倾角越大,载荷峰值越小,其出现时间越早,电磁辐射能量峰值越靠近载荷峰值,破坏前电磁辐射能量均值越低;加载速率越大,电磁辐射能量超前破坏时间越短.电磁辐射能量与电位增量、变化率、标准差、均值、变异系数可以作为研究煤岩破坏前兆特征的指标.     

煤岩力电耦合模型及其参数计算

电磁辐射技术已经在矿山煤岩动力灾害预报中得到了应用，根据煤岩强度的统计理论和损伤力学理论，建立了受载煤岩的力电耦合模型，推导得到了该模型中参数的确定方法，并结合实验结果对其中的参数进行了计算．结果表明：煤岩材料的破坏是内部代表性体元微损伤累积的结果，电磁辐射可以反映煤岩体的损伤程度，力电耦合模型能够较好地描述煤岩变形破裂过程的电磁辐射规律，参数的拟合相关系数较大说明该方法合理可行．     

基于DSCM的岩石蠕变变形场演化试验研究

采用分级加载方式对一种红砂岩试件进行单轴压缩蠕变试验,通过Charge-Coupled De-vice(CCD)相机采集加载全过程的试件表面散斑图像,以白光数字散斑相关方法(DSCM)对分级加载不同阶段试件表面变形场演化及裂隙位移演化进行观测和分析.结果表明:在分级加载过程中,试件的瞬时变形量随着载荷的增加而减小,蠕变变形量随着载荷的增加而增加;低应力水平,试件处于均匀变形状态,不发生蠕变或蠕变量较小;中等应力水平,裂隙产生及裂隙在整个恒载期间未发生蠕变扩展的变形累积阶段;高应力水平,裂隙在恒载初期的变形累积到恒载后期的裂隙稳定蠕变扩展,最终加速蠕变扩展;当岩石试件变形出现裂隙区域后,裂隙的位移错动和位移拉伸直接影响了岩石蠕变位移特征.裂隙的位移错动速率包括减速错动、稳定错动和加速错动3种形式.     

冲击倾向煤破坏断口微观特征及其机理研究

运用扫描电镜观测了冲击倾向煤破坏断口的微观形貌,分析了煤体受载破坏断面的裂纹、孔隙等缺陷特征及裂纹扩展特征,探讨了煤样破坏裂纹扩展途径及其微观断裂机理.结果表明,冲击倾向煤内部含有大量的孔隙裂隙,在其受栽破坏过程中,这些孔隙裂隙均充当了Griffith缺陷,促使大量新裂纹生成和煤样发生破坏.煤样中大量的尖锐孔隙及张性裂隙的微观断面特征表现出冲击倾向煤的脆性特征.由于煤的非均质性及煤样内部应力分布的非均衡性,其裂纹扩展也是不均匀、间歇式的,且裂纹的扩展路线也是曲折的,扩展过程中往往产生分岔、拐折等现象.孔隙、裂纹在应力作用下分岔、扩展、汇合贯通是导致煤体宏观断裂的直接原因.     

三轴压缩下含瓦斯煤体电阻率响应的实验研究

目的 受载含瓦斯煤体变形破裂过程中电阻率的变化规律是电阻率法预测预报煤与瓦斯突出发生的理论基础。因此,研究三轴压缩条件下含瓦斯煤体破裂过程中电阻率的变化规律十分必要。方法 自主研发一套测试低频条件下受载含瓦斯煤体变形破坏过程中电阻率的实验系统,测试三轴压缩条件下含瓦斯煤体电阻率的变化规律,对实验结果进行分析和解释。结果 结果表明：（1）受载含瓦斯煤体的电阻率变化与所受应力存在显著的对应关系,型煤的电阻率变化规律与应力的对应关系要优于原煤的,对应力降低比较敏感;（2）受载型煤的电阻率变化规律为先上升后下降型和下降型,受载原煤的电阻率变化规律仅有下降型;（3）从原煤和型煤的物理力学以及受载过程中的变形破坏类型、受载含瓦斯煤体变形破坏过程中的煤体结构变化情况、煤的孔隙结构以及导电类型3方面分析解释受载含瓦斯煤体的电阻率变化情况;（4）对受载含瓦斯型煤电阻率变化曲线出现的2种类型进行科学合理的解释。结论 研究成果可为电阻率法预测预报煤与瓦斯突出的发生提供技术支撑。     

含瓦斯型煤破坏临界慢化前兆特征研究

针对煤岩破坏前兆信号的有效性,开展了等效围压下的含瓦斯型煤加载试验,采集了加载破坏过程中的声发射信号,基于临界慢化原理计算了声发射计数-时间序列的方差和自相关系数,分析了煤样破坏的前兆信号.结果表明:等效围压下,含瓦斯煤在压缩破裂过程中,声发射累计计数随时间的响应经历了初始活跃期、稳定增长期、加速增长期和峰后衰减期;不同围压-孔隙压力下煤样压缩破裂声发射特征均存在临界慢化现象,声发射计数序列的方差和自相关系数在煤样破坏前均出现了增大并持续增加的趋势,可以作为煤样破坏的前兆信号.相比声发射累计计数所表征的前兆信号,缩短了前兆信号与破坏点之间的时间差,前兆信号对应的载荷也更接近试样所能承受的最大载荷,更加表明试样确实进入危险破裂阶段.     

电磁辐射法预测煤与瓦斯突出原理

研究了瓦斯对电磁辐射（ＥＭＥ）的影响规律及影响机制,对电磁辐射法预测煤与瓦斯突出原理进行了探讨,研究结果表明：煤体变形破裂时,电磁辐射与煤岩体的载荷及变形破裂过程密切相关,煤体中的瓦斯能使电磁辐射增强,瓦斯在煤体中的流动及冲击能产生电磁辐射;电磁辐射强度和脉冲数两项指标综合反映了工作面丧方煤体的突出危险程度,用电磁辐射法预测预报煤与瓦斯突出是可行的,煤岩电磁辐射技术在预测煤与瓦斯突出和冲击地压等方     

动载下层状岩体力学特性试验与数值模拟

为研究冲击载荷作用下层状复合岩体的动态力学性能和破裂机制,基于煤单体和白砂岩构成层状软硬煤岩复合体,利用分离式霍普金森压杆试验装置和LS-DYNA有限元分析软件,结合Holmquist-Johnson-Cook(HJC)本构模型,开展不同速率和不同冲击方向下层状软硬煤岩复合体加载试验。结果表明：静态载荷作用下,层状煤岩复合体的强度不会随加载方向变化,动态载荷下层状煤岩复合体的峰值应力和动态增长因子DIF都随冲击速度增加呈线性增大,并且波阻抗匹配效果更好的HS复合体力学性能始终优于SH复合体(S和H分别代表煤单体和白砂岩),随着冲击速度增加这种现象逐渐减弱;层状煤岩复合体耗散能密度与入射能密度呈二次增长关系,分形维数也随着速度增加而不断增大,其中,应力波由硬入软时得到的效果优于由软入硬;层状煤岩复合体破碎程度随冲击速度增加而愈发剧烈,HS复合体破坏程度大于同条件下的SH复合体,白砂岩多呈剪切状破碎,煤单体多呈粉碎锥形破坏;层状煤岩复合体交界处与其他区域强度不一致,造成复合体破坏顺序改变,复合体整体强度规律从小到大依次为煤单体非交界面区域、煤单体交界面区域、白砂岩交界面区域、白砂岩非交界面...     

Study of electromagnetic characteristics of stress distribution and sudden changes in the mining of gob-surrounded coal face

The incidence of dynamic coal or rock disasters is closely related to the distribution of stress in the surrounding rock. Our experiments show that electromagnetic radiation (EMR) signals are related to the state of stress of a coal body. The higher the stress, the more intense the deformation and fractures of a coal body and the stronger the EMR signals. EMR signals reflect the degrees of concentrated stress of a coal body and danger of a rock burst. We selected EMR intensity as the test index of the No.237 gob-surrounded coal face in the Nanshan coal mine. We tested the EMR characteristics of the stress distribution on the strike, on the incline and in the interior of the coal body. The EMR rule of rock bursts, caused by sudden changes in stress, is analyzed. Our re-search shows that EMR technology can be not only used to test qualitatively the stress distribution of the surrounding rock, but also to predict a possible occurrence of rock burst. Based on this, effective distress measures are used to eliminate or at least weaken the incidence of rock bursts. We hope that safety in coalmines will be enhanced.     

煤矿深部开采地质保障中的综合物探技术应用

在煤矿深部开采阶段,运用综合物探技术开展地质保障丁作,避免煤矿发生矿井地质灾害,建设和谐社会和提高煤矿经济效益意义重大。文章分析了煤矿深部开采中地质灾害与地质风险的地球物理特征,对正确运用综合物探技术和地质灾害防治进行了阐述,简述了采区地震勘探、电法勘探等方法的基本概念与勘探效果,展望了综合物探技术的应用前景。通过勘探实例阐述了综合物探方法在煤矿深部探测中实用性和有效性。     

Chaotic characteristics of electromagnetic emission signals during deformation and fracture of coal

Electromagnetic emission (EME) is a kind of physical phenomenon accompanying the process of deformation and frac-ture of loaded coal and rock and it is of importance in quantitatively analyzing its characteristics. This will reveal the process of deformation and fracture of coal and predicting dynamic disasters in coal mines. In this study, the G-P (Grassberger and Procaccia) algorithm, calculation steps of the (if only 1 dimension) correlation dimension of time series and the identification standards of chaotic signals are introduced. Furthermore, the correlation dimensions of EME and the acoustic emission (AE) signals of time series during deformation and fracture of coal bodies are calculated and analyzed. The results show that the time series of pulses number of EME and the time series of AE count rate are chaotic and that the saturation embedding dimensions of a K3 coal sample are, respectively, 5 and 6. The results can be used to provide basic parameters for predicting of EME and AE time series.     

Controlling the effect of a distant extremely thick igneous rock in overlying strata on coal mine disasters

Based on theoretical analysis, similarity simulation tests, numerical simulation analysis and field observations, we analyzed rock collapse and rules of fraction evolution of overlying rocks and studied the rules in controlling the effect of an extremely thick igneous rock, found above a main mining coal seam in an area prone to coal mine disasters in the Haizi Coal Mine. The results show that this igneous rock, called a "main key stratum", will not subside nor break for a long time, causing lower fractures and bed separations not to close. The presence of igneous rock plays an important role in rock bursts, mine floods, gas outburst and surface subsidence in coal mines. By analyzing the rules in controlling the effect of this igneous rock, we provide useful references for safety and high efficiency mining in coal mines under special geological conditions.     

Gas-dynamic phenomena caused by rock mass tremors and rock bursts

Similar to coal, rock and gas ejections, rock mass tremors and rock bursts are among the most serious natural hazards accompanying the underground extraction of coal. Gas-dynamic phenomena caused by rock mass tremors and rock bursts observed as transient states of air parameters in mining headings,are usually generated as a result of a change in the geometry of headings and the release of considerable amounts of gases. Particular significance is attributed to transient states caused by disasters, which are often accompanied by rapid incidents, presenting threats to the life and health of the underground crew.In Polish mining there are known examples of transient states of air parameters recorded during gasdynamic phenomena, e.g. tremors and rock bursts. The paper presents the case studies of rapid seismic incidents to show how records in mine monitoring systems broaden the knowledge about the transient states of air parameters in mining headings generated because of them.     

Multi-parameter numerical simulation of dynamic monitoring of rock deformation in deep mining

The level of deformation development of surrounding rocks is a vital predictor to evaluate impending coal mine disasters and it is important to establish accurate measurements of the deformed status to ensure coal mine safety. Traditional deformation monitoring methods are mostly based on single parameter, in this paper, multiple approaches are integrated: firstly, both electric and elastic models are established,from which electric field distribution and seismic wave recording are calculated and finally, the resistivity profiles and source position information are determined using inversion methods, from which then the deformation and failure of mine floor are evaluated. According to the inversion results of both electric and seismic field signals, multiple-parameter dynamic monitoring of surrounding rock deformation in deep mine can be performed. The methodology is validated using numerical simulation results which shows that the multi-parameter dynamic monitoring methods have better results for surrounding rock deformation in deep mine monitoring than single parameter methods.     

Focal mechanism caused by fracture or burst of a coal pillar

As a regional, real-time and dynamic method, microseismic monitoring technology is quite an appropriate technology for forecasting geological hazards, such as rock bursts, mine tremors, coal and gas outbursts and can even be used to prevent or at least reduce these disasters. The study of the focal mechanisms of different seismic sources is the prerequisite and basis for forecasting rock burst by microseismic monitoring technology. Based on the analysis on the mechanism and fracture course of coal pillars where rock bursts occur mostly, the equivalent point source model of the seismicity caused by a coal pillar was created. Given the model, the seismic displacement equation of a coal pillar was analyzed and the seismic mechanism was pointed out by seismic wave theory. The course of the fracture of the coal pillar was simulated closely in the laboratory and the equivalent microseismic signals of the fractures of the coal pillar were acquired using a TDS-6 experimental system. The results show that, by the pressure and friction of a medium near the seismic source, both a compression wave and a shear wave will be emitted and shear fracture will be induced at the moment of breakage. The results can be used to provide an academic basis to forecast and prevent rock bursts or tremors in a coal pillar.     

四川汉源县城新址煤窑采空区勘查与稳定性评价

近些年,煤矿开采逐渐对个体业主开放。由于个体企业管理的无序,致使采煤巷道的分布缺少必要的记录,采煤巷道可能诱发的地面塌陷、地裂缝等地质灾害给煤矿采空区的基础设施建设及人民的生命财产带来了潜在的威胁。因而,这次勘查工作,确立了高密度电法作为寻找采煤巷道的地球物理方法。本文利用在采空区高密度电法实测资料,依据其视电阻率分布特征,圈定了该区煤矿巷道位置、分布范围。在此基础上,结合地面调查资料、钻孔验证和岩土力学参数特性,对该采空区的稳定性作出了评价,并针对采空区的防治、土地的利用情况及工程建设给出了一些意见。     

System dynamics model of the support-surrounding rock system in fully mechanized mining with large mining height face and its application

Fully mechanized mining with large mining height (FMMLMH) is widely used in thick coal seam mining face for its higher recovery ratio, especially where the thickness is less than 7.0 m. However, because of the great mining height and intense rock pressure, the coal wall rib spalling, roof falling and the instability of support occur more likely in FMMLMH working face, and the above three types of disasters interact with each other with complicated relationships. In order to get the relationship between each two of coal wall, roof, floor and support, and reduce the occurrence probability of the three types of disasters, we established the system dynamics (SD) model of the support-surrounding rock system which is composed of “coal wall-roof-floor-support” (CW-R-F-S) in a FMMLMH working face based on the condition of No. 15104 working face in Sijiazhuang coal mine. With the software of Vensim, we also simulated the interaction process between each two factors of roof, floor, coal wall and the support. The results show that the SD model of “CW-R-F-S” system can reveal the complicated and interactive relationship clearly between the support and surrounding rock in the FMMLMH working face. By increasing the advancing speed of working face, the support resistance or the length of support guard, or by decreasing the tip-to-face distance, the stability of “CW-R-F-S” system will be higher and the happening probability of the disasters such as coal wall rib spalling, roof falling or the instability of support will be lower. These research findings have been testified in field application in No. 15104 working face, which can provide a new approach for researching the interaction relationship of support and surrounding rock.