Application of Roadway Spray Material to Fire Prevention in Goaf Excavation

In order to reduce the risk of spontaneous combustion in goaf during goaf excavation process, polymer modified cement mortar spraying material was used to spray and seal the roadway surface. The experimental application was carried out in the upper channel 2304 of a mine in Henan Province. The test results showed that polymer modified cement mortar spraying material could effectively support the roadway and greatly reduce the deformation rate of the roadway. The best spraying thickness is 5 mm. Through the monitoring of tunnel air leakage, it is concluded that the polymer modified cement mortar spraying material can reduce the tunnel air leakage and play a better sealing effect.

Numerical simulation and experimental research of surrounding rock deformation of floor roadway under short-distance coal seam group combined mining

According to the influence of the combination of short-distance coal seam group on mining roadway, using numerical simulation software FLAG2D to draw the abutment pressure distribution ahead the working face and the area of influence in fully-mechanized mining conditions, the variation rules of surrounding rock supporting pressure of floor roadway and the deformation rules were summarized. GYS-300 anchor dynamometer was used to measure the roadway surface displacement, and the conclusions of numerical simulation were verified.

Research on the feasibility of storage and estimation model of storage capacity of CO_(2)in fissures of coal mine old goaf

The concept of the carbon cycle in the old goaf of a coal mine based on CO_(2)utilization and storage was put forward adhering to the principle of low-carbon development,utilization of space resources in old goafs,and associated gas resources development.Firstly,the evolution characteristics of overburden fissures in the goaf of the case was studied using a two-dimensional physical similarity simulation test,the sealing performance of the caprocks after stabilization was analyzed,and the fissures were counted and classi-fied.Then,the process of gaseous CO_(2)injection in the connected fissure was simulated by Ansys Fluent software,and the migration law and distribution characteristics of CO_(2)under the condition of gaseous CO_(2)injection were analyzed.Finally,the estimation models of free CO_(2)storage capacity in the old goaf were constructed considering the proportion of connected fissure and the effectiveness of CO_(2)injection.The CO_(2)storage capacity in the old goaf of the case coal mine was estimated.The results showed that a caprock group of“hard-thickness low-permeability hard-thickness”was formed after the caprock-fissures system in the goaf of the case tended to be stable vertically.The connected fissure,occlude cracks,and micro-fractures in the goaf accounted for 85.5%,8.5%,and 6%of the total fissures,respectively.Gaseous CO_(2)first migrated to the bottom of the connected fissure after CO_(2)was injected into the goaf,then spread horizontally along the bottom of the connected fissure after reaching the bottom,and finally spread longitudinally after filling the bottom of the entire connected fissure.The theoretical and effective storage capacities of free CO_(2)at normal temperature and pressure in the old goaf of the case were 9757 and 7477 t,respectively.The effective storage capacity of free CO_(2)at normal temperature and pressure in the old goaf after all minefield mined was 193404 t.The research can provide some reference for the coal mining industry to help the goal of“carbon peaking and carbon neutrality”.

Algorithm for cavity flow in a new-born goaf and experimental verification

Prevention and control measures of spontaneous combustion of coal and gas accumulation in a goaf require an accurate description of its gas flow state.However,the commonly used fluid dynamics in porous media is not suitable for the new-born goaf with fracture cavity combination,multi-scale,and large blocks.In this study,we propose a cavity flow algorithm to accurately describe the gas flow state in the new-born goaf.The genetic algorithm(GA)is used to randomly generate the binary matrix of a goaf caving shape.The difference between the gas flow state calculated by the lattice Boltzmann method(LBM)and the measured data at the boundary or internal measuring points of the real goaf is taken as the GA fitness value,and the real goaf caving shape and the gas flow state are quickly addressed by GA.The experimental model of new-born goaf is established,and the laser Doppler anemometry(LDA)experiment is carried out.The results show that the Jaccard similarity coefficient between the reconstructed caving shape and the real caving shape is 0.7473,the mean square error between the calculated wind speed and the LDA-measured value is 0.0244,and the R2 coefficient is 0.8986,which verify the feasibility of the algorithm.

Short-Distance Low-Power Wireless Access System

The short-distance low-power technologies for wireless access communications, including Bluetooth, Ultra-Wideband (UWB) and Wireless Fidelity (Wi-Fi), focus on the physical layer and Medium Access Control (MAC) layer. Bluetooth is a wireless protocol for exchanging data over short distances. It is an alternative to RS232 data cables. UWB is a radio technology that can be used at very low energy levels for short range. It provides flexible high-bandwidth wireless access. Wi-Fi enables the wireless connection of fast-access devices and mobile devices in Wireless Local Access Network (WLAN) and it is suitable for long distances. The standardizations of the above technologies have been developed and published soon after the emergence of these technologies. Among all the standards, Bluetooth and Wi-Fi are the most important ones.

Effect of periodic wide atmospheric pressure change on CO emission in closed goaf

Atmospheric pressure fuctuation is one of the most important factors afecting the climate environment and gas emission in the fre area.To obtain the infuence rule of the surface atmospheric pressure change on the gas sampling and abnormal emission in the mine closed goaf,the No.1 coal mine in Dananhu was taken as the research object.Using Fourier transform and Fisher harmonic analysis and other statistical methods,the infuence of the periodic variation of atmospheric pressure on the gas leakage and outfow in the closed goaf was studied.The results showed that there were three atmospheric pressure periods of 15.2 d,1 d and 182.2 d,and the probability was greater than 95%.The time period with the highest number of atmospheric pressure peaks was 7:00–8:00,which accounted for 20.2%of total occurrence number in a day.And the time periods with the highest number of atmospheric pressure trough were 2:00,15:00 and 16:00,accounting for 27.4%.The peak-to-trough transition time was mainly concentrated around 6 h,and the diurnal variation curve of atmospheric pressure was mainly bimodal.The atmospheric pressure change rate was mostly concentrated in 10–50 Pa/h.It was determined that the distance that the gas sampling pipe was pre-laid into the inner side of the closed wall should be greater than 44.4 m,and the CO concentration and atmospheric pressure in the closed goaf were both periodic and negative with atmospheric pressure.The research results have important guiding signifcance for the monitoring,early warning and environmental protection of the goaf.

基于静力水准的采空区地表变形监测及误差分析

目前,采空区上方的地表沉降变形监测主要采用人工水准仪测量,该方法效率低、成本高、周期长,且无法实现自动化实时监测。为解决上述问题,引入静力水准自动化监测技术,在分析静力水准自动化监测工作原理及监测系统构成的基础上,对其可靠性、误差来源及消除方法进行了深入探讨,最后结合条带采空区上方地表监测实例从监测方案、测点布置、数据分析等多个角度进行了系统研究。研究结果表明:该技术能够满足条带采空区上方地表沉降变形自动化监测的要求,可为相关监测工作提供技术支撑。

基于层次分析法与频率比模型的采空塌陷危险性评价

采空塌陷危险性评价是编制地质灾害防治规划、开展地质灾害防治与监测预警工作的重要依据。本文采用层次分析法与频率比模型相结合构建了采空塌陷危险性评价模型(AHP-PF组合模型)。以沈阳市蒲河-清水矿区为例,考虑了地质条件、地表特征、开采条件等3方面影响因素,选取了第四纪覆盖类型、第四纪松散层厚度、地质构造复杂程度、可采煤层顶板强度指标、煤层倾角、地表沉陷速率、采深采厚比、采空区叠置层数等8个评价指标,利用AHP-PF组合模型计算各指标权重及频率比,最后进行采空塌陷危险性分区。评价结果表明,采空塌陷危险性高区主要集中在采深采厚比小、沉陷速率大及目前仍在开采的区域,该区域是地质灾害防治、搬迁避让的重点区域。

采空区场地高速铁路路基动力响应离散元数值模拟分析

目的高速铁路穿越采空区场地存在重大安全隐患,为探讨采空区场地高速铁路路基的动力响应规律,方法利用3DEC离散元软件建立17组采空区场地高速铁路路基数值模型,分析不同列车荷载作用下路基内部的沉降变形和动应力分布规律,对比分析无砟轨道和有砟轨道路基内部动力响应的分布差异,分析采空区开采宽度、厚度对动力响应分布规律的影响。结果与无砟轨道相比,有砟轨道路基内部的动应力幅值明显更高,但其动应力的衰减速率也更高;动应力、动位移的时程曲线沿着路基深度方向出现不断增大的相位差;路基内部动位移幅值随着荷载作用时间增加而逐渐增大,但增大的速度不断降低,动应力幅值基本保持不变;动应力、动位移幅值与列车轴重存在明显的线性关系,随着轴重增加而线性增大;采空区开采宽度、厚度越大,列车荷载造成的动位移幅值也越大,但当开采宽度大于一定数值后,动位移幅值反而出现减小趋势。结论列车荷载、路基轨道类型和采空区场地的差异都会对路基内部的动力响应分布情况产生影响,研究结果可为采空区场地高速铁路的安全运行提供理论参考。

小断层影响下的采空区瓦斯运移规律研究

在煤矿开采过程中,小断层会导致采空区瓦斯聚集形成瓦斯富集区,对生产安全具有很大威胁,因此有必要研究小断层影响下的采空区瓦斯运移规律。通过UDEC数值模拟采空区上覆岩层破坏过程,从而计算小断层影响下采空区上覆岩层的空隙率,并利用FLUENT软件数值模拟开采过程中考虑小断层影响的采空区瓦斯运移规律。研究表明:①工作面距离小断层20 m远处,小断层从顶部首先出现滑移现象,采空区上覆岩层的位移开始受到断层的影响;工作面到达断层时,由于断层滑移,上盘岩体在断层面滑移产生回转现象,支撑着采空区岩层,覆岩垮落位移量出现大幅度减小,并且岩层垮落出现滞后现象;小断层的影响范围有限,工作面过小断层60 m之后,采空区上覆岩层位移规律逐渐恢复正常。②通过分析含小断层采空区上覆岩层位移特征,得到了采空区上覆岩层位移及其拟合公式,计算得到了三维空隙率分布规律:垮落带范围内,覆岩空隙率在4个隅角位置最大,并且断层靠近进回风巷的位置也出现了空隙率增高;裂隙带范围内,除断层靠近进回风巷的位置空隙率较大,其他位置空隙率相对较低且变化不明显。③获得了小断层影响下的采空区瓦斯运移规律:在工作面距离断层50 m远处,采空区瓦斯运移几乎不受断层的影响;在工作面推进至断层时,瓦斯沿着断层及其附近的高空隙率覆岩产生的优势逃逸通道向采空区深部运移,同时上盘的瓦斯也向深部转移导致大量瓦斯积聚在断层下盘,可能导致瓦斯随漏风流入工作面及回风巷;在工作面过断层50 m时,采空区瓦斯继续向上隅角附近转移;工作面过断层100 m时,采空区上覆岩层瓦斯运移出现回转现象,上隅角和下盘垮落带瓦斯体积分数高。

倾斜矿体采空区非对称顶板-矿柱结构体协同承载机理

为解决倾斜矿体回采后大倾角顶板和非对称空区可能引发的采空区支撑结构体变形及破坏失稳问题,以某石灰石矿非对称顶板-矿柱支撑结构体为研究对象,构建结构体承载力学模型,求解顶板挠曲变形值及矿柱安全系数,分析不同倾角、跨度比下顶板变形特征及矿柱失稳破坏模式,研究其协同承载机理。结果表明:顶板变形、矿柱失稳破坏模式受采空区倾角θ和跨度比λ的双重影响,顶板变形大小随着θ的增加表现为双增长率,与λ的关系伴随着θ的变化而变化。矿柱失稳破坏模式受θ的影响程度随着λ的增加而减小,当0°<θ≤30°时,矿柱主要为小偏心受压破坏;当θ=0°和30°<θ≤60°时,随着λ值的增加,矿柱破坏模式从大偏心受压破坏向小偏心受压破坏转变。顶板维系采空区稳定的能力随着θ的增加逐渐降低,矿柱维系采空区稳定的最优λ值随着θ的增加逐渐减小,矿柱约束顶板变形作用大小随着λ的增加而降低。数值模拟和工程实例验证了理论计算结果的可靠性,为地下空场法矿山安全开采提供一定的理论支撑。

水力渗透型煤矿采空区三维音频大地电磁快速解译

煤矿采空区或回采阶段工作面常面临水力渗透威胁,如何快速有效且低成本地预判水力渗透成为难题。提出并系统论述了一种面向水力渗透型采空区的音频大地电磁三维反演及快速解译方案。通过设计采空区理论地电模型,探讨采空区电阻率三维反演可行性。实测数据反演解释结果揭示:采空区巷道顶板区域存在明显低阻分布,部分工作面存在顶板裂隙导水造成的富水低阻区域,局部垮落带与上覆含水层明显连通。为可疑透水位置定位、水位和涌水量监测,以及后续开采规划制订提供了参考。从理论和实证角度,为音频大地电磁法的采空区富水状态分析和动态监控应用提供了新思路,相关方法能够有效提高水力渗透型采空区的解译效果。

特厚煤层小煤柱沿空掘巷支护技术研究

小煤柱沿空掘巷过程中易出现巷道围岩变形大、局部鼓出等现象,针对这一问题,采用理论分析、数值模拟、工程类比的方法,对巷道基本顶破断方式进行了判断,并采用数值模拟分析不同宽度下煤柱的应力及位移变化规律,初步确定了煤柱留设宽度为8 m;对比邻近矿井的沿空掘巷案例,采用工程类比法最终确定了煤柱宽度,并对巷道支护方案进行设计,现场应用效果良好。

采空区积水对邻近巷道围岩稳定性分析研究

以山西某煤矿采空区为背景,针对采空区积水对邻近巷道围岩稳定性的影响,采用现场测试、室内试验、数值模拟等方法进行了研究分析。首先基于三维激光扫描和声呐建立了含水采空区的三维几何模型;然后对不同损伤程度下煤岩开展渗透率试验,获得了渗透率的变化规律;最后在充分考虑渗透率的动态变化基础上,采用数值软件对邻近巷道围岩的稳定性进行了模拟分析。结果表明:孔隙水压力已经影响到邻近巷道围岩和上覆岩体;采空区赋水后,围岩极易出现渗水和透水情况;受开采扰动和积水渗透的双重影响,采空区与巷道的煤柱出现大范围塑性区,其稳定性较差。为了保证井下生产安全,建议增加井下临时性排水设施,及时将积水排出,避免透水事故的发生。

深部条带老采空区覆岩破坏多参量监测研究

针对深部条带老采空区覆岩移动变形问题,确定了裂隙发育、拉压应变、岩层物性等主要参量指标,采用钻孔电视法、分布式光纤感测法、井间电法CT、微震法构建了采空区覆岩“点-线-面-体”多参量监测模式;运用该监测模式对工程实例进行实测分析,获取了采空区覆岩全方位、多层次的移动破坏特征,得出覆岩裂隙多集中在465 m以下,少量空洞位于垮落带及煤柱上方靠近采空区侧,煤柱塑性区范围约8 m的结论,综合判定采空区覆岩结构可在长时间内保持相对稳定。结果表明:“点-线-面-体”多参量监测模式在内容上能够有效涵盖条带采空区覆岩移动变形的各参量指标,时空上可实现点(静态)、线(动态)、面(静态)、体(动态)相互结合的全过程监测,监测结果间能相互验证,可满足深部条带采空区覆岩移动变形监测要求。

地空瞬变电磁法在煤矿采空区中的应用效果分析

煤矿采空区一直是工程中难以解决的重点难题之一,现工程中一般是结合开采资料及煤层分布进行综合分析。由于大型煤矿多采用自然塌落法来处理采空巷道,而非金属类矿山的填充法,随着时间的推移,会出现非常多的塌陷,导致采空区内部情况非常复杂,难以查清。尤其是在老旧的煤矿当中,由于过去技术落后,矿洞测绘资料存在一定的失真,导致很难明确定义现采空区的具体范围,为工程的顺利开展提出了重大的课题。结合黑龙江依兰煤矿(日伪时期的开采老旧煤矿采空区),在地形地貌条件特别差,人难以攀登的条件下,应用地空瞬变电磁法,初步解决了该采空区的范围和规模。

基于变分模态分解的采空区“三带”微震信号能量衰减规律

为探明微震信号能量在采空区“三带”结构中的衰减规律,拟开展采空区覆岩相似模型试验,采集人工激发微震波经由采空区结构传播的微震信号,通过变分模态分解(variational mode decomposition,VMD)处理微震信号,获取各频率下模态分量。针对采空区微震信号在VMD下各模态分量中心频率与能量之间的关系展开分析。根据中心频率法确定微震信号最佳模态数量,并计算微震信号欠分解状态、最佳分解状态、过分解状态下各分量能量;对各震源下信号最佳分解状态时各模态分量能量与中心频率分布关系进行拟合,分析在“三带”结构中,微震信号不同传播状态下各结构层对信号能量影响作用。研究结果表明:(1)在VMD过程中,人工激发震动信号有效模态数量在6~11范围内,微震信号能量随模态数量变化明显。(2)采用幂函数可实现对微震信号模态能量与频率关系的拟合,且拟合状态良好(决定系数大于0.9),其中低频模态分量包含能量占信号总能量近50%;采用高斯函数可以拟合震源各分量能量在频域上的分布表现,拟合状态较好,且表现出高斯单峰特征。(3)微震信号穿越采空区“三带”结构,微震信号能量随震源位置与传感器距离增加而减小,同时信号能量随震源位置到达传感器穿越岩层数量增加而减小,信号能量在经由垮落带时,能量变化明显,相较于裂隙带和弯曲下沉带,垮落带对信号能量衰减作用明显。

瞬变电磁法在煤矿灾害勘察评价的应用案例分析

为进一步明确某现状矿区内易发生地下水危害的区域,采用瞬变电磁法对煤矿地下环境进行勘察,勘察结果表明矿区内可能存在一含水构造带,该构造带纵向基本贯穿标高550~-200 m,可能会对采空区或者巷道的开发使用带来危害。此外在瞬变电磁法对矿区进行勘察时,采空区往往表现为低阻包围着的中高阻特征,而含水裂隙往往表现为低阻特征。本文研究内容对于指导后续矿产资源的开发具有一定指导意义。

采空区治理用尾矿砂注浆材料的制备及性能研究

为了解决常用的矿山采空区治理用注浆材料凝结时间长、析水率高、结石率低、水下浇筑时水泥流失量大、硬化后易脱空等问题,制备了一种尾矿砂注浆材料,并通过添加性能调节剂CA-Ⅳ、调整原材料配比对其性能进行了优化。结果表明:优化后的尾矿砂注浆材料工作性得到明显改善,凝结时间大幅缩短,24 h竖向膨胀率、结石率和28 d抗压强度均有大幅提高,水泥流失量显著降低。

基于Mathews稳定图法的采空区稳定性分析

采空区稳定性关系到矿山生产安全。为了方便准确地对采空区稳定性进行分析,以指导矿山安全生产。以某铅锌矿的某采空区为例,获取了采场的RQD值、节理组数、节理粗糙度、节理蚀变度等采空区力学指标或结构参数,分别计算出采空区的修正的岩石Q值、应力系数、节理方位系数、重力调整系数,进而计算得到采场的稳定数;统计了采空区的长度、高度和宽度等形状参数,以此为基础计算得到采空区的壁面积和壁周长,进而计算得到采空区的形状因子,以采空区的稳定数和形状因子为依据,在Mathews稳定图确定采空区所在的点,根据落点位置确定采空区稳定性,进而指导矿山安全生产。实践证明,Mathews稳定图法对采场稳定性分析是准确的。