Hydrogeochemical Characteristics and Groundwater Inrush Source Identification for a Multi-aquifer System in a Coal Mine

Correct identification of water inrush sources is particularly important to prevent and control mine water disasters.Hydrochemical analysis,Fisher discriminant analysis,and geothermal verification analysis were used to identify and verify the water sources of the multi-aquifer groundwater system in Gubei coal mine,Anhui Province,North China.Results show that hydrochemical water types of the Cenozoic top aquifer included HCO3-Na+K-Ca,HCO3-Na+K-Mg and HCO3-Na+K,and this aquifer was easily distinguishable from other aquifers because of its low concentration of Na++K+and Cl-.The Cenozoic middle and bottom aquifers,the Permian fissure aquifer,and the Taiyuan and Ordovician limestone aquifers were mainly characterized by the Cl-Na+K and SO4-Cl-Na+K or HCO3-Cl-Na+K water types,and their hydrogeochemistries were similar.Therefore,water sources could not be identified via hydrochemical analysis.Fisher model was established based on the hydrogeochemical characteristics,and its discrimination rate was 89.19%.Fisher discrimination results were improved by combining them with the geothermal analysis results,and this combination increased the identification rate to 97.3%and reasonably explained the reasons behind two water samples misjudgments.The methods described herein are also applicable to other mines with similar geological and hydrogeological conditions in North China.

A state‑of‑the‑art review on rock seepage mechanism of water inrush disaster in coal mines

Water inrush is one of the most dangerous disasters in coal mining.Due to the large-scale mining and complicated hydrogeological conditions,thousands of deaths and huge economic losses have been caused by water inrush disasters in China.There are two main factors determining the occurrence of water inrush:water source and water-conducting pathway.Research on the formation mechanism of the water-conducting pathway is the main direction to prevent and control the water inrush,and the seepage mechanism of rock mass during the formation of the water-conducting pathway is the key for the research on the water inrush mechanism.This paper provides a state-of-the-art review of seepage mechanisms during water inrush from three aspects,i.e.,mechanisms of stress-seepage coupling,fow regime transformation and rock erosion.Through numerical methods and experimental analysis,the evolution law of stress and seepage felds in the process of water inrush is fully studied;the fuid movement characteristics under diferent fow regimes are clearly summarized;the law of particle initiation and migration in the process of water inrush is explored,and the efect of rock erosion on hydraulic and mechanical properties of the rock media is also studied.Finally,some limitations of current research are analyzed,and the suggestions for future research on water inrush are proposed in this review.

Influential factors and control of water inrush in a coal seam as the main aquifer

In this paper, a combination of field measurement, theoretical analysis and numerical simulation were used to study the main control factors of coal mine water inrush in a main aquifer coal seam and its control scheme. On the basis of revealing and analyzing the coal seam as the main aquifer in western coal mine of Xiao Jihan coal mine, the simulation software of PHASE-2D was applied to analyze the water inflow under different influencing factors. The results showed that water inflow increases logarithmically with the coal seam thickness, increases as a power function with the permeability coefficient of the coal seam, and increases linearly with the coal seam burial depth and the head pressure; The evaluation model for the factors of coal seam water inrush was gained by using nonlinear regression analysis with SPSS. The mine water inrush risk evaluation partition within the scope of the mining field was obtained,through the engineering application in Xiao Jihan coal mine. To ensure the safe and efficient production of the mine, we studied the coal mine water disaster prevention and control measures of a main aquifer coal seam in aspects of roadway driving and coal seam mining.

Forecasting water disaster for a coal mine under the Xiaolangdi reservoir

Xin’an coal mine, Henan Province, faces the risk of water inrush because 40% of the area of the coal mine is under the surface water of the Xiaolangdi reservoir. To forecast water disaster, an effective aquifuge and a limit of water infiltration were determined by rock-phase analysis and long term observations of surface water and groundwater. By field monitoring, as well as physical and numerical simulation experiments, we obtained data reflecting different heights of a water flow fractured zone (WFFZ) under different mining conditions, derived a formula to calculate this height and built a forecasting model with the aid of GIS. On the basis of these activities, the coal mine area was classified into three sub-areas with different potential of water inrush. In the end, our research results have been applied in and verified by industrial mining experiments at three working faces and we were able to present a successful example of coal mining under a large reservoir.

Study on the non-linear forecast method for water inrush from coal seam floor based on wavelet neural network

Directing at the non-linear dynamic characteristics of water inrush from coal seam floor and by the analysis of the shortages of current forecast methods for water inrush from coal seam floor, a new forecast method was raised based on wavelet neural network （WNN） that was a model combining wavelet function with artificial neural network. Firstly basic principle of WNN was described, then a forecast model for water inrush from coal seam floor based on WNN was established and analyzed, finally an example of forecasting the quantity of water inrush from coal floor was illustrated to verify the feasibility and superiority of this method. Conclusions show that the forecast result based on WNN is more precise and that using WNN model to forecast the quantity of water inrush from coal seam floor is feasible and practical.

Study on Filling Cross-Roadway in Fully-Mechanized Coal Faces with High Water-Content Material

A new method using high water content material to mechanically fill cross roadways to form artificial bottom for coal faces was introduced. The reasonable determination of filling range, the optimization of the compounding ratio of high water content material, and the filling technique were discussed in detail. This new method has been spread after industrial testing in Baodian Colliery. Compared with the traditional method, the manual wooden chock method, the new one decreases about 40% of the filling range and cost in dealing every one set of cross roadway in the testing condition.

Predicting the height of water-flow fractured zone during coal mining under the Xiaolangdi Reservoir

It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failure and the development of the fractured zone while coal mining in Xin'an Coal Mine.The risk of water inrush in this mine is great because 40%of the mining area is under the Xiaolangdi reservoir.Numerical simulations combined with geophysical methods were used in this paper to obtain the development law of the fractured zone under different mining conditions.The comprehensive geophysical method described in this paper has been demonstrated to accurately predict the height of the water-flow fractured zone.Results from the new model, which created from the results of numerical simulations and field measurements,were successfully used for making decisions in the Xin'an Coal Mine when mining under the Xiaolangdi Reservoir.Industrial scale experiments at the number 11201,14141 and 14191 working faces were safely carried out.These achievements provide a successful background for the evaluation and application of coal mining under large reservoirs.

Risk assessment of fault water inrush during deep mining

With the gradual depletion of shallow coal resources,the Yanzhou mine in China will enter the lower coal seam mining phase.However,as mining depth increases,lower coal seam mining in Yanzhou is threatened by water inrush in the Benxi Formation limestone and Ordovician limestone.The existing prediction models for the water burst at the bottom of the coal seam are less accurate than expected owing to various controlling factors and their intrinsic links.By analyzing the hydrogeological exploration data of the Baodian lower seam and combining the results of the water inrush coefficient method and the Yanzhou mine pressure seepage test,an evaluation model of the seepage barrier capacity of the fault was established.The evaluation results show the water of the underlying limestone aquifer in the Baodian mine area mainly threatens the lower coal mining through the fault fracture zone.The security of mining above confined aquifer in the Baodian mine area gradually decreases from southwest to northeast.By comparing the water inrush coefficient method and the evaluation model of fault impermeability,the results show the evaluation model based on seepage barrier conditions is closer to the actual situation when analyzing the water breakout situation at the working face.

陕西省煤矿典型水灾隐患特征及治理技术

陕西省煤炭资源丰富,2022年煤炭产量达7.46亿t,是我国主要产煤省份之一。由于全省煤矿区地质及水文地质条件差异明显,煤矿水灾类型多样,随着近年煤炭开采强度的增大,水灾事故时有发生,防治水形势较为严峻。以煤炭赋存条件为基础,系统总结区域水文地质结构特征,界定典型水灾类型及各类水灾影响区域分布,论述典型水灾的形成机理及特征,并提出了相应的防控技术。研究表明:(1)陕西省主要煤炭产区分为陕北、黄陇、渭北三大区,陕北侏罗纪煤田主要有顶板松散沙层水灾隐患、厚层砂岩水灾隐患、溃水溃沙灾害,局部区域分布有烧变岩对煤矿造成水灾隐患;黄陇煤田主要受顶板巨厚砂岩水灾隐患、离层溃水隐患、泥砂溃涌灾害隐患威胁;陕北石炭—二叠纪煤田和渭北煤田,主要受到煤层底板奥陶系灰岩水灾隐患威胁。(2)陕北侏罗系煤田顶板水灾隐患主要为顶板含水层受开采导水裂隙带扰动形成,导水裂隙波及砂岩含水层或松散沙层可形成持续大流量涌水,部分区域充水强度较大,在短时间水量较大超过排水系统能力时造成顶板水灾,在薄基岩区域垮落带直接导通松散沙层时可转变为溃水溃沙灾害,导水裂隙带影响到烧变岩富水区域时可形成瞬时水量大且持续的烧变岩水灾;黄陇煤田顶板巨厚砂岩含水层受采动导水裂隙带波及形成高强度持续涌水并可能形成顶板水灾,当含水层下部隔水层厚度较大时,可能形成离层溃水灾害,当近煤层顶板岩层松软遇水易崩解时可转变为泥砂溃涌灾害;陕北石炭—二叠纪煤田和渭北煤田,煤层开采底板扰动破坏带或断层等构造导通奥陶系灰岩含水层时,会引发极为严重的底板突水灾害,该类灾害具突发性强、瞬时水量大的特征。(3)各区域的顶板水灾隐患治理技术主要包括钻孔疏泄、注浆治理、开采参数控制等,底板水灾隐患治理技术主要包括区域注浆加固及封堵等;烧变岩水灾隐患主要采取帷幕注浆与钻孔探放有机结合的防治技术。

特厚煤层底板断层破坏与顶板垮断联动效应的CFDEM模拟研究

特厚煤层采场空间大、覆岩扰动范围广,顶板垮断产生的强扰动加卸荷载易导致底板断层破坏加剧。通过数值模拟研究特厚煤层底板断层突水与顶板垮断联动效应机理规律是开展水害防治的基础,关键在于掌握加卸载下岩体渐进破坏与裂隙流耦合特征。构建加卸载下拉、剪损伤演化方程,结合有效偏/球应力为基本变量的屈服准则与塑性势函数,得到完整岩块的塑性损伤本构;建立拉/剪、混合型加卸载过程中塑性位移与强度劣化关系,以平方拉剪应力与B-K准则为初始、完全断裂准则,形成非贯通裂隙断裂本构;提出岩块分离、压缩、剪切判据,结合实验数据建立离散块体间挤压、剪切摩擦本构与剪胀方程。基于质量/动量守恒、状态方程,并结合流体体积与浸没边界方法,形成裂隙岩体气−水二相流模拟理论。由此形成CFDEM数值计算程序,并将加卸载下塑性损伤、断裂、挤压/摩擦、流体属性分别赋予实体单元(岩块)、黏聚力单元(非贯通裂隙)、接触对(贯通裂隙)、欧拉单元(水和气)。根据宁武煤田北部矿区工程地质条件,建立特厚煤层底板断层突水与顶板垮断联动效应数值计算模型。结果表明:①CFDEM耦合程序及相应的理论模型可数值实现特厚煤层覆岩及底板断层从(准)连续体到离散体转化,以及地下水在裂隙中运移;②模拟条件下特厚煤层含断层底板的采动裂隙包络线呈w形,最深处超过55 m位于断层及其上盘,最浅处23 m位于断层下盘,而无构造底板处的破坏深度为24~36 m,已导通奥灰含水层;③特厚煤层底板普遍出现二次破坏现象。表现为无构造底板在超前工作面处破坏深度为24.0~29.3 m,但在采空区内普遍增加至31.5~36.0 m;断层及其上盘在超前工作面处裂隙总开度为0.34~0.86 m,但在采空区内迅速增加至3.6 m,形成突水优势通道。④底板断层突水与顶板垮断联动效应的根源在于覆岩高位关键岩层垮断失稳、砌体梁下沉与二次断裂,并导致底板二次破坏,突水风险加剧。

新集矿区深部1煤层底板奥灰岩溶突水危险性评价

奥灰岩溶裂隙含水层是影响华北型煤矿深部开采的重要水害,在水-岩相互作用下奥灰含水层易导致煤层底板突水。为进一步认识奥灰岩溶突水问题,文章以新集矿区深部1煤层开采为例,利用矿区近些年最新积累的奥灰钻孔资料,选取断层强度指数、断层交叉点与尖灭点、含水层水压、富水性、隔水层等效厚度、脆塑比7个因素作为奥灰岩溶突水的主控因素,并结合层次分析法(analytic hierarchy process,AHP)确定各主控因素影响权重。运用地理信息系统(geographic information system,GIS)空间分析功能建立各主控因素专题图,通过对专题栅格图归一化处理,将各主控因素按照权重进行空间复合叠加,最终获得1煤层底板奥灰岩溶突水危险性评价分区结果。将评价结果与突水系数法计算结果对比分析可知,基于GIS的煤层底板突水危险性评价方法更符合矿区实际地质情况,可以为矿区深部煤层开采与水害防治工作提供参考依据。

煤层采动底板突水物理模拟试验研究进展与展望

【目的】底板突水受特定地质构造、水-岩-应力及采掘扰动等因素叠加作用影响,具有复杂性、隐蔽性、突发性等特点。【方法】物理模拟试验能较好地还原底板岩层与承压水赋存环境、直观展现采动底板裂隙扩展及突水路径演化全过程、实时获取灾变各阶段多源数据信息,因而在底板突水研究方面具有独特优势。【结果和结论】对底板突水经典理论、标准规范、模拟试验及工程实践等方面的研究成果进行了回顾,重点梳理了试验加载装置及水压模拟方式、相似材料研制及其特性指标、监测技术及其观测系统设计3个方面的研究进展,其中在模拟水-岩-应力耦合环境下的三维模型底板突水全过程信息捕捉方面有较大突破。面对数智化研究大背景,分析当前底板突水物理模拟试验领域存在的不足,并据此指出未来应重点关注大型三维底板突水综合试验平台研制、基于标准化的多特性相似材料配比数据库建立、多相多场多维耦合监测预警系统构建、人工智能等数智化技术融合应用研究等发展方向。提出的思考有助于从装置、材料、技术等方面提升未来物理模拟试验水平,从而更好支撑煤矿底板水害数智化防治基础研究工作高质量发展。

煤岩体突水通道骨料灌注运移堆积机制试验

为揭示突水通道中骨料运移堆积的演化规律,开展了动水条件下骨料灌注试验,得到了骨料的初始沉积位置、堆积体形成方向以及堆积体极限堆积高度与水流速、骨料灌注速度等影响因素的内在关联。结果表明:在1.0 m/s高流速动水环境中,骨料堆积体形成方向为先逆水流方向生长至投料孔底后转为顺水流方向生长;在0.3 m/s低流速条件下,采用口径36 mm漏斗投料同口径18 mm相比,骨料灌注总量相同时,其堆积体的极限高度提升了41%。基于数值力学模型——计算流体动力学-离散元方法(computational fluid dynamics and distinct element method,CFD-DEM),研究了骨料灌注期间突水通道内流场的时空分布特征以及骨料堆积体的过水阻力作用对突水通道内静水压力的影响机制。

井下动水截流施工骨料堆积生长机制研究

灌注骨料形成阻水屏障实现截流降速是井下治水工程的关键所在。为定量描述骨料堆积生长的时空演化机理,提出了将骨料沉降堆积过程切分为具有一定厚度的片状颗粒层堆叠过程的分析计算方法,以及动水环境中骨料灌注后从沉降到堆积全过程关键参量(颗粒水平移距xd,动水休止角ψ,未接顶区流速U,骨料留存临界流速U_(cr))的理论计算公式,在此基础上构建了骨料堆积体生长预测模型。通过CFD-DEM双向耦合算法研究了骨料灌注期间流场分布演化特征和骨料堆积形态差异,并验证了预测模型合理性。研究表明:空间上,依据初始流速U_(s)是否超过骨料起动流速U_(c)或骨料留存临界流速U_(cr),可将截流初期骨料沉积主域的所在位置划分为3个区域,若沉积主域位于③区,则将其视为无效灌注;时间上,骨料堆积体生长过程可归结为3个阶段:高度快速增长阶段、高度长度同步生长阶段、仅水平向伸长阶段;初始流速决定了第1阶段的有无,而灌注条件(骨料粒径、灌注速度)主导着第1阶段所持续的时间;基于泥沙运动力学中推移质输沙率、起动流速等概念,得出了堵孔现象发生及骨料能否留存的临界判据;数值模拟试验结果表明,预测模型能够较好地刻画骨料灌注后的堆积生长规律,骨料堆积稳定后,理论计算值与模拟试验值相对误差小于10%。

基于综合对抗解释结构模型的煤矿透水事故致因分析

为了更加科学高效地对煤矿透水事故致因进行辨识和分类管理,以2021年丰源煤矿“4·10”重大透水事故为例,运用24Model法对事故致因进行分类提取,采用综合对抗解释结构模型(简称TAISM),对致因进行层级结构划分和因果关系分析。通过计算得到了该起事故致因的1组7层对抗型有向拓扑层级图。研究结果表明:监督机构监督检查不力、当地政府安全发展意识不强是造成此次事故发生的最根本原因。此外,在事故致因层级图中出现了2个回路,而同一个回路中的不同事故致因存在较强的关联性,应对其进行一体化控制,最大限度减少煤矿安全事故的发生。为今后煤矿事故致因分析提供了新的思路。

生态脆弱煤矿区水体中微生物群落特征及矿井充水指示

我国生态脆弱矿区水资源整体匮乏,但局部地区矿井涌水却异常巨大。对生态脆弱矿区异常矿井充水水源识别,对矿区生态环境保护意义重大。研究以涌水量超过1 000 m^(3)/h的榆树湾煤矿为背景,在分析矿井涌水量特征的基础上,采集了研究区主要含水层和矿井涌水点的30个水样,开展了水样高通量微生物测序研究。对测序结果采用Alpha多样性分析、Beta多样性分析及微生物构成差异分析,系统研究了矿井水体中微生物群落特征,分析了矿井充水来源。研究结果表明:高通量测试结果通过了Coverage指数检验,验证了其用于矿井充水识别的可行性。但人类活动密切接触的水样显示出微生物更加丰富,需要在取样中有效规避。榆树湾煤矿浅表松散含水层中微生物丰富度和多样性都较高,以新鞘脂菌属(Novosphingobium)、梭杆菌属(Fusobacterium)和硫属(Sulfuricum)等微生物丰度最高;直罗组为代表的基岩含水层微生物丰富度较低,但微生物多样性较高,以丛毛单胞菌属(Comamonas)、蛲虫属(Vermiphilaceae)和巴氏杆菌(Paeniglutamicibacter)等微生物丰度最高。所有水样中最为优势的门类为变形菌门,占比达到35.5%~89.7%。Alpha多样性、PCoA和NSDM分析揭示了榆树湾矿井充水水源主要来自松散含水层和直罗组含水层。但Beta多样性分析发现,随着直罗组静储量的释放,松散层中离石组黄土充水比例进一步增大。综合分析显示,榆树湾煤矿目前为基岩含水层快速释水+离石组含水层持续释水模式的充水模式,矿井涌水统计分析结果验证了这一结论。研究为相似化学成分含水层充水识别,提供了新的方法。

大采深高承压水条件下煤层底板突水问题及解决对策

在当前煤矿普遍面临大采深、底板高承压水、高地应力等采掘条件下,正确评价煤层底板承压水突水危险是做好防治水工作的基础。以河南省受底板灰岩承压水突水威胁的大水矿井为例,就底板破坏深度计算、突水系数计算及临界值、脆弱性指数法、不同水文地质单元的“双层水位”效应等问题进行了剖析。分析表明:在大采深和高地应力开采条件下,底板破坏深度较现有用经验公式计算得到的值偏大,一些矿井突水系数虽小于全国临界值,但回采过程中却发生了突水,脆弱性指数法有待于规范化。此外,井田范围内水文地质条件存在着时空变化,甚至会出现“双层水位”等现象。鉴于此,提出了建立大采深和高地应力开采条件下的底板破坏深度计算模型、确定矿区或矿井范围的临界突水系数值、规范脆弱性指数评价方法、查明水文地质条件的时空变化和不同单元的水动力参数、制定同各单元水文地质条件相适应的防治水措施等各项对策。

底板突水危险性评价研究进展

回顾了煤层底板突水危险性评价的发展历程,提出其危险性评价的体系:指标(指标体系的建立)—方法(评价方法的选取)—工具(处理工具的革新),并对3个环节进行总结。指出指标体系的发展不再是因素集的扩充,而是因素与因素之间非线性关系的处理以及对以开采条件及地质条件为两大基本要素集的化繁为简;将现有方法依据处理数据的逻辑分为3类:以数据的基础信息为基准,将原始数据对评价对象所产生的大小、高低、优劣性影响进行考量、排序及综合形成评价结果的第一类方法;对数据列进行人工评判、加工分析、拓展和延伸,挖掘数据的潜在信息,并形成最终评价结果的第2类方法;整理具有相同指标的数据集,通过数据信息处理技术发现数据间的共有信息,从而获得最终评价结果的第3类方法。指出未来评价方法的发展方向一方面是对突水系数法的传承,修正其在厚、巨厚、极薄隔水层的不良表现,另一方面是对机器学习新型方法的创新,对其本身及组合模型进行开发与应用。提出了处理工具所需实现的三大目标:矿井立体化模型的建立、评价结果的动态化演示、“定位、定量、定概率”三定指标的实现。分别探讨了三者面临的问题并阐述具体解决手段。在上述基础上,总体阐明了煤层底板突水危险性评价体系各环节的研究展望。

黄陇煤田典型特厚煤层综放开采涌水机理与导水裂隙带发育规律

黄陇侏罗纪煤田厚煤层开采导水裂隙带发育高度大,易导通上覆白垩系洛河组巨厚砂岩含水层,区内青岗坪煤矿回采期间出现典型的“脉冲式”涌水特征,给矿井的安全回采造成严重影响。以青岗坪煤矿42105综放工作面为研究对象,采用3DEC离散元模拟、钻孔冲洗液漏失量、综合物探以及钻孔电视相结合的实测方法,对工作面回采过程中覆岩导水裂隙带和离层发育规律进行研究,探究该典型地质条件下矿井的涌水机制与导水裂隙带发育特征。结果表明:42105工作面导水裂隙带受覆岩周期性垮落影响不断向上发育,洛河组孔裂隙砂岩静储水不断释放,间歇性涌入工作面,形成幅值稍低的“脉冲式”涌水;在采动影响下巨厚砂岩含水层内不断出现离层,导水裂隙带导通砂岩含水层离层积水区,致使涌入工作面的瞬时涌水量突增,形成幅值较高的“脉冲式”涌水。结合现场钻孔冲洗液漏失量实测、综合物探以及钻孔电视结果,揭示了青岗坪煤矿洛河组孔裂隙砂岩静储水与离层水叠加影响的“脉冲式”涌水机理,确定导水裂隙带的最大发育高度为316.83~333.00m,裂采比为30.17~31.71。研究结果对于类似地层条件下矿井涌水的防治和安全高效回采具有指导意义。