In-situ gas contents of a multi-section coal seam in Sydney basin for coal and gas outburst management

The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO_(2) composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q_(1), Q_(2), and Q_(3)) of the coal seam. The results show that in-situ total gas content (Q_(T)) ranges from 9.48 m^(3)/t for the A2 section to 14.80 m^(3)/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q_(2) demonstrates the highest contribution to Q_(T), ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO_(2) sorption behavior, with ft coefcients (R^(2)) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q_(3)) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q_(1) and Q_(2) gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of efective gas management strategies and enhance the safety and efciency of coal mining operations.

A rapid and accurate direct measurement method of underground coal seam gas content based on dynamic diffusion theory

Coal seam gas content is frequently measured in quantity during underground coal mining operation and coalbed methane(CBM)exploration as a significant basic parameter.Due to the calculation error of lost gas and residual gas in the direct method,the efficiency and accuracy of the current methods are not inadequate to the large area multi-point measurement of coal seam gas content.This paper firstly deduces a simplified theoretical dynamic model for calculating lost gas based on gas dynamic diffusion theory.Secondly,the effects of various factors on gas dynamic diffusion from coal particle are experimentally studied.And sampling procedure of representative coal particle is improved.Thirdly,a new estimation method of residual gas content based on excess adsorption and competitive adsorption theory is proposed.The results showed that the maximum error of calculating the losing gas content by using the new simplified model is only 4%.Considering the influence of particle size on gas diffusion law,the particle size of the collected coal sample is below 0.25 mm,which improves the measurement speed and reflects the safety representativeness of the sample.The determination time of gas content reduced from 36 to 3 h/piece.Moreover,the absolute error is 0.15–0.50 m^3/t,and the relative error is within 5%.A new engineering method for determining the coal seam gas content is developed according to the above research.

Influence of Ground Stress on Coal Seam Gas Pressure and Gas Content

The influence of ground stress was quantitatively analyzed on coal seam gas pressure and gas content in this paper.Mining activities in coal mine can result in stress concentration in the coal(rock)body around the mining space,but porosity of the coal seam would not change too much.Therefore,gas pressure and gas content in the coal seam are slightly affected.Studies showed that the free gas was gradually transformed into adsorbed gas,and the gas adsorption volume was small,and then gas pressure increases roughly linearly when the porosity decreased because of stress influence.Additionaly,when porosity of coal seam reduced to 40%,the amount of adsorbed gas accounted for no more than 10%of coal seam gas content,and the increase of gas pressure did not exceed 15%of the original gas pressure.

Calculation of gas content in coal seam influenced by in-situ stress grads and ground temperature

On the basis of the analysis of coal bed gas pressure in deep mine, and the coal bed permeability ( k ) and the characteristic of adsorption parameter ( b ) changing with temperature, the author puts forward a new calculating method of gas content in coal seam influenced by in situ stress grads and ground temperature. At the same time, the contrast of the measuring results of coal bed gas pressure with the computing results of coal bed gas pressure and gas content in coal seam in theory indicate that the computing method can well reflect the authenticity of gas content in coal seam,and will further perfect the computing method of gas content in coal seam in theory,and have important value in theory on analyzing gas content in coal seam and forecasting distribution law of gas content in coal seam in deep mine.

Strength criterion effect of the translator and destabilization model of gas-bearing coal seam

Coal seam destabilization inflicts damage to equipment, causes property loss and personnel casualties,and severely threatens mining safety and efficient production. To further understand this destabilization based on the basic theory of Lippmann seam destabilization, a mathematical model was introduced for gas pressure distribution by considering intermediate principal stress and support resistance.Subsequently, we established a translation model suitable for the entire roadway coal seam with rocky roof and floor by applying the unified form of yield criterion in the state of plane strain. We also obtained the analytic expressions of coal seam stress distribution on both sides of the roadway and the widths of plastic and disturbance zones. Afterward, we analyzed several typical cases with different material yield criteria, obtained the plastic zone widths of the coal seam under different gas pressures, and assessed the effects of support resistance, roadway size, and coal strength on coal seam destabilization. Results showed that: the results obtained on the basis of Wilson and Mohr–Coulomb criteria are considerably conservative, and the use of Druker–Prager criteria to evaluate the rockburst-induced coal seam destabilization is safer than the use of the two other criteria; coal seam stability is correlated with gas pressure;and high-pressure gas accelerates the coal seam destabilization.

Discussion of the indexes of nonoutburst coal seam upgrade and its corresponding critical values

In view of the measurement difficulties of indexes recommended by the 50Items Experience of Coal Mine Gas Prevention in the process of the nonoutburst coalseam upgrade, this paper took the No.8 coal seam of Huainan Mining Group as research object. Discussed the suitability of indexes and corresponding critical values, putforward method in determining the indexes and its critical values by analysis and investigation of the gas geological condition and the-spot tracking near position where anoutburst occurred combined with laboratory experiment, and established the indexesand its critical values of nonoutburst coal seam upgrade in No.8 coal seam of HuainanMining Group. The results show that it is suitable to take gas content and tectonic softcoal thickness easily to gain in routine production as primary upgrade indexes that itscritical values are 7.5 m^3/t and 0.8 m, respectively. In addition, takefvalue and Ap valueas auxiliary indexes.

Gas effusion of full-mechanized top coal caving in Jiaoping Mine Area

According to the gas observational data,the gas spatiotemporal distributions were analyzed in full-mechanized top coal caving in thick,hard and high-gas seams.The factors influencing gas effusion were researched and the rules of gas effusion under the special conditions were educed,for example,the underground pressure,the output inten- sity,the working surface advancement,and the amount of ventilation in the working face on gas effusion,and so on.The research results can be the base of forecasting gas effu- sion and controlling gas in these special conditions,which can guarantee the safety of highly efficient full-mechanized top coal caving.

STUDY ON THE THRESHOLD GAS PRESSURE IN COAL AND GAS OUTBURST

Based on the statistical data of 26 outburst prone coal seams in China, this paper presents the relationship among the threshold gas pressure in coal and gas outburst and the volatile content and hardness of coal by mathematical statistics. The threshold value of gas pressure for outburst pmin in MPa may be calculated by formula Pmin =5(0. 1+0. 07Kf), where / is the hardness and V the volatile content (%) of a soft bed. In China, the value of Pmin of some outburst prone coal seams ranges from 0. 57 to 0. 1 MPa.

建新煤矿4^(-2)煤层瓦斯赋存规律及瓦斯富集区域判定

为了获得建新煤矿4^(-2)煤层的瓦斯赋存规律以及主控因素,从煤岩层特征以及煤层瓦斯含量入手,讨论地质构造、顶底板岩性、煤层厚度、煤层埋深及煤层底板标高各种因素对瓦斯含量的影响,明晰建新煤矿4^(-2)煤层瓦斯赋存的主控因素。研究结果显示,建新煤矿4^(-2)煤层的瓦斯含量与煤层厚度呈线性正相关,煤层的厚度直接影响着瓦斯含量的大小,煤层越厚,其瓦斯含量越大;煤层瓦斯含量与埋深呈正相关,随埋深的增加而逐渐增加;瓦斯含量与底板标高呈负相关关系。基于对建新煤矿4304工作面瓦斯含量的现场实测及分析,绘制瓦斯赋存规律等值线图,得到工作面瓦斯富集区。

刘庄煤矿11-2煤层底板砂岩富水规律及水化学特征研究

采用水化学测试、统计分析、水文地球化学分析等方法,对刘庄煤矿11-2煤层底板砂岩富水性规律及水化学特征进行系统研究。研究结果表明:井田范围内112煤底板砂岩类型、沉积厚度、裂隙发育、富水性以F25断层为界分区性明显,水质类型为Cl·HCO_(3)—Na或HCO_(3)·Cl—Na型,以采区边界断层为界,主要离子含量存在较大差异性,并分析了水样中阳离子Na^(+)、Ca^(2+)、Mg^(2+)主要来源。研究成果可为查清砂岩裂隙含水层分布规律、富水性和水化学特征提供指导,为制订矿井防治水方案提供重要依据。

前和煤矿3号煤层瓦斯分布规律研究

为掌握前和煤矿3号煤层瓦斯分布规律,依据该矿的地质构造特征和煤层赋存情况,通过现场实测煤层原始瓦斯含量、原始瓦斯压力和实验室测定瓦斯气体组分含量,结合煤层瓦斯垂直分带理论,对3号煤层瓦斯分布规律进行了研究。研究结果表明:前和煤矿3号煤层瓦斯含量较小,最大实测瓦斯含量为4.60m^(3)/t;原始瓦斯压力和CH_(4)组分含量较低,最大实测瓦斯压力为0.22 MPa,CH_(4)组分含量为70.07%;受井田东部大面积煤层隐伏露头的影响,判定前和煤矿3号煤层处于瓦斯风化带的N_(2)-CH_(4)带;在此带内,煤层瓦斯赋存不均衡,瓦斯含量、瓦斯压力与煤层埋深之间规律性不明显。该研究为矿井瓦斯涌出量预测和合理抽采方法选取提供参考依据。

综合物探方法在章丘多层煤矿采空区探测中的应用

为充分发挥综合物探技术在地下采空区的探测优势,探测地下煤矿采空区的分布特征,更好地服务于城市建设及生态环境保护,选择合适的物探方法至关重要.山东章丘煤矿采空区分布复杂,断裂构造发育,且存在多层煤开采的情况,从分析已有煤矿资料入手,总结煤层分布特征及采空区分布形态,选取高密度电阻率法和EH-4电导率成像法这2种方法对该矿采空区进行勘探,发挥浅层探测优势,选取适当参数,提高探测精度,明确精细化解释原则,推断出勘查区3煤、4煤、7煤、9煤和10煤采空区的分布范围及埋藏深度,并推测主要断裂构造的分布位置.针对物探推断解释的成果,后期进行钻探及井下电视,验证这2种方法组合勘探的效果良好,基本实现对深度30~400 m采空区异常的探测.将高密度电阻率法与EH-4电导率成像法同时运用于煤矿采空区勘查,可为同类场地条件下探测地下煤层采空区提供借鉴.

近距离煤层采空区气体分布特征及运移规律研究

为了防治近距离煤层采空区有毒有害气体的涌出,研究其分布以及运移行为具有重要意义。以山西晋神沙坪煤矿1818工作面为例,布置束管监测系统,以人工采样的方法,获取采空区及工作面相等间隔测点气体成分及体积分数;通过研究下煤层实体煤采动前后上下煤层采空区气体在空间上的分布情况,分别得出上、下采空区气体在采空区前方90 m、后方180 m范围内静态、动态分布规律;基于上、下采空区气体时空分布特征,探讨了近距离煤层开采采空区气体的4个方面的运移机制。研究发现:在采动过程中,近距离采空区有毒有害气体受漏风扩散现象、上下采空区气体运移效应和煤氧反应等多重影响而呈现出向回风侧集聚的显著时空分布规律。

特厚煤层小煤柱沿空掘巷数值分析及应用

沿空掘巷开采技术成功的关键主要取决于采场覆岩稳定的时间和沿空掘巷的位置。采场采动岩体运动导致围岩应力重新分布,动态采场应力作用于围岩并使其状态发生灾变是发生矿山灾害的根本原因。特厚煤层分层综采巷道布置(包括内错、外错和垂直),合理确定煤柱尺寸、巷道支护方式和参数选择能够最大可能发挥围岩的自承能力,是提高巷道稳定的重要保证。在稳定的内应力场范围内布置小煤柱护巷,能够明显提高巷道围岩稳定状态,减少巷道维护费用。通过理论分析、数值模拟和现场实测等方法,对特厚煤层下分层沿空掘巷小煤柱不同巷道布置设计,通过煤柱的应力、应变和位移进行对比分析,确定特厚煤层下分层沿空掘巷合理的巷道位置和煤柱尺寸及上覆岩层防控技术,并得到工程验证是正确可靠的,从而为特厚煤层小煤柱开采技术提供了重要的科学依据。

断层与瓦斯赋存分布规律的关系研究

用地质的观点研究煤层瓦斯赋存已获得实践检验,瓦斯赋存与地质因素密切相关。通过井下实测煤层原始瓦斯含量,选择各项煤层参数均达到要求的瓦斯含量数据,绘制瓦斯含量等值线,分析了两条断层之间煤层的瓦斯含量分布规律。绘制研究区域特定位置的煤厚、瓦斯含量剖面图,定性、定量地分析了断层对煤层产状、煤厚等煤层赋存条件的影响及其对瓦斯赋存规律的控制作用。结果表明,研究区域内的煤层及瓦斯分布受断层影响较大:沿煤层走向,煤厚呈现出"高-低-高-低"的变化,卸压带和应力集中带交互出现,瓦斯含量呈现"低-高-低-高-低"的分布规律;沿煤层倾向,随着埋深的增加,瓦斯含量呈现降低的趋势,小于8m/t的区域不断减少。

近距离煤层群下行开采底板应力分布规律研究

为研究近距离煤层群下行开采下位煤层巷道合理位置,通过建立力学计算模型,推导出底板岩层内应力分量。并结合吴官屯煤业开采实际条件,计算得出上部煤层开采后底板应力状况。结果表明:底板中垂直应力在水平及垂直方向最大影响范围分别达到31m和55m,水平应力在水平及垂直方向最大影响范围分别达到37m和12m,剪切应力在煤柱中心位置下方为0,应力峰值点出现在煤柱边缘,峰值为5.5MPa,该研究可为合理布置下位巷道位置和支护选择提供了依据。

近煤层岩巷掘进中防治煤与瓦斯突出技术研究

为了保证近煤层岩巷的安全快速掘进，采用FLAC加分别对煤层距巷道底板5，10m时的情况进行了数值模拟，研究了近煤层岩巷掘进工作面前方岩层、煤层的应力分布规律，结果表明：煤层距巷道底板5m时，前方5～20m为煤层应力集中区；煤层距巷道底板10m时，其应力集中区在10～25m，其应力峰值处在煤层距巷道底板5m时的集中应力区与原始应力区的交界处。根据煤层应力集中区情况，建议煤层距巷道底板5m时必需采取防突措施，防突长度为掘进工作面前方20m，并进行了合理的钻孔设计。

潘集矿区煤层层滑构造特征及其与潘集背斜的关系

通过对潘集矿区构造特征及矿区构造应力场分析,对潘集背斜两翼的潘北井田和潘一井田中的层滑构造进行研究,将矿区分为10个主层滑区及29个层滑亚区。研究结果显示:矿区层滑构造的产生与南北向主应力场及大型断裂所构建的局部应力场密切相关;层滑构造导致矿区形成近东西向薄煤带,发育以Ⅱ和Ⅲ类型为主的构造煤;层滑构造多发育在背斜两翼,且以断滑型和揉皱型为主,而在背斜核部则以断裂型为主;在纵向上,层滑构造类型也具有明显的规律性,在相对浅的区域,层滑构造以断裂型为主,往下是断滑型,而在较深部位及断裂构造交汇处,则主要表现为揉皱型。

大倾角煤层群下行开采底板破坏机理及工程应用

为保证本煤层正常回采以及下部近距离煤层安全开采,须对采动底板破坏机制进行深入研究。以淮南某矿大倾角大埋深厚煤层开采为背景,建立了底板破坏力学模型,分别从沿走向和沿倾向的理论公式得出各自底板最大破坏深度,再比对结果确定整个工作面底板的最大破坏深度以及最大破坏深度出现的位置。通过在底板不同层位铺设测线,得到回采时垂直应力和剪切应力的分布情况及峰值大小曲线。将所得曲线进行对比分析,揭示了底板破坏过程应力分布规律以及峰值出现部位。其研究结果对于大倾角近距离煤层群的安全回采以及大倾角大埋深厚煤层底板承压水采煤工作面制定防治水措施具有指导意义和参考价值。

北辰矿10煤层瓦斯赋存规律及影响因素分析

针对北辰矿10煤层瓦斯赋存不明的状况,对北辰矿10煤层以往数据进行可靠性评价和分析,采用井下钻屑解吸法对煤层瓦斯含量进行补测,并用瓦斯地质法分析了影响北辰煤矿10煤层瓦斯赋存规律的地质因素。结果表明,北辰矿瓦斯呈"两端大,中间小"规律,且与埋深、构造和岩浆岩有密切关系。这对矿井通风设计及下一步的采掘部署,以及相应的瓦斯防治措施具有重要的指导意义。