Surrounding Rock Failure Mechanism and Control Technology of Gob-Side Entry with Triangle Coal Pillar at Island Longwall Panel in 15 m Extra-Thick Coal Seams

Taking the return air roadway of Tashan 8204 isolated island working face as the background, the evolution law of the stress field in the surrounding rock of the widened coal pillar area roadway during the mining period of the isolated island working face is obtained through numerical simulation. The hazardous area of strong mine pressure under different coal pillar widths is determined. Through simulation, it is known that when the width of the coal pillar is less than 20 m, there is large bearing capacity on the coal side of the roadway entity. The force on the side of the coal pillar is relatively small. When the width of the coal pillar ranges from 25 m to 45 m, the vertical stress on the roadway and surrounding areas is relatively high. Pressure relief measures need to be taken during mining to reduce surrounding rock stress. When the width of the coal pillar is greater than 45 m, the peak stress of the coal pillar is located in the deep part of the surrounding rock, but it still has a certain impact on the roadway. It is necessary to take pressure relief measures to transfer the stress to a deeper depth to ensure the stability of the triangular coal pillar during the safe mining period of the working face. This provides guidance for ensuring the stability of the triangular coal pillar during the safe mining period of the working face.

On the analysis of the high-resolution sequence stratigraphy and coal accumulating law of jurassic in Ordos Basin

The strata of Jurassic was divided into three tectonic sequences and eight se- quences of third rank,according to the developing feature of the tectonic inconformity and the transforming feature of the depositional system tracts.Also the identification and the division of the base-level cycle of different period were carried through.Therefore three cycles of super period,eight cycles of long period,twenty-four cycles of middle period and some cycles of short period were identified.From the overall character of the coal-accu- mulation in the Mesozoic,we can see that the Yan'an formation is of the best nature of coal bearing.When the coal bearing systems of Jurassic were depositing,the Ordos area is the coal accumulating basin of terrene of large scale and located in the same tectonic unit.But the local structure of different part and the paleolandform are different in the basin which resulted in the difference of the depositional environment.So the layer number and the distribution of the thickness of the coal beds are different in the different part of the ba- sin.The coal-accumulating action migrated regularly along with the development,evolve- ment and migration of the depositional systems.The layer numbers of the coal beds, which can be mined,are more in the north and west fringe of the basin,whose distributing area is extensive,and they are more steady in the landscape orientation,also the total thickness is great.Therefore the nature of coal bearing and the coal-accumulating action of different part changed obviously in the space in Ordos area.

Development of a Raoult’s Law-Based Screening-Level Risk Assessment Methodology for Coal Tar and Its Application to Ten Tars Obtained from Former Manufactured Gas Plants in the Eastern United States

A Raoult’s law-based screening-level assessment methodology was developed to calculate the carcinogenic and non-carcinogenic risks from ingestion of coal tar-contaminated water and it was applied to ten coal tars obtained from sites in the eastern United States. This approach provides a simple risk screening based on the conservative assumptions of Tier 1 in both the ASTM RBCA methodology and the USEPA Soil Screening Guidance. Results across the ten tars exhibited similar patterns, even though the coal tars had significantly different chemical compositions, and in all cases the screening-level risks were above the USEPA thresholds. There was no appreciable difference in the total risks when using either the current USEPA 1993 PAH risk assessment guidance or the proposed 2010 guidance. Benzene, while present at low concentrations within the coal tars, posed the dominant risk and strong correlations were observed with the benzene mole fraction.

Research on the gas desorption law of the consumingly destruct coal

To solve the issues of calculating gas loss quantity during sampling,simulated gas desorption process of the consumingly destruct coal with the assembly simulation testing device.Through an analysis of the simulation test datum using SPSS software, established a new formula that can be better description on gas desorption process,more accurate calculation of the gas loss quantity during sampling process,and calculating re- leasable gas quantity during a certain period.Aimed at the new formula,the best time of taking sample is confirmed 3 minutes for consumingly destruct coal,the computative error is less than 10%.Through experiment at laboratory and locale,the new formula could well describe consumingly destruct coal gas desorption law,and it has high calculation preci- sion of gas loss quantity in sampling and desorption quanlity.

Overburden fracture evolution laws and water-controlling technologies in mining very thick coal seam under water-rich roof

Considering the danger of water inrush in mining very thick coal seam under water-rich roof in Majialiang Coal Mine,the universal discrete element(UDEC)software was used to simulate the overburden fracture evolution laws when mining 4#coal seam.Besides,this study researched on the influence of face advancing length,speed and mining height on the height of the water flowing fractured zones(HWFFZ),and analyzed the correlation of face advancing length and change rules of aquifer water levels and goaf water inflow.Based on those mentioned above,this research proposed the following water-controlling technologies:draining the roof water before mining,draining goaf water,reasonable advancing speed and mining thickness.These water-controlling technologies were successfully used in the feld,thus ensured safely mining the very thick coal seam under water-rich roof.

Propagation law of shock waves and gas flow in cross roadway caused by coal and gas outburst

In order to study the propagation law of shock waves and gas flow during coal and gas outburst,we analyzed the formation process of outburst shock waves and gas flow and established the numerical simulation models of the roadways with 45°intersection and 135°intersection to simulate the propagation of outburst gas flow and the process of gas transport.Based on the analysis of the simulation results,we obtained the qualitative and quantitative conclusions on the characteristics and patterns of propagation and attenuation of outburst shock waves and gas flow.With the experimental models,we investigated the outburst shock waves and gas flow in the roadways with the similar structures to the simulated ones.According to the simulation results,when the angle between the driving roadway and the adjacent roadway increased,the sudden pressure variation range in adjacent roadway and the influencing scope of gas flow increased and the sudden pressure variation duration decreased.The intersection between the driving roadway and the adjacent roadway has no effect on airflow reversal induced by the shock waves and gas flow.

Analysis on air-leakage law of goaf in condition of ascending mining for top-coal caving

Using the Jisan Coalmine's top-coal caving for the 3down coal seam with ascending mining as the project background, the air-leakage characteristics of the goaf wasanalyzed. Through data fitting of the in situ observation, the models of gas seepage, diffusion and air-leakage in the goaf were established in ascending mining. The ComputationFluid Dynamics software Fluent was used to simulate the air-leakage law of the goaf. Theresults of the numerical simulation provide a basis for the use of the technology of ventilation and fire prevention in the working face of an ascending mining, which ensures thesafety in production in the working face of the top-coal caving for 3_down coal seam in theJisan Coalmine.

冲击载荷下含瓦斯煤动力学破坏特征与瓦斯渗流规律分析

为探究不同冲击载荷和瓦斯压力作用下的含瓦斯煤动力学特征、裂隙扩展及瓦斯渗流变化规律,采用含瓦斯煤岩冲击损伤-渗流试验系统开展含瓦斯煤冲击试验以及原位渗流测试,并结合工业CT扫描系统进行试样裂隙结构的三维重构,分析含瓦斯煤内部裂隙扩展特征及其对瓦斯渗流的影响规律。研究结果表明,冲击载荷和瓦斯压力对含瓦斯煤的动力学性质、变形过程、裂隙扩展和渗流规律均具有重要影响,具体表现在:①受围压和轴压的影响,冲击载荷耦合瓦斯压力条件下的含瓦斯煤应力-应变曲线无明显压密阶段;含瓦斯煤的变形过程主要经历了弹性变形阶段、应变强化阶段及破坏阶段。②冲击载荷的增加对含瓦斯煤动力学参数具有强化作用,气体压力的升高则劣化了含瓦斯煤动力学参数;冲击载荷越大,瓦斯压力越高,含瓦斯煤的裂隙扩展愈充分,所形成的裂隙结构愈复杂。③含瓦斯煤的渗流规律受控于裂隙扩展,冲击载荷耦合瓦斯压力作用下,含瓦斯煤中存在孔隙流动、孔隙流动-裂隙流动并存及裂隙流动等3种气体流动形式;含瓦斯煤冲击破坏后,随着气体压力增加以及气楔作用的增强,瓦斯流动形式可由孔隙流动依次转变为孔隙流动-裂隙流动并存和裂隙流动;裂隙扩展和流动形式共同影响含瓦斯煤渗流规律,含瓦斯煤渗透率随瓦斯压力的增大总体上符合先增大后减小的变化趋势。

煤层透气性系数新的测试计算方法

煤层透气性系数是衡量煤层瓦斯流动难易程度的关键参数。现行的煤层透气性系数计算式中,将变压力非线性偏微分方程的系数假定为常数,理论推导结果存在较大缺陷,使得现场测定的透气性系数存在较大偏差。为解决煤层透气性系数测定失准的问题,推导了钻孔径向流量法测试煤层透气性系数的过程,并在推导过程中指出该方法存在的问题。以朗格缪尔式瓦斯含量和达西定律为基础,建立无量纲模型,将模型解算结果进行反演拟合,得到新的煤层透气性系数计算式,并通过现场实测钻孔数据进行验证,修正了现行的煤层透气性系数测试方法,提出准确可靠的计算煤层透气性系数的新方法。结果表明:用抛物线式表示煤层瓦斯含量并将变量煤层瓦斯压力p^(1.5)视为常量推导而来的煤层透气性系数计算式,相当于将瓦斯含量拟合成与压力平方成正比关系,理论与实际测算均存在较大误差。采用朗格缪尔式无量纲模型计算出的无因次瓦斯涌出速度Y’进行反演拟合,可解决现行计算方法的缺陷;当吸附常数b与原始瓦斯压力p_(0)的乘积(无因次原始瓦斯压力)不同时,Y’与无因次时间Fo’的函数曲线明显不同,由此得到了含有无因次原始瓦斯压力的透气性系数计算式;当煤层和钻孔条件一定时,由不同时间测试的瓦斯涌出量计算得到的煤层透气性系数λ值具有良好的再现性。新的煤层透气性系数现场测定方法与现行方法完全相同,不增加额外工作量,但新方法的计算更加精确可靠。

Simulation Test for Evolution Laws of Tensile Fractures in a Coal Mining Area

In order to study evolution laws of tensile fractures in a coal mining area, based on the classification of the fractures formed by mining, a physical simulation test was carried out to simulate the dynamic evolution process of tensile fractures in coal mining areas. The results showed that after the coal in the mining area was mined, the mining area underwent obvious movement and deformation and forms tensile fractures. As the min-ing working face was advanced, the tensile fractures underwent the dynamic process of generation, development and closure. The changing curves of density of tensile fractures with the increase of mining length of the working face liked a ladder （it increased slowly and then rapidly） and then had two peaks （the second peak was higher than the first peak）.

急倾斜巨厚煤层复杂空间结构区微震时空演化规律及诱冲机理

煤矿冲击地压灾害的发生与空间结构密切相关,尤其在复杂空间结构区灾害发生更频繁。掌握煤层开采复杂空间结构区煤岩灾变规律并揭示其发生机制对于冲击地压防控具有重要意义。以乌东煤矿为研究背景,采用数值模拟、微震监测、理论分析等方法,研究了岩柱应力异常尺寸效应,分析了复杂空间结构区微震时空演化规律,揭示了复杂空间结构下冲击地压发生机理,评估了煤层开采不同区域的冲击危险性。研究结果表明:①急倾斜岩柱厚度更窄、出露高度更大其撬动效应更强,岩厚变异应力异常形成5个分区。②岩柱厚度更窄区域微震频次更多,能量更高,时空活动度更强,离散性更高。高应力区、应力梯度区、应力平稳区依次呈现“低频次-高能量”、“高频次-高能量”、“低频次-低能量”的微震响应特征。③特殊空间结构区域微震事件簇集且能级增大,时空活动度及离散性陡增,尤其在结构边缘该特征更明显,能量积聚及释放速率增大,冲击地压发生的概率及强度更高。位于岩柱更窄区域的特殊空间结构内微震活动更剧烈。④岩柱厚度越窄(煤柱高度越大)则岩柱向深的弯矩及能量增长速率越快,冲击危险性更高。依据结构面强度效应推断出断裂带发生滑移错动,是能量积聚与释放的优势区域。揭示冲击地压发生机理为高静载及低临界载荷共同作用,基于应力集中特征评估煤层开采不同区域的冲击危险性。

不同含水率条件下含瓦斯煤改进邓肯-张模型

为建立能够合理反映含瓦斯煤在不同含水率和围压工况下的力学特性模型,首先基于已有的含瓦斯煤常规三轴试验,分析其在不同围压和含水率条件下应力-应变特性;其次结合邓肯-张模型与Janbu公式得到相关的邓肯-张模型参数;然后建立初始弹性模量、破坏应力与各影响因素的拟合公式,构建能表征不同应力水平下含瓦斯煤变形规律的改进邓肯-张模型;最后对修正后的模型进行验证,对模型精度进行评价。结果表明:含水率的增加是引起含瓦斯煤模型参数动态变化的重要原因;提出的改进模型预测曲线与实际的试验曲线具有良好的吻合度,该修正模型可以准确反应不同围压和含水率下含瓦斯煤的应力应变特性。

新疆七克台矿区1号井田煤质特征及清洁利用评价

基于新疆七克台矿区煤炭资源丰富及地理位置优越,对其进行煤质特征研究及清洁利用评价,可拓展优质煤炭资源的开发利用途径。以七克台矿区1号井田钻孔煤样为研究对象,结合各煤层地质资料、煤质数据、工艺性质等参数以探究各煤层煤质特征及其随地质条件的演化规律。结果表明:1号井田可采煤6层,煤层埋藏深度整体呈现南浅北深;有机显微组分主要以镜质组为主,含惰质组及少量壳质组;变质程度为中煤级煤Ⅰ,整体呈现南低北高趋势;各煤层主要以低灰、高挥发分、高发热量、中油产率和无黏结性的长焰煤为主,具有特低硫、低磷、低氯、低氟、特低砷和煤灰结渣倾向性严重的特点。参考煤炭清洁利用潜势评价体系及中低温热解、直接液化、气化工艺对煤质指标的要求可知,1号井田煤炭洁净潜势较好,可以用于气化用煤和中低温热解用煤,但不适宜于作为液化用煤。

黑龙江省东部珍子山组的沉积环境与聚煤特征

为全面认识黑龙江省东部珍子山组含煤岩系沉积体系、沉积环境的平面和垂向展布特征以及聚煤特征。采用地质剖面观察及钻孔岩心描述等方法,结合岩石薄片分析,研究了黑龙江东部晚石炭世-早二叠世珍子山组含煤地层的沉积环境和聚煤特征。结果表明:珍子山组岩相类型以砂岩相和黏土岩相为主,沉积环境主要为河流相、滨浅湖相和泥炭沼泽相;厚煤层主要形成在滨浅湖相,位于高位体系域早期和晚期。

彬长矿区胡家河井田4号煤层沉积环境及聚煤规律研究

为研究彬长矿区胡家河井田4号煤层的沉积环境,总结聚煤规律,归纳聚煤模式,综合运用煤田地质学、岩石学、沉积学、构造地质学等多学科交叉研究方法,野外观察和室内分析相结合,对胡家河井田4号煤层的沉积环境及聚煤规律进行分析。结果表明:井田内含煤地层主要为内陆河流相沉积,其中河漫沼泽、牛轭湖以及泛滥平原上的泥炭沼泽是4号煤层的主要沉积环境;富煤带分布于中部及南部,并向东部和西部延伸,富煤中心分布于中部和西南部,与地层沉积中心有较好的对应关系;在靠近西部的古河道时,煤层出现分岔、变薄、尖灭的现象,古河道流经区域富县组和延安组地层全部缺失,形成无煤区。研究成果对于该矿煤炭资源的可持续发展以及提高煤炭资源开发和利用效率具有重要的理论与实践意义。

近距离煤层重复采动覆岩破坏规律及“两带”发育高度分析

为研究近距离煤层重复采动下覆岩破坏规律与“两带”发育高度,预防工作面开采过程中由导水漏风通道引起的工作面顶板漏水、采空区自燃等各种安全事故,以鄂尔多斯市某煤矿为工程背景,采用井下窥视法和数值模拟对近距离煤层开采后覆岩破坏规律以及“两带”发育高度进行分析,揭示了规律形成的原因。研究结果表明:在近距离煤层重复采动影响下,“两带”发育高度远超过上煤层开采,下煤层推进80 m时裂隙带最大发育高度为88 m,与地表贯通形成导水漏风通道;初次采动与重复采动时的裂采比分别为19.33、29.33;裂隙带的发育呈台阶式上升,阶段间的变化表现为激跳形式;覆岩的破坏表现为“拱形→帽形→马鞍形→外O内蝶形”;数值模拟及拟合公式所预测的“两带”发育高度与实测值之间误差率为1%左右,验证了预测的准确性,可为相似工作面的开采以及相似工程提供借鉴。

大倾角大采高软弱顶底板工作面分区矿压规律研究

为研究内蒙古长城二矿大倾角大采高软弱顶底板复杂开采地质条件下,1305S工作面正常区、过渡区、卸压区的矿压显现规律及特征,建立了倾斜煤层采空区冒落矸石滑移充填数值模拟模型,采用数值模拟和现场实测相结合的研究方法进行研究。研究结果表明:沿倾斜方向,1305S工作面中上部所受垂直应力呈现出过渡区>正常区>卸压区的特点,工作面下部呈现出卸压区>过渡区>正常区的特点;1305S工作面推进过程中,平均周期来压步距为13.3 m,周期来压时支架工作阻力在26.75~33.05 MPa之间,沿工作面倾斜方向顶板所受垂直应力总体呈现出工作面上部>中部>下部的特点;巷道工作面一侧的边帮变形量较大。现场实测结果表明,回风巷顶板监测最大移进量为860.18 mm,运输巷顶板监测最大移进量为367.84 mm,两巷围岩移进量呈现出回风巷>运输巷的特点。

煤储层等效有效应力系数变化规律实验研究

煤储层进入饱和气体单相流后,储层有效应力系数的变化规律是正确评估储层渗透性的关键。本文采集不同变质程度的煤岩样品,对不同外界荷载和孔隙压力条件下煤储层的等效有效应力系数进行了研究,结果表明:在孔隙压力一定的条件下,外界荷载对煤储层等效有效应力系数具有负效应,随外界荷载加载,煤储层等效有效应力系数减小,且外界荷载越大负作用越强;在外界荷载一定条件下,随孔隙压力增加,煤储层等效有效应力系数增大,孔隙压力对煤储层等效有效应力系数具有正效应;相对于中阶煤和高阶煤储层,低阶煤储层由于孔隙类型多样,孔隙尺度大,储层的等效有效应力系数在外界荷载和孔隙压力耦合作用下影响程度相对较小。由于煤储层等效有效应力系数在不同外界荷载和孔隙压力下差异较大,煤储层进入饱和气体单相流后,在不考虑解吸收缩效应条件下,煤储层的有效应力变化并非等同于储层孔隙压力的变化,而与煤阶类型、地应力高低和孔隙压力大小密切相关,原位高地应力条件下,由于煤储层的等效有效应力系数较小,随孔隙压力降低,煤储层有效应力变化相对微弱。

通柘煤田二叠系含煤地层岩相古地理特征及其演化规律研究

为了进一步认识和理解通柘煤田二叠系的成煤环境和富煤带的分布及控制因素,通过综合地质分析,对二叠系岩相古地理进行了恢复,共编制出7张反映不同旋回时期特征的岩相古地理图。结果表明:MSC1的古地理单元有辫状河河道、曲流河河道、天然堤、泥炭沼泽、分流间湾洼地;区内主要煤层位于MSC1基准面由上升转为下降的阶段,即最大海泛面位置处;此时正处于大规模海进转海退的时期,海平面缓慢下降,研究区形成了以河流作用为主的三角洲平原,在曲流河河道两侧形成了大面积的泥炭沼泽,研究区内全区发育了煤田范围内厚度最大、可采性最好的二_(1)煤层。