卸围压条件下花岗岩强度特性及三维裂隙演化规律

为研究卸围压条件下花岗岩强度特性和三维裂隙演化规律,对花岗岩开展了常规三轴压缩、卸围压-加轴压和分级卸围压-加轴压循环加卸载3种不同应力路径力学试验,获得对应的轴、径向应力-应变曲线;采用CT扫描三维重构技术获得岩石卸围压过程中和破坏后内部裂隙分布三维图像.结果表明:相对于常规三轴压缩试验,试件在卸荷条件下脆性破坏特征更加显著,分级卸围压-加轴压循环加卸载会增大花岗岩的峰后延性,降低破坏轴压和破坏剧烈程度;两种卸围压方案都会使花岗岩的承载能力降低30%左右;卸荷作用下花岗岩宏观破裂为拉剪组合状,拉剪过渡不明显,表观裂隙是内部裂隙向外扩展的结果;花岗岩在卸荷作用下峰前产生的裂隙量较少,大量裂隙在峰后产生,破裂具有突发性和瞬时性,围压较低时宏观裂隙首先在试件边缘产生,围压较高时宏观裂隙首先在试件中部产生.     

三轴卸荷条件下煤体力学特性和能量耗散演化

孤岛工作面煤体和巷道受周边开采扰动影响,煤体受循环荷载作用存在卸荷力学行为而表现出动态破坏特性.为探讨不同路径下煤体力学特性,利用TAW-2000三轴电液伺服刚性试验机分别进行常规三轴(T)、三轴循环荷载(TC)以及相应卸围压试验(TU、TCU),分析不同围压下煤体卸围压强度、变形、声发射事件以及能量耗散演化特征,开展...     

A method of determining the permeability coefficient of coal seam based on the permeability of loaded coal

This study developed the equipment for thermo-fluid–solid coupling of methane-containing coal, and investigated the seepage character of loaded coal under different working conditions. Regarding the effective pressure as a variable, the variation characteristics of the gas permeability of loaded methane-containing coal has been studied under the conditions of different confining pressures and pore pressures. The qualitative and quantitative relationship between effective stress and permeability of loaded methane-containing coal has been established, considering the adsorption of deformation, amount of pore gas compression and temperature variation. The results show that the permeability of coal samples decreases along with the increasing effective stress. Based on the Darcy law, the correlation equation between the effective stress and permeability coefficient of coal seam has been established by combining the permeability coefficient of loaded coal and effective stress. On the basis of experimental data, this equation is used for calculation, and the results are in accordance with the measured gas permeability coefficient of coal seam. In conclusion, this method can be accurate and convenient to determine the gas permeability coefficient of coal seam, and provide evidence for forecasting that of the deep coal seam.     

不同围压下茅口灰岩渐进性破坏的试验研究

利用MTS815电液伺服控制刚性试验机进行不同围压下茅口灰岩三轴压缩试验,通过计算绘得相应裂隙体积应变图,分析得出裂纹起始应力、裂纹破坏应力。结果表明:随着围压的增大,应力门槛值均呈非线性增长态势,当围压超过17 MPa时,裂纹起始应力、裂纹破坏应力分别增加48.5%和20.1%,茅口灰岩延性开始增强;裂纹破坏应力为峰值强度的64%~75%,三轴压缩下茅口灰岩裂隙不稳定发展阶段较长;环向应变值随围压增大而增大,当轴力超过裂纹破坏应力进入裂隙不稳定发展阶段,环向应变增大2.7~3.2倍,用环向-轴向应力应变曲线图能较好的反映岩石应力门槛值。     

预应力路堤附加围压场与围压增强效应

利用ABAQUS建立预应力路堤（PE）三维有限元模型,以侧压板（LPP）宽度1.2 m,边坡坡率1∶1为例,分析其内部附加围压场的分布特征. 结果表明：随距路堤坡面水平向深度增加,板体覆盖侧附加围压由浅层 “腹鼓形”差异分布逐渐过渡至深部的较均匀分布;板体3个外延区的附加围压均随坡面水平向内深度先增后减,以不同峰值围压扩散角将预应力扩散至路堤受荷核心区,且峰值扩散角依次为：板外上侧<板外左、右两侧<板外下侧. 基于强度折减法,分析预应力路堤整体稳定性能,并探寻板间距的优化设计方法和思路. 开展典型路堤填料的系列静动三轴试验,论证预应力加固结构能有效提高填料的静动力抗载和抗变形性能,并建立填料临界动应力与围压间的经验式,可以为补强铁路路堤土围压提供参考.     

吸附气体对受载含瓦斯煤渗流特性影响的试验研究

利用自主研发的含瓦斯煤岩三轴压缩试验系统,进行了大量受载瓦斯煤的渗透特性室内试验,对比分析了CO2,CH4和N2的渗透率之间的异同.研究结果表明,在恒定瓦斯压力条件下,煤样渗透率随围压的增大而减小,均服从负指数函数变化规律;在恒定围压条件下,煤样渗透率随瓦斯压力的增加而减小,并且表现出幂函数变化规律;吸附性强弱不同的气体所表现出来的渗透性也不一样,气体吸附性越强,渗透性越弱;在轴向加载情况下,不同气体的渗透率都表现出先减小后增大的现象,并且具有一般的"V"字型变化规律.研究结果对深入认识煤层瓦斯运移规律具有一定的理论价值.     

Coupling effects of coal pillars of thick coal seams in large-space stopes and hard stratum on mine pressure

Concerning the issue of mine pressure behaviors occurred in fully mechanized caving mining of thick coal seams beneath hard stratum in Datong Mining Area, combined with thin and thick plate theory, the paper utilizes theoretical analysis, similar experiments, numerical simulations and field tests to study the influence of remaining coal pillars in Jurassic system goaf on hard stratum fractures, as well as mine pressure behaviors under their coupling effects. The paper concludes the solution formula of initial fault displacement in hard stratum caused by remaining coal pillars. Experiments prove that coupling effects can enhance mine pressure behaviors on working faces. When inter-layer inferior key strata fractures, mine pressure phenomenon such as significant roof weighting steps and increasing resistance in support.When inter-layer superior key strata fractures, the scope of overlying strata extends to Jurassic system goaf, dual-system stopes cut through, and remaining coal pillars lose stability. As a result, the bottom inferior key strata also lose stability. It causes huge impacts on working face, and the second mine pressure behaviors. These phenomena provide evidence for research on other similar mine strata pressure behaviors occurred in dual-system mines with remaining coal pillars.     

Mechanical behavior of coal under different mining rates: A case study from laboratory experiments to field testing

During deep mining, the excavation disturbance stress path is the domination factor for the stability of the surrounding rock mass as well as the ground pressure. One of the important parameters of the stress path is the loading or unloading rate of the disturbed rock or coal, which depended on the mining rate. To achieve a well understanding of the mining rate and its effect on the coal behavior, a preliminary case investigation of the mechanical properties of the coal at the various mining rates in both the laboratory scale and field scale was performed. Based on the uniaxial compression test and the digital image correlation(DIC) method, the mechanical behavior of the coal samples, such as the evolution of the strength,surface deformation, crack propagation, and elastic strain energy of the coal under the various loading rates were analyzed. A threshold range of the loading rate has been observed. The uniaxial compressive strength(UCS) and releasable elastic strain energy(Ue) increase with increasing loading rate when the loading rate is below the threshold. Otherwise, the UCS and Uemay decrease with the loading rate.Under the low loading rate( 0.05 mm/min), the tensile deformation of the original defects could result in crack coalescence, whereas failure of the coal matrix is the key contributor to the crack coalescence under the high loading rate(greater than 0.05 mm/min). Afterwards, with the consideration of the bearing capacity(UCS) and energy release of the mining-disturbed coal mass(Ue), a power exponential relationship between the mining rate(MR) in the field and the critical loading rate(vc) in the laboratory was proposed. The application potential of the formulas was then validated against the field monitored data.Finally, based on the critical loading rate, the released strain energy, and the monitored pressure on the roof supports, a reasonable mining rate MRfor the Ji 15-31030 working face was determined to be approximately 3 m/d.     

复合水体下急倾斜煤层开采的水害防治研究

淮南孔集煤矿山西组A1、A3煤层总厚6m,为第四系含水砂层下底板岩溶水上复合含水体威胁的急倾斜煤层。对于砂层水害防治,采用合理留设防水煤柱,沿用“小阶段、长走向、间歇开采”的方式方法;对于底板岩溶水患防治,采用“疏水降压、限压开采”的防治水方法;对于局部抽冒及流水钻孔涌砂造成地表抽冒漏斗及岩溶塌陷漏斗,采取了“按尺核产、严禁超限出煤”、“小流量、长历时、控砂疏水”的有力措施。实现了安全开采,取得了良好的效果。     

Exploitation technology of pressure relief coalbed methane in vertical surface wells in the Huainan coal mining area

Exploitation technology of pressure relief coalbed methane in vertical surface wells is a new method for exploration of gas and coalbed methane exploitation in mining areas with high concentrations of gas, where tectonic coal developed. Studies on vertical surface well technology in the Huainan Coal Mining area play a role in demonstration in the use of clean, new energy re-sources, preventing and reducing coal mine gas accidents and protecting the environment. Based on the practice of gas drainage engineering of pressure relief coalbed methane in vertical surface wells and combined with relative geological and exploration en-gineering theories, the design principles of design and structure of wells of pressure relief coaibed methane in vertical surface wells are studied. The effects of extraction and their causes are discussed and the impact of geological conditions on gas production of the vertical surface wells are analyzed. The results indicate that in mining areas with high concentrations of gas, where tectonic coal developed, a success rate of pressure relief coalbed methane in surface vertical well is high and single well production usually great. But deformation due to coal exploitation could damage boreholes and cause breaks in the connection between aquifers and bore-holes, which could induce a decrease, even a complete halt in gas production of a single well. The design of well site location and wellbore configuration are the key for technology. The development of the geological conditions for coalbed methane have a sig-nificant effect on gas production of coalbed methane wells.     

Resistivity response to the porosity and permeability of low rank coal

Laojunmiao coal samples from the eastern Junggar basin were studied to understand the relationship between coal resistivity and the physical parameters of coal reservoirs under high temperatures and pressures.Specifically,we analysed the relationship of coal resistivity to porosity and permeability via heating and pressurization experiments.The results indicated that coal resistivity decreases exponentially with increasing pressure.Increasing the temperature decreases the resistivity.The sensitivity of coal resistivity to the confining pressure is worse when the temperature is higher.The resistivity of dry coal samples was linearly related to φ~m.Increasing the temperature decreased the cementation exponent(m).Increasing the confining pressure exponentially decreases the porosity.Decreasing the pressure increases the resistivity and porosity for a constant temperature.Increasing the temperature yields a quadratic relationship between the resistivity and permeability for a constant confining pressure.Based on the Archie formula,we obtained the coupling relationship between coal resistivity and permeability for Laojunmiao coal samples at different temperatures and confining pressures.     

Principle and engineering application of pressure relief gas drainage in low permeability outburst coal seam

With the increase in mining depth, the danger of coal and gas outbursts increases. In order to drain coal gas effectively and to eliminate the risk of coal and gas outbursts, we used a specific number of penetration boreholes for draining of pressure relief gas. Based on the principle of overlying strata movement, deformation and pressure relief, a good effect of gas drainage was obtained. The practice in the Panyi coal mine has shown that, after mining the Cllcoal seam as the protective layer, the relative expansion deformation value of the protected layer C13 reached 2.63%, The permeability coefficient increased 2880 times, the gas drainage rate of the C13 coal seam increased to more than 60%, the amount of gas was reduced from 13.0 to 5.2 m3/t and the gas pressure declined from 4.4 to 0.4 MPa, which caused the danger the outbursts in the coal seams to be eliminated. The result was that we achieved a safe and highly efficient mining operation of the C 13 coal seam.     

Prediction of geotemperatures in coal-bearing strata and implications for coal bed methane accumulation in the Bide-Santang basin,western Guizhou,China

The geothermal fields of coal-bearing strata have become a key topic in geological research into coal and coal bed methane(CBM). Based on temperature data from 135 boreholes that penetrate the Upper Permian coal-bearing strata in the Bide-Santang basin, western Guizhou, the precisions of geothermal predictions made using a geothermal gradient model and a gray sequence GM(1,1) model are analyzed and compared. The results indicate that the gray sequence GM(1,1) model is more appropriate for the prediction of geothermal fields. The GM(1,1) model is used to predict the geothermal field at three levels with depths of 500, 1000, and 1500 m, as well as within the No. 6, No. 16, and No. 27 coal seams. The results indicate that the geotemperatures of the 500 m depth level are between 21.0 and 30.0 °C, indicating no heat damage; the geotemperatures of the 1000 m depth level are between 29.4 and 44.7 °C,indicating the first level of heat damage; and the geotemperatures of the 1500 m depth level are between35.6 and 63.4 °C, indicating the second level of heat damage. The CBM contents are positively correlated with the geotemperatures of the coal seams. The target area for CBM development is identified.     

Response characteristics of gas pressure under simultaneous static and dynamic load: Implication for coal and gas outburst mechanism

Coal and gas outbursts are dynamic disasters in which a large mass of gas and coal suddenly emerges in a mining space within a split second. The interaction between the gas pressure and stress environment is one of the key factors that induce coal and gas outbursts. In this study, first, the coupling relationship between the gas pressure in the coal body ahead of the working face and the dynamic load was investigated using experimental observations, numerical simulations, and mine-site investiga...     

轮胎侧偏力学特性的胎压影响分析及预测

利用平板式轮胎试验台进行了不同胎压及载荷下轮胎侧偏试验,辨识UniTire模型参数,分析侧向力和回正力矩特性参数与胎压变化的关系。提出预测胎压影响的试验方法,并据此构造胎压影响的预测模型,进而计算模型参数并实现另一胎压下轮胎侧偏特性预测。预测的侧偏侧向力及回正力矩精度都达到85%以上,验证了本文方法的有效性。     

Mechanical properties and failure modes of stratified backfill under triaxial cyclic loading and unloading

Multiple filling of gobs will lead to a layered structure of the backfill. To explore the influence of layering structure on the mechanical properties and failure modes of backfill, different backfill specimens were prepared with a cement/sand ratio of 1:4, a slurry concentration of 75%, and backfilling times of 1, 2, 3 and 4, separately. Triaxial cyclic loading and unloading experiments were carried out. The results show that with an increase in backfilling time, the peak strength of backfill decreases as a polynomial function and the peak strain increases as an exponential function. The cyclic load enhances the linear characteristic of backfill deformation. The loading and unloading deformation moduli have a linear negative correlation with the backfilling time. The unloading deformation modulus is always slightly higher than the loading deformation modulus. The failure modes of stratified backfill are mainly characterized by conjugate shear failure at the upper layer and tensile failure across the layer plane, and there is usually no damage in the lower layer away from the loading area.     

Evaluation and intelligent deployment of coal and coalbed methane coupling coordinated exploitation based on Bayesian network and cuckoo search

Coal and coalbed methane (CBM) coordinated exploitation is a key technology for the safe exploitation of both resources. However, existing studies lack the quantification and evaluation of the degree of coordination between coal mining and coalbed methane extraction. In this study, the concept of coal and coalbed methane coupling coordinated exploitation was proposed, and the corresponding evaluation model was established using the Bayesian principle. On this basis, the objective function of coal and coalbed methane coordinated exploitation deployment was established, and the optimal deployment was determined through a cuckoo search. The results show that clarifying the coupling coordinated level of coal and coalbed methane resource exploitation in coal mines is conducive to adjusting the deployment plan in advance. The case study results show that the evaluation and intelligent deployment method proposed in this paper can effectively evaluate the coupling coordinated level of coal and coalbed methane resource exploitation and intelligently optimize the deployment of coal mine operations. The optimization results demonstrate that the safe and efficient exploitation of coal and CBM resources is promoted, and coal mining and coalbed methane extraction processes show greater cooperation. The observations and findings of this study provide a critical reference for coal mine resource exploitation in the future.     

黔西地区煤储层压力发育特征及成因

为了查明黔西地区煤储层压力差异发育的成因,从区域和构造单元两个层次探讨了煤储层压力的分布特征以及保存条件、生气条件、渗透性和地应力特征等因素对储层压力的影响．结果表明：该区煤储层主要以正常压力（压力系数为0．9～1．1）和高压系统（压力系数大于1．1）为主,不同构造单元内同一煤层压力系数差别大,同一构造单元内不同煤层压力系数也存在较大差别．储层渗透性和地应力发育特征影响着各套煤储层的差异沟通能力,决定了储层压力的高低,是区域储层压力差异发育的主要原因．对于盘关向斜,由于具有较好的压力保存条件,煤储层压力的差异发育受到生气条件的影响,同时也遵循由应力主导下的渗透性控制规律．     

单轴循环冲击下花岗岩力学特性与损伤演化机理

为研究循环冲击荷载下黑云母花岗岩的动态力学特性,利用改进的分离式霍普金森压杆,选取4种不同的入射波应力幅值对花岗岩试样进行等幅循环冲击,并对相关机理和试验现象进行探析.结果表明:入射波应力幅值为110.57和90.48 MPa时,随着冲击次数的增加,岩样的峰值应力逐渐降低,最大应变、平均应变率和损伤值均呈现增大趋势;入射波应力幅值为70.82 MPa时,花岗岩的峰值应力随着冲击次数的增加表现出先增强后降低的特性,而最大应变、平均应变率与损伤值则表现出相反规律;入射波应力幅值降为50.69 MPa时,岩样的力学性质基本不变,岩样未见明显的损伤.此外,研究还发现基于岩样静态压缩应力-应变曲线推求的静态裂纹起裂应力,经强度增长比例系数放大后可得到动态裂纹起裂应力,籍此能较好地解释上述循环冲击试验中所观测到的现象.     

注水压裂条件下软煤裂隙损伤与煤层气渗透耦合特征

针对豫西"三软"煤层的低渗性与流变性,探讨了复杂地质条件下主采二1煤层生、储气层的变形特征.基于ABAQUS平台进行软件二次开发,讨论了注水压裂条件下二1煤裂隙的应力与损伤特性;利用T-P损伤演化准则的Cohesive单元,揭示了软煤裂隙的张裂宽度与延伸距离之间的近似线性关系.模拟结果表明,注水压力条件下,软煤裂隙的应力与损伤演化是一个随时间逐渐发展的过程,在5~10 MPa静荷载作用下,注水1~2 h,软煤裂隙的损伤范围约为80~100 m,从而大幅度地改善了"三软"煤层低渗性能.