深部极薄煤层钻采卸压增透作用机理研究

Coal, rock and gas outbursts can potentially happen when the coal seam group with high gas and deep burial depth is excavated. Pressure relief of the thin coal seam mining, low gas pressure and gas content is an effective way to avoid the above dynamic disasters. Current study of pressure relief and permeability enhancement mechanism is mostly focused on longwall mining face, the study of pressure relief and permeability enhancement mechanism of auger mining is very limited. Based on the research background of pressure relief of excavating the extremely thin seam of coal seam group, performance evaluation coupling model of pressure relief of “stress-damage- transfusion” in auger mining face is obtained in this study, based on the evolution laws of gas flow, stress and fissure of surrounding rock of protected seam. The relationship of the pressure relief effect, surrounding rock and the auger mining parameter can be analyzed. The design of interval coal pillar size can be reported with the analysis of the characteristics of surrounding rock stress, fissure and gas flow under the process of the temporary support and compression failure of the interval coal pillar. With the analysis of pressure relief of the protective seam and the arrangement of mining face and excavating face, and the time and space relationship of gas extraction of protected seam, application conditions of pressure relief of auger mining based on the extreme pressure relief range is proposed. The research results are positively significant to consummate the pressure relief theory of mining the protective seam.

在深部高瓦斯煤层群开采条件下，易发生煤与瓦斯突出、冲击矿压等动力灾害，通过先采瓦斯压力小、含量低、厚度小的薄煤层进行卸压保护是避免上述灾害的有效手段,现有关于卸压增透机理的研究成果多针对长壁式工作面，缺少对钻采工作面卸压增透作用机理的研究。本项目以深部极薄煤层钻采卸压开采为研究背景，在对极薄保护层钻采工作面及被保护层工作面围岩应力、裂隙演化规律、瓦斯流场特征研究的基础上，建立钻采面围岩“应力-损伤-渗流”耦合的卸压增透效果评价模型，分析钻采参数、围岩性质与卸压增透效果的相关关系；研究钻采面间隔煤柱暂时支撑、滞后压酥破坏过程的围岩应力、裂隙、瓦斯演化特征及其对被保护层工作面卸压增透效果的影响机制，给出间隔煤柱尺寸设计方法；探索保护层钻采卸压与被保护层工作面采掘布置及瓦斯抽采的时空关系，提出基于极限卸压范围的钻采卸压增透的适用条件。研究成果对完善保护层卸压开采理论具有积极意义。

在深部高瓦斯煤层群开采条件下，易发生煤与瓦斯突出、冲击矿压等动力灾害，通过先采瓦斯压力小、含量低、厚度小的薄煤层进行卸压保护是避免上述灾害的有效手段，现有关于卸压增透机理的研究成果多针对长壁式工作面，缺少对钻采工作面卸压增透作用机理的研究。本项目以深部极薄煤层钻采卸压开采为研究背景，提出了U型间断隔离通风的新型钻采工作面布置方式，研究了钻采面围岩应力、裂隙和渗流演化特征。由于间隔煤柱的存在，钻采工作面下沉与裂隙发育范围较长壁工作面小。采用数值模拟的方法确定不同钻采参数情况下，采动裂隙与渗透率变化关系，间隔煤柱宽度和钻采宽度对渗透率的影响较大。针对传统钻采方式卸压增透的不足，提出了一种保护层钻采参数设计方法，分析了间隔煤柱失稳对被保护层渗透率的影响机制。通过设置临时宽煤柱、增大一次钻采宽度、减小间隔煤柱宽度，提升被保护层的卸压增透效果，设计了钻采参数确定流程，建立了钻采主要参数确定的力学模型，确立了合理钻采参数，并分析了顶板岩性、煤层特征对上述参数的影响规律。间隔煤柱失稳前，受其支撑作用影响，覆岩裂隙不发育，卸压增透效果有限，间隔煤柱失稳后，覆岩裂隙发育范围变大。建立钻采卸压增透的“应力-损伤-渗流”耦合模型，分析了极薄保护层钻采与被保护层卸压增透的时空演化规律。针对采用不同钻采参数时被保护层应力特征、损伤特征及渗流特征进行对比研究，随着煤柱尺寸减小与钻采厚度与深度增加，被保护层增透效果增强。同时对比长壁开采与钻采卸压增透效果，本项目提出的新型钻采卸压增透效果能够达到长壁的84％，能够满足生产实际需求，为极近距离高瓦斯煤层群被保护层的瓦斯抽采提供依据。