煤与瓦斯共采三维大尺度物理模拟实验系统的研制与应用

Research and development of 3D large-scale physical simulation experimental system for coal and gas co-extraction and its application

为进一步解决煤与瓦斯共采模型实验研究手段不足的问题,自主研制了一套煤与瓦斯共采三维大尺度物理模拟实验系统。该系统采用模块化设计,高度集成机、电、液、气于一体,主要由大尺度箱体(3. 0 m×2. 5 m×1. 8 m)与基座、自动液压开采、柔性加载、自动通风、瓦斯抽采、瓦斯注入以及综合数据采集与控制等7个子单元构成。按几何相似比1∶100计,加载单元可模拟最大采深2 105 m,开采单元可模拟采高0～12 m以及推进距离200 m;通风单元可模拟U型、U+L型、Y型等多种通风方式以及实现不同风量通风;抽采单元可模拟高位巷、高位钻孔、地面抽采等多种立体化抽采方式;瓦斯注入单元采用独立注入方式,实现不同瓦斯涌出量、不同位置的瓦斯涌出;综合数据采集与控制单元实现覆岩裂隙、矿山压力、瓦斯运移、瓦斯抽采等表征参数的采集以及对整个实验系统进行自动控制。该实验系统可进行工作面煤层开采、通风、瓦斯涌出与抽采等功能的模拟,实现煤层开采过程中覆岩裂隙演化、矿山压力分布、卸压瓦斯运移、瓦斯抽采等科学问题的一体同步研究。运用该系统对山西某矿302工作面开采过程进行模拟实验,得到了该矿条件下基本顶初次来压步距45 m,周期来压步距20 m,覆岩破坏在空间上呈椭圆抛物形态等覆岩破断与裂隙演化规律;工作面推进过程中应力峰值不断前移,应力集中系数2. 11～2. 63,超前工作面距离6～11 m等动态应力变化规律;在卸压瓦斯储集与分布规律方面,得到采空区后部76～120 m瓦斯浓度增加较快,120 m之后趋于稳定,采空区上部5～60 m裂隙带中瓦斯浓度逐渐增加,裂隙带最上层瓦斯浓度达到65%～68%。实验结果表明,该系统能够较好进行工作面煤与瓦斯共采全过程的模型实验研究。

In order to overcome the shortcomings of experimental research methods for coal and gas co-extraction model,a set of 3D large-scale physical simulation experimental system for coal and gas co-extraction was developed.The system adopts modular design and highly integrates the machine,electricity, liquid and gas functions in one.It is mainly composed of seven sub-units including large-scale box body ( 3.0 m×2.5 m×1.8 m) and base,automatic hydraulic mining, flexible loading,automatic ventilation,gas extraction,gas injection,and integrated data acquisition and control. Following the geometric similarity ratio of 1 ∶ 100, the loading unit can simulate a maximum mining depth of 2105 m, the mining unit can simulate a mining height of 0-12 m and a face retreat distance of 200 m.The ventilation unit can simulate various ventilation modes such as U-type,U+L-type,Y-type with different flow quantities.The gas extraction unit can simulate gas drainage using different kinds of methods and a combination of them, such as a high-level gas drainage roadway,cross measure borehole and surface borehole. The gas injection unit adopts independent injection mode to realize gas emission at different positions and different gas emission rates.Comprehensive data acquisition and control unit is able to obtain the characterization parameters such as overburden fissures, strata pressure,gas migration, gas extraction and automatic control of the whole experimental system.Therefore, the experimental system can simulate coal seam mining process under different ventilation,gas emission and extraction conditions,making it possible to simultaneously study the overburden fracture evolution,mine pressure distribution,pressure relieved gas migration,gas extraction and other scientific issues during coal mining operation.The system was used to simulate the mining process at the 302 working face of a mine in Shanxi province,China.The laws of overburden breakage and fracture evolution were obtained, such as, the first weighting of the main roof was 45 m, the periodical weighting interval is 20 m,and the overburden failure shows a 3D elliptical parabolic pattern.The dynamic variation of stress was obtained, indicating the peak stress moves forward continuously with the stress concentration coefficient variation between 2.11 and 2.63,and the peak stress occurrence at about 6-11 m ahead of the working face.In terms of the storage and distribution of pressure relieved gas, it was found that the gas concentration increased rapidly at 76-120 m behind face in the goaf and became stable beyond 120 m.The gas concentration increased gradually from the lower section to the higher section of the fractured zone which was about 5-60 m above the extraction level, reaching about 65%-68% at the top of fractured zone. The experimental results show that the system can well carry out the model experimental study of the whole process of coal and gas co-extraction in working face.