载荷煤体渗透率演化特性及在卸压瓦斯抽采中的应用
发布时间：2018-10-12 17:42
【摘要】：煤层卸压开采是通过应力释放使煤体产生大量的新生裂隙，改变煤体结构特征，促使煤层渗透性发生了根本性的改变，实现煤层增透以促瓦斯抽采。本文以煤层卸压开采为主线，以载荷煤体渗透率演化特性和煤体裂隙扩展机制为重点，以理论分析、实验研究、数值模拟和工程实践为主要手段，研究加卸荷过程中煤体裂隙演化和渗透率变化过程，获得渗透率演化规律和建立相应模型，并将结果应用于卸压开采下被保护层渗透率的分布特性和卸压瓦斯抽采的研究。本论文的主要研究结论如下： （1）制取标准原煤样，采用与卸压开采煤层受力特征相同的力学路径，进行了不同加卸荷下的渗透率实验，得到了不同层理方向上渗透率比达7.5：1，分析卸荷过程渗透率演化差异原因，提出在相同卸荷点应力下试样初始损伤程度越大，卸荷极限承载强度就越低，致使在卸荷过程中试样损伤变形的加剧和大量新裂隙的产生，，最终渗透率剧增且大于加荷过程的渗透率。根据渗透实验结果获得了卸荷增透的实验现象和新认识。 （2）将损伤力学、卸荷力学和渗流力学相结合，运用RFPA2D Flow软件模拟了加卸荷作用下不同预置层理试件裂隙起裂、扩展、贯通机制和渗透特性，获得载荷条件下试件裂隙演化过程和渗透变化规律，渗透率的变化与裂隙演化具有一致性。并与渗透实验对比分析，指出卸荷点处试件内部出现的破坏点和损伤微裂隙越多，在卸荷后微裂隙扩展速度就越快，破坏点数量则更多，最终易产发生破断变形，渗透率剧增。 （3）根据在载荷条件下试样渗透实验和裂隙演化模拟，得出加荷过程试样渗透率随着有效应力的增大而减小；而卸荷过程试样渗透率随着有效应力的减小而增大，但卸荷过程渗透率并非是加荷过程的简单逆过程，并建立了载荷煤体渗透率与有效应力的关系。对比了试样渗透率演化的整体过程及规律，获得了卸荷过程渗透率演化的三种典型路径的概念模型，提出了与载荷煤体变形特征相对应的弹性渗透率模型、塑性渗透率模型和卸荷增透模型。 （4）根据铁法矿区大隆煤矿煤层赋存特点，利用FLAC3D软件对试验矿区被保护层采动变形和应力变化进行模拟研究，得出被保护层采动变形和应力变化规律。结合渗透率演化实验及模型，并利用Matlab中的Surf函数获得了下被保护层渗透率空间分布规律，把卸压采动影响区域的渗透率划分为原始渗透区、弹性渗透区、塑性渗透区和卸荷增透Ⅰ区、卸荷增透Ⅱ区。根据研究结果，选取底抽巷穿层钻孔对被保护层的卸压瓦斯进行抽采，并抽采钻孔的布置方式进行优化。
[Abstract]:The coal seam pressure relief mining is through the stress release causes the coal body to produce a large number of new fissures, changes the coal body structure characteristic, impels the coal seam permeability to have the fundamental change, realizes the coal seam to resist the permeation to promote the gas drainage. This paper focuses on the coal seam pressure relief mining, the evolution characteristics of the permeability of the loaded coal body and the mechanism of fracture expansion of the coal body, and takes the theoretical analysis, experimental research, numerical simulation and engineering practice as the main means. The evolution of fracture and permeability of coal body during loading and unloading are studied, the evolution law of permeability and the corresponding model are obtained, and the results are applied to the study of permeability distribution characteristics of protected layer and gas extraction under pressure relief. The main conclusions of this paper are as follows: (1) the permeability experiments under different loading and unloading conditions are carried out using the mechanical path which is the same as the mechanical characteristics of the unloaded coal seams, and the standard raw coal samples are made. The permeability of Prida 7.5: 1 in different stratification directions is obtained. The reasons for the difference in permeability evolution during unloading are analyzed. It is concluded that the greater the initial damage degree of the specimen is under the same unloading point stress, the lower the ultimate unloading load strength is. As a result, the damage and deformation of specimen and the emergence of a large number of new fractures in the unloading process, the final permeability increases sharply and is larger than the permeability in the loading process. According to the results of permeation experiment, the experimental phenomenon and new understanding of antireflection of unloading are obtained. (2) by combining damage mechanics, unloading mechanics and seepage mechanics, the fracture initiation of different pre-bedded specimens under unloading is simulated by using RFPA2D / Flow software. The fracture evolution process and permeability change law of the specimen under loading conditions are obtained. The change of permeability is consistent with that of fracture evolution. Compared with the permeation experiment, it is pointed out that the more damage points and microcracks appear in the specimens at unloading points, the faster the microcracks spread after unloading, and the more the number of failure points are, and finally, the fracture deformation will occur easily. (3) according to the experiment of specimen permeability and the simulation of fracture evolution under loading condition, it is concluded that the permeability of specimen decreases with the increase of effective stress during loading. The permeability increases with the decrease of effective stress, but the permeability of unloading process is not a simple inverse process of loading process, and the relationship between the permeability of loaded coal and the effective stress is established. By comparing the whole process and law of sample permeability evolution, the conceptual models of three typical paths of permeability evolution in unloading process are obtained, and the elastic permeability model corresponding to the deformation characteristics of loaded coal is proposed. Plastic permeability model and unloading antireflection model. (4) according to the characteristics of coal seam occurrence in Dalong Coal Mine of Tiefa Mine, the mining deformation and stress change of protected layer in test mining area are simulated by FLAC3D software. The law of mining deformation and stress change of protected layer is obtained. Combined with the permeability evolution experiment and model, and using the Surf function in Matlab, the permeability distribution law of the lower protected layer is obtained, and the permeability of the area affected by unpressurized mining is divided into the original permeability area and the elastic permeable zone. Plastic permeation zone, unloading antireflection zone 鈪
本文编号：2267023
[Abstract]:The coal seam pressure relief mining is through the stress release causes the coal body to produce a large number of new fissures, changes the coal body structure characteristic, impels the coal seam permeability to have the fundamental change, realizes the coal seam to resist the permeation to promote the gas drainage. This paper focuses on the coal seam pressure relief mining, the evolution characteristics of the permeability of the loaded coal body and the mechanism of fracture expansion of the coal body, and takes the theoretical analysis, experimental research, numerical simulation and engineering practice as the main means. The evolution of fracture and permeability of coal body during loading and unloading are studied, the evolution law of permeability and the corresponding model are obtained, and the results are applied to the study of permeability distribution characteristics of protected layer and gas extraction under pressure relief. The main conclusions of this paper are as follows: (1) the permeability experiments under different loading and unloading conditions are carried out using the mechanical path which is the same as the mechanical characteristics of the unloaded coal seams, and the standard raw coal samples are made. The permeability of Prida 7.5: 1 in different stratification directions is obtained. The reasons for the difference in permeability evolution during unloading are analyzed. It is concluded that the greater the initial damage degree of the specimen is under the same unloading point stress, the lower the ultimate unloading load strength is. As a result, the damage and deformation of specimen and the emergence of a large number of new fractures in the unloading process, the final permeability increases sharply and is larger than the permeability in the loading process. According to the results of permeation experiment, the experimental phenomenon and new understanding of antireflection of unloading are obtained. (2) by combining damage mechanics, unloading mechanics and seepage mechanics, the fracture initiation of different pre-bedded specimens under unloading is simulated by using RFPA2D / Flow software. The fracture evolution process and permeability change law of the specimen under loading conditions are obtained. The change of permeability is consistent with that of fracture evolution. Compared with the permeation experiment, it is pointed out that the more damage points and microcracks appear in the specimens at unloading points, the faster the microcracks spread after unloading, and the more the number of failure points are, and finally, the fracture deformation will occur easily. (3) according to the experiment of specimen permeability and the simulation of fracture evolution under loading condition, it is concluded that the permeability of specimen decreases with the increase of effective stress during loading. The permeability increases with the decrease of effective stress, but the permeability of unloading process is not a simple inverse process of loading process, and the relationship between the permeability of loaded coal and the effective stress is established. By comparing the whole process and law of sample permeability evolution, the conceptual models of three typical paths of permeability evolution in unloading process are obtained, and the elastic permeability model corresponding to the deformation characteristics of loaded coal is proposed. Plastic permeability model and unloading antireflection model. (4) according to the characteristics of coal seam occurrence in Dalong Coal Mine of Tiefa Mine, the mining deformation and stress change of protected layer in test mining area are simulated by FLAC3D software. The law of mining deformation and stress change of protected layer is obtained. Combined with the permeability evolution experiment and model, and using the Surf function in Matlab, the permeability distribution law of the lower protected layer is obtained, and the permeability of the area affected by unpressurized mining is divided into the original permeability area and the elastic permeable zone. Plastic permeation zone, unloading antireflection zone 鈪
本文编号：2267023
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