氣體壓力加卸載過程中無煙煤變形及滲透特性的試驗研究

摘　要:利用自主研發的含瓦斯煤熱流固耦合三軸伺服滲流裝置,以無煙煤型煤試件為研究對象,進行不同軸壓、圍壓條件下氣體壓力加卸載過程中滲流試驗研究,模擬不同煤層深度,以探討煤變形及瓦斯運移演化規律。研究結果表明：(1)在加載過程中,煤應變量減小,吸附瓦斯產生較大的膨脹變形,呈現線性關係,在卸載過程中,煤應變呈增大趨勢,煤逐漸被壓縮。隨軸壓、圍壓增大,下降單位氣體壓力引起的煤應變升高量降低,應變響應程度減小。(2)在加載過程中,隨氣體壓力升高,滲透率先減小後增大趨勢,煤滲透率呈類似"V"型變化趨勢,氣體壓力在1.2 MPa左右存在明顯的拐點,體現煤孔隙擴張的程度和吸附瓦斯層增厚程度影響,依賴於吸附作用或有效應力占主導地位。在卸載過程中,隨著氣體壓力降低,煤滲透率呈先減小後增大趨勢,滲透率增大且變化速度加快,主要依賴有效應力作用或基質收縮的主導地位差異。(3)隨有效應力的增大,煤滲透率呈先減小後增大的趨勢。煤滲透率隨有效應力增大呈對數函數或指數函數關係。(4)氣體壓力具有典型二階段特征,同時滲透率與體積應變具有密切關係,體現出有效應力、吸附膨脹與煤基質收縮同時對裂隙等內部結構的影響。

關鍵詞:采礦工程 氣體壓力 有效應力 滲透率 變形

分類號:　TD713EXPERIMENTAL STUDY OF PERMEABILITY AND DEFORMATION OF ANTHRACITE DURING PROCESS OF GASEOUS LOADING-UNLOADINGYUAN Mei, XU Jiang, LI Bobo, CAO Jie ZHANG Min, CHEN Yuting (1. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China; 2. State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam, Chongqing University, Chongqing 400044, China; 3. College of Mining, Guizhou University, Guiyang, Guizhou 550003, China; 4. Guizhou Key Laboratory of Comprehensive UtilizationofNon-metallic Mineral Resources, Guizhou University, Guiyang, Guizhou 550003, China)Abstract:The homemade triaxial servo-controlled seepage equipment was used to investigate the coal containing methane under the coupled action of thermo-fluid-solid. The gaseous loading-unloading tests under the different confining pressures and axial compressions were carried out to explore the process of the coal deformation and gas migration at different seam depths. During the loading process, the strain of coal decreases linearly withincreasing gas pressures, while during the unloading process, the strain of coal increased with the decreasing ot gas pressures. With the axial compression and the confining pressure increasing, the variations of the strain of coal under unit gas pressure reduce. As the gas pressure increases in the loading process, the permeability of coal decreases firstly then increases, which exhibits a V-shape. The permeability of coal has a turning point at the pressure about 1.2 MPa, which indicates that the expansion degree of coal porosity and the thickness of adsorption layer depends on the adsorption or the dominance of effective stress. As the gas pressure decreases during the unloading process, the permeability of coal decreases firstly then increases due to the effective stress or the effective stress dominance. With the effective stress increases, the permeability of coal decreases firstly then increases. The change of permeability caused by the effective stress is a logarithmic or exponential function in the different intervals. The gas pressure shows a typical of two-stage characteristics. The permeability and the volumetric strain are closely related to each other, indicating that the effective stress, the expansion due to absorption as well as the matrix shrinkage all affect the internal structures of coal.

Keyword:mining engineering： gas pressure; effective stress; permeability; deformation