割縫預抽後煤瓦斯吸附特性的變化特征

摘　要:為了研究割縫預抽後煤瓦斯吸附特性的變化特征,以楊柳煤礦10煤層7個煤樣為研究對象,采用甲烷等溫吸附實驗測定煤樣的Langmuir方程吸附常數a和b,通過壓汞實驗和低溫液氮吸附實驗的有機結合,表征煤樣孔徑分布和比表麵積的變化。結果表明：(1)隨著煤樣與割縫孔距離的增大,吸附常數a呈逐漸增大的趨勢,而吸附常數b的變化趨勢則相反,但與甲烷等溫吸附曲線的曲率變化趨勢一致。(2)隨著煤樣與割縫孔距離的增大,煤樣孔徑分布發生顯著的變化,吸附孔孔容比從33.27%增大到55.38%,比表麵積從7.254 m2/g增大到9.856 m2/g。(3)割縫預抽後,煤樣參數曲線(Langmuir方程吸附常數、吸附孔孔容比和比表麵積)的變化幅度均呈現出平緩→急劇→平緩的趨勢,具有有界性和非線性的特征,符合Boltzmann方程。割縫預抽後煤瓦斯吸附特性的變化存在明顯的分區特征：變化顯著區(小於1.8m)、變化過渡區(1.8~4.5m)和變化不顯著區(大於4.5m)。(4)割縫預抽後煤體瓦斯壓力下降,有效應力增大,進而控製煤體的吸附特性。研究結果可以為煤層水力割縫增透實踐提供可靠的基礎理論支撐。

關鍵詞:采礦工程 水力割縫 煤的吸附特性 Boltzmann方程

分類號:　TD712VARIATION OF GAS ADSORPTION OF COAL AFTER HYDRAULIC SLOTTING AND PRE-DRAININGZOU Quanle LIN Baiquan, LIU Ting, ZHU Chuanjie, YAN Fazhi, ZHOUYan (1. School of Safety Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China~ 2. State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China)Abstract:Experiments were carried out to investigate the variation of gas adsorption of coal after the treatment of hydraulic slotting and pre-draining using seven coal samples obtained from coal seam 10 of Yangliu mine. The experiment of isothermal adsorption of methane was adopted to measure the adsorption constants. The mercury injection capillary pressure(MICP) and the nitrogen gas adsorption(N2GA) were applied to obtain the variation of the pore size distribution and the specific surface area. With the increasing of the distance between the sampling locations and the slotted borehole, the adsorption constant a increases and the adsorption constant b decreases, which are consistent with the variation of the curvature of the curves of isothermal adsorption of methane. With the increase of borehole distance, the pore size distribution of coal sample varies substantially. The volumetric proportion of adsorption pore increases from 33.27% to 55.38% and the specific surface area increases from 7.254 m2/g to 9.856 m2/g. The curves of parameters(adsorption constants, volumetric proportion of adsorption pore and specific surface area) of coal within the slotting disturbance were found to be bounded and nonlinear and the curves varied gently initially, then drastically and finally gently again, obeying the Boltzmann equation. The gasadsorption of coal mass after the treatment of hydraulic slotting and pre-draining related closely to the distance from the slotting hole. The region below 1.8 m is significantly affected; the region between 1.8 and 4.5 m is transitional and the region over 4.5 m away is little influenced. Slotting disturbance leads to the decrease of the gas pressure and the increase of the effective stress, controlling the adsorption property of coal.

Keyword:mining engineering; hydraulic slotting; adsorption property of coal; Boltzmann equation