低瓦斯矿井封闭采空区“呼吸”现象特征及防控技术

低瓦斯矿井停采工作面进行封闭处理后，大量游离瓦斯会集聚在封闭空间内。当密闭质量下降到一定程度时，采空区外界空气压力的波动会引发封闭采空区“呼吸”现象，该现象会使密闭外侧存在瓦斯超限的安全隐患。以正利煤矿14-1103封闭采空区为研究对象，分析了不同大气参数条件下封闭采空区内、外气压以及密闭外侧瓦斯体积分数的变化规律。运用通风能量方程和理想气体状态方程分析了“呼吸”现象的产生机理，结合达西定律得到了密闭内外压差与密闭外瓦斯体积分数的关系表达式。结果表明，封闭采空区“呼吸”现象的产生是地面大气参数、井巷风流参数、井巷特征和采空区内气体状态参数综合作用的结果;在密闭内外压差的持续作用下，封闭采空区会与外界产生气体交换，当压差分别为正值和负值时，采空区内气体压力分别呈逐渐降低和逐渐升高趋势;封闭采空区内气压变化幅度很小，密闭内外压差产生正负交替的主导因素为密闭外空气静压的波动;当井巷特征和井巷风量稳定时，密闭外侧空气静压的变化趋势与地面大气压相似，与地面大气温度相反;在密闭渗透率和密闭外侧风量比较稳定的前提下，密闭内外压差为正值时，密闭外瓦斯浓度与密闭内外压差呈正相关关系，两者的变化趋势相似。为了预防密闭外侧瓦斯超限，设计了由监测信号采集子系统、现场自动控制子系统和管道抑爆子系统组成的瓦斯释放自动监测调控系统，确定了基于压差阈值和瓦斯浓度阈值的联合调控准则，提出了阀门开度的分级调控逻辑思路。

Characteristics and control technology of breathing phenomenon of sealed goaf in low gas mine

After the mining face of low gas mine is sealed,a large number of free gas gathers in the sealed space.When the quality of the seal drops to a certain extent,the fluctuation of the air pressure out of the sealed goaf will cause “breathing” phenomenon and lead to the gas concentration of the seal’s outside exceed safety limit.No.14-1103 sealed goaf of Zhengli Coalmine is selected as the research object,the variation law on inner and outer pressure of sealed goaf and gas concentration of the seal’s outside are analyzed under different atmospheric parameters.The mechanism of “breathing” phenomenon is theoretically analyzed with ventilation energy equation and state equation of ideal gas,and the expression of relationship between differential pressure and gas concentration is obtained with Darcy law.The results show that,“breathing” phenomenon results from the combining action of ground atmospheric parameters,airflow parameters,roadway characteristics and gas state parameters of sealed goaf.Under the continuous action of differential pressure between seal’s inside and outside,gas exchange will occur between sealed goaf and outside space.The gas pressure in sealed goaf is gradually decreasing or increasing as the differential pressure is positive or negative.The gas pressure in sealed goaf has small change,the fluctuation of static pressure of the seal’s outside is the dominant factor that results in positive and negative alternation of differential pressure.The variation trend of the static pressure of the seal’s outside is similar to that of the ground atmospheric pressure and opposite to that of the ground atmospheric temperature when roadway characteristics and air quantity are stable.On the premise that the seal’s permeability and the air quantity of seal’s outside are relatively stable,the gas concentration is positively correlated with the differential pressure when the positive differential pressure appears,so that,the change trend of gas concentration is similar to that of differential pressure.An automatic control system of gas release,which consists of monitoring signal acquisition subsystem,field automatic control subsystem and pipeline explosion suppression subsystem,is designed to prevent gas concentration of seal’s outside from exceeding safety limit.The joint control criteria is determined based on the threshold values of differential pressure and gas concentration,and the grading control logic of valve opening is put forward.