采空区三维漏风路径示踪测试

On the air leakage gas tracer test in the 3-D goaf of the coal seam group mining

采用SF6示踪气体探测技术,对Y型通风方式下采空区三维裂隙场漏风路径进行了测试。结果表明:示踪气体在采空区内发生弥散,采样点采集到的示踪气体体积分数随时间变化呈先快速增大后逐渐减小的规律,具有拖尾现象;距工作面155 m范围内,采空区裂隙带上部漏风速度较小,示踪气体体积分数高,裂隙带下部及冒落带漏风速度较大,示踪气体体积分数低;155 m后,冒落带、裂隙带下部和裂隙带上部示踪气体体积分数相差不大;采空区漏风路径是经顶板裂隙绕流后下降至冒落带的曲线渗流路径。

The present paper is concerned about the air leakage gas tracer test in the three-dimensional goaf in case of the coal seam group mining condition. As is known,it is one of the major factors to realize safety production in the mining workface under the condition of the gas control in the goaf. The defining of the gas flow range and its characteristic features may serve as the basis for the gas control and help to optimize the setting parameters of gas drilling extraction（ in case of the tunnel）. In 2013,we managed to carry out SF6 as the tracer gas test in hoping to find the gas flowing regularity in the Y-type ventilation goaf in the eastern part of Panji No. 1 Coal Mine. SF6 tracer gas is characterized in a way of continuous and equal release in the lower corner of coal working face through 5 groups of boreholes,which can be used as the sampling points arranged along the gob of the Y-type ventilation goaf. More exactly speaking,each group is given 3boreholes,whose ends are located in the caving zone,in the lower and upper areas of the fracture zone,respectively. What is more,each borehole should be sealed with polyurethane when the pipe is buried to result in an air chamber so that a 3-D space samples can be collected on different heights of the goaf with the help of a pump. At the same time,the gas concentration can be analyzed through the gas chromatography and find the change of the concentration of SF6 with the elapse of time,thus,working out the moving pace and speed of SF6. The results of the aforementioned experiment show that,the tracer gas diffusion tends to occur in the goaf at every sample point,while the volume fraction of the collected SF6 tends to increase at first,and then decrease as the time goes on. In addition,compared with the caving zone and the lower area of fracture zone,the air leakage in the upper part of the fractured zone tends to go slower within the 155 m from the working face in the goaf,whereas the tracer gas volume fraction may turn to be higher in a range of 155 m. However,just slight difference can be found,between the lower area and the upper area of fracture zone with the collected tracer gas volume fraction and the air leakage speed in the caving zone. Based on the above results,it can be deduced that the air leakage in the goaf,is supposed to experience a curved path,that is,flowing around the roof,breaking out and then lowering to the caved path.