被保护层双重卸压特性研究

为探索复合煤层群保护层开采时在双重卸压条件下被保护层的不同卸压特性,采用物理相似模拟试验和计算机数值模拟来研究其双重卸压规律。对比分析被保护层的膨胀率和卸压率后发现:在双重卸压条件下,被保护层的膨胀变形呈现"M"形态,膨胀率在不同时空下表现出叠加特性;另外,煤岩体的弹性势能因受首采保护层的影响而释放,被保护层卸压率表现出卸压区域边缘不连续而卸压程度和范围均增加的特点。最后,现场测试计算得到被保护层的透气性系数,其变化规律证实双重卸压效果明显。

On the depressurized effect likely to be produced by the double pressure relief on the protective coal seam

The paper is inclined to make a numerical simulated study for the double relief mechanism of the protective layers through a physical modeling experiment so as to identify and determinate the different depressurization characteristic features of the protective coal seam under the double pressure-relief conditions in the mining process of the composite protective seam layers.What is more,a careful contrastive analysis of the inflation rate and the unloading rate of the protected coal seam can also help to find that under the above said conditions,the protective coal seam tends to expand or extend and then deform into a letter "M" shape due to the super-polated effect inflation.In addition,the secondary development would like to lead to further stope fracture,which may in turn expand and deform the mined-out area,whereas the protected coal seam would like to be extended more seriously and significantly in the range of the relief threshold.Under such conditions,it would become easier for us to make observation more fully due to the more obvious fracture in the coal and rock through the mining of a double layer protection in the vivo connection.At the same time,it would also be possible to increase the permeability significantly in case of resulting in a convenient channel under way for the gas mining pumped out.Affected by the initial mining protective layer,the overlying coal and rock may also tend to release some potential elastic energy.Nevertheless,since the transformation from the elastic state into the plastic state,the bending square which the transformation tends to be subjected to may become smaller with the bearing capacity of the overlying rock getting somehow reduced.In such a situation,the protective coal seam may turn to be somewhat discontinuous with the area edge of the protective coal seam being unloaded.However,the unloading degree and the range of the protected coal seam may all turn to be significantly extended and enlarged.At this moment,the variation of the protected layer permeability coefficient can be worked out by calculating the permeability coefficient of the protective coal seam.Thus,the results of our simulation and the modeling experiment can demonstrate that the double pressure relief effect turns to be very obvious and realistically beneficial to the gas adsorption and drainage.