Experimental Study Of Methane Adsorption & Seepage Characteristics Of Coal In Taoyuan Colliery After Long-term Water Immersion

Currently, coal mine flooding is one leading hazard undermine coal exploitation.And it usually takes more than one year for once flooded working faces to take proper actions against it and to be re-exploited. During this period, the inflow water is bound to have influence on not only coal’s micro-structure but also its methane absorption and seepage characteristics, thereby affecting the stress field distribution in flooded working faces. However, its related in-depth studies are rarely reported. In this study,once flooded Taoyuan Colliery, Anhui Province, China was chosen to perform the experiments. Based on theory analysis and experiments simulation, how long-term water immersion affects coal mass during different stages was further studied. The results showed that:With the introduction of Mercury Porosimeterr, the increase of pore volume, pore area, average pore size and porosity were detected after long-term water immersion.And with the help of Fractal Theory, the increase in micro-pore amount due to long-term water immersion was confirmed.Based on different adsorption theories, Langmuir model, BET model and D-A model were adopted to analyze coal’s methane adsorption ability after long-term water immersion. The enhancement of methane adsorption ability due to long-term water immersion was revealed while liquid water left in coal would jeopardize this enhancement.Coal samples’ porosity was examined, including how long-term water immersion affects coal porosity and the role Klinken-berg Effect plays during methane seepage in coal. Experiment results illustrate that coal’s porosity demonstrate a upward trend after long-term water immersion, while liquid water which was left in coal would hinder this trend.All in all, the whole long-term water immersion can be divided into 2 stages,“water intrusion” and “dehydration”, specifically. In the 1st stage, the intrusion water’s effecting zone can be divided into the moisturized seepage zone, the inhibited seepage zone, and the original seepage zone. While in the next stage, dehydrated water’s effect zone can be divided into the air-dry seepage-increasing zone, the water-bearing seepage-increasing zone, and the original zone. Furthermore, stress field measurement found that after water lodging, the stress concentrated zone moved into the deep region and outburst risks in the area of 10~25 m from roadway increased. Therefore,this area should be paid great attention for gas prevention and control.