【正文】 er. The change of ground stress can visibly reflect the pressure relief level, but the stress is hard to measure in the field, so we adopted the extent of coal deformation and the coal seam permeability coefficient to reflect the level indirectly. Relative deformationWe adopted a base point method to investigate the deformation of the C13 coal seam. To start, we drilled a deep hole, and then installed test points in the roof and floor of the C13 coal seam, where the deformation was determined by the relative displacement of the two test points. The measured results are shown in . We can see that, during mining of the B11 coal seam, the C13 coal seam was first pressed, and then expanded, the maximum pression deformation was 27 mm and the maximum expansion deformation mm, so that the maximum relative pression deformation was %, and the maximum relative expanding deformation %. The bigger the expansion deformation, the better the effect of pressure relief. Variation of permeability coefficientThe orieinal coal seam nermeabilitv coefficient was only ().After mining the B11 coal seam, the pressure was relieved from the C13 coal seam and the permeability coefficient clearly increased. By using the amounts of residual gas and the borehole gas inrush, we calculated that the permeability coefficient had increased to m2(), an increase of almost 2880 times, which indicated that the C13 coal seam was now in the condition where gas has been drained.6 Drainage effect of pressure relief gas Amount and rate of gas drainage1) Analysis of drainage of pressure relief gasWhen the protective working face advanced 40 m over the suction drilling field, the amount of gas drained rapidly increased. shows the variation in the amount of gas drainage in the drilling yard of the Huainan coal mine. The original 20 days was the period of increased gas drainage, enhanced pressure releasing activity and the amount of gas drainage increased. The period between 2080 days was the active period of gas drainage, the pressure release activity became regular and permeability reached a maximum. Gas drainage was regular and the amount of gas drained from a single hole was over m3/min. After day 80 the attenuation period set in, where the coal seam became gradually pacted, permeability reduced, the residual pressure became small and the amount of gas drainage reduced exponentially. According to this research, a highly effective drainage period was 2 months, the length of the affected area was 160 m and the number of active drainage holes was 16. On average, the amount of gas drained from a single hole was about m3/min Aftter 4 months of continuous gas drainage ,the rate of gas drainage reached over 60%.2) Total amount of gas drainage and amount of residual gasThe total amount of gas drainage includes the amount drained from penetration boreholes and wind emission in the floor roadway. The period of working face 21213 for which statistics were obtained was from , 2000 to Jan. 31, 2001, 365 days in accumulated amount of gas drainage by penetralion boreholes was and the amount by wind emission Mm3.The reserves of the protected layer were Mm3 and the total amount of gas drainage ,so that the rate of gas drainage reached 60%. The amount of gas inrush and amount of gas flowing into workout areas of the protective layer were not inccluded in our calculation, so that the actual rate of gas drainage was larger than the calculated value,.,a rate over 60%. Since the orieinal amount of eas of the C13 coal seam was 13m3/t. the restauai eas content was , given our calculations. Gas pressureWith the advancement of the working face, the pressure gauge value gradually decreased from , when the working face was 100 m away from the pressure measured hole。由于過度的巖層運(yùn)動，變形減壓原則獲得一個好的氣體引流效果?；诋?dāng)前潘一煤礦的煤層狀況，在開采中我們采用了開采保護(hù)層開采技術(shù)進(jìn)而從保護(hù)層釋放瓦斯,在底板使用鋼筋混泥土網(wǎng)狀滲透鉆孔,有效地降低其瓦斯的含量,完全消除突出的危險,取得了安全、高效的開采環(huán)境。B11煤層是4～179。.d)煤層也穩(wěn)定且其地質(zhì)結(jié)構(gòu)簡單。/t，煤炭的濃度系上漲48%～100%。一方面，這個位置要保證安全，避免氣體從C13煤層涌出,防止另一個煤層開挖的錯誤。開孔的位置位于鉆場的頂部。測量結(jié)果顯示在圖2我們可以看到的B11煤炭開采過程中，最大的壓縮變形的C13煤層先壓縮，然后擴(kuò)大，％，％，膨脹變形越大，泄壓的效果更好。 經(jīng)過80天的衰減期，煤層逐漸壓縮，透氣性降低，殘余瓦斯壓力變小，抽放瓦斯量成倍減少。保護(hù)層的保障是減少瓦斯含量和卸壓。突出的危險已經(jīng)完全被