Shaanxi Huangling No. 2 Coal Mine Co., Ltd.

随着煤矿开采逐渐向深部发展,瓦斯超限事故危害增大,为保障煤矿生产安全,煤层瓦斯钻孔预抽技术是目前较有效的技术之一,钻孔质量对于抽采效果有着重要影响作用。采用FLAC3D数值模拟软件,研究煤体在不同因素影响下钻孔破坏特征,分析煤体纵向位移的变化规律。结果表明,随着钻孔直径的增大,钻孔顶部纵向位移增长1.10%,钻孔腰侧变化较小,钻孔底部纵向位移降低17.05%;随着稳压压力的增大,钻孔顶点纵向位移增大42.48%,钻孔腰侧纵向位移增大38.89%,钻孔底部纵向位移增大38.39%;随着加载速率的增大,钻孔顶点纵向位移最大为0.053mm,钻孔腰侧纵向位移最大为0.023mm,钻孔底部纵向位移最大为0.005mm。钻孔直径、稳压压力及加载速率与纵向位移呈负相关关系。通过对煤体钻孔试件在应力应变曲线中不同阶段进行机理分析,阐明了钻孔失稳全过程的变化情况,为保障煤层瓦斯钻孔安全预抽提供了理论依据。

to ensure the safety of coal mine production, coal seam gas drilling pre-extraction technology is one of the most effectivetechnologies. Drilling quality had an important influence on the extraction effect. Based on FLAC3D numerical simulationsoftware, the characteristics of borehole failure under the influence of different factors were studied. The variation law of coallongitudinal displacement was analyzed. The results show that with the increase of borehole diameter, the longitudinal dis-placement at the top of the borehole increased by 1. 10% . The change of the waist side of the borehole was small. The longi-tudinal displacement at the bottom of the borehole was reduced by 17. 05% . With the increase of the pressure, the longitudi-nal displacement of the borehole vertex increased by 42. 48% . The longitudinal displacement of the waist side of the bore-hole increased by 38. 89% . The longitudinal displacement at the bottom of the borehole increased by 38. 39% . With the in-crease of loading rate, the maximum longitudinal displacement of drilling vertex was 0. 053 mm. The maximum longitudinaldisplacement of the waist side of the borehole was 0. 023 mm. The maximum longitudinal displacement at the bottom of theborehole was 0. 005 mm. The borehole diameter, stabilizing pressure and loading rate were negatively correlated with the lon-gitudinal displacement. Through the mechanism analysis of different stages on the stress-strain curve of coal drilling speci-mens, the whole process of borehole instability was clarified. The study provides a theoretical basis for ensuring the safe pre-extraction of coal seam gas.