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为研究瓦斯渗流场作用下的煤层抽放钻孔周围应力分布情况,假定钻孔周围煤体中瓦斯的流动为稳定径向流动状态,建立了渗流力学模型,给出了瓦斯径向稳定渗流方程;在考虑瓦斯渗流场作用下,推导了钻孔周围煤体的微元体力学平衡方程,并引入应力调整系数,求解出其弹性应力解析解;再应用Mohr-Coulomb屈服准则,求解出钻孔周围煤体的塑性应力和塑性半径的解析表达式。通过实例分析表明:钻孔内的抽放负压对钻孔周围煤体应力、塑性区的半径等参数影响较小;在一定的抽放负压(15k Pa)下,随着煤层原始瓦斯压力的增大,钻孔周围煤体的塑性区半径随之增大,距钻孔足够远处的弹性区煤体的应力也随之增大,这比不考虑瓦斯渗流场作用时的经典弹塑性解更加符合实际情况。
In order to study the stress distribution around coal seam drainage holes under the action of gas seepage field, assuming that the flow of gas in the coal around the borehole is steady radial flow, a seepage mechanics model is established and the gas radial steady seepage equation Based on the gas seepage field, the mechanical equation of the micro-bodies of the coal around the borehole is deduced and the stress adjustment coefficient is introduced to solve the elastic stress analytical solution. The Mohr-Coulomb yield criterion is used to solve the borehole Analytical Expressions of Plastic Stress and Plastic Radius of Coal Around. The case study shows that the negative pressure of drainage in the borehole has little influence on the stress of coal and the radius of the plastic zone around the borehole. Under certain drainage negative pressure (15kPa), with the initial coal seam gas pressure , The radius of the plastic zone of the coal surrounding the borehole increases, and the stress of the elastic zone in the elastic zone far enough from the borehole increases, which is higher than that of the classical elasto-plasticity without considering the effect of gas seepage field Solutions more in line with the actual situation.