基于GSI原理瓦斯抽采钻孔收缩比评估方法及其应用

瓦斯抽采钻孔收缩是致使排渣阻力增大、钻孔发生堵塞的主要因素。基于地质强度指标(GSI)法，分析了评估煤体力学参数的方法，探讨了Mohr-Coulomb与Hoek-Brown准则内在关系，从而能够应用较为广泛的方法验证和求解不同煤层条件下钻孔的变形量；提出了钻孔收缩比概念和计算方法，应用GSI原理对不同强度煤的钻孔收缩比进行定性分析。分析结果表明，钻孔收缩比受煤体强度变化的影响非常敏感，对于强度较低的煤体，钻孔变形量大，钻孔收缩严重，其结果缩小了钻孔的排渣空间，间接增大了钻屑运移、钻杆旋转及退钻阻力，使钻孔施工更加困难。结合工程案例，根据施工地点地质条件，科学评估钻孔收缩比并提出钻孔施工改进方案，通过工业性试验，钻进深度提高40%，钻进效率提高97.5%。

The evaluation method and application of gas drainage borehole shrinkage ratio based on GSI principle

Abstract: Borehole shrinkage is the main factor that resulting slagging resistance increases and drilling clogging. Based on the GSI (geological strength index) method to analyze the evaluation method of coal and rock mechanical parameters. The inherent relationship between Mohr-Coulomb criterion and Hoek-Brown criterion was discussed, which can be applied more widely method solving the deformation in different seam conditions; The concept of borehole shrinkage ratio is proposed, analyzed the borehole shrinkage with different coal strength. The results show that the borehole shrinkage ratio is very sensitive to changes in coal strength, the lower coal strength, the greater the amount of deformation, drilling shrinkage would be more serious. As a result, slagging space decreases, indirectly increasing the drilling cuttings movement resistance, drilling rod rotation drag and retreat drag, drilling construction more difficult. According to the geological conditions of construction sites, borehole shrinkage ratio was evaluated, and drilling construction improvement schemed was proposed. Industrial test results show that the drilling depth increased by 40% and drilling efficiency increased by 97.5%.