基于不同弹性本构方程的塑性区宽度及封孔长度研究

Study of plastic zone width and sealing length based on different elastic constitutive equations

煤层注水是煤矿开采过程中重要的增透卸压手段,而封孔长度是影响注水压裂效果的一个关键因素。为了确定出合理的封孔长度,根据Lippmann煤层失稳基本理论,选取了6种不同的弹性区本构方程,引入非线性动态瓦斯压力分布的表达式,构建了含瓦斯煤层力学理论模型,得到煤层垂直、水平应力和塑性区宽度的解析式,之后结合高家堡的现场情况,对比分析6种弹性本构方程下的煤层应力分布曲线及塑性区宽度,并进行了现场封孔试验。结果表明:封孔长度在9.5 m时孔洞漏水量小、未出现异常现象,封孔效果良好,最终确定出了合理的封孔长度为9.5 m;相对于其他3种弹性本构方程,选取第i、v、vi种弹性本构方程对封孔长度进行理论计算分析,更加符合现场实际情况。

The water injection into coal seam is an effective means of increasing and discharging pressure during coal mining. The sealing length is a key factor affecting the effect of water injection fracturing. To determine the reasonable sealing length, six different elastic constitutive equations were selected according to the basic theory of Lippmann coal seam instability. The expression of nonlinear dynamic gas pressure distribution was introduced, and the mechanical theory model of gas-containing coal seam was constructed. Accordingly, this study obtained the formulas for the vertical, horizontal stress and plastic zone width of coal seam. Combined with the Gaojiapu coal mine, this study compared and analysed the stress distribution curves and the plastic zone widths of the coal seam calculated by three elastic constitutive equations. Moreover, the field sealing experiment was carried out. The results show that the hole leakage is small and not abnormal when the sealing hole length is 9.5 m, which indicates the sealing effect is good and a reasonable sealing length is 9.5 m. Compared with the other three elastic constitutive equations, the calculated results by i, v and vi elastic constitutive equations well confirm with the actual length of the sealing.