加载历程对配径碎煤渗透特性影响的试验研究

Experimental study of impact of loading history on permeability characteristics of broken coal with different grain size gradations

为了证实加载历程对破碎煤样渗透特性的影响,利用一套由齿轮泵、换向阀、溢流阀和渗透仪等组成的渗透回路,在CMT5305型电子万能试验机试验系统上测试了配径碎煤在两种不同试验方案下的渗透特性,得到了两种方案配径碎煤的渗流速度、渗透率、非Darcy流因子与孔隙度的关系。研究表明:①第1种试验方案的渗流速度和渗透率与孔隙度的关系用幂函数拟合,第2种试验方案的渗流速度和渗透率与孔隙度的关系可用指数函数拟合。②孔隙度较大时,渗透率和非Darcy流因子与加载历程有关;孔隙度较小时,渗透率和非Darcy流因子趋于稳定,与加载历程无关。③随着孔隙度的减小,方案1非Darcy流因子由负变正,配径碎煤的渗透性加强;方案2非Darcy流因子始终为负值,配径碎煤的渗透性减弱。④两种方案的非Darcy流因子与孔隙度均可采用三次多项式拟合,多项式的系数与加载历程有关。

In order to confirm the impact of the loading history on the permeability characteristics of broken coal, the permeability characteristics of broken coal with different grain size gradations are tested under two experimental schemes by the CMT5305 electronic universal testing machine with a seepage circuit which is composed of gear pump, reversing valve, overflow valve, permeameter, etc. And the relations between the seepage velocity, permeability, the non-Darcy flowb factor and the porosity are obtained under the two experimental schemes. The experimental results show： ①The power function fits the relationship between the seepage velocity, permeability and the porosity in the first experimental scheme; and exponential function fits the same relationship in the second scheme. ②When the porosity is large, the permeability and the non-Darcy flowbfactor bear a relation to the loading history, while when the porosity is small, they tend to be stable and are independent of the loading history. ③With the decrease of the porosity, the non-Darcy flowb factor changes from negative to positive in the first scheme; and the permeability characteristics of the broken coal with different grain size gradations are strengthened; but the non-Darcy flowb factor is always negative in the second scheme and the permeability characteristics are weakened. ④Relation between the non-Darcy flowbfactor and the porosity can be fitted by the cubic polynomial, of which the coefficients have connections with the loading history.