尾粉砂的结构构造特点决定了其临界水力梯度大于常规的砂性土,按常规计算公式得到的管涌型尾粉砂的临界水力梯度计算值远小于实测值,因此,常规土的临界水力梯度计算方法并不适用于尾粉砂。通过收集整理尾粉砂的物理与颗粒特征指标,对比分析流土型与管涌型尾粉砂的颗粒级配特征,得到尾粉砂产生管涌的颗粒级配条件。在分析尾粉砂颗粒形态特征、颗粒级配特征、孔隙特征与临界水力梯度之间的关系的基础上,用特定的尾粉砂试样测定发生管涌时的临界水力梯度与孔隙率(比)之间的函数关系,进而导出尾粉砂发生管涌的临界水力梯度的计算通式,最后通过室内试验检验按计算通式计算结果的可靠性。相关试验检验表明,该计算通式的计算结果与室内实测结果基本吻合,可用来估算尾粉砂发生管涌的临界水力梯度,估算值略偏于安全。

The critical hydraulic gradient of tailing silt is greater than that of conventional sand soil, which is determined by the tailing silt’s structure characteristic,and the calculated critical hydraulic gradient of piping-typed tailing silt by conventional formula is far less than the measured values. Therefore, the conventional calculation method can not be applied to tailing silt. Through collecting large amount of physical indexes and particles characteristic indexes of the tailing silt and comparing the grain size distribution characteristics of flowing soil-typed tailing silt with that of piping-typed tailing silt, we deduced the tailing silt’s grain size distribution conditions in which piping occurred. Afterwards, based on the analysis of the correlations between critical hydraulic gradient and the particle morphology or the grain size distribution, pore characteristics, the function relationship between the critical hydraulic gradient and the porosity (void ratio) of particular tailing silt was measured when the piping generates, and then a generalized computing equation of critical hydraulic gradient was exported. Finally, the reliability of the general formula calculation results is properly verified by laboratory test, and the results show that the measured value is basically in agreement with the calculated value. Therefore, this calculation formula can be used to estimate the critical hydraulic gradient of piping-typed tailing silt, and the estimation result is on the safe side.