露天矿保水材料持水效果及抗剪特性试验研究

Experimental research on water retention effect and shear resistance of water-retaining materials in open-pit mines

由于煤炭资源的大规模开采和高强度的采矿作业,特别是露天开采造成大面积地表挖损,植被退化和水土流失现象严重,保水材料在露天矿保水复垦工艺技术中得到越来越多的重视。通过对保水材料进行持水效果试验,总结出保水材料的吸水、释水特性,对不同配比的保水复垦土壤材料进行电导率EC值和pH值测试,分析了EC值和pH值变化规律,并基于直接剪切试验,揭示了保水复垦土壤材料的黏聚力、内摩擦角与保水材料含量的关系。试验表明:掺入60~100目(0.15~0.25 mm)的保水材料的保水复垦土壤材料持水效果较好;在常温和烘干条件下,不同目数的保水材料释水速率差距几乎相同,释水量大小差不多;随着测试时间的增加,质量分数为0.1%和0.33%保水复垦土壤材料的EC值逐渐减小且低于0.2,而0.50%和1.00%的EC值总体呈现增大趋势且在84 h时出现明显的突变,其pH值逐渐增大,且0.50%的pH值增大幅度较为缓和;保水复垦土壤材料的抗剪强度随着保水材料含量的增加呈现先增加后减小的趋势;黏聚力随着保水材料含量的增大逐渐减小,内摩擦角随着保水材料含量的增大呈现先增大后减小的趋势,当质量分数超过0.50%时,黏聚力下降速度增大,但内摩擦角达到最大值19.00°;在黏聚力相差不大的情况下,保水材料质量分数为0.50%时的内摩擦角比其他的都大,其保水复垦土壤材料的抗剪特性较好。

The large-scale mining of coal resources and high-intensity mining operations,especially open-pit mining,large-scale surface excavations have caused serious vegetation degradation and soil erosion.Water retaining materials have received more and more attention in the water-retaining and reclamation technology of open-pit mines.Through the water retention effect test of the water retention material,the water absorption and release characteristics of the water retention materials were summarized,and the Electrical Conductivity(EC)value and the pH value of the water retention reclaimed soil materials of different proportions were summarized,and the EC value and the pH value change law were analyzed.Based on the direct shear test,the relationship between the cohesion,the angle of internal friction and the content of the water-retaining reclaimed soil material was revealed.The tests show that the water-retaining soil materials mixed with water-retaining materials of 60-100 meshes have better water-holding effects.Under the conditions of normal temperature and drying,the water-retaining materials with different mesh numbers had almost the same water release rate difference,and the amount of water released was almost the same.As the test time increases,the EC values of 0.1%and 0.33%water-retaining reclaimed soil materials gradually decreases and are lower than 0.2.While the EC values of 0.50%and 1.00%show an overall increasing trend and appear obviously at 84 h,the pH value gradually increases,and the 0.50%pH value increases more moderately.The shear strength first increases and then decreases with the increase of the water-retaining material content.The cohesive force gradually decreases with the increase of the water-retaining material content,and the internal friction angle first increases and then decreases with the increase of the water-retaining material content.When the mass fraction exceeds 0.50%,the cohesive force decreases faster,but the internal friction angle reaches the maximum value of 19.00°.Under the condition that the cohesion is not much different,the internal friction angle of the water-retaining material with a mass fraction of 0.50%is larger than that of the others,and the shear resistance of the water-retaining and reclaimed soil material is better.