锚喷支护巷道喷射混凝土力学性能试验研究

Laboratory test on mechanical properties of shotcrete in bolt shotcrete supporting roadway

为研究煤矿锚喷支护巷道喷射混凝土的力学性能,采用“喷射大板法”在煤矿井下施工现场制作混凝土标准试块,通过实验室试验全面、简捷地测试了喷射混凝土在不同养护龄期下的抗压、抗拉、抗弯、抗剪系列强度以及粘聚力和内摩擦角等力学参数。试验结果表明:喷射混凝土的抗压、抗拉强度随时间呈对数式增长规律,前期增长迅速、后期增长缓慢,第7天的增长幅度高达373%~406%,第28d的增长幅度仅为9%~12%;抗弯、抗剪强度随时间呈抛物线式变化规律,前期一直增长,至21d左右达到峰值,最大抗弯、抗剪强度分别为5.04MPa、5.26MPa,之后呈下降趋势,28d抗弯、抗剪强度降幅分别为18%、19%;喷射混凝土28d基准抗拉、抗弯、抗剪强度为3.04MPa、4.11MPa、4.29MPa,分别为抗压强度的7%、9%、10%;喷射混凝土的粘聚力、内摩擦角分别约为C=0.20MPa、φ=50°。试验结果为喷射混凝土力学性能评估和数值模拟参数选取提供了依据。

In order to study the mechanical properties of shotcrete in bolt shotcrete support roadway of coal mine, the “shotcrete large plate method” was used to make concrete standard test blocks in the construction site of coal mine. Through laboratory tests, the compressive, tensile, flexural, shear series strengths, cohesion, internal friction angle and other mechanical parameters of shotcrete under different curing ages were comprehensively and simply tested. The test results show that the compressive strength and tensile strength of shotcrete increase logarithmically with time, with rapid growth in the early stage and slow growth in the late stage. The growth rate is as high as 373%~406% on the 7th day and only 9%~12% on the 28th day. The bending strength and shear strength change in a parabola with time. They keep increasing in the early stage, reaching the peak value at about 21d. The maximum bending strength and shear strength are 5.04MPa and 5.26MPa, respectively, and then they show a downward trend. The bending strength and shear strength decrease at 28d are 18% and 19%, respectively. The 28d benchmark tensile, flexural and shear strengths of shotcrete are 3.04MPa, 4.11MPa and 4.29MPa, respectively, that is 7%, 9% and 10% of the compressive strength. The cohesion is about 0.20MPa and the internal friction angle is about 50°. The experimental results provide a basis for the evaluation of mechanical properties of shotcrete and the selection of numerical simulation parameters.