垫条直径对岩石劈裂抗拉强度的影响研究

在岩石巴西劈裂试验中,垫条直径直接影响岩石抗拉强度的大小。为此,选取典型砂岩试样,进行了1.3 mm、1.8 mm、2.3 mm、2.9 mm、3.5 mm、4.0 mm 6种垫条直径的巴西劈裂试验。研究结果表明:(1)钢丝垫条直径从1.3 mm增大到4.0 mm,砂岩劈裂抗拉强度呈“减小—稳定—增大”的非单调变化规律,总体可以分为三个阶段,其中,垫条比为0.026～0.046、0.058～0.081时,砂岩的抗拉强度试验结果变化幅度较大,而且离散性比较明显;垫条比为0.046～0.058时,砂岩的抗拉强度趋于稳定,而且,试验结果离散性明显较小,破裂面平直,垫条对岩样的劈裂张拉破坏起到很好的导向控制作用。(2)钢丝垫条直径对岩石抗拉强度及破坏模式的影响,实际上是垫条直径与矿物颗粒粒径相互关系的影响,从试验结果来看,当垫条比为0.046～0.058时,也即垫条直径与矿物颗粒粒径比值在5.750～7.250时,试验得到的岩石劈裂抗拉强度比较稳定,离散性较小。因此,在岩石巴西劈裂试验中,建议根据岩石矿物颗粒大小选取合适的垫条直径,以保证试验结果的合理性和准确性。

Study on the Influence of the Diameter of the Strip on the Splitting Tensile Strength of Rock

In the Brazilian splitting test, the diameter of the strip directly affects the tensile strength of rock mass. Based on this, typical sandstone specimen was selected as the test object and Brazilian splitting tests were carried out for six pad diameters including 1.3mm, 1.8mm, 2.3mm, 2.9mm, 3.5mm and 4.0mm. The results show that: (1)The diameter of the wire strip increases from 1.3mm to 4.0mm, and the tensile strength of the sandstone splitting is a non-monotonic change law of “reduction-stability-increasing”, which can be divided into three stages. Among them, when the ratio of the strip is 0.026~0.0460 and 0.058~0.081, the tensile strength test results of the sandstone vary greatly, and the dispersion is obvious. When the strip ratio is 0.046~0.058, the tensile strength of the sandstone tends to be stable. The sample results are significantly less discrete, and the rupture surface is straight, and the spacers have a good guiding effect on the cracking and tensile failure of the rock sample. (2)The influence of the diameter of the wire strip on the tensile strength and failure mode of the rock is actually the influence of the relationship between the diameter of the strip and the particle size of the mineral particles. From the test results, when the ratio of the strip is 0.046~0.058, that is, the ratio of the diameter of the strip to the particle size of the mineral particles is between 5.750 and 7.250, the tensile strength of the rock obtained by the test is relatively stable and the dispersion is small. Therefore, in the rock Brazilian splitting test, it is recommended to select the appropriate strip diameter of the strip according to the rock mineral particle size to ensure the rationality and accuracy of the test results.