高温循环作用后大理岩裂纹扩展试验研究

Experimental study of crack propagation of marble after high temperature cycling

利用偏光显微镜对经历不同高温循环作用后的细粒大理岩进行观测,通过统计微裂纹长度、开度、数量等参数,探讨不同加热循环次数后岩样内微裂纹的扩展规律。结果表明,(1)经历不同热循环次数作用的岩样,微裂纹的数量和长度均不同,未经热处理岩样内颗粒致密,胶结较好,内部无明显的微裂纹。经历4次热循环作用后岩样内微裂纹发育明显,以晶界裂纹为主,开度和长度均显著增加。岩样经历16次热循环作用后开度持续增大,为55μm,是4次热循环的4倍;(2)对不同热循环处理后岩样内部发育微裂纹的方向进行了统计,发现微裂纹无明显的方向性,还表明细观切片的取样位置对微裂纹的发育影响不大;(3)线性裂纹密度随热循环次数的增加而增大,经历16次热循环作用后岩样的线性裂纹密度是没有经历热处理岩样的21倍。

The propagation and coalescence of microcracks of a fine-grained marble after treatment under different high temperature cycles is observed and analyzed using a polarizing microscopy in this study. The thermal cracking behavior in the tested rock specimen is investigated by statistically analyzing the length, width, and quantity of the generated microcracks. The main results obtained from this study are as follows:(1) The number and the total length of thermally-induced microcracks inside the rock specimens after different numbers of thermal cycles are disparate. For specimens without thermal treatment, the grains are compacted and cemented well with each other, and no obvious microcracks are observed. With four thermal cycles' treatment, the microcracks are generally observed in grain boundaries. The width and length are significantly increased as compared with those of specimens without thermal treatment. The width of micro-cracks in rock specimen with sixteen thermal cycles' treatment reaches 55 μm, which is about four times as compared with that in rock specimen with four thermal cycles' treatment.(2) The anisotropy of thermally-induced microcracks inside the rock specimens after different thermal cycles is also analyzed. The results show that there is no obvious preferred direction in the thermally-induced microcracks. It also shows that the sampling position of thin sections has negligible effect on the number of the thermally-induced microcracks.(3) The linear crack density is also found to increase as the number of thermal cycle increases. The linear crack density in rock specimen with sixteen thermal cycles' treatment is about 21 times when compared with that of rock specimens without thermal treatment.