冻融循环作用下卸荷砂岩微观损伤特性试验研究

Experimental Study on Micro-Damage Characteristics of Unloaded Sandstone Under Freeze-thaw Cycles

在"一带一路"倡议背景下,大量岩体工程建设在高寒地区,研究高寒地区岩石在冻融环境下的微观损伤演化规律对分析岩石宏观力学性能具有十分重要的意义。以砂岩为研究对象,开展了冻融循环试验;然后,对经历不同冻融循环次数的砂岩进行三轴卸荷试验,得到破坏断口典型部位的切片;最后,对切片进行扫描电镜试验,统计砂岩微裂纹长度、宽度、面积及方位角等微观损伤信息。试验结果表明:在不同的围压和冻融循环次数条件下,断口微裂纹长度由指数分布演化到对数正态分布,微裂纹宽度及面积分别符合对数正态分布和指数分布,微裂纹方位角变化均无明显规律性。初始围压对断口微裂纹的长度,宽度,面积发育起着抑制作用,而冻融作用一定程度上起着促进作用。此研究成果对损伤岩石的宏细力学性能分析提供了一定科学依据。

Under the background of"the Belt and Road"initiative,a large number of rock engineering are being carried out in the alpine region,so it is very important to study the micro-damage evolution law of rocks under the freezing and thawing environment in the alpine region.Taking sandstone as the research object,the freeze-thaw cyclic tests were carried out.Then,triaxial unloading tests were carried out on sandstone which experienced different freeze-thaw cycles to obtain the slices of typical fracture sites.Finally,scanning electron microscopy test was carried out on the slices and the micro-damage information such as the length,width,area and azimuth angles of the micro cracks in sandstone was obtained.The results showed that under different confining pressure and freeze-thaw cycles,the length of micro-cracks at fracture surface evolved from exponential distribution to lognormal distribution.The width and area of micro-cracks accorded with lognormal distribution and exponential distribution respectively,and the azimuth angle of micro-cracks had no obvious regularity.Initial confining pressure inhibited the microcrack length,width and area,while freeze-thaw effect promoted the growth of microcrack to a certain extent.The research results provided a scientific basis for the analysis of macro and micro mechanical properties of damaged rock.