循环三轴应力路径下钙质砂颗粒破碎演化规律

钙质砂广泛分布于中国南海区域,是吹填造陆的重要材料。钙质砂颗粒容易破碎,使得其力学特性相比于普通的陆源硅质砂有显著差异。对取自中国南海西沙群岛某岛礁的钙质砂开展了三轴排水循环剪切试验,研究了围压、循环应力比、循环振次对钙质砂颗粒破碎发展过程的影响。在试验所采用的围压范围内,钙质砂在固结过程中产生的颗粒破碎较少,但是在随后的循环剪切过程中产生了显著的颗粒破碎。在循环剪切作用下,钙质砂的颗粒破碎形式主要是尖角的磨损,剪切后试样的颗粒中出现了一些碎屑和微细颗粒,大颗粒的棱角有一定程度的磨圆,但粒径无明显减小。在常围压下的等幅循环剪切中,颗粒破碎程度随着循环剪切次数的增大而增加,增长速率逐渐降低,可以采用对数曲线来描述相对破碎指数的发展过程。再考虑围压和循环应力比的影响规律,初步建立了一个描述颗粒破碎演化过程的数学模型。

Evolution of particle crushing of carbonate sands under cyclic triaxial stress path

The carbonate sand is widely distributed in the South China Sea and used as the fill materials for land reclamation. Carbonate sand particles are fragile and can be easily crushed, making the carbonate sand exhibit distinctive mechanical behaviors compared with terrestrial silica sand. Triaxial cyclic shear tests under drained conditions are conducted on a carbonate sand taken from a reef in the South China Sea to investigate the evolution of particle crushing during cyclic shearing process. In the range of the adopted confining pressure, little particle crushing is observed in isotropic consolidation process. In contrast, remarkable particle crushing occurs during the following cyclic shearing process. Angular abrasion is the main form of particle crushing, leading to the increase of the fine particle content in the post-shearing grading. Along with the continuation of cyclic shearing, the amount of particle crushing increases continuously, but the increasing rate decreases gradually. For the cyclic shearing of constant amplitude under constant confining pressure, a logarithmic equation can be used to fit the curve of the relative breakage index versus the number of cycles. Based on with the observed influencing laws of confining pressure and cyclic stress ratio on particle crushing, a mathematical model is proposed to describe the evolution process of particle crushing during cyclic shearing process.