循环三轴应力路径下钙质砂颗粒破碎演化规律

Calcareous sand is widely distributed in the South China Sea area of China and is an important material for land reclamation by blowing and filling. The particles of calcareous sand are easily broken, making its mechanical properties significantly different from those of ordinary terrigenous siliceous sand. Triaxial drained cyclic shear tests were carried out on the calcareous sand taken from a reef in the Xisha Islands in the South China Sea of China, and the effects of confining pressure, cyclic stress ratio and number of cyclic vibrations on the development process of calcareous sand particle breakage were studied. Within the range of confining pressure used in the test, there was less particle breakage of calcareous sand during the consolidation process, but significant particle breakage occurred during the subsequent cyclic shearing process. Under the action of cyclic shearing, the form of particle breakage of calcareous sand is mainly the abrasion of sharp corners. Some debris and fine particles appeared in the particles of the sample after shearing, and the edges and corners of large particles were rounded to a certain extent, but the particle size did not decrease significantly. In the equal-amplitude cyclic shearing under constant confining pressure, the degree of particle breakage increases with the increase of the number of cyclic shearing times, and the growth rate gradually decreases. A logarithmic curve can be used to describe the development process of the relative breakage index. Considering the influence laws of confining pressure and cyclic stress ratio, a mathematical model describing the evolution process of particle breakage was preliminarily established.

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。