间断级配吹填珊瑚砂剪切和颗粒破碎特性

岛礁地基通过水力吹填的方式建造而成。吹填地层中常存在大小颗粒共存的间断级配状态，颗粒级配的间断条件对吹填珊瑚砂的力学特性有显著影响。针对吹填珊瑚砂开展不同有效围压、相对密实度和含砾量的三轴排水剪切试验，探究静力荷载作用下间断级配珊瑚砂砾混合料的强度与变形特性，并分析珊瑚砂砾混合料颗粒破碎的演化规律。结果表明：试样的应力—应变关系曲线受到围压和密实度的显著影响，珊瑚砂砾混合料的峰值摩擦角和峰值剪胀角均随有效围压的增大而减小，随密实度的增大而增大；同一有效围压水平下，随着含砾量的增加，密实程度不同的珊瑚砂砾混合料强度表现出不同的增长规律，这可能与珊瑚砂砾混合料中粗细骨料接触状态和组成比例有关。另外，还研究了剪切过程中不同含砾量条件下珊瑚砂砾混合料的塑性功与相对破碎指数的关联性，建立了相对破碎指数B_r与塑性功W_p的相关函数。

Shear and particle breakage properties of gap-graded coral sands

The foundations of islands in the South China Sea are constructed by hydraulic filling method. There are widely discontinuous gradation states in which large and small particles coexist in the hydraulic fill formation of island. The discontinuous conditions of particle gradation have a significant influence on the mechanical properties of the foundation material of coral sand. In this study, a series of drained triaxial shear tests under different effective confining pressures, relative densities, and coral gravel contents were carried out on coral sand-gravel mixtures, to investigate the strength and deformation characteristics of the gap-graded coral sand under static load. Also, the feature of particle breakage in the tested gap-graded soil has been studied. The results show that the stress-strain relationship curve of the coral sand sample is significantly affected by the confining pressure and relative density. The peak friction angle and dilatancy angle of coral sand-gravel mixtures decrease with the increase of the effective confining pressure, and increase with the increase of relative density. Under the same effective confining pressure, the strength of coral sand-gravel mixtures at different relative densities exhibited different growing patterns with increasing gravel content, which may be related to the contact state and composition ratio of the coarse and fine particles in coral sand-gravel mixtures. In addition, this study explored the correlation between the plastic work with relative breakage index for different gravel contents of coral sand-gravel mixtures and established the correlation function between the relative breakage index B_r and the plastic work W_p on this basis.