多次加-卸载条件下考虑颗粒破碎的钙质砂一维压缩特性研究

南沙群岛附近海域钙质砂多为珊瑚礁碎屑，是一种未胶结的疏松松散颗粒聚集体，颗粒极易产生破碎。为研究钙质砂颗粒破碎特性对其压缩特性的影响，对钙质砂开展多次加-卸载条件下的一维压缩试验，采用相对破碎率为度量指标，评价钙质砂在多次加-卸载过程中颗粒破碎情况；根据试验数据得到反复加-卸载过程中砂样的塑性功，通过建立塑性功与相对破碎率的关系，探讨颗粒破碎对钙质砂一维压缩特性的影响。研究表明:颗粒破碎率随压力的增大而显著增大，颗粒破碎过程具有明显的应力历史依赖性，随着反复的加-卸载，颗粒破碎率的增幅越来越小；同时钙质砂的颗粒破碎率与塑性功呈幂函数关系，且随着塑性功的增加，颗粒破碎率的变化率逐渐减小。

Study on one-dimensional compression characteristics of calcareous sand considering particle breakage under multiple loading-unloading conditions

The calcareous sand was taken from the sea areas near Nansha Island, mostly coral reef debris. It was an unconsolidated loose particle aggregate, which was easy to produce particle breakage. In order to study the influence of calcareous sand particle crushing characteristics on its compression characteristics, the one-dimensional compression test of calcareous sand was carried out under repeated loading-unloading conditions, and the compression characteristics was analysed. The particle breakage of calcareous sand in the process of repeated loading-unloading was evaluated by using the relative breakage rate B_r as the measurement index. Meanwhile, the plastic work of calcareous sand in the process of repeated loading-unloading was obtained according to the test data. By establishing the relationship between the plastic work and the relative breakage rate, the influence of particle breakage on one-dimensional compression characteristics was discussed. The results show that particle breakage increased significantly with the increase of loading pressure, and the process of particle breakage was obvious stress history dependent; with repeated loading-unloading, the increase of particle breakage rate became smaller and smaller; meanwhile, the relationship between particle breakage rate and plastic work of calcareous sand presented a power function, and the change rate of particle breakage rate gradually decreased with the increase of plastic work.