间断级配珊瑚砂地基渗流侵蚀稳定性试验研究

Stability of seepage erosion in gap-graded coral sand foundation

为解决降雨入渗导致的岛礁珊瑚砂地基沉降、塌陷等渗流侵蚀问题,利用自制渗透仪对不同D_(15)/d_(85)(D_(15)为粗粒组中小于某粒径的土颗粒累计百分含量为15%所对应的颗粒粒径,d_(85)为细粒组中小于某粒径的土颗粒累计百分含量为85%所对应的粒径)和细颗粒含量的间断级配珊瑚砂开展自上而下的单向渗透试验,厘清细颗粒迁移特征和流失的基本条件,揭示珊瑚砂渗透性变化规律,并借助微观手段对其内在机制进行分析。结果表明:(1)对于土骨架粒径为2~10 mm的珊瑚砂而言,粒径为0.25~0.50 mm的粒组是保证其渗流侵蚀稳定的关键粒组;(2)间断级配珊瑚砂地基D_(15)/d_(85)比值小于10且细颗粒含量在20%~30%之间时,渗流侵蚀稳定性较好;(3)与石英砂相比,珊瑚砂特殊的矿物成分及颗粒形貌导致其更难发生颗粒迁移,抗渗流侵蚀能力更强;(4)工程实践中,可通过提高相对密实度、优化颗粒级配或采取注浆胶结等措施提高地基渗流侵蚀稳定性。研究结果可为岛礁地基抗渗流侵蚀设计提供科学依据。

In order to address the issues of settlement and collapse of coral sand foundations on island reefs caused by rainfall infiltration,this study conducted top-down unidirectional penetration tests on gap-graded coral sand with varying D_(15)/d_(85) ratios(D_(15) represents the particle size corresponding to a cumulative percentage of 15%for soil particles smaller than a certain size in the coarse-grained group,while d_(85) represents the particle size corresponding to a cumulative percentage of 85%for soil particles smaller than a certain size in the fine-grained group.)and fine particle contents using a self-designed permeameter.It identified the migration characteristics and fundamental conditions for fine particle loss,revealed the patterns of permeability change in coral sand,and analyzed the underlying mechanisms through microscopic methods.The results show that:(1)For coral sand with a soil skeleton particle size ranging from 2 mm to 10 mm,particles measuring 0.25 mm to 0.50 mm are critical for ensuring stable seepage erosion.(2)Coral sand foundations with a D_(15)/d_(85) ratio below 10 and a fine particle content between 20%and 30%exhibit better stability against infiltration erosion.(3)Compared to quartz sand,the unique mineral composition and particle morphology of coral sand contribute to its increased resistance to particle migration and stronger resilience against seepage erosion.(4)In engineering applications,measures such as improving relative density,optimizing particle gradation,or implementing grouting consolidation can enhance the stability of foundations against seepage erosion.The research findings provide a scientific basis for the design of coral reef foundations with resistance to seepage erosion.