The formation and storage of fresh groundwater in coral reefs is affected by many factors. The permeability of porous media in island and reef formation is one of the main controlling factors. Coral sand is the only medium for the formation of coral reefs. Its permeability characteristics are very different from the permeability characteristics of quartz sand from land sources. In this study, a series of indoor model tests and microphysical property tests were designed in order to reveal the reasons for the special permeability of coral sand from the microcosmic point of view. The conversion equation of the hydraulic conductivity between quartz sand and coral sand was established. Finally, through numerical simulation, the variation rule and the parameter sensitivity of a freshwater lens were studied when the hydraulic conductivity changed within the reasonable range of natural existence. It was found that the special permeability of coral sand was caused by four factors, including roundness (Φ), roughness (Ψ), surface charge, and the surface hydrophilicity of the particles. Among the four factors, the main factors and the secondary factors were classified according to the influencing degree that changed with the sizes of the particles. The influencing sensitivity of the hydraulic conductivity on the properties of the freshwater lens had the following order: freshwater appearance time > steady-state freshwater reserves > thickness of the steady-state freshwater lens> lens stabilization time.

珊瑚礁中新鲜地下水的形成和储存受许多因素影响。多孔介质在岛礁形成中的渗透性是主要的控制因素之一。珊瑚砂是形成珊瑚礁的唯一媒介。它的渗透特性与陆地石英砂的渗透特性有很大的不同。在这项研究中，设计了一系列室内模型测试和微物理性能测试，以便从微观的角度揭示珊瑚砂特殊渗透性的原因。建立了石英砂与珊瑚砂导水率的换算方程。最后，通过数值模拟，研究了水力传导率在自然存在的合理范围内变化时，淡水透镜的变化规律和参数灵敏度。发现珊瑚砂的特殊渗透性是由四个因素引起的，包括圆度（Φ），粗糙度（Ψ），表面电荷和颗粒的表面亲水性。在这四个因素中，主要影响因素和次要影响因素根据影响程度随颗粒大小而变化。水力传导率对淡水镜片性能的影响敏感性按以下顺序排列：淡水出现时间>稳态淡水储量>稳态淡水镜片的厚度>镜片稳定时间。