钙质砂渗透性影响因素及预测模型

Factors affecting permeability of calcareous sands and predictive models

渗透性反映了砂土体内部孔隙传输流体的能力,渗透系数为衡量土体渗透性的重要指标。目前有关渗透性的研究主要集中于孔隙率、不均匀系数、曲率系数、粒径大小等方面,而具有特殊生物成因的钙质砂由不同含量的粗粒和细粒构成,粗颗粒形成骨架,细粒改变孔隙分布,且颗粒形状极不规则。为探究粗颗粒含量及颗粒形状对钙质砂渗透性的影响,采用PartAn^(3D)颗粒图像分析仪获取试样的形状参数并开展常水头渗透试验,探究混合砂各项物理性质参数值与渗透系数实测值之间的相关性。研究结果表明:混合砂的渗透系数并非简单的随粗颗粒含量的增大而增大,而是呈现先降低后增大的趋势;在形状量化参数中,凹度C_(a)、凸度C_(v)和最大Feret长F_(L)对渗透性的影响程度更大。在相关性分析的基础上,初步建立了考虑钙质砂颗粒形状参数在内的渗透系数预测模型,该模型可为中国南海人工吹填岛礁渗流场的计算分析提供科学依据。

Permeability reflects the ability of sand and soil bodies'internal pores to transmit fluids,and the permeability coefficient serves as a crucial indicator to assess the permeability of soil bodies.Current research on permeability predominantly focuses on aspects such as porosity,coefficient of uniformity,coefficient of curvature and particle size.C_(a)lcareous sand,characterized by its special biological origin,consists of varying proportions of coarse and fine particles.The coarse particles form the skeletal structure,while the fine particles alter the pore distribution.Additionally,the particle shapes are highly irregular.To investigate the influence of coarse particle content and particle shape on the permeability of calcareous sand,we employed the PartAn 3D particle image analyzer to obtain shape parameters of the samples.Furthermore,a constant head permeability test was conducted to explore the correlation between the physical property parameters of mixed sand and the measured permeability coefficients.The research findings indicate that the permeability coefficient of mixed sand does not solely increase with higher coarse particle content;instead,it exhibits a trend of decreasing first and then increasing.Among the quantified shape parameters,concavity(C_(a)),convexity(C_(v)),and maximum Feret length(F_(L))have a greater impact on permeability.Based on the correlation analysis,a preliminary predictive model for the permeability coefficient,incorporating the shape parameters of calcareous sand particles,has been established.This model can provide a scientific basis for calculating and analyzing the seepage field of artificially filled islands and reefs in the South China Sea.