一种筑坝料级配方程及其适用性研究

A gradation equation for rockfill materials and its applicability

利用级配曲线与土体土水特征曲线的相似性,提出了一个描述筑坝料连续级配的方程,分析了方程参数对不同形态级配曲线的反映能力,并利用两座在建水电站工程的筑坝料实测级配,验证了该方程对各种连续性级配筑坝料的普适性。研究表明:该方程能够描述出双曲线形、反S形和近乎直线等三种典型的级配曲线,针对堆石料、过渡料、反滤料等不同连续级配筑坝料都具有广泛的适用性。参数a和n对级配曲线的影响与VG模型类似,a主要决定级配曲线的形状,即双曲线形或反S形;n为大于1的值,决定级配曲线主体段的斜率,n越大,斜率越大,n趋向于1,则曲线很缓,近似于直线。利用该方程,可构造出用于描述间断级配土的级配方程。此外,良好级配条件的粗粒料参数取值范围为0.1<a<1.9且1.3<n<1.9。需要指出的是,该级配方程由岩土工程中广泛应用的VG模型发展而来,更容易被广大工程科研人员理解并接受,在筑坝料级配设计方面具有一定的应用价值。

Considering the similarity between gradation curve and water characteristic curve(SWCC)of unsaturated soils,a gradation equation which can be used to describe continuous gradation for rockfill materials is proposed.A parametric study was conducted to verify the capability of the proposed gradation equation to reflect the gradation curves with different shapes.After that,the measured gradation curves for different rockfill materials,which were collected from two hydropower stations under construction,were used to examine the applicability of the proposed equation.The results show that the equation could describe three typical soil gradation curves with the shapes as hyperbola,reversed S-shaped and approximate straight line,and has a wide applicability of materials for rockfill dam,such as the rockfill material,transitional material and inverted filter materials.Comparably,the physical conception of the parameters a and n is the same as that in VG model.Parameter a determines the shape of the gradation curve,namely hyperbola or reversed S-shaped.Parameter n is a value larger than 1.0,which determines the slope of the curve,and increases with the increase of slope.When the value of n is close to 1.0,the curve approaches to a straight line.In addition,the proposed equation can be furtherly developed to describe the gap-graded soils.Furthermore,the parameters corresponding the well-graded rockfill materials are 0.1<a<1.9 and 1.3<n<1.9.Note that,the equation in this study is more acceptable for engineers and researchers,since it is proposed based on the VG model which is wildly used in the geotechnical engineering.Besides,it will be valuable for gradation designing of rockfill materials in engineering.