Gradation equation of coarse-grained soil and its applicability

Gradation equation is one way to describe the gradation of coarse-grained soil conveniently, exactly and quantitatively. With the gradation equation, the influence of gradation on the mechanical behaviors of coarse-grained soil can be expressed quantitatively. A new gradation equation with a parameter is proposed. The basic properties and applicability of the new equation are studied. The results show that the proposed equation has the applicability to express coarse-grained soil gradation (CSG), and the range of the parameter beta is found to be 00.5, the gradation curve is sigmoidal, otherwise the gradation curve is hyperbolic. For well graded gradations, the parameter has the value of 0.13<beta<1. Several CSGs used in domestic and foreign earth-rockfill dams are probed, and the value of the parameter p falls in the range of 0.18 to 0.97. The investigation of the range of beta is of value to guide the design for CSG of earth-rockfill dam.