Dynamic changing model for permeability coefficient in sandy gravel soil piping erosion process

The invention discloses a dynamic changing model for permeability coefficients in a sandy gravel soil piping erosion process. The dynamic changing model is used for describing the change of soil permeability. The dynamic changing model is that k/ko=[(phi'/phi03(d'p/dp)2]beta, wherein the K represents the permeability coefficient in a piping dynamic development process, k0 represents the initial permeability coefficient, the phi' and the d' p respectively represent the porosity of soil and the particle diameter corresponding to the P percent of the weight content on a grading curve, the phi' and the dp respectively represent the initial porosity of soil and the particle diameter corresponding to the P percent of the weight content on an original grading curve, and beta represents the porosity character magnification indicator.