Clay contains a variety of clay minerals. The charged surface of clay particles makes the clay particles show active hydraulic properties

which can lead to the formation of a double layer on the surface of the soil. So clay particles are stacked on each other under various forces during the deposition process to form non-connected pore structures such as isolated pores and blind pores. As a result

when seepage occurs in the soil

the fluid only flows through the interconnected pores

but not through the unconnected pores. Unfortunately

the Kozeny-Carman equation (K-C equation) uses the total specific surface area of the particles as seepage specific surface

therefore

the K-C equation is not suitable for calculating the hydraulic conductivity of clay any more. In this paper

only the pore specific surface area of the interconnected pores in which the fluid can flow through is taken as the seepage effective specific surface area. And then

the seepage effective specific surface area is used to modify the original K-C equation. Test results show that the modified K-C equation has obvious advantages over the original K-C equation in describing the seepage law of clay.