The fundamental study of particle-particle interactions along their line of center in a viscous liquid is valuable on the measurement of atomic force microscopy in liquid phase and the surface force apparatus, and the determination of bulk properties of the suspension in solutions and granular fluid. An equivalent elastohydrodynamic lubrication (EHL) model is proposed for the fundamental study. The surface roughness on the particle surface is modeled as a sphere covered by a porous layer. The collisions between particles are modeled as pure squeeze EHL motion of circular contacts at impact loading. The Stokes equation and the Darcy law are used to describe the flow in the clear fluid region and porous region, respectively. The derived transient modified Reynolds equation, the elasticity deformation equation, ball motion equation, and lubricant rheology equations are solved simultaneously to obtain the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The effects of the porous layer thickness and the proportionality constant on the variations of pressure, film thickness, squeeze velocity, squeeze acceleration, relative impact force, total impact time, and the phase shift of the time are discussed.