Abstract: A series of compression crushing tests,quasi-static as well as dynamic loading and unloading tests were carried out to study the contact mechanical properties of marble spheres of 60 mm diameter.The elastic deformation of compressed marble spheres lasts shortly,while elastoplastic deformation dominates.With the increase of quasi-static loading and unloading cycles,the cumulative plastic deformation,the slope of contact stiffness-displacement curve,and the equivalent restitution coefficient of the marble spheres all increase gradually,and finally approach a stable value.The development of cumulative plastic deformation of marble spheres under dynamic cyclic loading can be divided into three stages:initial stage,constant velocity stage,and accelerated stage.The larger the upper limit load and load amplitude,the larger the plastic deformation in the initial stage,and the more cycles required for the cumulative plastic deformation curve to reach the constant velocity stage.The damping ratio at the beginning of dynamic loading increases apparently with the increasing of upper limit load and load amplitude;but such effect gradually weakens with the proceeding of the cyclic loading and unloading.The conclusion of this paper can be used as a reference for studying the stress and deformation characteristics of rock granular materials.

Key words: marble sphere, cyclic loading and unloading, plastic deformation, equivalent restitution coefficient, damping ratio