Characteristic parameters theoretical analysis of rockfall impact on ground

In accordance with the character of rockfall acceleration or impact force curve,impact force computation theory formulas of front impact are derived using momentum law.Supposing normal impact force is not affected by tangential impact force,a new friction model is proposed,using which tangential impact force and coefficient of restitution both are induced.Finally the change law of impact time,impact force and coefficient of restitution are analyzed when incidence speed,incidence angle or the ratio of the thickness of surface soil to rockfall radius are changed.It showed that:(1) With the impact velocity increasing and the incident angle fixed,the impact force increases linearly,the tangential restitution coefficient ascends with a small amplitude,while the normal restitution coefficient and impact time both descend.(2) With the augment of incidence angle,normal and tangential coefficient of restitution both are getting larger,the increment of tangential restitution coefficient is greater than that of normal restitution coefficient,and the collision time longer,while maximum impact force rise and then drop.(3) With the ratio increase of the thickness of surface soil to rockfall radius,the longer the collision time is,the larger normal coefficient of restitution is while the smaller tangential coefficient of restitution is,and maximum impact force goes up like a concave curve.