Analytical determination of the soil strength parameters by the number of impacts of the dynamic instrument falling weight

The analytical connection of the number of impacts with the energy of gravity forces of the falling weight and instrument has been determined. The energy realized when striking the rod has two components: energy of the free falling weight when moving relative to the casing which occurs before the moment of the impact with the collar, and energy of the gravity forces of the weight and casing, which arises additionally while vertical lowering to the rod penetration depth in the transition process. The soil strength is numerically determined as per the normal stress value at the end of the rod being penetrated into the soil. The numerical determination of the normal stresses has been performed by means of the theorem on the mechanical system motion quantity change and theorem on the kinetic energy change. The identity of the numerical figures of the normal stress value at the end of the rod and specific energy of the impact penetration of the cylindrical rod into the test soil has been determined. The analytical connection of the impact energy and soil strength parameters with the dynamic instrument parameters has been obtained – with the falling weight mass, instrument casing mass, weight falling height, rod penetration depth, instrument geometric parameter. For the first time in relation to the impact instrument the loss of the kinetic energy and efficiency of the falling weight impact process in case of the direct inelastic impact of two bodies has been determined according to Carnot theorem. The values of the soil deformation specific energy and of normal stresses under the flat end of the rod for soil classes in the function of the number of the dynamic instrument impacts have been determined. (paper)