The Determination of Soil Properties in Situ by an Impact Penetrometer

摘要

This report presents parts of the scientific investigations carried out under a task program related to the determination and assessment of surface dynamic soil properties by laboratory instrumentation. It first reviews the historical development of the hardness-penetrometer concept and presents a pilot model for a new aerial penetrometer. Basic theoretical considerations are then advanced regarding the stress-strain relationships in axial symmetry and the dynamic loads associated with a drop-impact penetrometer. The existing theory of elasticity solutions are then reviewed and the solutions for a sphere impacting on an ideally plastic and on an elasto-plastic semi-infinite solid are presented. The Hertz solution of an elastic sphere impacting on an elastic half-space is modified by using the elastic-viscoelastic analogy to find a solution for a sphere dropping onto a four parameter viscoelastic half-space. The problem of energy transfer during impact by vibrations is discussed shortly. The data for fifteen test series carried out with the pilot model penetrometer on natural soils and on some artificial materials are presented and evaluated. It is concluded that the principle of the drop impact-penetrometer is applicable in experiments for assessing the mechanical properties of a natural soil surface. (Author)