Justification of instrument parameters for the construction soil strength determination

Abstract

A portable instrument has been introduced in the construction industry of the Russian Federation for the determination of soil strength grades, which is based on the free weight falling principle. Until the present the theory of such instrument hasn’t yet been completely developed and needs to be improved. In this study on the basis of the theorem on normal stresses on surfaces of a cone to be penetrated into the soil, a logically justified theory of the instrument basic parameter selection has been developed. Stresses on horizontal areas of construction soils are equal to twice the stresses on inclined areas of the cone. At the end of the working section of a rod to be penetrated into the soil there is a round flat punch, which area is A=1 cm2. During the punch penetration into the soil by an impact method, a soil compacted cone body appears before the flat punch, which is affected by normal pressure forces and tangential friction forces. For the first time the equation of normal stresses σ1 has been obtained on inclined areas of the soil cone. The mathematical model of the instrument doesn’t contain soil parameters, that allows to recommend it for any soil and media. The obtained analytical dependences allow to design similar instruments in order to measure the soil strength using any value of the falling weight mass. In this paper the instrument parameter justification has been made with the impact weight mass m 1 = 2.5 kg.