Experimental investigation of surface roughness changes of an underground structure's material during its driving into the ground

Abstract

The mechanical interaction between dispersed soils and the surface of underground structures is fundamental in generating their load-bearing capacity. The technical and economic efficiency of piles and supporting structures depends on the friction forces that appear on the contact of their material with the soil. One of the main factors which has a significant influence on friction forces is the roughness of the material surface. Installation of underground structures, such as pile driving or vibro-driven sheet piling, is accompanied by long periods of material contact with dispersed soils: some structural segments can slip on the soil for tens of metres. As a result, it is likely that the surface properties of the underground structure material will change during this process. Although there is a considerable amount of tribological research, the methodology of such experiments does not fully represent the pile driving process in the soil mass. This means that it is not possible to accurately estimate the change in the surface properties of underground structure materials as they are driven into the soil using the results of these studies. The present paper describes a simulation of an underground structure made of three different materials: steel, fibreglass and fluoroplastic; in fine medium sand. The roughness of the materials was monitored while they were moving in the sand. It was found that with increasing diving depth the roughness of each material becomes less. And the value of this change is influenced by such material properties as material density, shear strength and hardness.