Experimental Investigation Into Changes in the Material Surface Roughness of Underground Structures During Their Driving Into Soil

Abstract

The mechanical interaction between dispersive soils and the surface of underground structures is fundamental in the formation of their load-bearing capacity. The technical and economic effectiveness of piles and flexible or reinforced retaining structures mainly depends on the friction forces between the structure material and the soil. One of the main factors that significantly affect friction is the surface roughness of a material. The installation process for certain underground structures, such as pile driving or vibratory pile driving, involves prolonged contact between the structure material and dispersive soils; some structural elements may slide dozens of meters through the soil. In view of this, changes in the material surface properties of an underground structure during this process may be quite likely. Despite a significant amount of tribological research, such experiments do not fully reflect the process of driving piles into soils and, accordingly, are not appropriate for evaluating with sufficient accuracy changes in the material surface properties of underground structures during this process. In this research, an immersion of an underground structure in fine sand of medium size was simulated using three different materials: steel, fibreglass and fluoroplastic. The surface roughness of the materials was monitored as they moved through the sand. It was established that the roughness of each of the materials decreased as the driving depth increased. The magnitude of this change is influenced by such material properties as density, shear strength and hardness.