Effect of surface roughness characteristics on the uplift capacity of piles: A physical modelling study

Abstract

Pile surface roughness is one of the significant variables affecting the load-bearing capacity of piles. Especially for piles subjected to uplift loads, this parameter can be considered as the main factor that affects the uplift capacity since there is no contribution originating from the pile tip. According to limited previous research, a pile surface can be evaluated as smooth if pile surface roughness parameter (Rn) is less than 0.02, whereas the pile surface is considered completely rough when Rn value is greater than 0.10. This paper, therefore, is aimed to investigate the validity and effectiveness of the numerical limits previously suggested for Rn and intends to determine the relationship between Rn and soil-pile friction angle. For this purpose, laboratory model tests were performed on 12 small-scale pile models embedded in cohesionless soils having varying densities (Dr=25%, 50%, and 75%). Pile surfaces were specially textured to produce different surface roughness values from 0 to 2. Test results indicated that increasing the relative density of cohesionless soil and the pile surface roughness had a considerable contribution to the uplift capacity and soil-pile friction angle. Furthermore, some typical values of Rn like 0, 0.04, and 0.10 were found to be critical for pile uplift behaviour and capacity, and Rn value should be accepted as zero to consider the pile surface as completely smooth.