Enhancing the Interface Friction between Glass Fiber-Reinforced Polymer Sheets and Sandy Soils through Sand Coating

Abstract

Soil-pile interface friction is an important geotechnical engineering factor to be considered in achieving a safe, cost-effective design. Conventional construction materials such as concrete, steel, and wood exhibit serious long-term soil substructure problems, particularly with regard to durability, deterioration, and corrosion. Fiber-reinforced polymer (FRP) composites are potential alternatives for addressing these long-term problems. FRP composites are corrosion resistant, with a higher strength to weight ratio and greater durability than conventional materials. More research and data, especially in terms of the interface with soil, are necessary to adapt these new materials to friction pile applications. This paper describes the results of an experimental study of the interface friction between sandy soil and glass FRP (GFRP) sheets coated with different ratios of sand per unit of surface area. A direct shear test was used to study 18 different groups of flat GFRP specimens. The test parameters were the amount of silica sand coating and normal stresses in the direct shear tests. The GFRP specimens were sheared against three types of soil: sand, silty sand, and sandy lean clay, of which the first two were used in both dense and loose states. The experimental results showed that coating the GFRP sheets with silica sand was effective in enhancing the interface friction with sandy soils under different normal stresses. A pile implication analysis was also performed to compare the effect of sand coated GFRPs on the load capacity of friction piles with different length to diameter ratios.