In order to delineate effects of surface roughness on the unit shaft resistance of piles embedded in a dry natural fine sand mass, a research program comprising 25 axial loading tests was carried out on 44 mm diameter model piles with different surface roughness. In order to provide piles with different surface roughness they were wrapped with sandpapers with different grits. The results indicate that when the average abrasive particles size of sandpapers varies from 18.3 to 425 microns, the lateral earth pressure coefficient increases from 0.95 to 1.75. This implies that pile surface roughness enhances the tendency of the sand to dilate during loading, which increases magnitude of the radial effective stress against the pile surface. Also, it was disclosed that when the average abrasive particles size of sandpapers varies from 18.3 to 425 microns, the unit shaft resistance increases from 2.5 to 9.1 kPa. These results indicate that the pile shaft resistance increases due partially to the fact that the sand mass-sand paper interface friction angle increases as the sand paper roughness increases. However, it also depends on the rise of radial effective stress due to dilation of sand during loading.
Keywords: pile, surface roughness, shaft resistance, sandpaper, sand
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