Effect of Loading Rate on the Settlement of Modeled Square and Circular Piles in Clay

Abstract

This paper presents the results of experimental investigations of the effect of loading rate on deformation and settlement of axially loaded modeled square and circular piles in clay. The modeled piles were sawn, sharpened and carved from strong wood. The configurations of both square and circular section consist of 20 mm and 200 mm for diameter and length respectively. Single pile as well as pile groups of 2x2 (4 piles) with centre to centre spacing (a) = 4d, and 3x3 (9 piles) with centre to centre (a) = 3d, were driven into clearly marked layered clay soils differentiated by moisture and density of w = 20%, γ = 17 kN/m3 for the weak layer, and w = 10%, γ = 19 kN/m3 with a third layer of reinforced weak soil having reinforcing bars placed in it. The tests were conducted in a specially designed testing equipment/tank. At the loading rates of 0.01, 0.05, 0.1 and 1mm/min, the modeled piles were subjected to axial compressive loads and the effect on the soils in the inter-pile spacing, as well as those under and around the piles were evaluated. The pile axial capacity increases with the loading rate. Also, the relationship between applied load and pile displacement within the load bearing limit was observed to be linear. The initial settlements of square piles are generally higher than circular piles, but the latter gives an over-all settlement of 14 - 18% higher than the former.