Settlement Analysis of Modeled Wooden Piles in Clay

Abstract

This paper presents the results of recent experimental study on the settlement analysis of modeled wooden piles of circular and square cross sections in clay. The modeled piles were carved from strong wood. The configurations of the circular section consist of 20mm and 200mm for diameter and length respectively. The square piles also have a surface width and overall length of 20mm and 200mm respectively. Single pile as well as pile groups of 2x2 (4 piles) with centre to centre spacing (a) of 4d, and 3x3 (9 piles) with centre to centre (a) of 3d, were driven into clearly marked layered clay soils differentiated by moisture and density of w = 20%, γ = 17 kN/m3 for the weak; w = 10%, γ = 19 kN/m3 for the strong), and a third layer of reinforced weak soil having reinforcing bars placed in it. The tests were conducted in a specially designed testing equipment/tank. 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 as the loading increases. The pile axial capacity increases with the loading rate. The load-settlement curves show exponential formats. The tests revealed a maximum shaft resistance at the pile tip. Also, the relationship between applied load and pile displacement within the load bearing limit was observed to be linear. The initial settlements of circular piles are generally lower than those for square piles, but the former gave a higher overall settlement than the latter. The load-settlement curves were also similar to that predicted by CAPWAP analysis which has been employed by many analysts. A failure bulb of deformation of roughly 3 zones with depths of 3d, 2.5d and 2d along the pile length downward has been identified.