Analysis of Behavior of Pile Groups in Layered Clay

Abstract

This paper presents the results of recent experimental investigation on the analysis of behavior of pile groups in layered clay. It’s a laboratory modeled experiment with the square and circular prototype test piles carved to shape from strong wood. The configurations of circular section consist of 20mm and 200mm for diameter and length respectively. The square section is 20 x 20 mm, with a length of 200 mm. Four modeled soil conditions were investigated: Strong modeled clay; weak modeled clay; weak on top of strong modeled clay; and reinforced weak modeled clay. 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; w = 10%, γ = 19 kN/m3 for the strong). The tests were conducted in a specially designed testing equipment/tank. The loadings were applied gradually at the rates of 0.01, 0.05, 0.1 and 1mm/min. The test results showed that pile displacement increases with increase in applied load. Increment in loading significantly affects the compressive axial capacity of modeled pile group in clay The initial settlements of square piles are generally higher than in circular piles, but the latter gives higher over-all settlement than the former. Lateral deformations decrease with increase in distance from the pile, and outward radial deformations around the pile decrease downwards along the pile depth. A pressure bulb of roughly three zones of deformation of length 3d, 2.5d and 2d respectively from the pile cap was identified after unloading.