An Experimental and Numerical Study on Behaviour of Single Pile and Group of Piles in Layered Soils under Vertical Load

Abstract

The behaviour of single and group pile in multiple layered soils is studied herein. This paper describes a prototype test on model pile groups of configuration 1×1, 2×2, and 3×3, for embedment length to diameter ratios (L/D) of 5, 6, 7 and 8, and spacing 3 times of diameter, subjected to vertical loads are conducted on three layers of different soil type maintaining equal depth for each of the layers. The model piles used for the test are 250 mm in length with 25mm diameter and a test tank of dimension 700mm × 700mm × 600mm was used. This work also uses 3D finite element modelling on ABAQUS to analyse the effect of soil properties, pile length-to-diameter ratio and time-dependent load-settlement behaviour on the capacity of a pile. Experimental investigations are made to relate the load-settlement characteristics of different pile configuration with their respective length-to-diameter ratio, ultimate load with respect to their length to diameter ratio, load improvement ratio with number of pile and efficiency of pile group in each pile configuration. The test results indicate that pile capacity increases with the increase of number of pile and length-to-diameter ratios and load improvement ratio increases with increase of number of piles. It is perceived that 3×3 group piles have almost 5-8 times and 2×2 group piles have almost 2-3 times greater load carrying capacity than the single piles. The numerical analyses i.e. finite element analyses (FEA) describe the variation of stress, strain and stain energy with respect to time and demonstrate the variation of pile-soil stress ratio with different embedded length. Keywords-Single and group pile, Embedment length to diameter ratio, Pile capacity, Load improvement ratio, FE analysis, Stain energy and Pile-soil stress ratios.