Behaviour of laterally loaded piles in layered soil

Abstract

Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. High rise structures supported by piles need analysis for lateral loading due to earthquake and wind. Piles are frequently subjected to lateral forces and moments, for example, in quay and harbor structures, where horizontal forces are caused by the impact of ships during berthing and wave action; in offshore structures subjected to wind and wave action and in transmission-tower foundations, where high wind forces may act. Pile lateral capacity can be analyzed using conventional statical approach. The linear spring model may be adopted in case where soil strains are small. Under extreme pile loading condition it is important to make use of a non-linear soil spring model referred to as ‘p-y’ curve. Considerable effort has been put into the refinement of p-y curve formulations on the basis of measurement of the behavior of laterally loaded piles. Frequently the pile is embedded in layered soil which consists soft clay layer over stiff clay. Some authors proposed dimensionless solutions for ultimate lateral capacity of piles in layered soils. It is noted that there are limited literature reporting on pile behavior under lateral loading in layered soil. In this study pile lateral capacity for free headed and fixed headed condition are presented. Piles embedded in homogeneous soil and layered soils are analyzed and the results are discussed. Soil is defined series of non linear spring having different spring constant for different soil shear strength. Piles are embedded in soil having different soil shear strength in different layers. Layered soils like soft clay layer over stiff soil of different thickness are analyzed. Piles are long pile of diameter 500 mm, 600 mm, 750 mm and 1000 mm. From the analysis of piles embedded in homogeneous soil it is seen that as the soil shear strength, diameter and allowable head deflection increases, corresponding lateral capacity increases. For a soft layer over laying a stiff layer, larger diameter piles are more effective than smaller diameter piles.