PRESSURE SETTLEMENT CHARACTERISTICS OF A PILE USING NON LINEAR CONSTITUTIVE LAWS OF SOILS

Abstract

Bearing capacity and settlement are two main criteria for designing a pile foundation. Several theories and experimental methods have been propounded for computation of the above parameters separately. However, the best estimation of bearing capacity and settlement is possible only if the pressure settlement characteristics of the foundation-soil are known. Pressure-settlement relationship is essentially a function of non-linear stress-strain behaviour of soil. Constitutive laws defining such a behaviour of soil have been used in this investigation to predict the relationships. The investigation has been carried out for clay soils, (i) Buckshot clay and (ii) Dhanori clay. Use of various constitutive relationships has been recommended in the available literature for the prediction of pressure settlement characteristics of surface footings in cohesive and cohesionless soils. No attempt has been made in the past to predict the pressure settlement behaviour of pile foundations using constitutive relationships established from triaxial test data. The soil mass below the pile tip has been divided into a large number of thin strips and stresses and strains in each strip have been obtained along a vertical section. To obtain the settlement of the point on the pile through which vertical section was taken, the strain has been multiplied by thickness of the strip and then numerical integration from pile tip to a depth upto which the strains become negligible has been carried out. The settlement of other points on the pile tip were similarly obtained by taking vertical sections passing through these points. The average settlement is computed by dividing the area of settlement diagram by the width of pile.