An Equivalent Solid Foundation Method To Predict The Settlement Of Pile Foundation

Pile foundations are widely used structures which safely transfer the load of heavy super-structures such as multi storey buildings and bridges.One of the hardest tasks in pile foundation is to estimate the settlement which may cause damages to structure,if not properly predicted.The theoretical methods in predicting the settlement are mostly used as they are easy and cheaper as compared to field/laboratory methods.The purpose of this thesis is to determine a simple,convenient and reliable method to compute the settlement of pile groups under vertical loading.The main work and achievements are as follows:1.The foundation,together with adjacent soil,is simplified into an equivalent solid foundation with large stiffness.The sides and base of the equivalent foundation are discretized into a number of elements to see the clear variation of distribution of pressure.The expression of settlement of an element is established based on Mindlin’s solution.With the compatibility of settlement between the foundation and the ground,the foundation’s settlement is computed and assumed to be constant.2.A MATLAB program is generated to solve the equations of settlement and to find the distribution of pressure not only along the depth but also along the width of equivalent foundation.This program is helpful to show the settlement results with no time by changing pile group dimensions,discretization,loading and soil parameters.Due to simplification of pile foundation and development of program,one of the main advantages of this method over others is that it doesn’t require lengthy and complex computation.Square foundations are analysed having same cross section but varying lengths with current analytical method.The settlement results,distribution of side friction and base pressure is shown graphically.3.The square foundations with the same plan dimensions and different depths are computed with the FEM respectively to verify the validity.Besides,the variation in length,the spacing is also considered in the computation of settlement results by FEM.It was found that the center to center spacing between the piles in a group doesn’t affect the settlement results appreciably.The comparison show that the proposed method gives a solution with sufficient precision in estimating settlement for the design the pile foundation.4.The computed results of settlement with present analytical method are further utilized to develop an equivalent shallow foundation.This equivalent shallow foundation will help to compute the settlement results of pile group foundation directly.A relationship between pile parameters and the width of equivalent shallow foundation is developed to make the computation of settlement quick and easy.This method is more useful in design process to get the quick results of settlement.5.The expressions are derived to compute the vertical stress due to uniformly distributed load on a rectangular area.These expressions are obtained by the integration of Mindlis’ s vertical stress solution due to a point load acting beneath the surface of a semi-infinite soil mass.Expressions of vertical stress due to uniformly distribute load on a vertical and horizontal rectangle is integrated separately.Finally,the results of vertical stress are obtained with the help of these expressions on the basis of theory of elasticity.