NON-LINEAR RESPONSE OF INFINITE BEAMS ON REINFORCED EARTH BEDS UNDER MOVING LOADS

Abstract

In view of scarcity of land having adequate bearing capacity, geotechnical engineers face many challenges for construction of foundation of various structures on poor soils. Use of geosynthetic for reinforcing such soil is adopted as one of the measure for increasing bearing capacity and reduction in settlement along with its function as a drainage measure. Present study deals with the development of a lumped parameter model of an infinite beam resting on geosynthetic reinforced granular fill - poor soil system. The beam is subjected to a concentrated load moving with constant velocity. The granular fill has been represented by Pasternak shear layer and the natural occurring poor soil by nonlinear Winkler springs. Geosynthetic layer has been assumed as an elastic membrane. Nonlinear behaviour of granular fill and the poor soil has been considered in the analysis by means of hyperbolic constitutive relationships. Governing differential equations of the soil-foundation system have been obtained and solved with the help of appropriate boundary conditions. The solution has been obtained by employing finite difference method by means of Gauss-Siedel iterative scheme. Detailed parametric study has been conducted to study the influence of various parameters on the response of soil — foundation system under consideration by means of deflection and bending moment in the beam and tension mobilized in the geosynthetic layer. These parameters include magnitude of applied load, velocity of load, damping, ultimate resistance of poor soil and granular fill layer. Range of values of parameters has been considered as per Indian Railway conditions. It has been observed that magnitude of applied load and ultimate resistance of poor soil has significant influence on the response of soil — foundation system. However, for the considered range of velocity, the response has been found to be insensitive towards velocity and the damping. Ultimate resistance of granular fill layer has also been found'to have no significant influence on response of the system.