SEISMIC BEARING CAPACITY OF STRIP FOOTING RESTING ON ,REINFORCED EARTH BED

Abstract

With an increase in demand for construction the use of poor soils becomes imperative. Soil bearing capacity and settlement play an important role in the design of foundations. Seismicity of the site is another important parameter in the design of the foundation for a structure. Hence seismic bearing capacity of soil becomes an important component in the design. In weak soils often deep foundations are recommended on account of the low soil bearing capacity available. In poor soils, ground improvement techniques are commonly used to improve the soil bearing capacity. Reinforcing earth with geo-synthetic is one such technique adopted in practice. This is preferred due to its cost effectiveness as in most of the engineering projects economy plays an important role. If the weak soil is improved by using geo-synthetic, then it becomes feasible to use shallow foundations instead of deep foundations for the same structure, thus effecting economy. Shallow foundations still remain the most used foundation type in construction due to its economy and ease in construction. Through this thesis, an attempt has been made to develop an analytical approach to obtain the seismic bearing capacity of a strip footing resting on reinforced earth. The approach is based on the analysis proposed by Binquet and Lee (1975b) for a strip footing subjected to static load. Both vertical and. horizontal accelerations have been considered in terms of seismic coefficients, a~, and a-,. Results have been presented in the form of non - dimensional charts from which seismic bearing capacity can be obtained, conveniently. Both rupture strength and frictional resistance criteria, have been taken into account in preparing these charts. Charts incorporate horizontal seismic acceleration coefficient, aj, = 0.0, 0.05, 0.10, 0.15 and 0.20. The value of vertical seismic acceleration coefficient, a,,, is taken as 2/3a~7. An illustrative example has been included for a logical understanding.