BEHAVIOUR OF BATTERED PILES

Abstract

The behaviour of single vertical and battered piles under lateral loads in cohesionless soil has been studied on the basis of theoretical and experimental investi gations. The available field data has also been analysed. A review of literature pertaining to analytical studies on single batter piles is presented. The experimental investigations have also been discussed. Piles are normally used in groups. Thus attempts have been made in the past to study behaviour of battered pile groups. Available analyti- . cal developments related to pile groups with battered piles have been reviewed. The review of literature indicates that the behaviour of abattered pile is different than that of a vertical pile and is non-linear. Further the available nondimensional approaches do not apply to battered pile with the load applied normal to the pile axis because of the changed boundary conditions. It is therefore essential to have a more rational approach to analyse battered piles. Pile analysis utilizing p-y relationship is considered to be more realistic as it is based on pile-soil characteristics. However, no attempt seem to have so far been made for the solution of battered piles utilizing actual p-y curves which are nonlinear. Atheoretical analysis has been developed utilizing beams on elastic foundation approach. To account for the non-linear behaviour of battered piles arelationship of the U) form p=kxy11 has been adopted and analytical approach has been developed to analyse single vertical and batter (both positive and negative) piles. An experimental investigation on 22 mm aluminium pipe piles has been carried out to establish p-y relationships, Tests were carried out on long piles. All piles were installed in dry cohesionless soil placed at three relative densities of 40 percent, 57.5 percent and 66 percent. The piles were instrumented using electric resistance strain gages. The piles were tested at batter angles of 0°, + 15°, + 30° and +45°. Only horizontal load close to the sand surface was applied to the model piles. The bending strains along the length of pile were noted under different magnitudes of load levels. The observed data was analysed to obtain the variat ion of parameters k and n in the relation, p = kxy11. The analysis of test data indicates that the coeffi cient k is a function of relative density of sand and batter angle of pile whereas the exponent n is a function of relative density of sand only. The values of parameters obtained from model tests have been utilized and the loads on the pile have been computed utilizing the proposed analysis. Agood tally between the computed load and the applied load is noted. The available field data on prototype pile has balso been,analysed by the analysis developed in the investigation. The computed results show a good agreement with the observed field data. (xi) Comparing the values of parameters obtained from tests in p-y relationship it is noted that the variation in the exponent nas obtained from the model tests and prototype tests is not much. However there is a large variation in coefficient k as obtained from model tests vis a vis the field data.