LATERAL DYNAMIC RESPONSE OF GROUP PILES FOUNDATION SUBJECTED TO AXIAL AND LATERAL LOAD IN SANDY SOIL

Abstract

ABSTRACT In the current era, the most regions of the world are subjected to seismic loads that result periodic (cyclic) lateral forces. There are also regular loads resulting from wind and marine waves, which act on offshore structures. Therefore, it is important to take influence of these forces and add to the loading effect, which mainly includes of the vertical load that generally results from the self-weight of the structures. The main aim of this study is to investigate the influence of the vertical load and pile shape on the behavior of piles group embedded in sandy soil under lateral cyclic loads by applying lateral cyclic regular loading system on the top of group piles (1 × 2, 2 × 1 and 2 × 2) which simulates the wave movements in the nature. The effect of a number of variables is studied, and their influence on the behavior of group piles (piles spacing S/D = 3, 5, 7 and 9, cyclic load ratio, number of load cycles, shape of pile and configuration of piles). This study is conducting a series of tests with 48 samples instill in dry sandy soil which have relative density (Dr=70%) by using (Raining Technique) under frequency of (0.2 Hz.). According to the results, the presence of the allowable vertical load has a positive effect on the behavior of cyclically loaded groups. By other mean, this is caused reduction in lateral displacement and bending moment along the pile in a group by approximately (60%) and (50%) respectively. VIII On the lateral. pile group response under cyclic loads, the spacing piles in-group (1 × 2) has no significant effect on the lateral displacement. Nevertheless, it is observed with the group model (2 × 1) and (2 × 2) where the lateral displacement increased with decrease pile spacing. In addition, the ,shape, of the pile in group has clear, effect on the group response to cyclical loads a rounded of (25-30%). Finally, the maximum bending occurs at the first upper of the embedded length of the pile (1/4) L. It is also noted that the piles in the leading row take a larger share of the load than rear row a rounded by (18%).