A STUDY OF BEHAVIOUR OF BATTERED PILE GROUPS UNDER LATERAL CYCLIC LOADS

Abstract

The behaviour of single battered piles and nattered pile groups subjected to lateral loads have been discussed on the basis of both experimental and theoretical evidence. The importance and influe- nce of the group action and extent of rotation of pile cap in controlling the behaviour of laterally loaded piles and pile groups have been stressed. method to control the rotation of the pile cap has been deve- loped. '. critical review of literature on single battered piles and pile gropus containing battered piles is presented in chronological order. The experimental and theoretical reports are discussed in two seperate headings. None of the experimental investigations study the phenomenon of groups action and the effect of rotation of the pile cap. Also no literature is reported concerning the behaviour of battered pile groups subjected to lateral c;clic loads. Majority of the theoretical investigations neglect the soil restraint, and some of those which take into account the same use unrealistic form of variation of soil modulus with depth. The more realistic theories are too complicated for design purposes and also possess some short comings or other. The above mentioned points have been resolved. kn experimental investigation wis -2- performed on 1.5 c; O.D. aluminium model piles. The w=l11 thickness was 0.25 cm. The piles were embedded in a tank97.# cm x,3.5 cm x 86.4 cm containing uni-form s-ind placed at medium density conditions. The tests were performed on four pile groups only. All the batter piles used had a batter angle of 300 with the vertical. The behaviour of the pile groups under static and cyclic lateral loads and the effect of controlling the rotation of the pile cap were studied in detail. The lateral loads were app- lied only at ground surface. The disposition and bat=:er ritio of the groups were varied the spacing was kept constant. A device was fabricated to apply cyclic loads in single steps. The ground deflections were measured using mechanical dial g,ges. The rotation of the pile cap was observed using a tilt meter fabri-cated solely for this purpose. The pile groups tested under measured rotation conditions have been analysed theoretically. The computations were programmed in an IBM 1620 digital computor. The stay indicated the followvin beha-viour in addition to that already discussed- 1. The pile groups containing battered piles can very safety be assumed -3- to act individually. 2. In general pile groups containing battered piles are more stiff, thin vertical pile groups, with an excep-tion of the pile groups containing 311 the four piles as positive batter piles. 3. Controlling the rotation of the pile cap results in increasing the stiff-ness of the group. 4. Pile groups containing vertical piles alone show maximum stability under cyclic loading conditions. 5. The negative battered piles and pile groups containing negative bitter piles displayed least resistance to cyclic loading in lateral direction. 6. The theory proposed by Hrennikoff, (1949) with proper modifications can be used for the analysis of pile groups containing parallel and non parallel piles.