VERTICAL PULLOUT CAPACITY OF MODEL BATTER ANCHOR PILES IN MARINE CLAYS

Many offshore structures are subjected to overturning moments due to w ind load wave pressure, and ship impacts. For foundations in such stru ctures, usually a combination of vertical and batter piles ir used. Li ttle information is available in the literature about estimating the c apacity of piles under uplift. In cases where these supporting piles a re not vertical the behavior under vertical pullout is not well establ ished. In this article the vertical pullout behavior of batter piles i s examined through an experimental investigation carried out on model batter anchor piles. The tests are conducted on model aluminum pipe pi les of 19 mm diameter with different embedment ratios in a soft marine clayey bed at different consistencies and with various batter angles of 0 degrees, 10 degrees, 20 degrees, and 30 degrees. Results indicate that the pullout capacity of a batter pile is less than that of a ver tical pile. This reduction is explained in terms of reduced area avail able for skin friction. Based on this, pullout behavior of batter anch or piles is described as ''short anchor'' and ''long anchor'' failures . However with increase in the embedment length, the capacity of batte r pile remains unaffected.