Effect of pile geometry and soil saturation degree on point bearing capacity for bored piles in sands

Abstract

In the present paper, an experimental study was conducted to determine the factors affecting the point bearing capacity of pile foundations constructed in dry and saturated sandy soils. Model piles were installed as reinforced concrete bored piles cast-in-situ. Model pile foundations of various geometries resting at different depths in homogeneous sand of different saturation degrees (%0-100) were loaded statically to failure. The test results showed that the bearing capacity of piles did not significantly affect by the loading rate. At most 10% difference was observed in pile bearing capacity when the loading rate was between 0.7 and 2.5 mm/min. Subsequently, the load bearing capacities of the piles were determined at a specified constant loading rate. The point and total capacities of the piles were measured separately in the experiments, then test results were compared with theoretical values. Pile point capacities provided from pile load tests are smaller than the theoretical values. The differences between experimental and theoretical results have been attributed to the Nq values. The Nq values not only dependent on the internal friction angle of the soil but also the saturation degree of the soil, the pile diameter, and the effective stress. Nq values decrease since the pile length/pile diameter ratio increases.