Load distribution in pile group embedded in sandy soil containing cavity

Abstract

The present study investigates the influence of presence of cavities on the bearing capacity and settlement of piled foundation. The work included experiments carried out to study the behavior of pile models constructed in sand with a dry unit weight 16.8 kN/m3. Pile models were tested in a sand container under a load applied through a hydraulic mounted jack and measured using a load cell. Three strain gages were proved to piles to evaluate the strains and then estimate the load transformed to each pile in the group by a strain indicator. Three groups of piles (single pile, group of piles (1 × 2), and group of piles (2 × 2)) were tested in the laboratory as a free standing pile group. A prototype of a cavity was used and placed adjacent to the piles at various distances from the centerline of piles and various depths below the surface. The effect of variation of cavity location (X), cavity depth (Y), and cavity diameter (d) on the load and settlement of the pile and groups of piles has been studied for all tests. It was found that the load in pile increases with increase of (X/D, D is the pile diameter) due to decrease of the zone affected by the presence of cavity. When the cavity is located at a close distance to the pile, it will reduce the soil density and hence decrease the shaft friction along the pile and lead to decrease in the pile failure load. The failure load is not affected by the presence of a cavity at a distance of 5.5 pile diameters at all depths. The presence of the cavity in the soil reduces the ultimate failure load of the pile. For pile group (1 × 2), the reduction rate is about (40% to 80%) at (d/D = 1), while the rate at (d/D = 2) is about 65% to 85%.