Effect of Cavity in Sandy Soil on Load Distribution of Pile Group

Abstract

The present study investigates the influence of presence of cavities on adjacent buildings especially in the case of piled structures. The presence of cavity affects on the bearing capacity and settlement of piled foundation. This paper presents an experimental study to investigate the behavior of model piles embedded in sandy soil of dry unit weight 16.8 kN/m3. Model piles were tested in a sand box with load applied by a hydraulic compression jack and measured by means of a load cell. The settlement of the piles was measured by means of two dial gages; three strain gages were attached on piles to measure the strains and to calculate the load carried by each pile in the group by the strain indicator. Two types of piles (single pile and group of piles (1x2)) 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 different distances from the pile centerline and different depths from the surface. The effect of variation of cavity locations (X), cavity depths (Y), and cavity diameter (d) on the load and settlement of the pile and groups of piles have been studied for all tests. It was found that the presence of the cavity in the soil reduces the ultimate failure load of the pile. For single pile, the reduction rate is about (10% to 60%). For pile group (1x2), the reduction rate is about (40% to 80%). As intuitively expected, induced pile axial force is largest for the case where the level of the cavity is located below pile tip because the cavity is located within the zone of large displacement

Keywords

• cavity
• tunnel
• pile group
• sandy soil