Stress Distribution in Soils under Pile Cap of Tapered Piles in Compressible Clay

Abstract

-This research paper presents the results of comprehensive investigations on stress distribution in soils under pile cap of tapered piles in compressible clay. Compressible clay from Urucha and Shabani, area of Minsk province, Belarus was investigated in this work. The former was used for laboratory investigation, while field tests were conducted on the latter respectively. The results show the influence of axial compressive load on the magnitude, pattern and orientation of stresses in soils under the pile cap of loaded modeled instrumental piles bored into compressive clay soil. Stresses in the soils at different depths under the pile cap with reference to pile center lines were measured and compared with those obtained using Boussinesq's theory. Measured stresses are slightly higher than those calculated using the theory. The investigations also showed that, for tapered piles bored in compressive clay, the stress increases towards the center line of pile-pile cap joint irrespective of tapering angle only up to 0.5m below the cap, (model), beyond this point, the magnitude and pattern of stress changes. The vertical normal stress under the pile cap increases from zero at the surface to 42% in depth lower than 3.5R, and 55% beyond this point. The maximum principal stress is directed along the radius vector R and reduces radially outward from the pile centerline. The normal and shear stress vectors are less in pile with higher center to center spacing. In addition, stress distribution under pile cap is also a function of pile spacing and tapering angle. Clearly striated stressed zones of deformation under loaded pile cap, having depth in multiples of pile diameter were observed.