Comparative lateral load field tests on straight-sided and belled piers in sloped ground

Comparative lateral load field tests were conducted on two straight-sided and two belled piers in a natural arid loess sloping ground with an inclination angle of 20° in the western Chinese Loess Plateau. The pier-head displacements, sloping ground surface deformations and soil pressure distributions were measured. The lateral load–displacement curves of the straight-sided and belled piers in the sloping ground generally exhibited the same three-phase non-linear behaviour, and their performances were similar to those of laterally loaded drilled shafts in horizontal ground. The ‘interpreted failure load’ of the laterally loaded piers in sloping ground was obtained using the representative lateral interpretation criteria and their extensions. Compared with the normalised lateral load–displacement curves of the drilled shafts in horizontal ground under drained and undrained lateral loadings, the displacement required to completely mobilise the lateral resistance for piers in sloping ground was much smaller. It was found that the use of belling can cause greater load transfer depths and can effectively mobilise more soil to resist lateral load. In addition, for both straight-sided and belled piers, an additional embedment of the shaft in sloping ground can increase lateral resistance to match the level-ground lateral capacity.