RESEARCH ON ADDITIONAL STRESS CAUSED BY SKIN FRICTION OF Y-SECTION PILE CONSIDERING ABNORMALITY EFFECT

Y-section pile is a newly abnormal pile with reversed-arch surface. The lateral earth pressure and skin friction surrounding the pile shaft are of non-uniform distribution. Although the calculated results of additional stress caused by assumed uniformly distributed skin friction are more suitable to the actual distribution law when compared with those caused by the assumed concentrated skin friction, there is still a certain error. Based on spherical cavity expansion theory, non-uniform distribution model of lateral soil pressure around Y-section pile is established; and then the non-uniform distribution model of skin friction is built up as well, which can be used to calculate the additional stress. Taking outside circle radius R and template radian θ as variables, variation laws of additional stress are comparatively studied under three distributed patterns of skin friction around Y-section pile respectively, namely the concentrated distribution, the uniform distribution, and the non-uniform distribution considering the abnormality effect. In addition, the calculated method of additional stress due to skin friction is employed to calculate the settlement by considering abnormality effect. According to the field static load tests, it was found that the calculated settlements agree better with the measured results using the calculation method of additional stress due to skin friction by considering abnormality effect.