EVALUATION OF SIDE RESISTANCE CAPACITY FOR DRILLED SHAFTS

This paper presents an extensive evaluation of axial side resistance of drilled shaft foundations. A wide variety of load test data are used and these data are divided into drained and undrained databases. Representative analytical models, including alpha (alpha), beta (beta), and lambda (lambda) methods, are examined in detail using both measured and predicted results to assess their relative merits for the drilled shaft design. Based on these analyses, the undrained shear strength (alpha-s(u)) correlations have exhibited better statistics for undrained side resistance prediction, and the undrained strength ratio (alpha-USR) correlations can be adopted as an alternative analytical method, especially in the case of smaller s(u). For beta method, the stress factors (K/K(o)) are developed from the back-analysis of field load tests. However, the beta method has presented more varying results for short shafts in both drained and undrained loading. Among all analytical methods, the lambda method is relatively the less reliable prediction model. Specific design recommendations for side resistance analysis of drilled shaft are suggested.