Field Tests and New Design Procedure for Laterally Loaded Drilled Shafts in Clay

摘要

Lateral load tests were conducted on three drilled shafts in predominantly CH soil. Shaft sizes varied from 30 in. (760 mm) to 36 in. (910 mm) in diameter and 15 ft. (4.6 m) to 20 ft. (6.1 m) in length. Loads were applied incrementally at a point 2.6 ft. (790 mm) above the ground surface. Duration of the tests was 57, 24 and 205 days. Measurements of lateral earth pressure at various points along the length of the shaft, displacement near the ground surface, and rotation in the plane of loading were obtained for each increment of load. Additional data on five shafts tested under similar conditions were obtained from the literature. Based upon an analysis of the test data, the ultimate lateral load capacity of a rigid shaft was defined as the load required to produce a shaft rotation of 2 degrees. This definition was used to obtain an empirical correlation of rotation with lateral load. A correlation of the coefficient of ultimate resistance at the groundline, Np, with soil shear strength was also made. A design procedure utilizing the two correlations was developed. Several analytical methods described in the literature were used to calculate the capacity of the eight test shafts. The results were compared with computed capacities obtained by use of the design procedure developed for this research study.