FULL-SCALE PILE LOADING TESTS ON INSTRUMENTED CONCRETE PILES IN CLAY TILL, IN EDMONTON, ALBERTA

ABSTRACT: Cast-in-place concrete belled piles founded in clay till are commonly used for support of heavily loaded foundations in the Edmonton area. Full-scale pile loading test on instrumented piles not only verifies load-carrying behavior and performance of the piles but also allows for the break-down of shaft and toe resistances for the pile design. Based on the results of the pile loading test, an increase of geotechnical resistance factor from 0.4 to 0.6 can be applied in the geotechnical resistance design. For projects with a large number of piles required, the overall benefit gained from the increase in design reliability and the reduction in total piling costs can be substantial. This paper presents the results of three full-scale pile loading tests on instrumented cast-in-place concrete belled piles constructed in three separate project sites in the downtown area of Edmonton, Alberta. The shaft diameters of the test piles ranged from 0.9 m to 1.2 m, bell diameters from 1.8 m to 2.7 m, and test loads were up to 9,000 kN. Embedded strain gauges and tell-tales were installed in the test piles, which provided a reliable assessment on the shaft and toe resistances. Considerable variability in the test results was identified at the test sites and the design implications are discussed in the paper.