Dae-Hong Kim

Axial Response and Bearing Capacity of Tapered Piles in Sandy Soil

14 calibration chamber tests were performed to investigate the axial responses of tapered piles in sandy soil. Three instrumented model piles with different taper angles, designed to have the same volume, were used in the tests. Results of the model pile load tests showed that the shaft load of tapered piles continuously increased with pile settlement, whereas that of cylindrical piles reached the ultimate values at a settlement equal to about 2 % of the pile diameter. The ratio of the load capacity of tapered piles to that of cylindrical piles was found to vary with both the taper angle of the piles and the soil condition of the sands. The ultimate unit shaft resistance of tapered piles was always greater than that of cylindrical piles irrespective of soil condition, whereas the ultimate unit base resistance of tapered piles was greater than that of cylindrical piles for dense sand with lateral earth pressure coefficients higher than 0.42. It was also observed that the ultimate unit shaft resistance of piles increases with increasing taper angle regardless of the relative density and stress state of the sand. However, the ultimate unit base resistance of piles increases with increasing taper angle for medium sand, but decreases for dense sand. In addition, based on the results of the model pile tests, taper factors for the ultimate unit base and shaft resistances, which can be used to estimate the base and shaft load capacities of tapered piles, were proposed.

Estimation of Ultimate Lateral Load Capacity of Piles in Sands Using Calibration Chamber Tests

Current practice for the estimation of the ultimate lateral load capacity of piles is typically based on the vertical effective stress σ′v, while the effect of the lateral effective stress σ′h is not specifically considered. In the present study, calibration chamber lateral pile load tests are conducted to investigate the load response and ultimate lateral load capacity Hu of laterally loaded piles under various soil and stress conditions. In order to determine Hu from load-deflection curves, different criteria are explored and analyzed. From the test results, it is shown that Hu increases significantly with increasing σ′h for a given σ′v. It is also found that lateral deflection of pile at ultimate state tends to increase as the relative density and lateral stress increase. On the basis of the test results, the lateral stress correction factor reflecting the effect of the lateral effective stress σ′h on Hu is proposed. From the test results, it is seen that the proposed procedure using the lateral stress correction factor produces more realistic estimation of Hu. Case examples are selected from the literature and used to compare results measured and predicted using the proposed approach.