Load Tests on Pipe Piles for Development of CPT-Based Design Method

Abstract

Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration. AbstractThis research focused on the drivability and load-carrying capacity of both open and closed-ended steel pipe piles. Two pipe piles (one open-ended, the other closed-ended) were installed in a sandy soil to the same depth. The site was extensively characterized. SPT and CPT tests were performed both before and after pile installation. A variety of soil indices and shear strength parameters (such as the constant-volume friction angle) were measured in the laboratory. The piles were fully instrumented, permitting separate measurement of shaft and base capacity for the closed-ended pile and shaft, annulus and soil plug capacities for the open-ended pile.The results are presented in a variety of ways. In particular, values of pile resistance are presented normalized with respect to CPT cone resistance values both along the shaft and base of the piles for quick reference. The test results for the openended piles are quite unique. Two design methods are proposed for open-ended piles based on the field load test as well as on results found in the literature. In one method, pile resistances are referred to either the soil plug length or incremental filling ratio. In the other method, pile resistances are correlated to the CPT cone resistance.Comparisons of the proposed methods with the load test results and with methods currently in use are quite favorable. The present research suggests current pile design methods may be excessively conservative. It seems that cost savings from similar research, where complete measurement of all variables of interest both for the piles and for the soil deposit where the piles are installed are done, can be very substantial if the methods proposed here are validated further. It appears that such savings would be in the interest of DOT's and the FHWA. IntroductionBoth open-ended and closed-ended pipe piles are often used in practice, but high-quality information available on the bearing capacity of these piles is very limited. The core of the present study was the pile load tests done on two pipe piles: one open-ended and the other closed-ended. The information generated by the load tests is particularly useful for engineers interested in the design of openended pipe piles in sand, as detailed data was collected on soil plug formation during driving and on static plug resistance. Better understanding of the load-carrying capacity of these piles can lead to significant cost savings.This appears to be especially true for open-ended piles. Both the driving response and static bearing capacity of openended piles are affected by the soil plug that forms inside the pile during pile driving. The formation of the soil plug and its effect on pile load response are still not completely understood.In order to investigate the effect of the soil plug on the static and dynamic response of an open-ended pile and the load capacity of pipe piles in general, field pile load tests were performe...

Assessment of Axially-Loaded Pile Dynmaic Design Methods and Review of INDOT Axially-Loaded Design Procedure

“…Kim et al 2002 found that it underpredicts significantly the load capacity of both closed-and open-ended piles for the conditions investigated by these authors. Regarding drivability, INDOT engineers have reported that predictions of the final driving depths and, thus, of the pile capacity made by design engineers are often unsatisfactory.…”