A Study on the Allowable Bearing Capacity of Pile by Driving Formulas

Lee, Jean-Soo; Chang, Yong-Chai; Kim, Yong-Keol

Journal of Navigation and Port Research 2002;26(1):106-111.
Published online March 31, 2002.

각종 항타공식에 의한 말뚝의 허용지지력 연구

이진수, 장용채, 김용걸

A Study on the Allowable Bearing Capacity of Pile by Driving Formulas

Jean-Soo Lee, Yong-Chai Chang, Yong-Keol Kim

Abstract

The estimation of pile bearing capacity is important since the design details are determined from the result. There are numerous ways of determining the pile design load, but only few of them are chosen it the actual design. According to the recent investigation in Korea, the formulas proposed by Meyerhof based on the SPT N values are most frequently chosen in the design stage. In the study, various static and dynamic formulas have been used in predicting the allowable bearing capacity of a pile. Further, the reliability of these formulas has been verified by comparing the perdicted values with the static and dynamic load test measurements. Also, in most cases, these methods of pile bearing capacity determination do not take the time effect consideration, the actual allowable load as determined from pile load test indicates severe deviation from the design value. The principle results of this study are summarized as follows : As a result of estimate the reliability in criterion of the Davisson method, it was showed that Terzaghi & Peck ＞ Chin ＞ Meyerhof ＞ Modified Meyerhof method was the most reliable method for the prediction of bearing capacity. Comparisons of the various pile-driving formulas showed that Modified Engineering News was the most reliable method. However, a significant error happened between dynamic bearing capacity equation was judged that uncertainty of hammer efficiency, characteristics of capacity. It was found out that it would be possilbe to increase the skin friction capacity 1.99 times higher than a driving. As a result of considering 7 day’s time effect, it was obtained that Engineering News, Modified Engineering News, Hiley, Danish, Gates, CAPWAP(CAse Pile Wave Analysis Program) analysis for relation, respectively Q _u(Restrike) / Q_u(EOID)= 0.98 t^0.1, 0.98 t^0.1, 1.17 t^0.1, 0.88 t^0.1, 0.89 t^0.1, 0.97 t^0.1

Key Words: Pile bearing capacity;Standard Penetration Test;SPT;Static;Dynamic;Time effect;Skin friction;Allowable bearing capacity;CAPWAP