关键词: 自平衡法, 双模内力测试, 等效转换, 桩身压缩量

Abstract: The deformation-loading characteristics of the cast-in-place reinforced concrete piles are evaluated throughout the bi-directional loading tests and the loading results are compared with the conventional top-town loading test results. When the test pile reaches the limiting state, the tested end bearing resistance results from the bi-directional loading test is usually greater than that of from the conventional pile loading tests and the side friction values are similar in both testing methods. In the bi-directional loading tests, the side friction values are different in the upper portion and the lower portion of the testing device. Usually, the tested mobilized side friction in the upper portion is less than the limiting value tested in the conventional top-down loading tests and the mobilized value in the lower portion from the bi-directional loading test is greater than that of from the conventional loading test. An improved equivalent top-down loading-settlement curve conversion method is proposed by comparing the pile top settlement in the conventional loading test and the deflection in the upper shaft in the bi0directional loading test. It is found that the proposed method is more accurate than the code suggested method. Although the converted equivalent top-down settlement-loading curve predicts larger pile settlement than that of the conventional loading test, the deflection-loading curves from both test methods have similar trend and it is demonstrated that the bi-directional loading test can provide an effective loading test results for the pile design. 

Key words: Self-Balanced Method, Bi-Directional Loading Tests, Equivalent Conversion, Pile Compression