Abstract: The traditional analysis method of self-balanced pile test has many shortcomings. Based on load-displacement curves of upper and lower piles, a total displacement method of self-balanced static loading test is proposed. Preliminary numerical analyses show that, when the load-cell position deviates from equilibrium, the total-displacement method yields smaller deviations than the equivalent-displacement method. The analysis of various cases with different displacement conditions shows that the results obtained by the total displacement method are highly consistent with those of the conventional methods. When the displacement difference between the top and bottom piles is large or exhibits abrupt changes, the total-displacement method is more appropriate than the conventional method. The total displacement method can solve the problem that the conventional method cannot analyze the upper and lower piles as a whole pile. Moreover, the equivalent-displacement method may be inapplicable when the upper-section displacement is smaller than the lower-section displacement; the total-displacement method remains applicable. The load-displacement curve obtained by the total displacement method is more complete than that obtained by the equivalent displacement method. For ultimate bearing capacity and displacement values not reported in the literature, the total-displacement method provides corresponding results. In addition, the total-displacement method can effectively mitigate site- and environment-related disturbances in obtaining the ultimate bearing capacity of self-balanced pile tests, providing theoretical guidance for similar projects.

Key words: self-balanced method, load-displacement curve, displacement regulation, total displacement method, relative displacement