Research On Key Technique Of Pile Self-Balanced Load Test Method And Its Engineering Application

Traditional load test is generally accepted as s most directly and reliable method for determining the bearing capacity of piles. Because the method needs special reaction system, it will take more time and money and require high condition for test field. So it cannot be done randomly and widely, and cannot be done under hard conditions. Load test is difficult to be carried with the development of higher bearing capacity and long length. As s new measuring technology, self-balanced method has its advantage on technology and economy. At present, it is first load test method in north American and it has been applied in some province in China. Because of the difference of loading way and load transfer mechanism, its transferred result has some deflection with traditional load test. So how to transfer. As a result, how to transfer scientifically self-balanced test data into top load curve according to its actual working behavior, becomes the obstacle of its practical application.In this paper, a new loading test—self-balanced loading test is introduced, which can separate friction and bearing. It has advantages of simple equipment, short test period, safety, saving investment. In it, test principle, test device, test technique and pile type is presented. And some problems are discussed, such as the characteristics of the test and the differences between this method and the traditional Heap-Weight pile test. In accordance with actual forcing behavior and reaction mechanism between pile and soil, the article analyzes the relation between top part and bottom part, load transferring mechanism and difference with other loading way by finite element method. So the reliability of determine bearing capacity by self-balance method has been proved. This paper analyzes the main influencing factors in the self-balanced test for pile and the comparison with vertical capacity determined by the same piles after the introduction of pint-sized bearing plates. The final conclusion of this paper is that when used for evaluating the actual bearing capacity conditions. The self-balanced test for piles after the introduction of pint-sized bearing plates is very safe and possesses good value for application. The experiment displays that the problems resulted from great difference of end bearing plates. that is to say. the introduction ofsmall load can be employed to test large bearing capacity. Therefore, the vertical bearing capacity determined by self-balanced test for piles is very safe and this method can be extended to the test for high bearing capacity. It shows that the transferred curves are well consistent with top load curves, so it can satisfy the engineering requirement and its accuracy can amount to about ninety percent. Finally, some problems deserving further study are suggested based on concluding the whole research in Tianjin.