The Analysis Of Static Load Test With Pile Self-Balancing Method And The Improvement And Application Of Theload Box

The static load test with self-balancing method is a new type of pile bearing capacity test method, it makes full use of the basic principle of the pile friction and end resistance as the balance force.When testing the load bearing capacity of super-long pile, it is basically not affected by the limit of bearing capacity and site conditions. At the same time, many aspects of test data are provided, the application range of the pile static load test is expanded, the test cost is reduced and the safety of test process is enhanced.The analysis and research on the static load test of the self-balancing load test and the significance of the load box, and the development status of the domestic are briefly described; The load transfer mechanism of pile foundation of different test methods, the basic principle of static load test with self-balancing method, equivalent conversion methods, the identification of balance point and the embedding of load box etc. are introduced. The emphasis is on the improvement of the load box used for the static load test and the application of practical engineering. Load box is the key equipment of the self-balancing load test, the design and quality directly affect the test results of the static load test with self-balancing method. Because the top and bottom of traditional load box is easily to hold laitance and other undesirable medium, which can cause uniformity of the quality at these parts of the pile body. When loading, the stress and deformation of the load box are complicated and uneven. and the observed value of the displacement measurement device which is installed on the top and bottom of the load box is not in conformity with the actual stress and strain value of the pile. And these parts of load box are easily to be invaded by impurities, which can affect the effect of the later grouting reinforcement. At the same time, there are complex and difficult problems in traditional load box. In order to overcome the technology shortcomings of conventional load box, and to improve the quality and performance of load box, the key research contents for the improvement of the load box is:low oil pressure and high output lifting, specially designed tube structure, displacement device, layout of the observation point, acoustic pipe connection at the load box, high pressure grouting after the test etc. And, through the engineering example, compare the test with the improved load box and the traditional load box under the same conditions, to verify the design purpose and product quality performance. It is confirmed by the engineering pile test that under the same conditions, the new type of load box has advantage in low oil pressure high output, the maintained normal of the test load, reasonable displacement of observation point, accurate test data, good acoustic pipe connection and significant effect of grouting reinforcement and other advantages. At the same time, the new type load box obtained the utility model patent certificate, the certificate number:ZL201420192943.4; at present, the load box has been widely used in a number of projects, and the test tasks are all successfully completed.Finally, the test data and analysis results of static load test with the self-balancing method are concluded. It shows that the design of pile axial reflexive force test tube load box is reasonable, the quality is reliable, and with the development of self-balancing test technology, it will be gradually recognized and popularized.