A novel measurement method of toe debris thickness for bored piles based on one-dimensional wave theory.

The existence of toe debris at the bottom of the bored pile will reduce the bearing capacity of the pile. This paper develops a novel equipment to measure the thickness of toe debris for bored piles. The equipment consists of a test rod, test hammer, velocimeter, transmission cable and data receiving and processing device. Based on the one-dimensional wave theory, the mechanism of the sudden change of the velocity time curve received at the top of the test rod is analyzed, which is caused by the change of the wave impedance at the interface between the test rod and the sediment, thus the feasibility of the equipment is verified in theory. Finally, numerical simulations of toe debris under various working conditions are carried out to verify the reliability of the equipment. The results show that the test curves are sensitive to the materials of test rod using proposed equipment when the thickness of toe debris is equal or greater than 50 cm, and the test values are all larger than actual values, which meet the requirement of relevant specifications. The test results are more accuracy when the thickness of toe debris is less than 50 cm. when the excited force is large, not only the sudden change is easy to be discriminated, but also the test accuracy can be assured. The remainder toe debris meet the requirement of relevant specifications after clearing pile hole according the proposed method. And the device is not affected by the properties of the sediment material, which indicates that the proposed equipment can perform well to test the thickness of toe debris. [ABSTRACT FROM AUTHOR]