Reasonable evaluation of pile soundness based on pile integrity test

What is it about?

When existing piles are reused, they are inspected using the pile integrity test (PIT) to judge whether they are appropriate for reuse. The evaluation of pile soundness heavily depends on the experience of PIT examiners. This paper describes the objective and quantitative evaluation method for pile soundness using PIT. The major findings of the study are summarized as follows. 1) The size of pile crack depends on the amplitude characteristics of PIT waves. 2) The size of pile crack can be evaluated using proposed “crack factors” that are calculated from the quantified values of the amplitude characteristics.

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Why is it important?

1) The size of pile crack depends on the amplitude ratios b/a and b/c calculated from the quantified values of the amplitude characteristics of PIT waves (see Fig. 9). In this paper, b/a is the ratio of amplitude height of crack reflection to the pile head input, and b/c is the ratio of amplitude height of crack reflection to the pile end reflection. 2) The amplitude heights of PIT waves of piles under the ground are smaller than those for piles in the air because of pile internal damping and radiation damping. When the amplitude heights are enlarged to offset radiation damping, the size of pile crack is in proportion to the depth of crack reflection. This is because when the crack depth is deeper to its pile end, the effect of pile internal damping gets larger and the reduction ratio of amplitude increases linearly (see Fig. 17). 3) Considering the above findings of the amplitude characteristics of PIT waves, we propose the crack factors B/A and B/C in the equations (13) and (14). The size of pile crack can be evaluated using the crack factors (see Figs. 20c, 20d, 21c). The crack factors are calculated from five quantified values of the amplitude characteristics: i) the amplitude height of pile head input “a”, ii) the amplitude height of crack reflection “b”, iii) the amplitude height of pile end reflection “c”, iv) crack depth “Lb”, and v) pile end depth “Lc”. 4) The distributions of the crack factors based on tests and analyses are consistent with the distributions based on field measurement in buildings (see Fig. 22).