Impact-Echo Response of Hollow Cylindrical Concrete Structures Surrounded by Soil and Rock: Part I—Numerical Studies
The studies summarized in this paper and the following paper in this issue demonstrate that the impact-echo method can be used for integrity testing of concrete pipes, mine shaft liners, and tunnel liners in contact with soil or rock. Results obtained from numerical (finite element) studies are presented in this paper (Part I), and results obtained from experimental studies on mine shaft liners are presented in the following paper (Part II). These results show that the impact-echo response depends upon the acoustic properties of the surrounding material, as well as on the acoustic properties, geometry, and condition of the concrete structure. It is shown that cracks and voids in the concrete structure can be detected independent of the surrounding material. If the concrete structure is solid, the thickness of the concrete can be determined, except when the acoustic properties of the rock and concrete are similar and the concrete is in contact with the rock. The presence of delaminations or voids (air- or water-filled) at the concrete/rock interface can be identified when the acoustic impedance of the rock is similar or larger than that of the concrete.