Impact-Echo Response of Hollow Cylindrical Concrete Structures Surrounded by Soil and Rock: Part II—Experimental Studies
The studies summarized in this paper demonstrate that the impact-echo method can be used for integrity testing of mine shaft and tunnel liners in contact with rock. Results obtained from experimental studies on mine shaft liners are presented. These results show that the measured impact-echo response depends upon the acoustic properties of the surrounding material as well as the acoustic properties 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 bonded to the rock. The presence of delaminations or voids (either air- or water-filled) at the concrete/rock interface can be identified when the acoustic properties of the rock are similar or larger than those of the concrete.