Evaluation of damage level for rock slopes using acoustic emission technique with waveguides

Rock slopes can fail as a result of external factors such as heavy rainfall, earthquakes, and weathering after construction. Therefore, ongoing monitoring is required to confirm their stability. The brittle nature of rock can make it difficult to detect the early symptoms of failure using conventional indicators such as displacement or stress. However, if acoustic emission (AE) generated by deformation within slopes could be measured, it would be possible to detect in advance the symptoms of developing slope instability. Since rock slopes are generally large and include discontinuities, AE may not reach the sensor or may be attenuated and/or distorted, making them difficult to analyze. To overcome this problem, in this study authors propose an improved monitoring apparatus and method to evaluate the damage level by means of an AE technique with a waveguide and a wavegenerator. The procedure involves performing laboratory tests on the same apparatus as that installed in the field to establish general damage level criteria in the laboratory. The authors suggest criteria for fracture types and damage levels using the trends and ranges of AE parameters. To evaluate the applicability of the proposed method, the authors installed the apparatus in a potentially unstable slope. From this field application, the authors were able to evaluate the current damage level of the slope and fracture type based on the suggested criteria, and thus to validate this method of damage evaluation.