Technical Studies


Review Of Monitoring Problems And Application Of Non-destruction Testing Methods For Evaluation Dam Performance

Malfunctions of monitoring system and lack of systematic feedback analysis from monitoring data are common problems for dam safety management in Taiwan. On the other hand, there is a great demand for effective non-destructive methods to examine the interior of the reservoir structures. The objectives of this study are to develop improved monitoring techniques, evaluate and improve non-destructive testing methods, and eventually established a more effective diagnosis system for dam safety.

In non-destructive testing methods, this study was aimed at assessing the performance of ERT applied to the investigation of dam leakage. Several technical investigations were made to improve the testing accuracy and understand the uncertainty involved in ERT. Measurement repeatability of different electrode arrays was investigated to suggest a more reliable survey type for ERT monitoring. Forward model was used to simulate field measurements and gain insights on the resolution and uncertainty of the inverted resistivity tomograms. ERT surveys were conducted at several dams and compared with field observations and monitoring data. Electrodes were installed permanently at Shin-Shan earth dam for subsequent monitoring.

Interpretation of monitoring data for seepage-related problems in earth dames are complex. This project made use of numerical simulations to investigate unusual earth dam responses associated with internal seepage regarding defects occurred within or under the earth dam. Li-Yu-Tan Dam and Sin-San Dam, respectively, were taken as typical examples to represent a well symmetrical and a poorly symmetrical zoned earth dam. The features in the response of seepage problems for these two types of zoned earth dam are distinctive. Critical seepage flow, pore water pressure, water head, and hydraulic gradient, for each case were examined and deliberated to identify crucial signs that can be helpful for the planning of instrumentation locations and for the interpretation of monitored data.

By using the seismometer-recorded ground excitation and vibration response time history data of the arch dam, the vibration frequency and damping ratio of the arch dam can be identified to determining if there is any unusual change of the dam’s dynamic characteristics. The identified results can be used as the basis of the safety diagnosis of the dam.