應用地電阻影像法於壩體潛在滲漏調查之研究

Abstract

水庫壩體的安全評估有非破壞性檢測方法上的迫切需求，為了能瞭解壩體內部的滲漏疑慮及可能路徑，本研究目的在探討地電阻影像探測法（ERT）於土石壩與混凝土廊道上應用的可行性，由土石壩的試驗結果顯示地電阻對於壩體滲漏調查具有良好的可行性；由混凝土廊道結果顯示地電阻對於裂縫位置與深度相當具有潛力。另外也嘗試利用地電阻來進行監測，結果顯示ERT應可以成為滲漏問題監測的有效工具。 為了提昇施測準確度及掌握ERT施測結果之不確定性，本研究進行了一系列的問題探討。在現地施測方面，本研究嘗試利用注入導電液來提昇電極與地表間的耦合，測試結果顯示注入導電液能夠提高淺層的資料品質。為了瞭解不同電極施測排列的重複性及提供監測時選用電極排列方式的參考依據，以各種電極排列方式進行重複性試驗，測試結果Wenner及Pole-Pole排列方式分別對於淺層探測及深層探測具有較佳的重複性，較適合監測不同時間電阻率的變化。最後本研究利用正算模型模擬現地施測情形，ERT之解析度隨深度增加而降低，比較正算模型之模型電阻率影像與反算之電阻率影像可探討反算結果之解析度與不確定性，增加資料判讀之合理性。

There is a great demand for effective non-destructive methods to examine the interior of the reservoir structures. This study was aimed at applying ERT to the investigation of dam leakage. Results of field testing on an earth-fill dam and a concrete structure show that ERT is quite useful for mapping seepage anomalies and holds a great potential for regular dam inspection. The study also tested the applicability of ERT on dam monitoring. The case study indicates that ERT can be an effective tool for monitoring potential leakage and leakage evolution inside the dam. Several technical investigations were made to improve the testing accuracy and understand the uncertainty involved in ERT. In the field survey, two kinds of electrolytes were used to enhance the coupling between the electrodes and the ground. The testing results show the electrolytes（CuSO4）can reduce variation in the raw data for top layers. Measurement repeatability of different electrode arrays were investigated to suggest a more reliable survey type for ERT monitoring. The results show that Wenner array is good for shallow depth measurements while Pole-Pole array is suggested for deeper depth measurements. Finally, the forward model was used to simulate field measurements and gain insights on the potential . Finally, the forward model was used to simulate field measurements and gain insights on the resolution and uncertainty of the inverted resistivity tomograms.