Evaluation Of Earth-Fill Embankments In Romania Using Electrical Methods And Ground Penetrating Radar

During the 1970s embankments were constructed along several hundred kilometres of<br>rivers in Romania In recent years, several leaks have developed along the berms.<br>The aim of this study is to check whether GPR and electrical methods are efficient for<br>characterizing anomalies above the known leaks and, if so, to extrapolate the results into<br>unknown areas for systematic surveillance. GPR revealed variations of 5 to 10% in the<br>apparent water level, whereas piezometric measurements showed variations of less than<br>5%. Such large variations in the apparent water level may be due to variations in EMwave<br>velocity. CMP results confirmed a lower EM-wave velocity in the landslip area than<br>in the safe zone. The apparent water level drops in the area affected by the landslip.<br>Electrical soundings revealed that resistivity is higher in the anomalous crest areas than in<br>the secure parts of the embankment. One striking feature recorded in the anomalous zones<br>was that resistivity anomalies were positive along the crest, yet negative along the berm,<br>i.e. high resistivity along the crest but low along the berm for the landslip area. One<br>explanation is that the weak crest areas are made up of porous material, whereas those<br>along the berm consist of saturated material.<br>This study has demonstrated the correlation between known leakage areas and geophysical<br>anomalies. Furthermore, the coupling of GPR and electrical soundings proved efficient<br>for detecting most of the known anomalies. Due to its good spatial resolution and high<br>acquisition speed, GPR is perfectly adapted to this type of application.<br>2-D GPR tomography along the dams also provided detailed and interesting results.