Abstract:

To detect the hidden leakage problem of a dam body accurately, a new geophysical method, magnetic resonance sounding (MRS), is introduced, which can directly detect water molecules and quantitatively measure them. The basic principle and inversion method of MRS is research to determine the coil type and measurement mode for dam leakage problem. Field experiment of dam leakage detection was performed on Cuijiajie dam in Huanren, Liaoning Province, using JLMRS system developed by Jilin University. 15 points on the dam crest were measured with a 4-rurn square coil of 12.5 m side length for maximum depth 35 m. By data processing and inversing, the water content profile of the dam body in 2D is achieved. Furthermore, for eliminating the effect of upstream water, a correction method is used and the relative water content in 2D is updated. The interpretation results show that there are three leakage points (140 m, 180 m and 240 m away from the spillway, respectively) and two infiltration areas (rang of 100 m to 150 m and 170 m to 250 m) at depth of -20 m to -10 m inside Cuijiajie dam, which are gravel layer leakage. The measurement result is confirmed consistent with the engineering geology and downstream water percolation.

Key words: magnetic resonance sounding, dam leakage, correction method, direct water detection, two dimensional