The combined use of MASW and resistivity surveys for levee assessment: A case study of the Melvin Price Reach of the Wood River Levee

摘要

Capacitively-Coupled Resistivity (CCR) and Multichannel Analysis of Surface Waves (MASW) were performed on the Melvin Price reach of the Wood River Levee that has experienced considerable piping through the foundation soil causing numerous sand boils along the landside toe of the levee. Tests were performed along the centerline crest, the landside toe, and the riverside berm of the levee. This study combined the strengths of MASW and CCR testing to resolve the distribution and stiffness of cohesive and non-cohesive materials in the body and foundation of the levee, where invasive testing was not ideal. MASW and CCR were shown to complement each other in the evaluation. CCR successfully classified the near surface clay and sand deposits along the levee and was particularly effective for soil deposits with a high degree of saturation. MASW revealed that a deeper clay layer, appears to be discontinuous at locations where old river bars cross under the levee. These bars may have eroded portions of the deeper clay layer, locally enhancing seepage rates through the foundation materials and influencing the formation of sand boils during large flood events. The use of MASW and CCR also successfully detected the locations of the major utilities crossing the levee. While CCR was the most effective method for detecting conductive utilities, MASW was more effective at detecting utilities which increased the overall stiffness of the subsurface either due to the utility itself or the backfill material around the utility. A site-specific SPT-Vs correlation was developed from the co-located boreholes and shear wave velocity profiles. Comparison of the correlation with previous studies indicates that soil stiffness and geologic age are important factors affecting SPT-Vs correlations. For levee soil deposits, which are typically young, a lower bound SPT-Vs correlation developed using similar soil deposits to the study area should be considered.