Evaluation of the consolidation progress of a slurry by the SASW method

Abstract

For several years a vacuum consolidation was applied on a disposal of dredged sludge in order to speed up the consolidation. The disposal with an initial thickness of about 8 m was covered with a sand layer of 0·5 m and topped with an high-density polyethylene (HDPE) cover. Since initially it was not allowed to cut open the HDPE for environmental reasons, it was decided to use the nondestructive spectral analysis of surface waves (SASW) method to evaluate of the degree and homogeneity of the consolidation. After a short description of the SASW field procedure and data processing, this paper presents the results of the evaluation of the stiffness of the sludge by the SASW method, which were later compared with laboratory test results. This SASW campaign showed that the consolidation was quite homogeneous in the disposal, although still a very low stiffness was measured. The SASW method was fast, cost-effective and well suited to the in situ evaluation of the vacuum consolidation technique.