Electrical Imaging Of Engineered Hydraulic Barriers

Electrical resistance tomography (ERT) was used to image the full scale test<br>emplacement of a thin-wall grout barrier installed by high pressure jetting. ERT was also<br>used to monitor the waterflood of a thin-wall grout barrier to vertfy its hydraulic integrety.<br>Both case studies were done by comparing images of electrical resistivity before and after a<br>change was induced in the subsurhace. Barrier materials or flood water were imaged as<br>anomalies which were more electrically conducting than the native sandy soils at the test<br>sites. Although the spatial resolution of the ERT was not sufficient to resolve flaws in the<br>barrier under construction smaller than a reconstruction voxel(50 cm on a side), the images<br>did show the spatial extent of the barrier materials and therefore the general shape of the<br>structure.