In situ flow testing of a cement borehole seal in welded tuff

The experimental determination of the hydraulic conductivities of cement borehole plugs in welded tuffs and the effects of field installation and in-situ environment is described. The field results are compared with those from related laboratory experiments which give hydraulic conductivity values nearly two orders of magnitude lower. This improved performance in sealing characteristics is brought about by the controlled installation procedures and conditions in the laboratory. Seal performance can be improved in the field by developing controlled emplacement techniques and careful evaluation of site conditions preparation prior to installing the plug. (4 figures, 1 table, 14 references) (UK)