68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

PERFORMANCE OF FULLY GROUTED PIEZOMETERS SUBJECTED TO TRANSIENT FLOW CONDITIONS

Session: Groundwater / Eaux souterraines

Vahid Marefat, PhD candidate (Canada)
François Duhaime, Professor (Canada)
Robert P. Chapuis, Professor (Canada)

Piezometers can be installed within clay layers with either the fully grouted or traditional method. With fully grouted piezometers, there is no sand filter around the piezometer and the borehole is grouted completely after having positioned the transducer. Advocates of this method claim that it has the following advantages: no risk of failure for the sand pack of deep wells, ease of installation, and reduced installation costs, especially from the opportunity to install several piezometers and geotechnical instruments within the same borehole. This paper presents a numerical model using the finite element code SEEP/W to assess the performance of a fully grouted piezometer under transient flow condition. The results indicate that the fully grouted transducer provides representative pore pressure data, without producing a significant piezometric error, when the permeability contrast between grout and surrounding clay is between 0.1 and 10. For a grout with a much lower permeability than the surrounding clay, the cement-bentonite grout should be stiffer than the clay to provide representative pore pressure data.