Summary: SUCTION BREAK TO CONTROL SLOPE-INDUCED MOISTURE
VARIATION IN LAYERED COVERS
Abdelkabir Maqsoud, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada.
Bruno Bussière, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada.
Mamert Mbonimpa, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada.
Fanta Cissokho, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada.
Michel Aubertin, École Polytechnique de Montréal, Montréal, Québec, Canada.
Covers with capillary barrier effects (CCBE) can be used to limit gas flux into or out of waste disposal sites. Numerical
modeling and field test results showed that the hydraulic behaviour of such type of cover is influenced by slope
inclination, which can induce a local desaturation that is detrimental to its efficiency. This negative effect can be
minimized by placing a suction break in the moisture-retaining layer of the inclined cover. This concept was applied on a
small portion of the South-east dam of the LTA tailings site cover, and tests were conducted under various conditions.
The results under natural climatic conditions show the presence of a saturated zone near the suction break, which
confirms the validity of this concept in the field. The volumetric water content of this saturated area was not affected even
after 78 days without water infiltration. Also, in situ tests with large precipitation lead to a better understanding of the
influence of a suction break on the hydraulic behaviour of the inclined CCBE, in terms of water and suction distribution in
the different layers and of the ensuing water diversion capacity. This study showed that a suction break could be used to
improve the performance of inclined CCBE used to limit gas migration, and that it can also influence the diversion length
under particular conditions.