Project Description
In 2016, Foundex was retained to complete a curtain grouting program along a dam abutment to reduce foundation permeability and improve overall structural performance. The work included drilling nine primary inclined holes, with seven set at 55° from horizontal and two set at 35° and 15°. Each hole was advanced through the dam fill and into the underlying foundation materials, with typical lengths of approximately 35 metres, based on the anticipated curtain depth and fill thickness.
In accordance with project specifications, secondary holes were planned where grout take in any stage of a primary hole exceeded a pre‑determined volume at pressure. The secondary holes were split‑spaced between the primary holes at matching inclinations, with the same criteria used to determine the need for tertiary holes. This staged approach supported progressive curtain closure as grout takes and hydraulic conductivity responses decreased.
A top‑drive rotary drill equipped with a down‑the‑hole hammer overburden casing system was mobilized to advance through the overburden while minimizing disturbance and maintaining efficient penetration. Bedrock drilling was completed using a top‑hammer drilling system, supported by continuous water flushing to maintain clean returns. At target depth, each hole was flushed with fresh water and high‑volume air before receiving an EZTrac downhole alignment survey and selective Lugeon‑type water‑pressure testing.
Grouting was conducted using up‑stage grouting methods, progressing from the bottom up in short stages, using heated and enclosed mixing and pumping systems to maintain grout quality in harsh winter conditions. Mix viscosities were adjusted as required based on real‑time monitoring to achieve refusal criteria and support consistent, controlled curtain closure. Check holes were completed to verify grout coverage and effectiveness, confirmed through additional Lugeon testing. The completed work resulted in a reliable and effectively sealed grout curtain along the abutment.