Rock Curtain Grouting

Rock curtain grouting is the filling of fractures and fissures in rock to reduce permeability, strengthen or stabilize the rock, or both. The most common application is to reduce water seepage and pressure beneath a dam or other structure. Curtain grouting techniques are also utilized to control seepage for deep excavation and shaft construction through rock.

Over time, water seepage through joints and erosion piping paths in the weathered or semi-permeable rock foundations of a dam constructed without a cut-off can create unacceptable uplift pressures leading to instability of the dam structure. Unacceptable groundwater inflow through highly permeable rock can also create significant problems during shaft sinking, particularly under high hydraulic pressure at depth. In extreme cases, this can lead to site abandonment and costly shaft relocation. For situations like these, permeation grouting contractors use curtain grouting techniques prior to excavation, which can effectively reduce rock can effectively reduce rock permeability to resist the hydraulic gradient, strengthen and stabilize the rock, or both.

Installation

Rock curtain grouting is accomplished by vertical and/or angled drilling to intersect joints, fissures and voids in the rock, cleaning of drill holes and water testing, then pressure grouting with specially formulated cement-based grouts. Grouting is typically accomplished in a primary/secondary/tertiary sequence to ensure complete-cut-off.

Applications

  • Remediation of seepage through existing dams
  • Pre-treatment of rock prior to shaft excavation
  • Curtain grouting of permeable rock beneath a proposed dam core to ensure complete cut-off

Advantages

  • Proven, well-established technique
  • Can be applied through a wide range of rock conditions
  • Grout can be formulated to suit a wide range of conditions from small fractures to significant voids

Permeation grouting was the method of choice for the OARS relief sewer groundwater cut-off in Columbus, OH. At Watres Dam in Pennsylvania, rock curtain grouting was used to reduce permeability of the weathered rock upstream of a proposed bare rock spillway expansion.