The limited mobility grout injected into void spaces within soil or rock, soft soils, or the soil-filled cavities of the bedrock, improved the subsurface soil and rock conditions by filling the void spaces and replacing soft, loose soils with high internal friction grout that improved stress transfer. The grout was then intended to remain in a globular mass which increased in size as pumping proceeded.
The objective was to remedy sinkhole activity on an active state roadway. To accomplish this, the underlying voids and loose soils required compaction grouting.
The limited mobility grout is incapable of flowing under its own weight into small discontinuities in the rock. It is the intent of this procedure to limit the lateral extent of grout travel, but to fill void spaces, compress soft soils, impede future migration of soil particles in areas of potential sinkhole activity, and provide additional indirect support to roadway pavements.
LF of drilling
CY of group injected
Injection holes drilled
The project began upon receipt of the approved submittals and the Notice-to-Proceed. Coastal then mobilized to the site and began drilling activities.
The holes were laid out and adjusted as necessary to prevent damage to the pavement and to avoid any interference with utilities. A hydraulic track mounted drill was used to drill the risers which consisted of standard 5 ½” O.D. flush joint grout casing with an inside diameter of 4.325 inches and 10-foot lengths. The grout casing was advanced to the required tip elevation by the use of percussion drilling techniques utilizing a down-the-hole hammer and concentric bit utilizing air flush. The steel casing was left in-place until grouting and then extracted by the drill rig as the hole was grouted. All holes were drilled 10’ below top of rock and a minimum of 1’ beyond any void. Grout was injected below the maximum allowable rate of 2 cubic feet per minute as determined by the grout verification test program. In total, Coastal drilled 312 grout holes totaling 17,200 LF and approximately 1,500 CY of low mobility grout with a 2 inch slump was required. As always, Coastal adhered to strict safety and quality assurance standards throughout the entirety of the project.