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Sinkhole
Repair Process
Remediation Techniques
Grouting and Underpinning are the
techniques used by licensed contractors in the Sinkhole Repair Process.
The discovered sinkhole activity can be remediated by the injection of
grout into the sinkhole activity zones.
The identified sinkhole activity zones can be remediated by injecting a
low to moderate slump cementicious grout, under pressure, into the
subsurface. The purpose of the grout injection program is to grout within
and along the top surface of the limestone about the affected area to
restrict and/or seal breaches in the surface of the limestone (where
evident) that connect the soils that overlie the rock surface to suspected
cavernous bedrock zones, thereby reducing the potential for future subsoil
raveling and migration. In addition, the grouting may serve to compress
and reinforce the subsidence of the overlying undisturbed soil zones into
the weak zones.
The grout materials will consist of a combination of Portland cement, fine
aggregate and water. Additives may be used, provided the grout mixture
meets slump requirements. Hydro-active and micro-fine grouts are
acceptable. For filling grouting of voids and cavities and compaction of
surrounding sands, using conventional cementicious grout, the grout mix
will have a target slump of 3 inches, with a plus or minus 1-inch
tolerance in the field, as measured at the truck. The grout mix design
shall have a 28-day compressive strength of at least 300 psi, or more.
Underpinning is a stabilization technique used to stabilize the property.
Pin piles are drilled down to the bedrock and used to support any unstable
part of the property. In certain grouting programs it is recommended that
the property have underpins installed prior to grouting to minimize the
chance of any further structure damage caused to the property from the
grout displacing any extremely weak subsurface material.
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