A new rental-home community was losing its only street. Sinkholes had opened in the pavement, soil was still washing out beneath it, and residents had no other way in or out. Every utility ran under that same road. The county DOT wanted answers from the developer.
Initial Assessment
SiteMix Pressure Grouting found the cause 10 feet down. Test borings hit rock at 10 to 12 feet, leaving infiltrating groundwater nowhere to go but sideways. It found the blasted sewer trench running down the center of the street, backfilled with shot rock, and used it as a drain, carrying soil out with it. The borings came back with low N values across the area, plus two to three large voids. The only conventional fix, full excavation, meant closing that road and tearing out every utility beneath it.
Proposed Solution
The engineer specified AP Lift 475 with the Deep Lock® process. The resin expands into the loose soil, filling the weak zones the washout left behind and compacting what remains.
Procedures
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Mapped the loose-soil zone from the geotech borings
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Laid out a 4-foot injection grid across 98 points
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Drove injection rods to 10 feet
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Injected the prescribed volume of AP Lift 475 at the 10-foot level
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Repeated at 5 feet, compacting the soil between lifts
Results
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Stabilized ~1500 square feet of loose soil and restored support under the street
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Avoided road excavation and utility replacement
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Finished injection in 5 days
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Kept the neighborhood’s only route in and out open throughout
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