Case Study - Chemical Grout Box for Interior Elevator Pit Stabilization

An interior elevator pit needed for ADA retrofit in a multi‑level building, inside an old stairwell beside a load‑bearing wall on sandy soils. Conventional shoring wasn’t feasible indoors with tight footprint and headroom limits.​ Stable Soils of Florida was called in to assess and remedy the situation.

Initial Assessment

• Sandy, below‑water‑table soils at a planned 7 ft pit depth.​

• Footing and slab at risk of undermining if excavated untreated.​

• No practical option for sheet piling, slurry wall, or trench box.​

Proposed Solution

Engineers designed a perimeter grout “box” using AP Soil 600, a low‑viscosity, single‑component permeation resin that bonds wet sands into a rock‑like, load‑bearing mass.

Procedures

1. Lay out pit and grout‑box perimeter around the planned excavation.​

2. Drill and set probes to depths below the final pit grade.​

3. Inject AP Soil 600 while slowly extracting probes to form overlapping treated columns.​

4. Allow cure, then excavate the pit inside the treated zone.​

5. Grind exposed treated face flat and use it as the outer form for the concrete pit.​

Results

Stable excavation adjacent to the load‑bearing wall with no observed soil loss.​
Interior elevator pit completed without conventional shoring or large equipment.​
Enabled ADA‑compliant vertical access using permeation‑stabilized in‑place soils.

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