An Amelia Island Plantation homeowner chose to demolish and rebuild his home that was the end building of a five-unit complex. It would be necessary to perform an 8-foot-deep excavation immediately adjacent to the neighboring structure. To prevent the unit next door from settling as a result of the demolition and adjacent excavation sodium silicate was chosen to glue the soils together. Sheet pile walls were not an option due to limited site access.
After performing the excavation, the builder noticed a crack forming in the wall of the adjacent structure and noted settlement was occurring to the building. Further inconsistent permeation of the sodium silicate was noted as large volumes of sand began to fall out from under the adjacent structure.
Immediately after noticing the sodium silicate began to break down, the builder contacted Alpha Foundations to stabilize the adjacent building and lift it to its previous level position. Due to the nature of the situation, this project was escalated to emergency status and eight (8) Model 288 Helical Piers were installed just one day after we received the initial call. These piers supported the exposed bottom of the slab and foundation. More than 7 feet of the piers were exposed, so they were fitted with a 3.5 inch external sleeve for the entire exposed section of pile and each shaft was grouted to resist the bending moments being put on the piers.
The structure was then lifted to its previous level position. These piers were later replaced by concentrically loaded piers directly under the foundation so as not to conflict with construction of the new unit. In normal pier applications, the moment of the eccentrically loaded bracket only occurs in the first couple feet and resistance is gained from the soils surrounding the bracket. Therefore, typically only the top 2 to 4 feet is equipped with an external sleeve.
Hardened “soil columns” were created using 500 pounds of Poly Renewal 100 Soil Stabilization to reinforce the soils under the adjacent structure and the sections of the exposed soil wall where the sodium silicate did not permeate. Additionally, 400 pounds of Poly Renewal 400 Joint Stabilization were used to fill the void areas between the soil columns and the foundation wall of the new building to eliminate voids left after excavation.