Alley Settlement Correction

Polyurethane grouting by CJGeo to raise alley pavement

Polyurethane grouting to raise alley pavement

Challenge:

Dewatering associated with a basement excavation caused settlement of an adjacent alley’s pavement.  The alley pavement consisted of 4″ concrete base, 2″ course of asphalt, and 3″ thick pavers.  The alley served as the sole service and parking entrance to an adjacent residential tower, so could not be shut down.  Due to the unpredictability of deliveries, the repair also had to allow for intermittent traffic during work.

The pavement had settled up to 3 inches, with nearly 3,000 square feet affected.  In addition to being adjacent to two 50+ feet deep basements, one end of the work area was bound by the Navy Yard metro station. 

Solution:

While the customer was familiar with, and inquired about cementitious pressure grouting, CJGeo proposed polyurethane grouting.  Polyurethane grouting allows for immediate traffic after repairs, and also for intermittent traffic during repairs.  With in-place unit weights of around 4 PCF, polyurethane grouts are significantly lighter than cementitious grouts, which reduces the propensity of future consolidation of underlying soils.  

Polyurethane grouting is done using compact equipment, as well.  Instead of large pumps, mixing equipment and hard to maneuver hoses, polyurethane grouting is all down out of a box truck, with lightweight, small hoses that are easy to move out of the way if needed.

Result:

A CJGeo polyurethane grouting crew spent two days raising the alley.  Sawing was done prior to lifting in order to facilitate differential movement between the settled slabs & the adjacent paved areas.  Multiple trash pickups and material deliveries were made to the adjacent property during the grouting work, without disruption to either party.