PROJECT OVERVIEW
Phoenix Project #2218
Phoenix’s final contribution to an emergency culvert repair project in Cromwell, CT was to provide soil stabilization through the use of compaction grouting. The intent was to improve the strength of the weaker fill soils underlaying the roadway and above the recently replaced culvert. Without this work, a busy highway off-ramp and intersection would once again be at risk for unwanted settlement.
A strategic mix design and hole layout was used to maximize the treatment area while also avoiding subsurface utilities and a nearby embankment face. Phoenix’s initial design called for more than 50 compaction grout hole locations, through which a mixture of cementitious grout and sand were pumped into the ground. Verification testing by means of soil borings taken at various stages during the grouting work was implemented to ensure that the design intent was being achieved.
A very challenging element of this project was that the roadway was to remain active throughout the entirety of our work. With careful planning and coordination between our team and the client, the work was executed in two distinct phases to allow the busy roadway and intersection to remain open at all times. Additionally, Phoenix was able to drill and case many hole locations prior to grout placement, optimizing the project schedule and minimizing the length of time that traffic would be impeded by the work. Any drilled and ungrouted holes were left partially cased at the end of each shift such that the casing did not protrude up into the roadway. Road plates were positioned to cover the work area to allow for vehicles to safely travel the area between working shifts.
The pressure grouted columns were installed to a depth of approximately 20 feet. During the compaction grouting process, the temporary casing was extracted in stages while additional grout was pumped until a design pressure or pumping volume was achieved. This process was repeated in two foot intervals until the tip of the casing was only 5 feet below ground surface elevation. The remainder of the drill casing was then removed, the drill hole was topped off with ground under gravity pressure, and the operation moved to the next grout hole location. In the end, all borings demonstrated sufficient soil improvement, and the roadway was quickly restored to full use.
