Abstract:
A remedial grouting procedure to develop a grout curtain around the slurry wall excavation was required at the Boston Children’ s Hospital Hale Family Clinical Building in Boston, MA. The Children’ s Medical Center Corporation is the owner; Suffolk was the general contractor; J.F. White was the excavation contractor; Trevi Icos was the slurry wall contractor; Thornton Tomasetti was the slurry wall designer; and Haley and Aldrich was the geotechnical engineer.
The perimeter foundation wall consisted of a continuous slurry wall. While excavating for a slurry panel trench, the basement slab of the adjacent building experienced structural distress. This resulted in the basement, which happened to be the morgue at Children’ s Hospital, filling with a mixture of slurry and concrete. A grout curtain was proposed to be installed around the planned slurry wall to solidify the sand layer and provide enough stability to complete the slurry walls.
The grouting procedure consisted of 119 grout injection holes that were installed from 25 to 30 feet below present grade. The holes were drilled with a 5.5-inch O.D. drill casings that utilized an internal flush wet rotary drilling method. After the casing was advanced to the required tip depth (about 25 to 30 ft.) a tube-a-manchette (TAM) pipe was grouted and the casing was extracted. After a minimum of 12 hours, each hole was pressure grouted by inserting a double packer into the TAM pipe. The packer allowed each grout injection port to be isolated when pressure grouting occurred. The grouting was performed in a primary hole – secondary hole sequence. The primary grouting was performed on every other hole with the secondary grouting occurring the following day on the skipped holes. Haley and Aldrich reviewed the pressure-volume results of each location and evaluated whether secondary grouting was required.
The project began in January 2018 utilizing two drill rigs for the full duration. The grouting program was completed in February 2018. The overall grouting program was very successful and it allowed for the completion of the slurry wall at that section of the foundation without any further issues.