King of Prussia, PA –
This project is a multi-stage projecting occurring over the course of 3 years. We are currently preparing for the third stage. This complex consists of multiple condominium buildings and parking garages. This area is notorious for sinkhole development which is why compaction grouting was chosen as the premier method of soil stabilization pre-construction.
1st Phase
For the first portion of this series of projects, we provided proof drilling and pressure grouting to minimize sinkhole activity in what is now the upper northern section of the apartment structure. The multi-family development was to include 339 residential units with a 500 space, 8-story parking garage. We worked together with the project engineers to develop grouting refusal criteria. As was expected, test borings revealed areas of weathered limestone with varying depths of silts and clay. Rock and subsurface characteristics resembled potential sinkhole activity. By the time we concluded the first portion of the project, we drilled 11,551 linear feet and injected grout into 298 hole locations.
2nd Phase
In preparation for the second phase of construction for a proposed, 6-story residential building with attached 7-story parking garage, we provided test proof drilling and grouting. This consisted of working 4 days, drilling 506 linear feet into a total of 12 grout injection locations. The grouting program for this 2nd portion included preparing the soil to handle the proposed residential building and garage. We planned according to the test proof drilling, test boring results and the work we performed from the project during the first stage on the adjacent property. We also considered the engineers’ subsurface investigation information.
We worked with the engineer to develop a pressure grouting program to treat the subsoils beneath the proposed foundations and floor slab areas under the northeast quadrant of the residential structure. The residential building and garage were to be supported by shallow spread column footings and continuous wall footings with maximum residential column and wall loads of 500 kips and 10 klf, respectively, and maximum garage column and wall loads of 1,500 kips and 30 klf, respectively. The subject area of the project site seemed fairly level with minor fills, (2 to 3 feet high) expected. The lump sum proposal approximated up to 389 total grouting locations and 14,782 linear feet of drilling. Included in this total was the possibility of secondary and tertiary locations.
We were able to successfully complete the project by injecting grout into 266 hole locations and performing 10,660 linear feet of drilling. The intent was to perform the work using up to 2 drilling crews and 4 grouting crews full time. We were able to complete the project in 4 working weeks and in less time and than quoted.
3rd Phase
Updates to this project for phase 3 will be added as we move through late Spring/Summer.