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Excavation/Structural Support

Danville, PA: Deep Soil Mixing Excavation Support


This project involved the design and construction of a permanent shoring system, utilizing Geo-Con's Deep Soil Mixing (DSM) technology, as excavation support for a new roadway project. Steel "H" beams were placed into the freshly mixed soil-cement columns on 4.5-foot centers to create the shoring system. The shoring was installed along either side of a residential street where a new 600 foot tunnel would be built. The shoring allowed excavation and construction of the tunnel without disturbing or damaging the homes only a few feet away. A total of 43,000 square feet of soil-mixed wall to depths of 45 feet was installed. The length of each side of the permanent shoring was 610 linear feet, for a total length of 1,220 feet of structural, soil-mixed wall. The site soils consisted of sands and gravels. When mixed with the specified grout mixture, an average 28-day strength of 476 psi was achieved.


Geo-Con completed this project on a residential street in the small town of Danville, Pennsylvania. Two large cranes were required to complete the project in close proximity to historic homes and buildings. One crane held the DSM augers, which were operated as close as 8 feet from existing homes. The homes were guarded with plastic sheeting to prevent the soil-cement mixture from splashing onto them. Some temporary entrances had to be constructed so that the homeowners would not be inconvenienced. The other crane was used to set steel beams into the soil-cement columns. Due to concerns over ground vibrations, the PA DOT required seismic monitoring. Geo-Con needed to exercise extreme caution when using the beam vibrator to set the beams so as not to exceed the allowable ground vibrations. The limits were not exceeded throughout the project and Geo-Con performed the work without incident.

Due to the fact that the project was completed on a residential street in a small town, there was a tremendous amount of community interest in our work. On a typical day, there were 10 to 40 people watching us work at any given time. Geo-Con employees had to continuously maintain ropes and barricades to make sure the spectators kept a safe distance, and to maintain a polite, professional manner when interacting and fielding questions from the public. Geo-Con had to abide by strict work hour constraints and noise limitations as well. Overall, Geo-Con was able to minimize the impact to the community and successfully complete our project on schedule.


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