Significant Project Features:
- Densification of sink hole affected area with vibrating beam pile;
- Installation of 329 jet grout columns to a maximum depth of 120 feet below ground surface;
- Chemical grouting within a 30-inch manhole shaft down approximately 80 feet below ground surface;
- Project site was in the middle of a residential street with houses on both sides;
- High voltage power line and underground utilities needed to be preserved and worked around.
Geo-Solutions was contracted by the City of Kingston to complete the Washington Avenue geotechnical work in Kingston, New York. A portion of the residential street, Washington Avenue, had been shut down for multiple years due to a sinkhole engulfing sections of the roadway. Approximately 80 feet below the roadway runs an underground aqueduct which was partially installed into bedrock. Portions of the aqueduct or tunnel that aren’t in bedrock are surrounded by loose soils. These loose soils had eroded over time and are said to have caused the sinkhole at the ground surface due to settlement. The solution was first to perform densification of the soils within the most sinkhole affected area and then to create an archway around the tunnel to stabilize the loose soils. The final aspect of the work was to seal off a water leak occurring between a vertical manhole shaft and the tunnel.
The densification portion of the work was performed first and lasted approximately 2 weeks. An H-Pile was driven and vibrated 40 feet into the ground using a variable moment vibratory hammer. The H-Pile was vibrated for two minutes at the bottom of each location prior to being retracted. Densification was performed at 113 probe locations. Geo-Solutions performed survey monitoring before and after the densification work. Once the work was completed the site was graded and compacted with a smooth drum roller. A final topographical survey was performed and submitted to the city.
Following the densification work, a civil contractor reestablished the work platform and rerouted underground and overhead utilities. A high voltage power line running the length of the site was left in place but was de-energized for the work.
The purpose of the jet grouting was to create a stabilized soil-crete archway around the underground tunnel. The dimensions of the archway were 30 feet wide by 180 feet long. Geo-Solutions installed 329 jet grout columns during the construction of the archway. Columns were 5 feet in diameter and drilling depths ranged from 70 to 120 feet below ground surface. Two Soilmec drill rigs, SM14 and SM20, were used to perform the work. Two high pressure jet pumps and an automated batch plant were used for creating and sending grout to the rigs. A jet grouting test section was installed and tested prior to beginning full scale production. Wet grab samples and full depth cores were taken during the course of the work. All samples and coring was accepted by the Geotechnical Engineer. The jet grouting portion of the project lasted approximately 3 months.
The final phase of the project involved chemical grouting at the bottom of a manhole shaft to stop water infiltration and to fill voids above the underground tunnel. Chemical grouting took place approximately 80 feet below ground surface within a 30 inch diameter shaft. Confined space entry procedures were followed and a dedicated rescue team was on site for the duration of the work.