Deep Excavation Project under High Ground Water Table

The excavation project for the Shopping Center in Turkey with a depth of 17.0m was performed in cohesionless sandy and gravelly soils. Impervious pile walls were constructed using 80-cm diameter reinforced concrete piles and jet grout columns in between due to ground water table. Three levels of ground anchors were used to support the piles. Excavation was monitored using inclinometers placed inside the piles. Test excavation of approximately 300m² of basement area was performed to examine the need for jet grout base plug due to water infiltration from the base. The excavation was completed successfully using an effective dewatering system in 6 months. Observed pile wall displacements were in the order of 2 –3 mm. The construction operations were stopped for approximately 12 months of time. Due to the possibility of failure of ground anchors and the potential stability problem in jet grout columns under high hydrostatic pressures, it was decided to stop dewatering and let the ground water table rise to its original level. After 12 months construction operation was restarted and dewatering was successful to lower the water level below the base of the excavation. Inclinometers showed some additional displacements (maximum 5mm) during re-dewatering operations.