Nam Dan sewer foundation pit roof slide incident
(Baonghean) -At 6:30 p.m. on April 4, 2011, at the construction site of the Nam Dan culvert and canal system upgrade and expansion project, phase I, an incident occurred where the foundation pit roof of the upstream culvert and boat lock slid.
The slide is 73m long, 14m wide on average and 13m deep, with a volume of soil sliding down about 3,100m.3. The sliding arc caused the entire row of Larrsen piles upstream of the culvert and the boat lock to tilt about 30o from the vertical. It caused the ground surface of the foundation wall of the right wing upstream of the culvert to rise from 0.8-1.7m (the thickness of the heaved soil layer was greatest near the row of piles and gradually decreased downstream, the affected area was about 20m).
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Motor vehicles are not allowed on Dyke 42. |
On the morning of April 5, after examining the site, representatives of the investor, the Project Management Board, the Supervision Consultant and the representative of the construction unit agreed that the main cause of the landslide was: The difference in soil column H = 13.70m was quite large (from the height (+11.20m) to the foundation bottom elevation (-2.50m)); the traffic volume was too large, prolonged rain caused the foundation pit roof soil to become waterlogged, and the soil in the construction area was weak, with complex soil layers.
The immediate solution is to not allow vehicles to pass through the construction area, rebuild the cofferdam with a slope coefficient higher than the old foundation pit roof using hilly soil, with dike bases at elevations (+6.00) and 9 (+300); dig the soil column to the same height as the existing foundation pit, bend and adjust the Larrsen sheet piles, rebuild with hilly soil and compact thoroughly.
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Workers are straightening the Larsen piles and backfilling them with hill soil. |
It is known that the project: "Upgrading and expanding Nam Dan sluice and canal system" is invested by Nghe An Department of Agriculture and Rural Development, the construction unit is 3 contractors, including Hoa Hiep Company Limited (Vinh City), Hai Phong Irrigation Construction Company and Nghe An Irrigation Construction Joint Stock Company 1. The project was started in early 2009, planned to be completed in 2012 with a total investment capital of over 500 billion VND.
Ngoc Anh
