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| Construction Technology for Bridge Foundation in Deep Water and Gradient Bedrock under Complex Geological Conditions |
| YAO Fa - hai |
| (China Railway Major Bridge Engineer Group Co. Ltd，Wuhan，Hubei 430050，China) |
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Abstract Research purposes： The newly constructed Baisliatuo Yangtze River bridge is located at upstream of Yangtze River and the riverbed is mostly gradient bedrock without covering layer due to current scour. Meanwhile， the water level varies rapidly，the speed of the current varies greatly. Pier No. 3 is located at the middle of the river where the bedrock is uncovered with a altitude difference of 17 meters and shallow blasting is adopted for the bedrock above the water and underwater controlled blasting is adoptd for the bedrock below water. A platform is installed firstly before boring，and boring and cofferdam erection are carried out simultaneously during the foundation construction. Eight steel casings and the auxiliary piles for gantry crane support tlie higher platform so that boring wont stop in case of flood and then construction progress is continuous. Research conclusions:(1) To decrease the damage effects of the blasting on the existing bridge，millisecond blasting and shock relieve vent are adopted. (2)To fit the gradient bedrock，movable strips with a certain height and stiffness are erected at the bottom segment of the cofferdam. When the cofferdam takes its place，drop the strips in time，then pad and fill in the gap between cofferdam and gradient bedrock. ( 3 ) Throw fill inside and outide the cofferdam and botom sealing for the cofferdam. After the hang with the platform is removed，cast concrete into the cabins of cofferdam first which can save the thickness of the concrete for bottom sealing. (4 ) The research result can provide reference for otlier similar project with deep water and gradient bedrock.
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Received: 15 January 2016
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2016, Vol. 33 
