研究目的：新白沙沱长江特大桥位于长江上游，河床受水流冲刷，多为倾斜无覆盖层的基岩，同时上游受 雨季的影响，水位变化快，流速变化也大。3：墩位于江中，墩位处岩面裸露，高差达17 m。对露出部分采用水 下浅孔控制爆破，基础施工采用先平台后钻孔作业与围堰同步作业方案，8根支撑钢护筒和门吊辅助桩共同 支撑的高位平台，安全度洪，保证钻孔作业不受洪水影响，达到连续作业。 研究结论：( 1)采用微差爆破、减振孔消除爆破振动对既有线桥梁的有害影响,（2)为适应倾斜岩面，在底 节围堰刃脚部位设置具有一定刚度、高度的活动插板，围堰下放后，吊挂于钻孔平台上，及时将插板下放并进 行抄垫，封堵,（3)对围堰内外抛填堵漏、封底，解除围堰吊挂后，进行壁舱浇筑混凝土，能够有效减少封底厚 度,（4 )本研究成果可为裸露倾斜岩面基础施工项目提供经验。

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.