大水头差条件下防撞导向井钢围堰内承台基础开挖关键技术研究  

Research on the Key Techniques of Foundation Excavation in Cofferdam of Anti-collision Guide-well under the Condition of Large Water Head Difference

作　　者：谭科 冯玉涛[2] 向中富 TAN Ke;FENG Yu-tao;XIANG Zhong-fu(School of Civil Engineering and Architecture,Chongqing Jiaotong University,Chongqing 400074,China;Chongqing Communications Planning Survey & Design Institute,Chongqing 401121,China;Sichuan Vocational and Technical College of Communications,Chengdu 611130,China)

机构地区：[1]重庆交通大学土木工程学院,重庆市400074 [2]重庆市交通规划勘察设计院,重庆市401121 [3]四川交通职业技术学院,成都市611130

出　　处：《公路》2018年第12期97-101,共5页Highway

基　　金：交通运输部建设科技项目,项目编号2011318350990;重庆市交委科技项目,项目编号201206;重庆市基础科学与前沿技术研究,项目编号cstc2017jcyjAX0078

摘　　要：曾被誉为“世界第一钢筋混凝土拱桥”的万州长江公路大桥,随着三峡库区175m水位的蓄水,两岸拱脚全部被淹入长江水下,主拱圈遭受船舶撞击的风险加剧。结合库区水位变动及大桥防撞特点,采用了一种能自动适应水位变动、实现即时防护的“自浮式弧形水上升降防撞装置”。而1号导向井承台基坑能否顺利开挖直接决定着防撞工程项目的成败。采用围堰槽套孔取芯掏槽和原槽浇筑水下混凝土技术,克服了29m大水头差压力下刃脚段封底混凝土与基岩间的大渗漏风险;采用在刃脚内外侧及底部设置12mm厚止水环板,克服了地下水沿刃脚与混凝土基础间隙大渗漏的风险;采用基础岩体帷幕注浆技术,克服了大水头差压力下因砂岩孔隙、裂隙等自身缺陷而存在的基坑涌水风险。ABAQUS有限元仿真结果表明,围堰内抽水并开挖承台基坑后,钢围堰基础整体稳定。现场承台基础的顺利施工进一步验证了计算结果的正确性。Boasted as the“First Reinforced Concrete Arch Bridge in the World”,all the arch-legs on both sides of the Wanzhou Yangtze River Highway Bridge are submerged into the water with the waterlevel of 175meters in the Three Gorges Reservoir,and the main arch rings suffers from the high risk of ship collision.Combined with the change of water-level in the Reservoir area and the anti-collision characteristics of the Bridge,a “self-floating curved water-lifting anti-collision device”that could automatically adapt to water-level fluctuation and realize instantaneous protection is adopted.The key to the success of the anti-collision device is the foundation excavation in cofferdam of the first guiding well.In order to overcome the great leakage risk between the bottom concrete and the bedrock,the underwater concrete coring technology of the core cut and the original groove are used.In order to overcome he risk of leakage of the groundwater along the gap between the foot and the concrete foundation,a 12 mm thick water-stop ring plate is used in the lateral and bottom of the edge of the blade.Based on the grouting technique of foundation rock mass,the risk of water inflow in the foundation pit is overcome because of the defects of sandstone pore and fissure under the pressure of large water head.The results of ABAQUS finite element simulation show that the foundation of steel cofferdam is stable as a whole after pumping water in the cofferdam and excavation of foundation pit.The successful construction of the site foundation further verifies the soundness of the calculation results.

关 键 词：双壁钢围堰 承台基础 大水头差 防渗止水 岩体稳定 技术 

分 类 号：U443.25[建筑科学—桥梁与隧道工程]