摘要
常泰长江大桥主航道桥为主跨1 176m公铁合建斜拉桥,通过技术经济综合比选,桥塔基础采用沉井方案。针对超大型沉井基础截面尺寸大、自重重、入土深等问题,提出了减自重、减冲刷的新型台阶型沉井基础方案,通过模型试验及数值分析确定了沉井相关设计参数,并基于地基中土体的三维应力状态和摩尔-库伦强度破坏准则,建立了深大基础三维地基承载力计算表达式。沉井基础成功实施的关键是可控的取土下沉措施,研究了超大型沉井下沉机理,探明随着沉井平面尺度的不断增大,端阻力与井壁侧摩阻力相比逐渐成为控制因素,沉井下沉施工必须进行盲区取土。通过对沉井刃脚下土体破坏形态的研究,提出土体破坏的临界宽度控制法和台阶式取土法,可为沉井下沉施工提供指导。
The main navigational channel bridge of Changtai Changjiang River Bridge is a rail-cum-road cable-stayed bridge with a main span of 1176 m.To balance technology and economy,caisson foundations are chosen for the pylons.However,super-large caisson foundation also means large cross-section dimension,hefty body,and great depth in soil.To address these issues,a novel type of scour-reducing stepped caisson foundation(SRCF)is proposed,which has the advantages of reduced self-weight and enhanced scour resistant capacity.Model tests and numerical analysis were conducted to determine the related design parameters of the SRCF.And based on the three-dimensional stress state of the soil and the Mohr-Coulomb failure criterion,the formulas to calculate the three-dimensional load bearing capacity of the deep and large foundation were established.The controllable soil excavation and sinking measures dictate the success of the caisson construction.The sinking mechanism of the super-large caisson was studied,and the results reveal that as the plan dimension of the caisson increases,the resistance of caisson ends gradually surpasses the skin friction of the caisson and becomes the dominant factor,thus,soil in the blind area should be excavated to ensure the smooth sinking of the caisson.The failure modes of soil under the cutting edges of the caisson were studied,on the basis of which the threshold width control method and stepped excavation method that can prevent the soil failure are proposed.The methods can be used to guide the sinking construction of the caisson.
作者
秦顺全
谭国宏
陆勤丰
傅战工
郭明伟
魏凯
QIN Shun-quan;TAN Guo-hong;LU Qin-feng;FU Zhan-gong;GUO Ming-wei;WEI Kai(China Railway Major Bridge Reconnaissance&Design Institute Co.,Ltd.,Wuhan 430050,China;Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan 430071,China;Department of Bridge Engineering,Southwest Jiaotong University,Chengdu 610031,China)
出处
《桥梁建设》
EI
CSCD
北大核心
2020年第5期1-9,共9页
Bridge Construction
基金
中国中铁股份有限公司科技研究开发计划项目(2018-专项-Ⅱ类-01)。
关键词
常泰长江大桥
台阶型沉井
下沉措施
盲区取土
临界宽度控制法
台阶式取土法
Changtai Changjiang River Bridge
stepped caisson
sinking measure
soil excavation in blind area
threshold width control method
stepped soil excavation method
