Key Technical Issues in the Design of High Cofferdams on Deep-seated Cohesive Soil Foundations

TIAN Ying-hui; WANG Ying; WU Wen-hong; HOU Shu-peng; XU Hai-liang

doi:10.12396/znsd.2500218

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拉哇水电站围堰地基覆盖层含50 m厚的湖相沉积低液限黏土层，地层具有厚度大、承载力低、渗透系数低、抗剪强度低等特点，围堰快速填筑加载在地基饱和黏性土中会产生超静孔隙水压力，降低土体抗剪强度，带来围堰与基坑开挖形成的130 m高联合高边坡稳定问题、围堰大变形问题等等。通过研究及现场试验，首次采用70 m级深度的超深碎石桩加固软弱地基，加速土体排水、提高复合地基变形模量及抗剪强度。着重介绍针对复合地基的抗滑及变形稳定分析中遇到的关键技术问题。抗滑稳定计算建议采用极限平衡法，抗剪强度指标，按不同部位及不同计算工况取值，饱和黏性土要注意超孔隙水压力的不利影响，应分析超孔隙水压力时程变化；复合地基抗剪强度可按面积加权分析求得；复合渗透系数可按固结度相似原理推求。对拉哇围堰地基处理方案及施工情况进行介绍，为类似工程提供借鉴。

","endNoteUrl_en":"https://irrigate.whu.edu.cn/EN/article/getTxtFile.do?fileType=EndNote&id=21701","bibtexUrl_cn":"//www.fangxunbeng.com/irrigate/CN/article/getTxtFile.do?fileType=BibTeX&id=21701","articleType":"A","abstractUrl_en":"//www.fangxunbeng.com/irrigate/EN/10.12396/znsd.2500218","qi":"1","id":21701,"nian":2026,"bianHao":"1769492707134-394660946","juanUrl_en":"https://irrigate.whu.edu.cn/EN/Y2026","shouCiFaBuRiQi":"2026-01-27","qiShiYe":"168","accepted":"2025-05-06","received":"2025-02-19","qiUrl_cn":"https://irrigate.whu.edu.cn/CN/Y2026/V0/I1","lanMu_cn":"水利工程","pdfSize":"1263KB","risUrl_cn":"//www.fangxunbeng.com/irrigate/CN/article/getTxtFile.do?fileType=Ris&id=21701","title_cn":"深厚黏性土地基上建高围堰设计关键技术问题","doi":"10.12396/znsd.2500218","jieShuYe":"172","keywordList_en":["Lawa","deep overburden","excess pore-water pressure","ultra-deep gravel pile","composite foundation"],"endNoteUrl_cn":"//www.fangxunbeng.com/irrigate/CN/article/getTxtFile.do?fileType=EndNote&id=21701","zhaiyao_en":"

The overburden of the cofferdam foundation at the Lawa Hydropower Station contains a 50 m-thick lacustrine sediment low-liquid-limit clay layer， characterized by large thickness， low bearing capacity， low permeability coefficient， and low shear strength. Rapid filling and loading of the cofferdam generate excess static pore water pressure in the saturated cohesive soil of the foundation， reducing soil shear strength and causing stability issues for the 130m-high combined high slope formed by the cofferdam and foundation pit excavation， as well as significant deformation of the cofferdam. Through research and field tests， ultra-deep gravel piles with a depth of 70 m were used for the first time to reinforce the soft foundation， accelerating soil drainage and improving the deformation modulus and shear strength of the composite foundation. This paper focuses on the key technical issues encountered in the analysis of slip resistance and deformation stability of the composite foundation. It is recommended to use the limit equilibrium method for slip stability calculations， with shear strength indices determined according to different components and calculation conditions. For saturated cohesive soils， the adverse effects of excess pore water pressure should be noted， and the time-history variation of excess pore water pressure should be analyzed. The shear strength of the composite foundation can be obtained through area-weighted analysis， and the composite permeability coefficient can be derived based on the similarity principle of consolidation degree. This paper introduces the foundation treatment scheme and construction of the Lawa cofferdam， providing reference for similar projects.

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