软土地基沟渠开挖诱发远处围堰失稳的实例分析  

Case study on the cofferdam collapse induced by distant trench excavation in soft soil foundation

作　　者：楼晓明 孙逸玮 张蓟 LOU Xiaoming;SUN Yiwei;ZHANG Ji(Shanghai Geoharbour Construction Group Co.Ltd.,Shanghai 200434,China)

机构地区：[1]上海港湾基础建设(集团)股份有限公司,上海200434

出　　处：《水利水电技术（中英文）》2024年第S01期151-159,共9页Water Resources and Hydropower Engineering

基　　金：国家自然科学基金资助项目(52078060)

摘　　要：以福建滨海软土地基上因地基处理需要修建的临时围堰局部失稳垮塌的工程为例,通过围堰破坏段与远处沟渠施工段的时间、空间对应关系,推断远处沟渠开挖是造成围堰失稳的主要因素。然而围堰与沟渠间隔相对较远,且沟渠开挖规模较小,两者间的相互影响在施工期间没有得到关注。为了验证事故原因,分别采用考虑偏心荷载的条形基础圆弧滑动解析解、极限平衡条分法和数值分析法计算了沟渠开挖前后的最危险滑动面安全系数,同时分析了沟渠开挖对总位移场的影响。结果显示:3种方法在最危险滑动面安全系数计算结果上具有一致性。沟渠开挖对围堰整体稳定性有显著影响,沟渠开挖后位移场出现贯通,最危险滑动面呈现圆弧+长直线组合滑动形态。由于上覆土无法有效发挥抗滑作用力,安全系数明显小于常规圆弧滑动面。结果表明:尽管围堰与沟渠间的净距达20 m,净距与围堰平均宽度比达3.3倍,但从围堰失稳的现场特点和计算分析两方面,均证实远处沟渠开挖是造成围堰失稳的根本原因。本案例围堰失稳垮塌值得软土地区工程界重视。This paper presents an engineering failure case of local collapse of a temporary cofferdam built for foundation treatment on the soft soil foundation in Fujian coast.It is inferred that the excavation of distant trench is the main factor inducing the failure of cofferdam based on the time and space correspondence between the damaged section of cofferdam and the excavated trench.However,the distance between cofferdam and trench in this case is relatively far,and the excavation scale of trench is small,so the interaction between them was not paid attention to during construction.In order to verify the reason of this accident,the factors of safety the most dangerous sliding surface were calculated by the analytical solution of circular sliding method of strip foundation considering eccentric load,the limit equilibrium slice method and the numerical analysis method respectively.Meanwhile,the influence of trench excavation on the magnitude displacement field was analyzed.The result indicate that the three method are consistent in calculating the safety factor of the most dangerous sliding surface.Trench excavation has a significant influence on the overall stability of cofferdam.After trench excavation,the displacement field appears through,and the most dangerous sliding surface presents a combined sliding form of arc+long straight line.For the reason that the overlying soil can not exert the antisliding force effectively,the safety factor is obviously smaller than that of the conventional circular sliding surface.The result show that although the clear distance between cofferdam and trench is 20 m,and the ratio of the clear distance to the average width of the cofferdam is 3.3 times,both the site characteristics and calculation analysis of the instability of the cofferdam prove that the excavation of the distant trench is the root cause of the cofferdam collapse.The cofferdam collapse in this case deserves the attention of engineering field in soft soil area.

关 键 词：软土地基 圆弧滑动面 组合滑动面 极限平衡条分法 强度折减法 

分 类 号：TU47[建筑科学—结构工程]