三门核电循环水泵房超深基坑支护设计实例
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摘要
三门核电循环水泵房基坑为超深基坑(最深处为32.3m),处于基岩面埋藏较浅且上部覆盖较厚淤泥层和回填石层的特殊区域。本工程依据地层条件,将基坑边坡划分为完全基岩边坡、基岩埋深浅且无淤泥地层的边坡、基岩埋深较大且有较厚淤泥层的边坡3种类型。分别采用3种支护型式:放坡、排桩+岩锚、排桩+深搅重力墙+岩锚,有效解决了滨海软土区的地下水位高,淤泥质软土黏聚力及内摩擦角小,基坑侧壁受水平荷载大、易失稳等难题。典型断面计算结果表明,锚拉力最大为361.84kN;基坑侧壁最大水平位移为19.26mm,支护桩最大正负弯矩值为711.36kN.m和-787.52kN.m,基坑顶部最大沉降量为50mm,均满足设计与规范要求。
The circulating water pump house foundation pit is ultra-deep with the deepest point of 32.3m and is located in a special area where bedrock is shallowly buried and mud and backfill layers in the up per level are deep,so the support requirement for foundation pit is much higher.According to the stratigra phy distribution,three types of side slope of deep foundation pit were divided:complete bedrock,shallow ly buried bedrock without sludge layer and deeply buried bedrock with big depth of sludge layer.Three sup porting methods were respectively applicated: step-slope excavation for bedrock,piles in row and pre stressed anchor cables,and the combination of piles in row and cement-soil wall and prestressed anchor ca bles,which effectively solved the difficult problem in coastal soft soil region with the higher ground water level,lower c and φ,easier instability of side of foundation pit due to the great horizontal load.The re sults of typical section analysis show that the maximum tension of prestressed anchor is 361.84kN,the max imum horizontal displacements is 19.26mm,and the maximum positive and negative bending moment value is 711.36kN.m and-787.52kN.m,which meet the standard and design requirements.
The circulating water pump house foundation pit is ultra-deep with the deepest point of 32.3m and is located in a special area where bedrock is shallowly buried and mud and backfill layers in the up per level are deep,so the support requirement for foundation pit is much higher.According to the stratigra phy distribution,three types of side slope of deep foundation pit were divided:complete bedrock,shallow ly buried bedrock without sludge layer and deeply buried bedrock with big depth of sludge layer.Three sup porting methods were respectively applicated: step-slope excavation for bedrock,piles in row and pre stressed anchor cables,and the combination of piles in row and cement-soil wall and prestressed anchor ca bles,which effectively solved the difficult problem in coastal soft soil region with the higher ground water level,lower c and φ,easier instability of side of foundation pit due to the great horizontal load.The re sults of typical section analysis show that the maximum tension of prestressed anchor is 361.84kN,the max imum horizontal displacements is 19.26mm,and the maximum positive and negative bending moment value is 711.36kN.m and-787.52kN.m,which meet the standard and design requirements.
引文
[1]赵同新,高霈生.深基坑支护工程的设计与实践[M].北京:地震出版社,2010.
[2]YB9258-97,建筑基坑工程技术规范[S].北京:冶金工业出版社,1998.
[3]JGJ120-99,建筑基坑支护技术规程[S].北京:中国建筑工业出版社,1999.
[4]GB50007-2002,建筑地基基础设计规范[S].北京:中国建筑工业出版社,2002.
[2]YB9258-97,建筑基坑工程技术规范[S].北京:冶金工业出版社,1998.
[3]JGJ120-99,建筑基坑支护技术规程[S].北京:中国建筑工业出版社,1999.
[4]GB50007-2002,建筑地基基础设计规范[S].北京:中国建筑工业出版社,2002.
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