超大空间基坑中部既有建(构)筑物保护支护设计方案研究

Protection Design of Existing Buildings in Middle of a Foundation Pit with Large Spaces

为解决大面积地下空间开发过程中超大空间基坑中部存在需要保护的既有建(构)筑物问题,在对比中心岛法和盖挖逆作法的基础上,提出钢绞线张拉法处理方案,并得出以下结论:1)当被保护的建(构)筑物无地下室或者地下室埋置深度较浅时,可以采用钢绞线对拉法,其围护结构为正四边形或正六边形;当被保护的建(构)筑物地下室埋置深度较深时,可以采用钢绞线环箍法,其围护结构为圆形。2)可以根据基坑深度和被保护建(构)筑物的变形要求调整竖向支护间距。3)采用钢绞线对拉法在地层中钻孔时应配合套筒跟进,以减少上部建筑物沉降。4)钢绞线环箍法应设置2-4个张拉端,同时在围护结构侧向设置槽钢。5)钢绞线张拉法施工方便、造价低、对地下空间的施工无影响,同时钢绞线可以较方便地拆除。

When constructing a foundation pit with large spaces,existing buildings in the foundation pit should be protected.Based on a comparison between the central island and cut-and-cover top-down methods,a steel-strand tensioning method is proposed.The steel-strand tensioning method can be used in a case where the protected building(structure)has no basement or the basement is shallow,and the retaining structure should be a regular quadrilateral or hexagon;however,for deep basements,the steel-strand hooping method can be used,and the retaining structure should be round.Vertical support spacing can be reasonably adjusted according to the depth of the foundation pit and the deformation requirements of the protected building.When using the steel-strand tensioning method,the sleeve is used when drilling holes in the ground to reduce the settlement of the upper building.On the contrary,when the steel-strand hooping method is employed,2~4 tension ends are provided,and channel steel is installed on the side of the retaining structure.The steel-strand tensioning method has many advantages,including convenient construction,low cost,and no influence on the underground space construction,which can be easily dismantled.