温州软土地区基坑支护选型调查及坑外深层土体变形的实测与规律研究

Investigation on Type Selection of Foundation Pit Support in Wenzhou Soft Soil Area and Actual Measurement and Law Study of Deep Soil Deformation Outside Foundation Pit

通过对温州市城区2007年以来基坑工程(220个)的支护选型进行统计分析,获得了不同工况下的基坑选型规律:深度4 m及4 m以内的基坑主要采用土钉墙支护形式;超过4 m深度的一般采用围护结构加内支撑支护形式,围护结构一般采用钻孔灌注桩,且多选用水泥土搅拌桩作为围护桩外侧止水结构,其中,深度7.5 m以内的一般采用1道内支撑,超过7.5 m的则采用2道内支撑。在此基础上,再通过对典型支护类型的现场实测数据分析,获得了坑外深层土体变形规律,即:随着基坑开挖深度的增加,深层土体最大水平位移值不断增大,土体内部位移加剧;在地下室底板混凝土具有支撑强度后,坑外深层土体水平位移量趋于稳定;深层土体最大变形点发生在坑底以上0.5~ 1.0m处。

Based on the statistical analysis of support selection of 220 foundation pit projects in Wenzhou City since 2007, the rules of foundation pit selection under different working conditions are obtained. The results show that soil nailing wall is the main support type for foundation pits with a depth of 4 m or less;retaining structure with internal support is generally adopted for foundation pits with depth of more than 4 m, and bored cast-in-place piles are generally used for retaining structure, and the cement-soil mixing pile is often used as the outer water-stop structure of the retaining pile, in which one inner support is generally used for foundation pits with depth of less than 7.5 m, and two inner supports are used for those with a depth of 7.5 m or more. On this basis, through the analysis of field measured data of typical supporting types of foundation pit, the actual measurement deformation law of deep soil outside the foundation pit is obtained, that is, with the increase of the excavation depth of the foundation pit, the maximum horizontal displacement value of deep soil increases continuously, and the internal displacement of the soil body intensifies;after the basement floor concrete has the supporting strength, the horizontal displacement of deep soil outside the pit tends to be stable, and the maximum deformation point of deep soil occurs at 0.5-1.0 m above the pit bottom.