Design of large ring support system in soft soil area of Ningbo
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摘要: 软土地区深基坑的支撑体系设计直接关系到项目的安全与效益。宁波软土地区某深大基坑支护设计中，水平支撑采用了直径180 m的超大圆环混凝土支撑，竖向支撑利用静钻根植桩作为立柱桩，实现了工厂预制。相比常规基坑支撑体系，该支撑体系可减小支撑覆盖面积达20%，在保证基坑安全的前提下，大幅降低支撑对施工作业的影响；同时，特殊立柱桩的应用极大降低了工程造价。数值模拟结果与工程实测结果的对比分析表明，三维有限元法可较为合理地预测超大直径圆环撑基坑的变形情况，并且超大直径圆环撑可满足软土地区深大基坑的变形控制要求。Abstract: The design of the support system of the deep foundation pit in the soft soil area is directly related to the safety and efficiency of the project. In the design of a deep and large foundation pit support in the soft soil area of Ningbo, the horizontal support adopts a super-large circular concrete support with a diameter of 180 m, and the vertical support uses the static drilling rooted pile as the column pile, which realizes the prefabrication of the factory. Compared with the conventional foundation pit support system, the innovative support system can reduce the support coverage area by up to 20%, and greatly reduce the impact of the support on the construction operation under the premise of ensuring the safety of the foundation pit. The application of special column pile greatly reduces the project cost. The comparative analysis of the numerical simulation results and the engineering measurement results shows that the three-dimensional finite element method can reasonably predict the deformation of the super-large diameter annular brace foundation pit, and the super-large diameter annular brace can meet the deformation control requirements of deep and large foundation pits in soft soil areas.
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Key words:
- deep excavation /
- ring support /
- static drilling rooted pile /
- soft soil area /
- numerical simulation
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表 1 土体参数表
土层
编号土层
名称层厚
/m重度
/(kN·m−3)黏聚力
/kPa内摩擦角
/(°)含水量
/%钻孔桩桩侧阻力
特征值/kPa压缩模量
/MPa割线刚度
/MPa卸载再加载
刚度/MPa①-1 杂填土 1.20～0.40 (18.5) (5) (15) 3.00 3.00 9.00 ①-2 粉质黏土 1.90～0.80 18.7 26.3 15.4 30.3 12 4.56 4.56 13.68 ②-1 淤泥质粉质黏土 12.7～8.5 17.4 13.2 9.2 41.5 6 3.08 3.08 9.24 ②-2 淤泥质黏土 10.2～1.8 16.8 12.9 8.7 48.4 7 2.44 2.44 7.32 ③ 含粉砂粉质黏土 6.40～0.9 19.0 20.2 16.1 28.0 14 2.45 2.45 7.35 ④-1 淤泥质粉质黏土 8.40～1.00 16.9 12.9 8.6 48.8 8 3.01 3.01 9.03 ④-2 淤泥质黏土 6.60～0.50 17.3 13.2 8.6 44.1 9 6.93 6.93 20.79 ⑤-1 黏土 15.4～6.0 18.8 38.0 15.3 29.7 29 4.56 4.56 13.68 注：“（）”内为经验取值。 
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表 2 支护结构参数表
结构名称 规格 材料 本构关系 备注 支护桩 ϕ900(850)@1150 mm C25混凝土 弹性 板单元 混凝土支撑 第一道截面尺寸：
800（700） mm×700 mm
第二道截面尺寸：
800（700） mm×800 mmC30混凝土 弹性 梁单元 圆环撑 第一道截面尺寸：
2400 mm×900 mm
第二道截面尺寸：
2600 mm×1000 mmC30混凝土 弹性 梁单元 地下室底板 厚度800 mm C35混凝土 弹性 板单元 地下室中板 厚度120 mm C35混凝土 弹性 板单元 地下室顶板 厚度 200 mm C35混凝土 弹性 板单元
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