Analysis and Treatment of Shallow Pit Accident in Deep Soft Soil Areas in Reclamation Area
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摘要: 以深圳地区某深厚软土浅基坑工程为例，介绍了该基坑支护型式、隆起事故、事故原因分析和处理措施，并与第三方监测结果作了对比分析，得出如下结论：（1）深厚软土浅基坑采用放坡形式支护时，设计应至少验算基底以下2倍基坑深度范围内的土体稳定性，并严格限制坡顶荷载，否则坑底易发生隆起破坏；（2）深厚软土浅基坑采用悬臂桩支护时，应确保支护桩穿透淤泥层，以保证足够的有效嵌固深度；（3）在深厚软土浅基坑的被动区采用搅拌桩加固，可提高被动区土体力学性能，能够有效地控制支护结构变形，同时避免坑底隆起变形。该工程经验及分析结论对类似工程具有参考意义。Abstract: Taking a shallow foundation pit in deep and soft soil in Shenzhen as an example, the support type, uplift accident, accident cause analysis and treatments of the foundation pit were introduced. Compared with the third-party monitoring results, the conclusions are as follows: (1) When the deep soft soil shallow foundation pit is supported by slope, the soil stability within the range of at least twice the depth of the foundation pit below the base should be calculated, and the load on the slope top should be limited strictly, otherwise the pit bottom is prone to uplift failure. (2) When the cantilever pile is used to support the shallow foundation pit in deep and soft soil, the supporting pile shall penetrate the silt layer to ensure sufficient effective embedded depth. (3) Strengthening the passive area of shallow foundation pit in deep soft soil with mixing pile can improve the mechanical properties of soil, effectively control the deformation of supporting structure and avoid the uplift deformation of pit bottom. The engineering experience and analysis conclusion have reference significance for similar projects.
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Key words:
- deep and soft soil /
- shallow foundation pit /
- improvement of shallow pit /
- uplift failure
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表 1 场地岩土层的主要物理力学参数
土层编号 土层名称 重度γ/(kN·m−3) 变形模量E0/MPa 含水量w/% 孔隙比$ e $ 泊松比ν 黏聚力c/kPa 内摩擦角$\varphi$/（°） 渗透系数k/(m·d−1) ① 杂填土 17.0 0.35 10.0 15.0 5.0 ② 淤泥 16.0 3.0 67.29 1.862 0.3 8.0 3.0 0.005 ③ 砾砂 18.5 0.4 5.0 25.0 15.0 ④ 残积粉质黏土 18.5 25.0 27.15 0.827 0.35 22.0 20.0 0.5 ⑤1 全风化砂岩 19.0 60.0 20.85 0.694 0.3 15.0 25.0 0.8 ⑤2 强风化砂岩 21.0 100.0 0.28 22.0 32.0 1.5 ⑤3 块状强风化砂岩 21.5 0.2 25.0 35.0 1.8 
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