Analysis on the Depth of a Soft Soil Deep Foundation Pit Supporting Pile
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摘要: 软土深基坑支护,一般采用桩锚或桩撑支护结构,支护桩的入土深度直接影响支护结构稳定和支护工程造价,合理确定支护桩的入土深度是软土地区深基坑支护设计的一项重要内容。结合某软土区基坑工程实例,按国家基坑规范和上海基坑规范分别对支护桩多种入土深度进行相关计算和分析比较,并考虑工程桩对支护桩入土深度的有利影响,力求支护桩的入土深度安全、合理、经济。按上海基坑规范计算,软土深基坑支护桩的入土深度可以明显缩短,适当考虑坑内工程桩的有利影响,支护桩的入土深度可以进一步优化,为类似基坑支护设计提供参考。Abstract: Pile anchor or pile bracing structure is generally used in soft soil deep foundation pit supporting. The depth of supporting pile directly affects the stability of supporting structure and the cost of supporting engineering. Determining the depth of supporting pile is an important content of deep foundation pit support design in soft soil area. Combined with an example of foundation pit in a soft soil area, the relevant calculation and analysis of various depth of supporting piles are carried out according to the national foundation pit code and Shanghai foundation pit code, and considering the favorable influence of engineering pile on the depth of supporting pile to ensure a safe, reasonable and economical depth of supporting pile. According to the code of Shanghai foundation pit, the depth of supporting pile of soft soil deep foundation pit can be shortened obviously. Considering the favorable influence of the engineering pile in the pit, the depth of the supporting pile can be further optimized, which could provide reference for similar foundation pit supporting design.
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Key words:
- deep foundation pit of soft soil /
- supporting pile /
- depth of entry
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表 1 基坑深度涉及的土层物理力学指标
分层 土层名称 土层
厚度/m重度/
(kN·m−3)直剪固结
快剪渗透系数/
(10−6 cm·s−1)c/kPa φ/(°) 水平kh 垂直kv ① 淤泥质粉质黏土 2.0 17.7 12.8 10.1 15.6 12.02 ② 砂质粉土 3.5 18.5 2.1 28.7 438.0 373.7 ③ 淤泥质粉质黏土 3.0 17.6 11.5 6.5 12.1 10.3 ④ 砂质粉土 8.5 18.6 2.1 31.3 485.4 407.1 ⑤ 淤泥质粉质黏土 11.0 17.5 15.5 10.9 10.9 9.3 ⑥ 粉质黏土 15.3 18.4 17 12 表 2 按国家规程JGJ120—2012计算结果
方 案 支护桩入
土深度/m最大弯矩(2根桩)
/(kN·m)最大位移
/mm锚拉力
/(kN·m–1)抗倾覆
安全系数整体稳定
安全系数坑底抗隆起
安全系数墙底抗隆起
安全系数① 16 −684.1~1075.4 −8.2~17.2 135~220.4 1.23 1.41 1.38 1.89 ② 20 −685.9~1075.2 −8.2~17.2 135~220.3 1.36 1.61 1.60 2.23 ③ 26 −686.0~1075.1 −8.2~17.2 135~220.3 1.54 1.93 1.92 2.35 国家规程要求的安全系数 1.20 1.30 1.90 1.60 表 3 按上海规范DG/TJ 08—61—2010计算结果
方案 支护桩入土深
/m最大弯矩(2根桩)
/(kN·m)最大位移
/mm锚拉力
/(kN·m–1)抗倾覆
安全系数整体稳定
安全系数坑底抗隆起
安全系数墙底抗隆起
安全系数① 16 −724.6~1107 −8.5~17.6 135~223.6 1.18 1.41 1.79 1.89 ② 20 −726.7~1106.8 −8.5~17.6 135~223.6 1.22 1.61 2.06 2.23 ③ 26 −726.6~1106.7 −8.5~17.6 135~223.6 1.34 1.93 2.46 2.35 上海规范要求的安全系数 1.10 1.25 1.90 2.00 -
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