基于不排水强度的黏土基坑抗隆起稳定计算方法

黄茂松; 李弈杉; 唐震; 袁聚云

doi:10.11779/CJGE202009001

基于不排水强度的黏土基坑抗隆起稳定计算方法 English Version

黄茂松^{1, 2,},
李弈杉^{1, 2},
唐震^{1, 2},
袁聚云^{1, 2}

1.
同济大学地下建筑与工程系,上海　200092
2.
同济大学岩土及地下工程教育部重点实验室,上海　200092

基金项目:

国家自然科学基金重点项目 51738010

国家重点研发计划项目 2016YFC0800202

详细信息

作者简介:
黄茂松(1965—),男,浙江玉环人,博士,教授,博士生导师,从事岩土工程方面的教学与科研工作。E-mail：mshuang@.tongji.edu.cn

中图分类号: TU473
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出版历程
- 收稿日期: 2019-12-25
- 网络出版日期: 2022-12-07
- 刊出日期: 2020-08-31

Analysis method for basal stability of braced excavations in clay based on undrained shear strength

HUANG Mao-song^{1, 2,},
LI Yi-shan^{1, 2},
TANG Zhen^{1, 2},
YUAN Ju-yun^{1, 2}

1.
Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
2.
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China

摘要

摘要: 目前的基坑抗隆起稳定计算方法多是直接采用固结不排水强度指标进行计算,这种方法对于软黏土地层的计算在理论上是不合理的,且传统的圆弧滑动法未考虑最下道支撑以上土体强度的发挥。针对上述问题,通过将固结不排水强度指标转换成不排水抗剪强度,考虑最下道支撑以上土体强度的发挥,对传统圆弧滑动法进行了改进,并进一步提出了基于不排水强度的圆弧机构上限分析方法。工程算例分析表明,传统圆弧滑动法得到的安全系数普遍偏高,而所提出上限分析方法计算得到的结果则更为合理。
- 基坑 /
- 圆弧滑动法 /
- 抗隆起稳定 /
- 不排水强度 /
- 极限分析法
Abstract: At present, the analysis method for basal stability is mostly based on the consolidated undrained shear strength index. The method is unreasonable in theory for the soft clay and does not consider the strength of the soil above the lowest support. To solve the above problems, the traditional analysis method for basal stability is improved. The consolidated undrained shear strength index is converted into undrained shear strength, and the strength of the soil above the lowest support is considered. Furthermore, the circular arc mechanism of the upper bound limit analysis based on the undrained shear strength is proposed. Through the calculations of engineering cases, the factors of safety obtained by the traditional circular sliding method is generally high, while the results obtained by the proposed upper-bound solution are more reasonable.
- braced excavation /
- circular sliding method /
- basal stability /
- undrained shear strength /
- limit analysis method

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图 1 圆弧滑动法计算图示

Figure 1. Sketch of arc sliding method

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图 2 破坏和固结Mohr圆^[18]

Figure 2. Mohr circles at consolidation and failure states^[18]

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图 3 挡墙插入比D/H对安全系数的影响（M_p=0）

Figure 3. Influences of embedded depth of retaining wall on factor of safety（M_p=0）

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图 4 破坏机构及速度场

Figure 4. Failure mechanism and velocity fields

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图 5 挡墙极限弯矩对安全系数的影响

Figure 5. Influences of limit bending moment of retaining wall on factor of safety

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图 6 挡墙插入比D/H对安全系数的影响

Figure 6. Influences of embedded depth of retaining wall on factor of safety

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图 7 破坏机构及速度场（M_p=∞）

Figure 7. Failure mechanism and velocity fields

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图 8 圆弧滑动法计算图示（M_p=∞）

Figure 8. Sketch of arc sliding method

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图 9 挡墙插入比D/H对安全系数的影响（M_p=∞）

Figure 9. Influences of embedded depth of retaining wall on factor of safety（M_p=∞）

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图 10 算例1主楼基坑剖面图

Figure 10. Main building section of excavation Case 1

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图 11 算例1裙楼基坑剖面图

Figure 11. Annex building section of excavation Case 1

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图 12 算例2基坑剖面图

Figure 12. Section of excavation Case 2

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图 13 湘湖地铁站北2基坑剖面图及土层分布

Figure 13. Subsurface soil layers (from site reinvestigation) and a typical cross section of N2 excavation

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图 14 湘湖地铁站北2基坑不排水强度分布

Figure 14. Undrained shear strengths at a typical cross section of N2 excavation

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表 1 算例1基坑土层计算参数

Table 1 Soil parameters of excavation Case 1

土层	层厚/m	重度/(kN·m^-3)	ϕ_cu/(°)	c_cu/kPa
1-1	0.84	18.0	20.0	0
1-2	0.50	18.6	20.0	0
2-1	1.80	18.5	33.0	4
2-2	8.50	18.5	33.0	4
4	3.70	17.0	11.5	12
5-1a	6.30	17.5	12.5	15
5-1b	6.20	17.9	16.5	19

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表 2 算例2基坑土层计算参数

Table 2 Soil parameters of excavation Case 2

土层	层厚/m	重度/(kN·m^-3)	ϕ_cu/(°)	c_cu/kPa
1-1	2.13	18.0	20.0	0
2-3	4.95	18.5	32.5	5
4	10.33	16.9	11.0	9
5-1	5.11	17.7	15.5	12

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表 3 算例3基坑土层计算参数

Table 3 Soil parameters of excavation Case 3

土层	层厚/m	重度/(kN·m^-3)	ϕ_cu/(°)	c_cu/kPa
2-2	5.7	19.0	22.3	7.1
4-2	13.5	17.1	18.8	19.6
6-1	17.0	17.2	16.7	20.3

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表 4 基坑抗隆起稳定验算结果

Table 4 Calculated results of basal stability analysis

验算方法	圆弧滑动法				圆弧机构(c_u)分层地基
验算方法	（c_cu,ϕ_cu）分层地基		(c_u)分层地基		圆弧机构(c_u)分层地基
是否考虑最下道支撑以上土体强度	否	是	否	是	是
算例1主楼	1.88(2.44)	2.02(2.57)	1.52	1.83	1.45
算例1裙楼	1.76(2.33)	1.82(2.39)	1.54	1.67	1.51
算例2	1.50(2.13)	1.51(2.15)	1.41	1.43	1.22
算例3	2.03(2.23)	2.20(2.39)	1.601.17*	1.801.29*	1.340.98*
注：(c_cu,ϕ_cu)分层地基：括号内为加权等效均质地基条件下所得安全系数；(c_u)分层地基：扣除了开挖土体自重影响所得安全系数,*号表示采用现场实测不排水强度所得安全系数（未扣除开挖土体自重影响）。

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