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Journal of ZheJiang University (Engineering Science)  2022, Vol. 56 Issue (2): 356-367    DOI: 10.3785/j.issn.1008-973X.2022.02.017
    
Dynamic adjustment method of diaphragm wall supporting system in deep foundation pit and its application
Teng-fei YAN1(),Bao-guo CHEN1,*(),Lei ZHANG1,Jie-xing HE1,Ye-qin ZHANG2
1. Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
2. Sinohydro Bureau 7 Limited Company, Chengdu 610081, China
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Abstract  

There is a great difference between the engineering deformation value and the theoretical design value of the diaphragm wall supporting system in deep foundation pit, and it is difficult to adjust dynamically. Thus, the dynamic adjustment method of supporting structure was adopted to solve the above problem. Using the numerical model verified by the measured data, the coordinated deformation law of the diaphragm wall support system in deep foundation pit was studied, and the stress deformation law and the coordinated deformation curve of the support system with different adjustment schemes were obtained. At the same time, based on elastic foundation beam theory, an analytical model of support system mechanics that reflects the dynamic adjustment of supporting structure and is suitable for multi-layer supporting structure was put forward. It is found that it is not that more strict displacement control can get safer results in engineering, but that reasonable stress balance point should be found and the stress parameters of support system should be controlled in the optimal range. The optimal range of mechanical parameters of the supporting system was obtained. The ratio of maximum axial force to yield strength of steel support was 0.32 to 0.38, and the ratio of wall displacement to excavation depth was 0.80‰ to 0.92‰.



Key wordsdeep foundation pit      diaphragm wall      internal support      dynamic adjustment      coordinated deformation      earth pressure     
Received: 14 March 2021      Published: 03 March 2022
CLC:  TU 476  
Corresponding Authors: Bao-guo CHEN     E-mail: tengfei_yan@cug.edu.cn;baoguo_chen@126.com
Cite this article:

Teng-fei YAN,Bao-guo CHEN,Lei ZHANG,Jie-xing HE,Ye-qin ZHANG. Dynamic adjustment method of diaphragm wall supporting system in deep foundation pit and its application. Journal of ZheJiang University (Engineering Science), 2022, 56(2): 356-367.

URL:

https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2022.02.017     OR     https://www.zjujournals.com/eng/Y2022/V56/I2/356


深基坑地连墙支护体系动态调整方法及应用

深基坑地连墙支护体系工程变形与理论设计值之间存在较大差异且难于动态调整. 采用支护结构动态调整方法解决此问题,提出动态调整方法,并运用经实测数据验证后的数值模型研究深基坑地连墙支护体系协调变形规律,得出不同调整方案下支护体系受力、变形规律及协调变形曲线(即轴力-位移关系曲线). 基于弹性地基梁理论,给出反映支护结构动态调节思想的适用于多层支撑结构的支护体系力学解析模型. 研究发现,在工程中,更严格的位移控制不一定能够带来更安全的结果,应该寻找合理受力平衡点并将支护体系受力参数控制在最优区间内. 研究得到本工程支护体系受力参数最优区间,最大轴力与钢支撑屈服强度比值为0.32~0.38,墙体位移与开挖深度比值为0.80‰~0.92‰.


关键词: 深基坑,  地连墙,  内支撑,  动态调整,  协调变形,  土压力 
Fig.1 Axial force servo system of steel support
Fig.2 Foundation pit model test device and model diagram
Fig.3 Influence of support expansion on mechanical deformation characteristics of support system
Fig.4 Flow chart of dynamic adjustment method of support system
Fig.5 Standard section of foundation pit
材料 E/MPa μ φ/(°) c/kPa ρ/(kg?m?3)
素填土 5 0.340 18.0 5.0 1780
砾质黏性土 10 0.300 23.5 27.5 1840
全风化粗粒花岗岩 55 0.300 27.5 30.0 1900
强风化粗粒花岗岩 400 0.300 30.0 35.0 1950
中风化粗粒花岗岩 2000 0.260 40.5 40.5 2400
地连墙 31.5×103 0.167 ? ? 2500
砼支撑(S1) 31.5×103 0.167 ? ? 2500
钢支撑(S2/S3/S4) 200.0×103 0.167 ? ? 7800
Tab.1 Material parameters of stratum and support system
Fig.6 Schematic diagram of foundation pit numerical model
接触关系 kn / GPa ks / GPa c/kPa φ/(°) Ψ/(°)
土层-地连墙 3×105 3×105 0 28 0
Tab.2 Contact surface parameters between diaphragm wall and soil
Fig.7 Comparison curve of axial force and displacement of support system after excavation
Fig.8 Law of axial force and deformation of support system under scheme of shortening 10 mm for S2 and S3
Fig.9 Law of axial force and deformation of support system under scheme of elongating 10 mm for S2, S3 and S4
工况 调整方式
A 调整S2的长度
B 调整S3的长度
C 调整S4的长度
D 调整S2和S3的长度
E 调整S2和S4的长度
F 调整S3和S4的长度
G 调整S2、S3和S4的长度
Tab.3 Working condition table for dynamic adjustment of support system
Fig.10 Horizontal displacement of diaphragm wall under different adjustment schemes
方案 土层1 土层2 土层3 土层4
A,伸 100%?5.4% 100% 100% 100%
A,缩 100%+5.4% 100% 100% 100%
B,伸 100%?1.5% 100%?1.3% 100%?0.3% 100%
B,缩 100%+1.5% 100%+1.6% 100%+0.3% 100%
C,伸 100%+0.2% 100%?1.4% 100%?2.5% 100%?1.6%
C,缩 100%?0.4% 100%+1.8% 100%+2.5% 100%+1.6%
D,伸 100%?6.2% 100%?1.3% 100%?0.2% 100%?0.4%
D,缩 100%+6.0% 100%+1.8% 100%+0.1% 100%+0.4%
E,伸 100%?5.0% 100%?1.7% 100%?2.4% 100%?1.6%
E,缩 100%+4.8% 100%+1.8% 100%+2.4% 100%+1.6%
F,伸 100%?0.8% 100%?3.1% 100%?2.8% 100%?1.2%
F,缩 100%+0.6% 100%+3.1% 100%+2.7% 100%+1.2%
G,伸 100%?6.0% 100%?3.1% 100%?2.6% 100%?1.2%
G,缩 100%+5.8% 100%+3.1% 100%+2.6% 100%+1.2%
Tab.4 Deformation sensitivity value of each soil layer
Fig.11 Axial force of internal support under different adjustment schemes
Fig.12 Coordinated deformation relationship curve of support system
Fig.13 Scatter diagram of optimum stress points of support system
Fig.14 Schematic diagram of calculation model based on elastic foundation beam method
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