Research on Coordinated Relationship Between Deformation and Force in Shaft Foundation Pit Support Structures
Abstract
1. Introduction
2. Scaled Model Test Design
2.1. Model Test Components
2.2. Test Schemes and Test Conditions
3. Numerical Investigations
3.1. Numerical Model
3.2. Calculation Result Validation
4. Prototype Engineering Analysis
4.1. Numerical Model of Prototype Pit
4.2. Simulation Results of Excavation of Foundation Pit
4.3. Comparison of Internal Support Schemes
5. Discussion
- (1)
- In previous studies [25,26,27,28,29], scholars commonly combined a servo jack with an internal strut in the foundation pit, utilizing the adjustable servo jack pressure to realize the active adjustment of internal supports. This combination has obvious disadvantages, i.e., the jack and the internal strut are relatively separated, especially for the concrete internal strut. Although the steel strut improves this disadvantage to a certain extent, the use of connecting bolts likewise introduces a new force concentration problem and weak points to the internal support structure. Various new types of axial force adjustment devices proposed by scholars [30,31,32] also suffer from poor practicality problems such as operation difficulties and the inability to measure and feedback the axial force adjustment amount. In addition, existing research only discusses the influence of internal support adjustment on the mechanical behavior of the foundation pit support system, ignoring the coordinated relationship between the force and deformation of the support structure itself. Blindly pursuing strict deformation control may bring more serious safety hazards to the internal support. In this study, a novel integrated support axial force servo system is adopted to effectively combine the axial force-adjusting device with the inner strut, which can achieve the real-time monitoring and adjustment of support axial force while maintaining the integrity of the internal support structure, and it has great practicability and wide application prospects. In terms of research content, this study focuses on the coordinated relationship between the axial force of the internal support and lateral deformation of the diaphragm wall in the shaft foundation pit, aiming to provide a reference for the design of foundation pit support structures that considers both deformation and support force.
- (2)
- The limitations of this research include the following: On the one hand, although the support scheme with synchronized adjustment of multiple internal supports is discussed, the adjustment amount of different internal supports in each scheme is the same, ignoring the variability in internal support lengths at different depths. On the other hand, the novel axial force servo device used in this study is only applied to the steel support, so only active adjustment of the steel supports is realized, and the adjustment of concrete supports is not included.
- (3)
- In order to overcome the limitations of this study in future research, the design idea of the axial force servo device proposed here will firstly be used to develop a novel type of concrete support axial force servo system that effectively combines the internal concrete strut and the axial force adjustment device. Then, the influence of independent adjustment amount of each support on the mechanical behavior of the foundation pit support system and the coordinated relationship between the support force and lateral deformation in the diaphragm wall will be analyzed.
6. Conclusions
- (1)
- There is a typical negative correlation between horizontal internal support axial force and lateral displacement of the diaphragm wall. Therefore, strict displacement control of the diaphragm wall will significantly increase internal support axial force.
- (2)
- The active adjustment of inner strut length can obviously affect the lateral deformation of the diaphragm wall and the axial force of the internal support. Under various support schemes considered in this prototype project, the change in maximum horizontal displacement of the diaphragm wall ranged from −4.34% to 7.80%, and the change in axial force of the internal support ranged from 19.04% to 181.79%.
- (3)
- Under a variety of support conditions, the maximum lateral displacement of the diaphragm wall was 0.59~0.66‰ of the excavation depth, and the maximum axial force of the internal support was 0.11~0.30 times the yield load of a single steel strut.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Dimensions | Prototype Pit [m] | Scaled Model [mm] |
---|---|---|
Length | 24.5 | 1000 |
Width | 19.6 | 800 |
Depth | 29.2 | 1200 |
List | Adjustment Element | |||
---|---|---|---|---|
Surface Surcharge [KPa] | F1 Height | F2 Height | F3 Height | |
A0 | 0 | C1 | C2 | C3 |
A3 | 0.9 | |||
A5 | 1.5 | |||
E5 | C2 |
Material | Application | Thickness [mm] | Density [kg/m3] | Elastic Modulus [MPa] | Poisson’s Ratio | Internal Friction Angle [°] | Cohesion [Pa] |
---|---|---|---|---|---|---|---|
Acrylic plate | Diaphragm wall | 5 | 1200 | 3000 | 0.36 | - | - |
Aluminum tube | Internal strut | 3 | 2700 | 70,000 | 0.30 | - | - |
Sand sample | Trial soil | - | - | 50 | 0.3 | 32.27 | 0 |
Material | Elastic Modulus [MPa] | Density [kg/m3] | Poisson’s Ratio |
---|---|---|---|
C30 concrete | 30,000 | 2450 | 0.3 |
Steel | 209,000 | 7850 | 0.3 |
No. | Soil Layer | Thickness [m] | Density [kg/m3] | Internal Friction Angle [°] | Cohesion [KPa] | Elastic Modulus [MPa] | Poisson’s Ratio |
---|---|---|---|---|---|---|---|
1 | Plain fill | 2.0 | 1850 | 15 | 10 | 15 | 0.3 |
2 | Silty clay | 4.5 | 1900 | 20 | 3 | 15.7 | 0.3 |
3 | Fully weathered hornstone | 2.8 | 1850 | 22 | 1.5 | 30 | 0.25 |
4 | Intensely weathered hornstone | 3.0 | 1880 | 22 | 24 | 20 | 0.3 |
5 | Medium weathered hornstone | 32.7 | 2500 | 30 | 35 | 45 | 0.27 |
Condition | Adjusted Support | Length Change [mm] |
---|---|---|
L1 | F2 | ±2, ±4, ±6, ±8 |
L2 | F3 | ±2, ±4, ±6, ±8 |
L3 | F5 | ±2, ±4, ±6, ±8 |
L4 | F2 and F3 | ±2, ±4, ±6, ±8 |
L5 | F2 and F5 | ±2, ±4, ±6, ±8 |
L6 | F3 and F5 | ±2, ±4, ±6, ±8 |
L7 | F2, F3 and F5 | ±2, ±4, ±6, ±8 |
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Xu, C.; Hou, J.; Liu, B.; Lei, F.; Song, L. Research on Coordinated Relationship Between Deformation and Force in Shaft Foundation Pit Support Structures. Buildings 2024, 14, 3438. https://doi.org/10.3390/buildings14113438
Xu C, Hou J, Liu B, Lei F, Song L. Research on Coordinated Relationship Between Deformation and Force in Shaft Foundation Pit Support Structures. Buildings. 2024; 14(11):3438. https://doi.org/10.3390/buildings14113438
Chicago/Turabian StyleXu, Chuanzhao, Jian Hou, Bingfeng Liu, Fangchao Lei, and Li Song. 2024. "Research on Coordinated Relationship Between Deformation and Force in Shaft Foundation Pit Support Structures" Buildings 14, no. 11: 3438. https://doi.org/10.3390/buildings14113438
APA StyleXu, C., Hou, J., Liu, B., Lei, F., & Song, L. (2024). Research on Coordinated Relationship Between Deformation and Force in Shaft Foundation Pit Support Structures. Buildings, 14(11), 3438. https://doi.org/10.3390/buildings14113438