Numerical Investigation on Deep-Foundation Pit Excavation Supported by Box-Type Retaining Walls
<p>Location of the considered project: (<b>a</b>) picture of foundation pit zoning; (<b>b</b>) graphic layout of foundation pit zoning.</p> "> Figure 2
<p>Construction site images: (<b>a</b>) Excavation of pit inside box-type retaining wall; (<b>b</b>) Excavation construction of the foundation pit to the bottom; (<b>c</b>) Completed box-type retaining wall; (<b>d</b>) Completed foundation pit site; (<b>e</b>) Schematic diagram for lateral deformation (inclinometry) monitoring of retaining walls.</p> "> Figure 3
<p>(<b>a</b>) The cross-section of the foundation pit with box-type retaining wall. (<b>b</b>) Soil profiles and material properties at the site.</p> "> Figure 3 Cont.
<p>(<b>a</b>) The cross-section of the foundation pit with box-type retaining wall. (<b>b</b>) Soil profiles and material properties at the site.</p> "> Figure 4
<p>Numerical simulation model. (<b>a</b>) FLAC 3D calculation model of the whole foundation pit. (<b>b</b>) Model boundary conditions.</p> "> Figure 5
<p>Detailed numerical simulation model. (<b>a</b>) Underground diaphragm wall. (<b>b</b>) Back wall of box-type retaining wall. (<b>c</b>) Three-axis mixing pile. (<b>d</b>) Bored pile.</p> "> Figure 6
<p>Comparison of measured and simulated deformations at measurement location of the front wall of the box-type retaining wall displacement.</p> "> Figure 7
<p>(<b>a</b>) Settlement curve of the foundation pit. (<b>b</b>) The influence zone behind the wall.</p> "> Figure 7 Cont.
<p>(<b>a</b>) Settlement curve of the foundation pit. (<b>b</b>) The influence zone behind the wall.</p> "> Figure 8
<p>Settlement cloud map after excavation at different steps: (<b>a</b>) first layer excavation; (<b>b</b>) second layer excavation; (<b>c</b>) third layer excavation.</p> "> Figure 9
<p>(<b>a</b>) Numerical simulation of soil settlement curve around foundation pit; (<b>b</b>) schematic diagram of the distance from the edge of the pit.</p> "> Figure 10
<p>Displacement cloud diagram of each supporting structure: (<b>a</b>) Underground diaphragm wall; (<b>b</b>) Back wall of box-type retaining wall; (<b>c</b>) Three-axis mixing pile; (<b>d</b>) Bored pile.</p> "> Figure 11
<p>Influence of box-type retaining wall dimensions: (<b>a</b>,<b>b</b>) Horizontal displacements of front wall of box-type retaining wall; (<b>c</b>,<b>d</b>) Surrounding surface settlements with variations in the box length and width.</p> "> Figure 11 Cont.
<p>Influence of box-type retaining wall dimensions: (<b>a</b>,<b>b</b>) Horizontal displacements of front wall of box-type retaining wall; (<b>c</b>,<b>d</b>) Surrounding surface settlements with variations in the box length and width.</p> "> Figure 12
<p>Influence of the internal fill material of box-type retaining walls: (<b>a</b>) Horizontal displacement of the front wall of box-type retaining wall; (<b>b</b>) settlement of the surrounding surface from the edge of foundation pit.</p> "> Figure 12 Cont.
<p>Influence of the internal fill material of box-type retaining walls: (<b>a</b>) Horizontal displacement of the front wall of box-type retaining wall; (<b>b</b>) settlement of the surrounding surface from the edge of foundation pit.</p> "> Figure 13
<p>Influence of concrete materials used for pouring box-type retaining walls: (<b>a</b>) Horizontal displacement of the front wall of box-type retaining wall; (<b>b</b>) settlement of the surrounding surface from the edge of foundation pit.</p> "> Figure 13 Cont.
<p>Influence of concrete materials used for pouring box-type retaining walls: (<b>a</b>) Horizontal displacement of the front wall of box-type retaining wall; (<b>b</b>) settlement of the surrounding surface from the edge of foundation pit.</p> ">
Abstract
:1. Introduction
2. Project Information
2.1. General Description of Foundation Pit
2.2. Overview of Foundation Pit Support and Geological Conditions
3. Three-Dimensional Numerical Simulation
3.1. Three-Dimensional Model Establishment
3.2. Construction Process
3.3. Model Rationality Verification
4. Results and Discussion
4.1. Settlement of Foundation Pit Bottom and Surrounding Site Surface
4.2. Horizontal Displacement of Support Structure
4.3. Discussion of Influencing Factors on the Supporting Structure
- (1)
- Analysis of the influence of box-type retaining wall dimensions
- (2)
- Analysis of the influence of varying filler types within the retaining wall
- (3)
- Analysis of the influence of cement materials in the box-type retaining wall
5. Conclusions
- (1)
- In soft soil foundation deep excavation projects, the novel box-type retaining wall demonstrates remarkable support performance. Compared to other types of retaining walls, it boasts advantages such as simple structure, unsupported excavation construction, and convenient sourcing of filling materials. Key factors influencing the support effectiveness of the box-type retaining wall were analyzed, focusing on three aspects: wall dimensions; filling materials within the box; and constituent materials;
- (2)
- During foundation pit excavation, rebound appears at the center, while settlement occurs at the edges. Simulations analyzed the impact of box-type retaining wall dimensions, fill materials, and constituent materials on settlement. Results showed that dimension changes caused settlement variations of 1–3 mm. Except for the no-fill condition causing soil expansion and continuous settlement, settlement trends were consistent under the other three fill conditions. Changes in constituent materials had insignificant effects on settlement;
- (3)
- By altering the dimensions of the box-type retaining wall, it was observed that when the wall width was held constant, a reduction of 1 m in wall length led to approximately a 7% decrease in wall displacement at the base of the excavation pit. Conversely, when the wall length was held constant, a reduction of 1 m in wall width resulted in approximately a 6.8% increase in wall displacement at the base;
- (4)
- The advantages of adopting box-type retaining walls are as follows: (a) enabling unsupported excavation construction; (b) featuring a simple structure, primarily filled with plain soil and stone materials; (c) demonstrating excellent stability, high shear strength, and adaptability to various foundation types; (d) resulting in significant savings in concrete materials; (e) serving as a permanent exterior wall structure when integrated with retaining piles, thereby enhancing the overall rigidity, stability, safety, and reliability of the retaining system.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
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Structure Name | Unit Type | Elastic Modulus/GPa | Poisson Ratio | Unit Weight /(kN/m3) | Size |
---|---|---|---|---|---|
Underground continuous wall | Solid Elements | 30 | 0.3 | 24.5 | Thickness 800 mm |
Back wall of box-type retaining wall | Solid Elements | 30 | 0.2 | 17.8 | Thickness 800 mm |
Three-axis mixing pile | Solid Elements | 30 | 0.2 | 24.5 | Pile diameter 850 mm |
Bored piles | Solid Elements | 30 | 0.2 | 24.5 | Pile diameter 1000 mm |
Step | Construction Process | Construction Diagram |
---|---|---|
Step 1 | Stress balance | |
Step 2 | Apply envelope structure and box-type retaining wall | |
Step 3 | Excavation of 1st layer of soil (4.7 m); Pump to 5.7 m | |
Step 4 | Excavation of 2nd layer of soil (8.0 m); Precipitation to 14.6 m | |
Step 5 | Excavation of 3rd layer of soil (13.6 m); Precipitation to 14.6 m |
Filler Type | γ | K0 | ν | E | c | φ |
---|---|---|---|---|---|---|
kN/m3 | /kPa | /kPa | /(°) | |||
Filler-1 | 17.8 | 0.380 | 0.281 | 27,180 | 15 | 27 |
Filler-2 | 18 | 0.350 | 0.259 | 31,140 | 12 | 15 |
Filler-3 | 17.7 | 0.510 | 0.338 | 19,140 | 10 | 16.8 |
No fillers | / | / | / | / | / | / |
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Peng, P.; Kong, W.; Huang, S.; Long, Y.; Lu, Y. Numerical Investigation on Deep-Foundation Pit Excavation Supported by Box-Type Retaining Walls. Buildings 2025, 15, 109. https://doi.org/10.3390/buildings15010109
Peng P, Kong W, Huang S, Long Y, Lu Y. Numerical Investigation on Deep-Foundation Pit Excavation Supported by Box-Type Retaining Walls. Buildings. 2025; 15(1):109. https://doi.org/10.3390/buildings15010109
Chicago/Turabian StylePeng, Peng, Weiyao Kong, Saishuai Huang, Yi Long, and Yang Lu. 2025. "Numerical Investigation on Deep-Foundation Pit Excavation Supported by Box-Type Retaining Walls" Buildings 15, no. 1: 109. https://doi.org/10.3390/buildings15010109
APA StylePeng, P., Kong, W., Huang, S., Long, Y., & Lu, Y. (2025). Numerical Investigation on Deep-Foundation Pit Excavation Supported by Box-Type Retaining Walls. Buildings, 15(1), 109. https://doi.org/10.3390/buildings15010109