# Numerical Analysis on the Behavior of Floating Geogrid-Encased Stone Column Improved Foundation

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## Abstract

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## 1. Introduction

## 2. Model Preparation and Validation

#### 2.1. General

#### 2.2. Soft Soil

#### 2.3. Aggregates

#### 2.4. Biaxial Geogrid

#### 2.5. Interface

#### 2.6. Model Validation

## 3. Results and Discussion

#### 3.1. Load-Settlement Behavior

#### 3.2. Bulging Deformation

#### 3.3. Failure Mode

#### 3.4. Load Transfer Coefficient

## 4. Conclusions

- (1)
- The bearing capacity of F-OSCs increased with the increase in column and encasement length, and a critical length (i.e., 4D) was found in improving bearing capacity. The geogrid encasement could increase the bearing capacity of F-OSCs, and also had a critical length (i.e., 4D) in settlement improvement.
- (2)
- The bulging deformation was significant in F-OSCs and observed at the top of a long column and the full length of a short column. The geogrid encasement could constrain the OSC to decrease the bulging deformation due to excellent tensile strength. The short encasement length (e.g., 2D) could not effectively confine the column, and only the deformation transferred deeper.
- (3)
- The failure mode in F-OSCs was mainly a punching failure with bulging deformation for a short column (e.g., less than 4D), and was relative to the vertical pressure for a long column. The failure mode in F-ESCs was a punching failure with a slight bulging deformation due to a good integration improved by geogrid, and the punching degree increased with an increase in geogrid encasement length.
- (4)
- The load transfer coefficient in the short column would increase in a later stage due to a punching failure. The load transfer coefficient of F-OSCs or F-ESCs was relatively stable as the column length increased to a critical value (e.g., 4D) or the encasement length increased to a critical value (e.g., 4D).

## 5. Limitations

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 5.**Comparison of load-settlement curves between the model test and numerical simulation in F-OSC4D and F-ESC6D-4D composite foundations.

**Figure 8.**Bulging deformation of F-OSC with different column lengths: (

**a**) F-OSC2D, (

**b**) F-OSC4D, (

**c**) F-OSC6D, and (

**d**) F-OSC8D.

**Figure 9.**Bulging deformation of F-ESC with different geogrid lengths: (

**a**) F-ESC6D-2D, (

**b**) F-ESC6D-4D, and (

**c**) F-ESC6D-6D.

Description | Stone Column | Geogrid | Model Box | ||
---|---|---|---|---|---|

Diameter (D) | Length (L) | Length (l) | Diameter (D_{e}) | Height (H) | |

F-OSC2D | 100 mm | 200 mm | - | 300 mm | 1000 mm |

F-OSC4D | 400 mm | ||||

F-OSC6D | 600 mm | ||||

F-OSC8D | 800 mm | ||||

F-ESC6D-2D | 600 mm | 200 mm | |||

F-ESC6D-4D | 600 mm | 400 mm | |||

F-ESC6D-6D | 600 mm | 600 mm |

Parameter | Value | Parameter | Value |
---|---|---|---|

Elastic modular | 0.3 MPa | Friction angle | 0° |

Poisson’s ratio | 0.3 | Density | $1900\text{}\mathrm{kg}/{\mathrm{m}}^{3}$ |

Cohesion | 4.06 kPa |

Parameter | Value | Parameter | Value |
---|---|---|---|

Elastic modular | 9.2 MPa | Friction angle | 42.9° |

Poisson’s ratio | 0.27 | Density | $1500\text{}\mathrm{kg}/{\mathrm{m}}^{3}$ |

Cohesion | 0 kPa |

Parameter | Value |
---|---|

Elastic modulus | 330 MPa |

Passion’s ratio | 0.33 |

Coupling spring cohesion (kPa) | 3.2 |

Coupling spring friction angle (°) | 0 |

Coupling spring shear stiffness (N/m^{3}) | 3.2 × 10^{4} |

Thickness | 1 mm |

Interface Position | Cohesion (kPa) | Friction (°) | Shear Stiffness (N/m) | Normal Stiffness (N/m) |
---|---|---|---|---|

Column side | 3.2 | 0 | 3.0 × 10^{8} | 3.0 × 10^{8} |

Column bottom | 3.2 | 0 | 1.9 × 10^{8} | 1.9 × 10^{8} |

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**MDPI and ACS Style**

Cheng, Y.; Cai, X.; Mo, H.; Gu, M.
Numerical Analysis on the Behavior of Floating Geogrid-Encased Stone Column Improved Foundation. *Buildings* **2023**, *13*, 1609.
https://doi.org/10.3390/buildings13071609

**AMA Style**

Cheng Y, Cai X, Mo H, Gu M.
Numerical Analysis on the Behavior of Floating Geogrid-Encased Stone Column Improved Foundation. *Buildings*. 2023; 13(7):1609.
https://doi.org/10.3390/buildings13071609

**Chicago/Turabian Style**

Cheng, Ye, Xiaocong Cai, Haizhao Mo, and Meixiang Gu.
2023. "Numerical Analysis on the Behavior of Floating Geogrid-Encased Stone Column Improved Foundation" *Buildings* 13, no. 7: 1609.
https://doi.org/10.3390/buildings13071609