Preparation and properties of pea-gravel grouting with sodium bentonite for hydraulic shield tunnel
Abstract Pea-gravel grouting (PGG) is a composite material backfilled between segment and surrounding rock of a shield tunnel, requiring balanced mechanical properties and impermeability. However, the practice always faces an issue of the defects of harden PGG with local cavity, less dense or insuff...
Saved in:
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-07-01
|
| Series: | Scientific Reports |
| Subjects: | |
| Online Access: | https://doi.org/10.1038/s41598-025-12061-z |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Abstract Pea-gravel grouting (PGG) is a composite material backfilled between segment and surrounding rock of a shield tunnel, requiring balanced mechanical properties and impermeability. However, the practice always faces an issue of the defects of harden PGG with local cavity, less dense or insufficient strength. In this paper, an experimental study was firstly carried out on the grouting slurry to determine its mix proportion by evaluating the workability and density, which showed that the rational w/b = 0.5 and 0.6 with a sodium bentonite content within 5 ~ 15%. A method was developed to simulate the construction process of PGG to cast the blocks with a size of 900 mm×500 mm×250 mm. Using the samples drilled from the blocks, the cylinder specimens with a diameter of 100 mm and a height of 200 mm were manufactured for testing the axial compressive strength and the modulus of elasticity of PGG, while those with a diameter of 170 mm and a height of 150 mm were repaired to be the circular truncated conic specimens for testing the PGG impermeability. Results show that whatever the w/b, the axial compressive strength and the modulus of elasticity of PGG decreased while the impermeability increased with the increase of sodium bentonite content. The increase of w/b results in the decrease of mechanical properties and impermeability of PGG. The optimal content of sodium bentonite with different w/b can be selected in a range of 5 ~ 15% regarding for the practical requirements and the economic feasibility and beneficial effect on environment protection. Formulas are proposed for predicting the axial compressive strength and the modulus of elasticity of PGG in practical application. |
|---|---|
| ISSN: | 2045-2322 |