What Is Soil Nailing Technique? Common Types and Applications of Soil Nails

I. Introduction to Soil Nailing Technique

A. Definition and Basic Concept

Soil nailing technique stands tall as a pioneering slope reinforcement construction method, utilizing in-situ soil reinforcement to enhance stability. The core concept involves inserting slender rebars into the soil, laying reinforcing mesh on the slope surface, and applying concrete to form a composite body. This structure, akin to a gravity retaining wall, securely bonds reinforced rods with the surrounding soil.
soil nail wall

B. Importance and Benefits of Soil Nailing

The significance of soil nailing lies in its ability to prevent the collapse and displacement of foundations or slopes. Further highlighting its importance are its applications in slope stabilization, foundation excavation, and retaining wall reinforcement.
The benefits of soil nailing range from cost-effectiveness and time efficiency to versatility in various soil conditions, all with minimal disruption to surrounding structures. Cause it is a very versatile process. With soil nails, curves and surfaces can be shored easily, and installation methods can be modified to meet access restrictions. Soil nailing is more feasible and more economical than driven piles for shoring walls above about 10 feet. Compared to driving piles, it is also quieter. The footprint of soil nailing is significantly smaller than that of laying back a slope when space for shoring is limited, especially for tall retaining structures.

II. Common Types of Soil Nails

A. Self-drilling Soil Nail

1. Definition and Characteristics

Self-drilling soil nails employ a self-drilling hollow anchor bolt, suitable for loose geological conditions where forming holes is challenging. The use of hollow bars and simultaneous drilling and grouting speeds up the process, providing enhanced corrosion resistance compared to driven nails.

2. Installation Process and Materials Used

The installation involves drilling into the slope surface, injecting grout during the process, and offering corrosion-resistant properties to the nails. The use of self-drilling anchor bolts combines drilling, grouting, and anchoring, providing practical, safe, and economical solutions.

B. Drilled and Grouted Soil Nailing

1. Definition and Characteristics

Drilled and grouted soil nails involve drilling holes into the soil with equipment such as drilling rigs and subsequently placing rods into these holes, injecting cement slurry. These nails are versatile, with high pullout resistance, reliable quality, and cost-effectiveness.

2. Installation Process and Materials Used

The process includes drilling holes in walls or slope faces, inserting nails into pre-drilled holes, and filling the holes with grouting materials such as concrete. The diameter of these nails ranges from 100-200mm, with a spacing of 1.5m.

C. Driven Soil Nailing

1. Definition and Characteristics

Driven soil nails employ various materials like steel pipes, angle steels, or logs driven directly into the soil without grouting. While fast in construction and suitable for temporary stabilization of soil slopes, they face challenges in hard cohesive soil and have limitations on service life.

2. Installation Process and Materials Used

Driven soil nailing involves driving nails into the slope face during excavation, with small diameters ranging from 19mm to 25mm and spacings of 1m to 1.2m. Despite its speed, this method does not provide corrosion protection to the reinforcement steel.

D. Grouting Steel Floral Tube

1. Definition and Characteristics

Grouting steel floral tubes involve setting grouting holes in the middle and tail of a steel pipe, forming a tube directly driven into the soil. This method is particularly suitable for soft soil layers and offers high pull-out resistance.

2. Installation Process and Materials Used

The process includes driving the steel floral tube into the soil and subsequent grouting to form soil nails. While this method provides high pull-out resistance, it is not cost-effective for projects requiring long-term anti-corrosion performance.

III. Applications of Soil Nails

A. Slope Stabilization

Slope stability is a critical concern in civil engineering projects, where factors like soil type, water content, and external loads contribute to instability.
Soil nailing mitigates slope instability by reinforcing the soil, preventing collapse, and enhancing overall slope stability.


B. Retaining Wall Construction

Retaining walls are structures designed to hold back soil and prevent erosion, commonly used in hilly terrain or areas with elevation changes.
Retaining walls rely heavily on soil nails to reinforce and stabilize them to ensure their durability and structural integrity.


C. Tunneling and Underground Excavations

Tunneling and underground excavations encounter challenges such as ground movement, soil collapse, and the need for stable support.
Soil nails could provide crucial ground support in tunneling and underground excavations, reducing the risk of collapses and ensuring the safety of structures above.


IV. Advantages and Limitations of Soil Nailing Technique

A. Advantages of Soil Nailing

1. Cost-effectiveness and Time Efficiency

Soil nailing proves to be a cost-effective and time-efficient solution, reducing construction periods and associated expenses.

2. Versatility in Various Soil Conditions

The technique exhibits versatility, adapting to different soil conditions, making it applicable in a wide range of geological settings.

3. Minimal Disruption to Surrounding Structures

Soil nailing minimizes disruption to surrounding structures, making it a preferred choice in urban environments and areas with existing infrastructure.

B. Limitations of Soil Nailing

1. Depth Limitations

One limitation lies in depth constraints, where the effectiveness of soil nailing diminishes with increased depth.

2. Dependency on Soil Conditions

The efficacy of soil nailing is highly dependent on soil conditions, and unsuitable conditions may impact the overall stability achieved.

3. Maintenance and Monitoring Requirements

Regular maintenance and monitoring are essential for ensuring the long-term effectiveness of soil nailing, adding to the overall project costs.

V. Conclusion

The significance of soil nailing in civil engineering projects cannot be overstated, as it addresses critical issues in slope stabilization, retaining wall construction, and underground excavations.
As technology advances, the soil nailing technique holds the potential for further enhancements, addressing current limitations and expanding its applicability in diverse geological conditions.
As the leading expert in the ground support industry, the Sinorock team has years of experience providing complete geotechnical service. If you have any needs or questions about the self-drilling anchor bolt system and its application, please feel free to contact us at sinorock@sinorockco.com.

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