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

With the development of construction engineering, how to protect and stabilize foundations cost-effectively has received extensive attention and research. At present, there are many methods for foundation protection and retaining, such as retaining wall, soil nailing, gravity retaining wall, and so on. Among them, soil nailing is a special kind.

In this article, the definition of soil nailing technique and common types and applications of soil nails will be introduced.


What Is Soil Nailing Technique? What Is Soil Nail?

Soil nailing technique is a slope reinforcement construction method by an in-situ soil reinforcement technique. This technique involves the insertion of rebars into the soil, then the reinforcing mesh is laid on the slope surface. And finally, concrete is sprayed with the combination of the earthwork slope.

Its supporting structure is similar to the gravity retaining wall. It is constructed as a composite body formed by reinforced rods arranged in the slope, firmly bonded with the surrounding soil.

Soil nails, in simple terms, are slender rods used to reinforce the soil and prevent the collapse and displacement of foundations or slopes.

soil nail wall


 

Common Types of Soil Nailing Techniques:

According to the construction method, soil nails can be roughly divided into four categories:

Self-drilling Soil Nail

It means drilling and grouting simultaneously with a self-drilling hollow anchor bolt, which is suitable for loose geological conditions that are not easy to form holes.

self drilling soil nail

Drilled and Grouted Soil Nailing

First, drill holes in the soil with equipment such as drilling rigs, and then place the rods into the holes and inject cement slurry.

Drilled and grouted nails are suitable for almost all kinds of soil layers, with high pullout resistance, reliable quality, and low cost, which are the most commonly used types of soil nails.

Driven Soil Nailing

Directly drive steel pipes, angle steels, steel bars, bamboo, logs, etc. into the soil without grouting. The driven soil nails arrangement is relatively dense. And due to its small diameter, low bonding frictional strength, low bearing capacity, and limited nail length, driven soil nails can be inserted by manpower or vibration impact drills, hydraulic hammers, and other machines.

The advantages of driven soil nails are that no pre-drilling is required, so the construction period is short for the small disturbance to the in-situ soil.

But it is difficult to operate in hard cohesive soil, also unsuitable for permanent support with a service life of more than 2 years. The cost is relatively higher for its metal materials.

Grouting Steel Floral Tube

Grouting holes are set in the middle and tail of the steel pipe to form a steel floral tube, which is directly driven into the soil and then grouted to form soil nails.

The steel floral tube has a high pull-out resistance after grouting. It is especially suitable for soft soil layers such as silt, silty soil, various filling soils, and sandy soils that are difficult to form holes, now is widely used.

The disadvantage is that the cost is slightly higher, and is not suitable for permanent projects for poor anti-corrosion performance.

Apllication of Self-Drilling Anchor Bolt Used As Soil Nail

Usually, soil nails are suitable for slope support, foundation excavation, or reinforcement of existing retaining walls. However, ordinary steel bars will be slightly insufficient when applied in complex and easy-to-collapse geological conditions.

Self-drilling anchor bolts combine the functions of drilling, grouting, and anchoring, which can solve the problem of easy-to-collapse holes to some extent when used as soil nails for construction. The advantage of the self-drilling bolt technology is that the disturbance to the slope is small, and it is practical, safe, and economical.

Foundation Support Methods Disscussion

Construction Process:

1. Preparation. Check that the rig is functioning properly and that the drill bit and bolt are not damaged. After checking, install the drill bit and connect the rod to the drilling rig.

2. Drilling test. Drilling at different angles (such as 20°-30° angle, vertical angle) to test the drilling conditions of different construction geology.

3. Simultaneous drilling and grouting. Adjust to a suitable angle, start the drilling rig, and the grouting is completed synchronously when the drilling is completed.

4. Install the flat plate and nut.

Summary

The above is an introduction to the current types and applications of soil nails. Without using casing pipe, the self-drilling anchor system can greatly improve the construction efficiency, shorten the construction period and reduce the overall cost when applied as soil nails. At present, the self-drilling anchor system is suitable for broken rock and surrounding rocks which are difficult to drill holes. It is widely used for slope stabilization, foundation support, tunnel pipe proofing, etc.

Sinorock is a manufacturer specializing in self-drilling rock bolts. 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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