1. Soil Nailing by Devsoth Naresh & Ravindra Prasad 1.1. Introduction

Soil nailing is one of the ground improvement techniques used for reinforce and strengthen the

existing ground. This technique includes installation of steel bars with specified spacing into a finite

slope or excavation as excavation proceeds from top to bottom. It is an effective and economical

technique of constructing retaining wall for excavation support, support of hill cuts, bridge

abutments and highways etc. This technique effective in cohesive soil, brocken rock and shale. By this

technique it is possible to construct the slopes of slope angle of 900

also. It is also applicable for

stabilizing the slopes of about 60m height.

Soil nailing evolved from the New Austrian Tunneling method which is a system for underground

excavations in rocks. First application of soil nailing was implemented in 1972 for a railroad widening

project near Versailles, France.

1.2. Applications of Soil Nailing

As this method is good in economic and stability point of view, it is extensively used in day to day

construction practices. Some of the applications are

A. Tunnel portals in steep and unstratified slopes

B. For stabilization of railroad and highway embankments

C. For stabilizing steep cuttings to reduce the area of utilization

D. Excavation retaining structures in city areas, for underground stability, etc..,

1.3. Types of Nails Used

Various types of nails are used in various construction practices depending on the conditions

available. Typical types are

A. Driven Nails

B. Grouted Nails

C. Jet grouted Nails

D. Launched Nails

1) Driven Nails:- Generally these are small-diameter nails(15-46mm) with a relatively limited

length(20m). These are the quickest and economical to installation.

2) Grouted Nails:- These are similar to driven nails in shape but has strength greater than driven nails.

These are inserted in boreholes of 10-15 cm and then grouted with cement slurry.

3) Jet grouted nails:- This type of nails are composite of grouted soil and a central steel rod, up to 40cm

thick. In this method nails are installed using a high frequency vibro percussion hammer, and cement

grouting is injected during installation. These nails are good in pullout strength and corrosion

resistance.

1. Soil Nailing by Devsoth Naresh & Ravindra Prasad 4) Launched nails:- Nails consists of 25 to 38 mm diameter and around 6m length, are fired directly into

the soil with a compressed air-Launcher. Primarily this is used in slope stabilization. Least site

disturbance.

1.4. Equipments used

Drilling Equipments

Grout mixing Equipments

Shortcreting Equipments

Compressor

1.5. Materials used

Steel Reinforcement

Grout Mix

Shortcrete

1.6. Advantages

By using nailing one can arrive at below benefits or advantages

Installation of nails creates less noice and traffic obstructions

Less effect on nearby structures

With the right soil and site conditions, a rapid and economical means of constructing

earth retention support systems and retaining walls

Allow excellent working space in front of wxcavation face

Can be used for strengthening of natural slopes, or man made cut slopes

Grouting only once required, saving time and labour

This method is flexible, can be easily modified

1.7. Disadvantages

Some disadvantages of using nailing are

Generally larger lateral soil strain during removal of lateral support and ground surface

cracking may appear.

Tendency of high ground loss due to drilling technique, particularly at course grained

soils.

Less suitable for course grained soils and soft clayey soils, which have short self support

time, and soils prone to creeping.

Suitable only for excavation above ground level.

Nail encroachment to retained ground rendering unusable underground space.