Soil nailing seminar report by ankush choudhury

VISVESVARAYA TECHNOLOGICAL UNIVERSITY,
BELAGAVI
A SEMINAR REPORT ON
“SOIL NAILING”
A seminar report submitted in partial fulfillment of requirements of 8th semester
of bachelor of engineering course during the year 2014-2015
Submitted by:
ANKUSH CHOUDHURY
Under the Guidance of
Prof. MANIK DESHMUKH
DEPARTMENT OF CIVIL ENGINEERING
GURU NANAK DEV ENGINEERING COLLEGE
BIDAR-585403, (KARNATAKA)

SOIL NAILING
DEPT. OF CIVIL ENGG. G.N.D.E.C BIDAR Page 2
GURU NANAK DEV ENGINEERING COLLEGE
BIDAR, 585401(KARNATAKA)
DEPARTMENT OF CIVIL ENGINEERING
CERTIFICATE
This to certify that the seminar on “SOIL NAILING” is a bonafide work
carried out by ANKUSH CHOUDHURY in partial fulfilment of the
requirements for the award of Degree of Bachelor of Engineering in Civil
Engineering from the Visvesvaraya Technological University, Belagavi
during the academic year 2014-2015. It is certified that the seminar report
satisfies the academic requirement in respect of seminar work described for the
Bachelor of Engineering degree.
Prof. Manik Deshmukh Prof: Manik Deshmukh Prof: Obappa Agrahar
Seminar Guide Seminar Co-ordinator Head of Civil dept

SOIL NAILING
ACKNOWLEDGEMENT
I would like to express my deep sense of gratitude to our principal Dr. Ashok Biradar,
Guru Nanak Dev Engineering College, Bidar for his motivation and for creating a
inspiring atmosphere in the college by providing state of art facilities for preparation and
delivery of seminar.
My sincere thanks to Prof. Obappa Agrahar Head of Department Civil Engineering for
his whole hearted support in complementation of the seminar.
I am highly indebted to my seminar co-ordinator and my seminar guide Prof. Manik
Deshmukh for guiding and giving timely advices and suggestion in the successful
completion of the seminar.
Last but not least, I would like to thanks The Teaching & Non-Teaching Staff of Civil
Engineering Department, I would like thank one and all who have helped me during the
course of this seminar.
ANKUSH CHOUDHURY

SOIL NAILING
ABSTRACT
Soil nailing is an in-situ reinforcement technique by passive bars which can withstand tensile
forces, shearing forces and bending moments.
This technique is used for retaining walls and for slope stabilization. Its behaviour is typical
of that of composite materials and involves essentially two interaction mechanisms:
The soil- reinforcement friction and the normal earth pressure on the reinforcement. The
mobilization of the lateral friction requires frictional properties for the soil, while the
mobilization of the normal earth pressure requires a relative rigidity of the inclusions.
Taking into account these mechanisms, multi-criteria at failure design method is proposed. It
is derived from the slice methods used in slope stability analysis. The criteria lead to a
yielding curve in the shear – tensile forces plane and the consideration of the principle of the
maximum plastic work enables to calculate the shear and tensile forces mobilized at failure in
each inclusion.
Using a formulation determinate, the slope stability analysis take into account the passive
force of reinforcement.

SOIL NAILING
CONTENTS
Page no.
1. INTRODUCTION 3
2. ORIGIN AND DEVELOPMENT 4
3. FAVOURABLE GROUND CONDITIONS FOR SOIL NAILING 5-6
4. COMPONENTS OF A SOIL NAIL WALL 7-9
5. TYPES OF NAILS USED 10
6. MACHINERIES USED IN SOIL NAILING 11-12
7. MATERIALS USED IN SOIL NAILING 13-14
8. DESIGN REQUIREMENTS 15-17
9. CONSTRUCTION SEQUENCES 18-19
10. APPLICATIONS 20
11. ADVANTAGES 21
12. CONCLUSION 22
13. REFERENCES 23

SOIL NAILING
CHAPTER 1
INTRODUCTION-WHAT IS SOIL NAILING ?
Soil nailing consists of the passive reinforcement of existing ground by installing closely
spaced steel bars (i.e. nails), which may be subsequently encased in grout.
As construction proceeds from the top to bottom, shotcrete or concrete is also
applied on the excavation face to provide continuity. In a soil-nailed retaining wall, the
properties and material behaviour of three components—the native soil, the reinforcement
(nails) and the facing element—and their mutual interactions significantly affect the
performance of the structure.
Soil nailing is typically used to stabilize existing slopes or excavations where
top-to-bottom construction is advantageous compared to other retaining wall systems. For
certain conditions, soil nailing offers a viable alternative from the viewpoint of technical
feasibility, construction costs, and construction duration when compared to ground anchor
walls, which is another popular top-to bottom retaining system.
An alternative application of passive reinforcement in soil is sometimes used to
stabilize landslides. In this case, the reinforcement (sometimes also called “nails”) is
installed almost vertically and perpendicular to the base of the slide. In this alternative
application, nails are also passive, installed in a closely spaced pattern approximately
perpendicular to the nearly horizontal sliding surface, and subjected predominantly to shear
forces arising from the landslide movement.

SOIL NAILING
CHAPTER 2
ORIGIN AND DEVELOPEMENT
 Tunnelling Method in the 1960’s.One of the first applications of soil nailing was in
1972 for a railroad widening project near Versailles, France, where an 18 m (59 ft)
high
 The origin of soil nailing can be traced to a support system for underground
excavations in rock referred to as the New Austrian cut-slope in sand was stabilized
using soil nails.
 In Germany, the first use of a soil nail wall was in 1975 (Stocker et al. 1979).
 The United States first used soil nailing in 1976 for the support of a 13.7 m deep
foundation excavation in dense silty sands.
 In India use of soil nailing technology is gradually increasing and guidelines have
been made by IRC with the help of Indian Institute of Science, Bangalore.

SOIL NAILING
CHAPTER 3
FAVOURABLE GROUND CONDITIONS FOR
SOIL NAILING
Soil nail walls can be used for a wide range of soil types and conditions. Project experience
has shown that certain favourable ground conditions make soil nailing cost effective over
other techniques.
Soil nailing has proven economically attractive and technically feasible when:
 The soil in which the excavation is constructed should able to stand unsupported in a
1- to 2-m (3- to 6-ft) high vertical or nearly vertical cut for one to two days.
 All soil nails within a cross section are located above the groundwater table.
 If the soil nails are below the groundwater table, the groundwater does not adversely
affect the face of the excavation, the bond strength of the interface between the grout
and the surrounding ground, or the long-term integrity of the soil nails (e.g., the
chemical characteristics of the ground do not promote corrosion).
 It is advantageous that the ground conditions allow drill holes to be advanced without
the use of drill casings and for the drill hole to be unsupported for a few hours until
the nail bars are installed and the drill hole is grouted.
The results from the Standard Penetration Test provides the SPT value
‘N’ which can be used to preliminary identify the favourable soil conditions for Soil
Nailing. Based on the general criteria for favourable conditions noted above, the
following ground types are generally considered well suited for soil nailing
applications:
 Stiff to Hard Fine-Grained Soils: Fine-grained (or cohesive) soils may include stiff
to hard clays, clayey silts, silt clays, sandy clays, sandy silts, and combinations
thereof. These types of soils have the SPT value (N) around 9 blows/300mm.Fine-
grained soils should have relatively low plasticity i.e. PI<15.
 Dense to Very Dense Granular Soils: These soils include sand and gravel with SPT
N-values larger than 30 and with some fines about 10 to 15 percent and with weak
natural cementation that provide cohesion. To avoid excessive breakage of capillary
forces thereby reducing apparent cohesion the movement of water toward the

SOIL NAILING
excavation face needs to be minimized by redirecting surface water away from the
excavation face.
 Weathered Rock with no Weakness Planes: Weathered rock may provide a suitable
supporting material for soil nails as long as weakness planes occurring in
unfavourable orientations are not prevalent (e.g., weakness planes dipping into the
excavation).
 Glacial Soils: Glacial outwash and glacial till materials are typically suitable for soil
nailing applications as these soils are typically dense, well-graded granular materials
with a limited amount of fines.
In addition to these above conditions certain other aspects
Should be considered for the construction of soil nailed structures:
 The prolonged exposure to ambient freezing temperatures may cause frost action in
saturated, granular soils and silt; as a result, increased pressures will be applied to the
temporary and permanent facings.
 Repeated freeze-and-thaw cycles in the soil may reduce the bond strength at the soil
nail grout-ground interface and the adhesion between the shotcrete and the soil. A
suitable protection against frost penetration and an appropriate concrete mix must be
provided.
 Granular soils that are very loose (N ≤ 4) and loose (4 < N ≤ 10) may undergo
excessive settlement due to vibrations caused by construction equipment and traffic.

SOIL NAILING
CHAPTER 4
COMPONENTSOF A SOIL NAIL WALL
Fig 4.1: Main Components of a Typical Soil Nail.
The components of a soil nailed wall are shown above in the (Fig 4.1) they are as follows:
 Nail Bars: Steel reinforcing bars used for soil nails are commonly threaded and may
be either solid or hollow. Bars generally have a nominal tensile strength of 420 MPa
(Grade 60) or 520 MPa (Grade 75). Bars with a tensile strength of 665 MPa (Grade
95) and as high as 1,035 MPa (Grade 150) may be considered for soil nailing, but
their use should be restrictive. Bars with lower grades are preferred because they are
more ductile, less susceptible to corrosion, and readily available. Grade 150bars
should not be used because they are more brittle under shear and more susceptible to
stress corrosion than steel at lower grades. Threaded bars applications are available in
19-, 22-, 25-, 29-, 32-, 36-, and 43-mm diameter (No. 6, 7, 8, 9, 10, 11, and 14 in
English units) up to approximately 18 m (59 ft) in length.

SOIL NAILING
 Nail Head: The nail head comprises two main components, the bearing-plate, hex
nut, and washers; and the headed-stud. The bearing plate is made of Grade 250 MPa
(Grade 36) steel and is typically square 200- to 250-mm (8- to 10-in.) side dimension
and 19-mm (¾-in.) thick. The purpose of the bearing plate is to distribute the force at
the nail end to the temporary shotcrete facing and the ground behind the facing.
Washers and nuts are steel with a grade consistent with that of the nail bar commonly
of 420 or 520 MPa (Grade 60 or 75).
 Grout: Grout for soil nails is commonly a neat cement grout, which fills the annular
space between the nail bar and the surrounding ground. Sand-cement grout can also
be used in conjunction with open hole-drilling (i.e. for non-caving conditions) for
economic reasons. Cement Type I (normal) is recommended for most applications.
Cement Type III is grounded finer, hardens faster, and can be used when target grout
strength is required to be achieved faster than for typical project conditions. Cement
Type II hardens at a slower rate, produces less heat, and is more resistant to the
corrosive action of sulphates than Cement Type I. The water/cement ratio for grout
used in soil nailing applications typically ranges from 0.4 to 0.5.
Fig 4.2: Grout is being placed with the help of pipes
 Centralizers: Centralizers are devices made of polyvinyl chloride (PVC) or other
synthetic materials that are installed at various locations along the length of each nail
bar to ensure that a minimum thickness of grout completely covers the nail bar (Fig
4.3). They are installed at regular intervals, typically not exceeding 2.5 m (8 ft), along
the length of the nail and at a distance of about 0.5 m (1.5 ft) from each end of the
nail.

SOIL NAILING
Fig 4.3: Typical PVC centralizers
 Corrosion Protection Elements: In addition to the cement grout, this provides both
physical and chemical protection to the nail bars. Protective sheathings made of
corrugated synthetic material [HDPE (High Density Polyethylene) or PVC tube)
surrounding the nail bar are usually used to provide additional corrosion protection.
 Wall Facing: Nails are connected at the excavation surface (or slope face) to a facing
system, which most commonly consists of a first-stage, temporary facing of shotcrete
during construction and, a second-stage, permanent facing of CIP concrete. The
purpose of the temporary facing is to support the soil exposed between the nails
during excavation, provide initial connection among nails, and provide protection
against erosion and sloughing of the soil at the excavation face. The purpose of the
permanent facing is to provide connection among nails, a more resistant erosion
protection, and an aesthetic finish. Temporary facing typically consists of shotcrete
and WWM and additional shorter reinforcement bars (referred to as waler bars)
around the nail heads. Permanent facing is commonly constructed of CIP reinforced
concrete and WWM-reinforced shotcrete.
 Drainage System: To prevent water pressure from developing behind the wall facing,
vertical geo-composite strip drains are usually installed between the temporary facing
and the excavation. The drainage system also includes a footing drain and weep holes
to convey collected drainage water away from the wall face.

SOIL NAILING
CHAPTER 5
TYPES OF NAILS USED
The types of nails used in the construction of soil nailed walls are as follows:
 Drilled and grouted soil nail
 Driven soil nails
 Self-drilling soil nails
 Jet-grouted soil nails
 Launched soil nails
These are explained as follows:
 Drilled and grouted soil nail: These are approximately 100- and 200-mm (4- to 8-
in.) diameter nail holes drilled in the foundation soils. These holes are typically
spaced about 1.5 m (5 ft) apart. Steel bars are placed and the holes are grouted.
Grouted soil nails are the most commonly used soil nails for FHWA projects and they
can be used as temporary and permanent applications, provided that appropriate
corrosion protection is in place.
 Driven soil nails: These soil nails are relatively small in diameter [19 to 25 mm (¾ to
1 in.)] and are mechanically driven into the ground. They are usually spaced
approximately 1 to 1.2 m (3 to 4 ft) apart. The use of driven soil nails allows for a
faster installation as compared to drilled and grouted soil nails.
 Self-drilling soil nails: These soil nails consist of hollow bars that can be drilled and
grouted in one operation. In this technique, the grout is injected through the hollow
bar simultaneously with the drilling. This soil nail type allows for a faster installation
than that for drilled grouted nails and, unlike, driven soil nails, some level of
corrosion protection with grout is provided.
 Jet-grouted soil nails: Jet grouting is performed to erode the ground and allow the
hole for the nail to be advanced to the final location. The grout provides corrosion
protection to the central bar. In a second step, the bars are typically installed using
vibro-percussion drilling methods.
 Launched soil nails: In this method, bare bars are “launched” into the soil at very
high speeds using a firing mechanism involving compressed air. Bars are 19 to 25
mm (¾ to 1 in.) in diameter and up to 8 m (25 ft) in length. This technique allows for
a fast installation with little impact to project site.

SOIL NAILING
CHAPTER 6
MACHINERIES USED IN SOIL NAILING
The following tools or machineries are used for soil nailing:
 Drilling Equipments
 Grout Mixing Equipments
 Shotcreting / Guniting Equipments
 Compressor
They can be broadly explained further as follows:
 Drilling Equipments: It’s a rotary air-flushed and water-flushed system. It consists
of a down the hole hammer with a tri-cone bit(Fig 6.1).It is important to procure
drilling equipment with sufficient power and rigid drill rods.
 Grout Mixing Equipments: In order to produce uniform grout mix, high speed shear
colloidal mixer should be considered. Powerful grout pump is essential for
uninterrupted delivery of grout mix (Fig 6.2).If fine aggregate is used as filler for
economy, special grout pump shall be used.
 Shotcreting / Guniting Equipments: Dry mix method will require a valve at the
nozzle outlet to control the amount of water injecting into the high pressurized flow of
sand/cement mix (Fig 6.3).For controlling the thickness of the shotcrete, measuring
pin shall be installed at fixed vertical and horizontal intervals to guide the nozzle man.
 Compressor: The compressor shall have minimum capacity to delivered shotcrete at
the minimum rate of 9m3/min. Sometimes, the noise of compressor can be an issue if
the work is at close proximity to residential area, hospital and school.
Fig 6.1: Typical drilling equipment

SOIL NAILING
Fig 6.2: Grout Mixing Instrument
Fig 6.3: Shotcreting is done with the help of a pipe with a nozzle

SOIL NAILING
CHAPTER 7
MATERIALS USED IN SOIL NAILING
This presents information on construction materials used for the construction of a soil nailed
wall. They are:
 Steel Reinforcements: Steel reinforcements are used in the construction of soil nailed
walls. For corrosion protection; all steel component shall be galvanized. If machine
threading after galvanization is unavoidable, then proper zinc based coating shall be
applied onto the thread. For double corrosion protection, the PVC corrugated pipe
used shall be of good quality and adequate thickness.
Fig 7.1: Reinforcements used in Soil Nailing
 Grout Mix: For conventional soil nail, the water cement ratio of the grout mix ranges
from 0.4 to 0.5.As most cementitious grout will experience some grout shrinkage,
non-shrink additive can be used to reduce breeding and grout shrinkage. The
resistance at grout-soil interface of nail will significantly reduced when the grout
shrink.

SOIL NAILING
Fig 7.2: Grout Mix is being formed in the Grout Mixing Machine
 Shotcrete/Gunite: Shotcrete or gunite can be continuous flow of mortal or concrete
mixes projected at high speed perpendicularly onto the exposed ground surface by
means of pneumatic air blowing for dry mix or spraying for wet mix.
Fig 7.3: Shotcreting is being done on the wire mesh

SOIL NAILING
CHAPTER 8
DESIGN REQUIREMENTS
The design of a soil nailed wall is organized to first introduce the technical concepts related
to the mechanisms underlying soil nail wall response to construction and operation.
Following this introduction, specific topics related to analysis and design are introduced,
starting with a presentation of the two specific limit states that must be considered by the
designer, namely, the strength limit states and service limit states. This is followed by a
description of potential failure modes for soil nail walls. Then it introduces and compares
calculations resulting from SNAIL and GOLDNAIL, two of the most widely used computer
programs in the United States.
8a) LOAD TRANSFER CONCEPT IN SOIL NAIL WALLS
Fig 8.1

SOIL NAILING
 Soil excavation is initiated from the ground surface and the Excavation Phase 1 is
completed (Figure 5.1). Because of the soil ability to stand unsupported, the upper
portion of the soil behind the excavation is stable (or at least marginally stable) before
the first row of nails (Nails 1) is installed.
 As Nails 1 and the temporary facing are installed, some load derived from the
deformation of the upper soil is transferred to these nails through shear stresses along
the nails and translate into and axial forces. The top portion of Fig shows
schematically the axial force distribution in Nails 1 at the end of excavation Phase 1.
At this point, the temporary facing supports the excavation surface and provides
connectivity between adjacent nails in row of Nails 1.
 As excavation proceeds to Excavation Phase 2, the uppermost and the unsupported
portions of the soil nail wall deforms laterally. At this point, another potential sliding
surface, one originated from base of Excavation Phase 2 is formed.
 Nails 2 are then installed. Subsequently the temporary facing between the bottom of
excavation Phases 1 and 2 is installed and integrated to the facing constructed in
Phase 1. Movements of the soil above the Phase 2 depth will cause additional loads to
be transferred to Nails 1 and generate loads in Nails 2.
 To provide global stability, the soil nails must extend beyond the potential failure
surface. As the depth of excavation increases, the size of the retained soil mass
increases, as shown in Fig.
 As the size of the retained zone increases, the stresses at the soil/nail interface and the
axial forces in the nails increase.
 The upper portion of Fig shows schematically that the axial force distribution for
Nails 1 at the end of the last excavation Phase N does not exhibit the largest values.
 As the critical failure surface becomes deeper and larger, the contribution of the upper
nails to the stabilization of this larger sliding mass diminishes.
8b) LIMIT STATES
The analysis and design of soil nail walls must consider two distinct limiting conditions:
Strength Limit States and the Service Limit States.
 Strength limit states: These limit states refer to failure or collapse modes in which
the applied loads induce stresses that are greater than the strength of the whole system

SOIL NAILING
or individual components, and the structure becomes unstable. Strength limit states
arise when one or more potential failure modes are realized.
 Service limit states: These limit states refers to conditions that do not involve
collapse, but rather impair the normal and safe operation of the structure. The major
service limit state associated with soil nail walls is excessive wall deformation.
 Other service limit states: These are beyond the scope of this document; include
total or differential settlements, cracking of concrete facing, aesthetics, and fatigue
caused by repetitive loading.
Fig 8.2: Modes of Failure

SOIL NAILING
CHAPTER 9
CONSTRUCTION SEQUENCES
The sequence of construction for typical soil nail walls was described in and consisted of:
 Excavation;
 Drilling of nail holes;
 Installation and grouting nails;
 Construction of temporary shotcrete facing;
 Construction of subsequent levels; and
 Construction of a final, permanent facing.
Fig 9.1: Steps in constructing a soil nailed wall

SOIL NAILING
Fig 9.2: Initial Excavation Lift and Nail Installation
Fig 9.3: Typical Drilling of Soil Nails with Rotary Method

SOIL NAILING
CHAPTER 10
APPLICATIONS
 Stabilization of railroad and highway cut slopes
 Excavation retaining structures in urban areas for high-rise building and underground
facilities
 Tunnel portals in steep and unstable stratified slopes
 Construction and retrofitting of bridge abutments with complex boundaries involving
wall support under piled foundations
 Stabilizing steep cuttings to maximize development space.
 The stabilizing of existing over-steep embankments.
 Soil Nailing through existing concrete or masonry structures such as failing retaining
walls and bridge abutments to provide long term stability without demolition and
rebuild costs.
 Temporary support can be provided to excavations without the need for bulky and
intrusive scaffold type temporary works solutions.

SOIL NAILING
CHAPTER 11
ADVANTAGES
Soil nail walls exhibit numerous advantages. Some of these advantages are described below:
11a) CONSTRUCTION:
 Requires smaller ROW than ground anchors as soil nails are typically shorter
 Less disruptive to traffic and causes less environmental impact compared to other
construction techniques
 Installation of soil nail walls is relatively rapid and uses typically less construction
materials
 Soil nailing is advantageous at sites with remote access because smaller equipment is
generally needed
11b) PERFORMANCE:
 Soil nail walls are relatively flexible and can accommodate relatively large total and
differential settlements
 Total deflections of soil nail walls are usually within tolerable limits
 Have performed well during seismic events owing to overall system flexibility.
11c) COST:
 Soil nail walls are more economical
 Soil nail walls are typically equivalent in cost or more cost-effective than ground
anchor walls
 Shotcrete facing is typically less costly

SOIL NAILING
CHAPTER 12
CONCLUSION
 Conventional design procedure using FHWA (2003) provides a safe but conservative
design.
 Provision of facing results in the significant improvement of the stability and
performance of soil nail walls.
 Intermittent facing with a small offset in each construction stage is found to be more
effective in reducing the lateral deformation of soil nail walls than regular continuous
vertical facing.
 The overall stability (i.e. external as well as internal) and performance of the soil nail
walls is dependent on the other spectral properties (e.g., strong motion duration and
peak displacement) of the time history data of an earthquake.
 Pseudo-static analyses are found to provide conservative estimate of displacements
and factor of safety values.

SOIL NAILING
REFERENCES
 http://www.deepexcavation.com/en/soil-nail-wall
 http://www.moretrench.com/b_literature_article.php
 http://en.wikipedia.org/wiki/Soil_nailing
 Manual for Design and Construction Monitoring of Soil Nail walls,
US Department of Transportation, Federal Highway
Administration.
 Guide to Soil Nail Design and Construction, Geotechnical Engg
Office, Civil Engineering and Development Department, The
Government of the Hong Kong.
 http://www.google.com

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