Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 113-117
113
Investigation and Presentation of the Valuation Type Graphs and
Plans to Design Protection System of Soldier Pile Excavation Wall
Mojtaba Askari
1
, Babak Mansouri
2
*
1- Department of Civil Engineering, Firouz Abad Branch, Islamic Azad University, Firouz Abad, Iran
2- Department of Civil Engineering, Meymand Center, Islamic Azad University, Meymand, Iran
Received: 08/04/2015 Accepted: 08/06/2015 Published: 30/06/2015
Abstract
In recent years with regard to development of our country different towns and thereby the necessity of special and deep
excavations, many wall collapses were observed. The stability of excavation walls can be supplied by various methods depending
on the conditions of land, depth and wall surrounding live loads. One of these methods is to use Soldier Pile system along with
anchor bolt. The important advantages of this system is the significant reduction of occupied space by soldier structure and the
reduction of time and running cost in big projects. Components design of this system depends on various parameters such as soil
physical properties, including soil cohesion (C), angle of internal friction (φ), soil bulk density (ϒ) and excavation conditions
including excavation height (H), fixed length (D), the amount of live load (ω) and anchor situations. This paper presents wide
parametric studies by changing aforementioned parameters and uses Support IT software to analyze different states, type
valuations graphs and running plans as the charts used by engineers in rapid designing of this system to stabilize excavation.
Key words: Protection system, soldier pile, design protection system
1 Introducing Soldier Pile System
1
Soldier pile consists of different materials and profiles
and mostly is applied in connection with timbers as ground
support system like a continuous wall. In soldier pile
elements, H or IPB profiles or shield profiles are used. The
materials which are applied between profiles are wooden
timbers with metal plates or concrete sections. A part of
soil force by timbers and another part by arc phenomena
are transported to soldier pile profiles [3].
The method is to excavate speculations in the intended
ground margins in certain distances while the depth of these
speculations is equal to excavation depth plus fixed length.
After excavating these speculations profiles are installed
within them then the fixed length which is obtained with
calculation is concreted. After running above steps, the
excavation operation is ran in steps which in this step
anchor bolts are used to control soil if necessary which the
necessity of using anchor bolts is specified in calculations.
Then wooden timbers or prefabricated concrete panels are
installed between the vertical profiles and control them to
profiles and anchor-bolts. All of mentioned operations are
implemented from top to bottom [2].
Corresponding author: Babak Mansouri, Department of
Civil Engineering, Meymand Center, Islamic Azad
University, Meymand, Iran.
2 The Advantages of Soldier Pile System
Soldier structure is not in fixed excavation and doesn’t
occupy excavation space. 2- The time and cost of running
operation decreases in big projects. 3- The amount of soil
drift decreases using anchor-bolts. 4- The existing soil is
used to control excavation wall. 5- Grouting injection
results in the reinforcement of soil physical properties [1].
3 The Methods of System Designing and the
Effect of Various Variables:
3. A Effective width and proximity factor
Effective width is the width of the pile parallel to wall
(b) or the depth of used pit to install the pile (w). (Figure 1)
Fig. 1:Effective width and proximity coefficient
Laboratory observations show that cohesion-less soil
resistance acts on a width larger than actual width.
Resistant soil wedge develops under excavation depth and
it is like a pile which rotates around itself. Hence the factor
is defined as following:
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ISSN: 2309-1185
Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 113-117
114
The final proximity width must not exceed from piles
distance.
Method 1: proximity factor is applied only for resistant
area. In this method, the factor affects only in resistant part.
Method 2: proximity factor is applied for resistant and
active area. Figure (2)
Soldier piles can be analyzed like shields, if we assume
the width of active loading area is equal to the width of
resistant loading part. In this case, we define Arching factor
which is as following:
All of the equations under the depth of excavation are
multiplied by this factor and the final response is multiplied
to the distance between the profiles (S). The fixed depth
achieved in this method is larger than the first method [3].
Fig. 2: The forces diagram
4 The Effective Variables and Factors in
Designing
Design and the panels between them depend on
different parameters such as soil physical properties
including soil cohesion (C), angle of internal friction (φ),
soil bulk density (ϒ) and excavation conditions including
excavation height (H), fixed length (D), the amount of live
load (ω) and anchors situations h1, h2. Figure (3)
Fig. 3: Effective width and proximity coefficient
5 Introducing Support IT software
This is a type of designing and analyzing software to
modeling the anchored excavations by shields and soldier
piles. The computational methods are based on US
BRITISH STEEL PILING, STEEL SHEET PILING
DESIGN handbook.
5-A Software outputs
SupportIT software has many abilities to design soldier
pile which a number of them are indicated in following.
1- The modeled full graphical shape 2- the calculation
of pressure, moment, displacement and shear force
maximum 3- the entire output calculation of soldier
piles and timbers 4- Drawing pressure, moment,
displacement and shear force plots 5- the table of
pressure, moment, displacement and shear force
output in different depths 6- Drawing excavations and
anchors plots. Figure (4)
b- The amount of force in anchor bolts a- Pressure distribution
behind retaining walls
Fig. 4: An example of software output a- pressure distribution behind
retaining walls b- the amount of force in anchor-bolts
6 The Designing Procedure of Soldier Pile
System Components
6-A Section designing for soldier pile
To design the proper section for soldier pile, the
existing profile in Iran market was used in the aim of
simplicity in implementation. To design the pile, the
regulation of steel building national rules (section 10),
allowable stress method has been used.
The basic of required section for soldier pile is
calculated using the following formula.
where, S
re
is the basic of required section and M max is
flexural moment maximum of the design, F
b
is steel
allowed flexural stress which is 0.6f
y
and f
y
is the yield
stress of steel St37 which is equal to 2400 kN/m
2
.
6-B Anchors designing (anchor bolts)
Anchors (anchor bolts) are the stretching oblique steel
members. Usually, steel bars are used to reduce the flexural
moment created in soldier pile. Anchor-bolts have three
main components according figure 5.
The system of the connection to soldier pile (Anchorage),
stress-less part or unbound length and bond length [3].
Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 113-117
115
Fig. 5: Anchor bolt components
6-C Bond strength
The transferred force between anchor and soil depends
on various factors including method and pressure of
concrete injection, excavating type, excavated hole’s
diameter, bond length and soil type which is called bond
strength. This strength is defined based on laboratory
results [3].
6-D Anchor diameter calculation
To design anchors, the steel bars, type A3 with
characteristic strength of Fy=4000 kg/cm
2
are used. Based
on Iran concrete regulations, for designing tensile bars,
reduction coefficient of steel strength is considered equal to
0/85. Hence the required diameter is calculated for anchor.
6-E lagging designing
The designing of laggings thickness in soldier pile
system is performed based on empirical relations. The
suggested amounts of wooden timber thickness (lagging)
are offered depending on the type of soil, excavation depth
and the distance between soldier piles [3].
6-F The computation of axial capacity required for
a soldier pile
The axial capacity required to a soldier pile is
computed using relation 5. In this relation, the first term is
relevant to pile friction strength with confidence coefficient
of 2 and the second term is the strength of pile’s tip with
the confidence coefficient of 2/5 [3].
Q
a
is pile axial capacity, f
s
wall strength, A
s
pile wall
area, q
t
tip strength and A
t
the area of pile tip.
6-G Computation of total axial load
Total axial load is the result of summing vertical forces
of anchors and the weight of soldier pile, concrete and
wooden timbers, which is compared to pile axial capacity
[3].
7 Parametric Studies
Some of the parameters that influence the behavior of
this system are soil type, excavation depth and the amount
of live load. In this paper, a wide parametric study has been
performed to determine the effect of these parameters. To
include different soils the range of C values of soil
cohesion is considered from 0 to 100 kN/m
2
(0,20,40,60,80,100) and φ the internal friction angle of soil
from 0 to 40 degrees (0,5,10,15,20,25,30,35,40) and ϒ soil
bulk density with the amounts of 17, 18, 19 and 20 KN/M
3
.
Also, modeling for excavation depths are 3, 6, 9 and 12
meters. Also to apply excavation surrounding live load, the
neighbor building loads is considered from 0 to 10 floors
for each floor the love load is 10 kN/m
2
.
Excavation conditions with respect to soil type, excavation
depth and different live loads are modeled in SupportIT
software. In this software, available flexural moment in pile
is picked and the section correspond to that moment is
designed. If the existing flexural moment in piles lead to
designing non-economical section, using steel anchors
(anchor bolts) in different heights of excavation, the
moment is diminished and the proper section is designed.
Anchor bolts in different situations are modeled in software
and the existing force is taken from them, then their
diameter and length is designed. Wooden timbers
(Lagging) which locate between profiles to protect soil are
also modeled in this model and then the required designing
is performed.
According the multiplicity of modeling, the results are
presented as executive charts in terms of C (soil cohesion),
φ (the internal friction angle of soil), depths, different live
loads and also soil different bulk densities and then these
charts are classified in valuation types [1].
8 Study of Different Parameter Effect in
Designing Soldier Pile System
8-A Effect of excavation side live load (ω) on the amount
of moments in soldier pile
To show the effect of live load changes on the amount
of moments in the different intervals C, φ, a model with
fixed characteristics has been taken into account. And the
anchors situation and ω are considered as variable. With
investigating results, it can be said that live load changes
with other conditions being constant in poor soils (with low
C and φ) are very impressive on united moments. But the
live load changes in high shear strength soils (with high C
and φ) are not impressive on created moments. Figure (6)
[1].
Fig. 6: Chart of live load effect on the amount of moments
8-B Investigation of soil bulk density (ϒ) effect on
flexural moment
To show the effect of soil bulk density on flexural
moment, a model with constant live load and variable
Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 113-117
116
conditions of C, φ was considered for different bulk
densities. Seeing the results, it can be said that bulk density
changes has not remarkable impact in the amount of
different areas moment except the areas that have low C
and φ. Figure (7) [1].
Fig. 7: Chart of bulk density impact on the amount of moments
8-c Investigation of soil cohesion impact on the amount of
moment in soldier pile
To indicate soil cohesion effect, the model is considered
with live load and friction angle in terms of the changes in
parameter C and the results of moment changes was
registered. Investigating the results, it can be concluded that
with increase of soil cohesion (C), the amount of moment
increases at first then decreases and finally it remains
constant. Figure (8) [1].
Fig. 8: Graph of cohesion impact on the amount of moments
8-5 Effect of internal friction angle on the amount of
moment in soldier pile
To investigate soil internal friction angle, a model is
investigated with considering constant cohesion and the
changes of parameter φ. From the results of moment
changes, it can be understood that with increasing φ, the
amount of moment decreases at first and finally it remains
constant. Figure (9) [1].
Fig. 9: Diagram of internal friction angle effect on the amount of moments
8-6 Effect of number, situation and angle of anchors on the
amount of moment in soldier pile and the created force in
anchors
To observe the effect of number and locations of anchors
on the amount of moment in soldier pile, a model
considering φ and C as constants is investigated for
different states of anchor’s laying. We find that at one-
anchor state with moving the anchor from top to down, the
amount of moment decreases at first and then it increases.
In two-anchor state with increasing anchor’s number to a
certain number in soldier pile system, the moment is
decreased significantly but there will be no effects with
more number than that and also the location and situation
of anchors affects the amount of created moment in soldier
pile. With increasing anchors number, the existing force is
decreased in them and the situation of anchors is impressive
in the created force in them. To investigate the effect of
moment inclination angle on the created force in models, it
is considered in one-anchor state under different angles.
Investigating these changes, we understand that with
increasing anchor inclination angle, the existing force in
them increases and the anchor vertical component which
causes increasing axial force in pile, increases. Also, the
changes of anchor inclination angle are not impressive in
the created moment in pile [1].
9 Basis of Chart Drawings and the Valuation
Type of Plans and How to Use Them
After analyzing all the models, the results registered in
tables (bending moment and the location and number of
anchor). After the result investigation, the moments having
close values and having the equal situation and number of
anchors are introduced as a type and their relevant charts
are drawn; with regard to high volume of charts and
running plans, one chart and two plans are shown in figures
(10), (11) and (12). Observing the graph of figure 10 we see
that having soil cohesion (C) and internal friction angle (φ)
and the perpendicular drawn from them, it is possible to
specify the structure type and then observing its relevant
designing plan. Observing the plans figures 11 and 12, it is
easy to obtain all of structure designing information
including soldier pile characteristics (profile, the distance
between piles and fixed length) and anchors characteristics
(bond and un-bond length, their distance, anchors diameter,
angle and …). There is an area in the graph called as zero
type and this area is relevant to data that have high moment
values and using this system in this area needs more
investigation and this area is introduced zero type.
In this research, we tried to supply and present graphs
and plans for simplicity in calculating and determining the
system component of soldier pile. These graphs and plans
make easier the possibility of designing for engineers. The
complete set of plans could be observed in the reference
number 1. With regard to the performed work load and the
limitation of presentable contents, a part of the performed
work is presented here and the interested readers can refer
to author’s master thesis.
Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 113-117
117
Fig. 10: A sample of soldier pile valuation type graph (depth of 6 meter for
live load 20 KN/M
2
)
Fig. 11: An example of soldier pile valuation type plan (depth of 6 meters
type 4)
Fig. 12: An example of soldier pile valuation type plan (depth of 6 meter,
type 5)
10 Conclusions
1- The changes in soil bulk density has no effect on
the form of valuation type graphs and also has not
significant impact in the amount of moment in
the different areas of valuation types except zero
type area.
2- The changes of live load is very impressive in
poor soils or low shear strength (with low C and
φ) but the changes in live load has not sensible
impact on strong soils with high shear strength.
3- With increasing soil cohesion in soldier pile
system, the amount of moment is reduced at first
and then it remains constant and thereby the pile
profile section becomes smaller with increasing
soil cohesion.
4- With increasing internal friction angle of soil, the
amount of created moment in soldier pile reduces
at first and then this moment remains constant.
References
1- M. Asqari, 2011, Investigation and valuation type of excavation
protection method by Soldier Pile system, a master thesis,
Islamic Azad University, Bushehr branch
2- A. Sarmad Nahri, 2008, principles of excavation and soldier
systems, Simaye Danesh publications.
3- Sabatini, june 1999, Ground anchors and anchored system, Us
department of-transportation
4-Vermeer, Pieter, 2000, Arching effects behind a soldier pile wall,
Computers and Geotechnics 28 (2001).
