CUT-OFF WALL DESIGN USING PLAXIS

1. Presented by
MANISH SHARMA
M.TECH (Geotechnical Engg)
2020PGCEGE12
UNDER THE GUIDANCE OF
DR. A. K. SINGH
HOD, Department of Civil Engineering
NIT Jamshedpur, Jharkhand

2. CONTENT
 Introduction
 Literature Review
 Scope and Motivation
 Objectives
 Methodology
 Illustrative Example
 Model Validation
 Result and Discussion
 Conclusions
 References

3. INTRODUCTION
 The hydraulic structures are built on pervious foundations and water flows through the voids present in the
soil from high hydraulic head to lower head. This phenomenon of flow of water, movement of water through
the soil is called seepage.
 Cut-off walls are mainly installed in the subsurface to control horizontal movement of groundwater.
 Based on the requirement of depth, cut-off wall are mainly of two types
 Fully penetrating cut-off wall
 Partially penetrating cut-off wall

4. Location of sheet pile cut-off wall
 At centre
 At upstream end
 At downstream end
 Types of vertical cut-off wall
1. Rigid cut-off wall
2. Flexible cut-off wall
Fully penetrating cut-off wall (blocks seepage)
Partially penetrating cut-off wall (lengthens seepage
path)

5. Rigid Cut-off Wall
 There are mainly three types of rigid cut-off wall which
are as flows:
 R. C. C Cut-off Wall
 Sheet Pile Cut-off Wall
 Geo-membrane Cut-off Wall
 Sheet pile cut-off wall
 It has a long history as it is used for many
applications.
 The steel sheet pile cut-off wall is quite popular, as
they are easy to install.
 Thick steel sheet pile cut-off wall are designed for
long life.
Fig. 3 Sheet Pile Cut-off Wall

6. AUTHOR OBJECTIVE METHODOLOGY OUTCOME
Singh et al.
(2006)
To design a rigid cut-off
wall.
The seepage force on
active and passive thrusts
is calculated by
considering limiting
equilibrium forces acting
on a trial failure wedge.
There is approximately 10% between the
passive thrust for a rigid cut-off wall of
normal length computed by Terzaghi’s
method.
Mansuri et al.
(2013)
To introduce the
effectiveness of using
horizontal drain and cutoff
wall in reducing seepage
flow from an assumed
heterogeneous earth dam
Numerical simulation were
carried out using SEEP/W
software.
With increase of the cut off depth, the exit
hydraulic gradient reduces and with
increase of the horizontal drains length,
the seepage discharge increases, but it also
reduces piping danger.
Shayan et al.
(2015)
To investigate the
effectiveness of measures
of cut-off wall, drains and
blanket for reducing the
uplift pressure and exit
gradient
A laboratory model and
GEOSTUDIO software
was conducted for
investigating the effects of
cutoff wall’s angle on the
amount of uplift force,
seepage, and exit gradient.
It is observed that the best position of
cutoff wall to reduce seepage flow is at the
downstream end.
LITERATURE REVIEW

7. AUTHOR OBJECTIVE METHODOLOGY OUTCOME
Koda et al.
(2019)
To monitor the cut-off wall
and dewatering system as
an effective method of
contaminated sites
reclamation process
In this paper two case
studies were taken and the
two groups were set for
performing test.
The protection from ground water against
leachate is achieved by the containment
system consisting of cut-off wall and a
periphery drainage mainly.
Sivakumar et
al. (2019)
To analysis deformation of
suspended type cut-off wall
of diversion structures.
Two dimensions model is
prepared using FEM
software for analysing
deformation, stability and
ground water flow.
With the change in location of cut-off wall,
the effect on the analyzing parameter were
observed. The lowest and second lowest
maximum bending moment in cut-off wall
is at upstream and downstream end. And
the maximum seepage rate has been
observed at middle of dam.
Salmasi et al.
(2019)
Effect of Location and
Angle of Cutoff Wall on
Uplift Pressure in Diversion
Dam
Finite element method
using SEEP/W model a
part of Geo-Studio 2007
software was used
When the cutoff wall gets close to down
stream heel of dam and when the
placement angle gets more then there will
be decrease in uplift pressure

8. AUTHOR OBJECTIVE METHODOLOGY OUTCOME
Sazzad et al.
(2019)
To monitor the effect of
width, length and position
of cut-off wall on the
seepage characteristics of
earth dam
The numerical analysis of
the models of the earth
dam with cut-off wall
using SEEP/W.
The location of cut-off wall is most
important parameter for performing better
and effective performance, the effect of
width has negligible effect on velocity
and seepage discharge on dam.
Arnold et al.
(2020)
To describe the installation
of seepage cut-off wall
using cut-off wall using
Cutter Soil Mixing.
BAUER successfully
finished task work and
install cut-off wall to a
depth of 84 feet deep.
The CSM method was proven to be
successfully adaptable to the challenging
existing ground conditions, easy
adjustable wall depths and it also
included the replacement of unsuitable
organic soils.
Chai et al.
(2020)
Plastic-damage analysis of
concrete cutoff wall for a
concrete face rockfill dam
A 3D numerical model
that uses a plastic-damage
model for the stress–strain
relationship of the
concrete was developed to
predict the behavior of the
concrete cutoff wall.
The results indicated that the location of
the cutoff wall is a deterministic factor
affecting the behavior of the wall.

9. AUTHOR OBJECTIVE METHODOLOGY OUTCOME
Angelov et al.
(2021)
To investigate the
efficiency of cut-off wall
when it is placed at
various angle of
inclination.
The analysis was done by
using PLAXIS 2D.
The variations of angles
was from 00 to 1800
progressively in interval
of 30 degrees.
The minimum seepage discharge is
observed at 60 degrees and least value of
uplift pressure was observed at 120
degree.
Beiranvand et
al. (2021)
The investigation was
done to reduce seepage
from foundation and in
dam bodies.
A comparatively study
was observed between
instrument and numerical
analysis on seepage rate
and pore water pressure of
Evesham earth dam.
A very good and accurate result of
observed data and predicted data for pore
water pressure.
The sudden drop in pore water pressure
was observed at downstream end which
indicates the correct functioning of cut-
off wall.

10. SCOPE AND MOTIVATION
 We get some ideas about the working of cut-off wall and the effect of angle of inclination of cut-off
wall with respect to dam at various location.
 We have also studied that most effective parameter which is seepage force in the analysis and design
of cut-off wall
 Scope of the proposed study concludes that the analytical study as presented by Singh et al. (2006) of
rigid cut-off wall can be also analysed and designed using PLAXIX 2D and verification of results
can be made.

11. OBJECTIVE
 To perform the design of rigid cut-off wall using PLAXIS and compare with analytical result given by Singh
et al. (2006).
 The depth of sheet pile cut-off wall will be calculated up-to the required effectiveness.
 The objective is to develop a model and verified the results, ensuring the depth up to which it will be
effective.
 The various soil parameters and their effect on seepage force acting on various penetrated depth of cut-off
wall.

12. METHODOLOGY

13. Illustrative Example
 An illustrative example is considered to compute seepage force and details are as follows:
 Top width of dam bT = 5 m, base width b = 65 m, depth of rigid cut-off wall = 8 m, cohesion in foundation
soil c1 = 2 kN/m2, c2 = 12 kN/m2, angle of internal friction for foundation is ∅1 = 300
, levee soil ∅ = 150
,
specific gravity G = 2.6 and void ratio e = 0.4. The void ratio and specific gravity of levee soil and foundation
soil are taken to be the same for simplicity.
 Solution: The above problem is solved by PLAXIS 2D.
 The material property has been defined as dry unit weight of soil and levee (𝛾) is 18.21 kN/m2, saturated unit
weight of soil and levee (𝛾) is 21.02 kN/m2. The depth of cut-off wall is considered 12 m for analysis.

14. Parameters used in Modelling
PARAMETERS VALUE
Type of material Plate
Material type Elastic and Isotropic
EA (kN) 15.5 E6
EI (kN-m2/m) 4.51 E5
W (Unit Weight) –
kN/m3
10
Poisson’s ratio (υ) 0
PARAMETERS VALUE
Type of material SUBSOIL
Material model Mohr-Coulomb
Material behaviour Drained
Unsaturated unit weight
(KN/m3)
18.21
Saturated unit weight (KN/m3) 21.02
Void ratio 0.4
E’ 30.00E3
Cohesion(c) 2
Poisson’s ratio (υ) 0.3
Friction Angle (φ) 30
Angle of Dilatancy (ψ) 0
Groundwater parameter
Data Set Hypres
Model Van Genuchten
Permeability in Horizontal
direction (m/day), kx
0.01
Permeability in Vertical
direction (m/day), ky
0.01
Interface Reduction Factor
(Rinter)
0.5
Table 1 Parameters used in Cut-off wall
Table 2 Parameters used in Foundation soil

15. PARAMETERS VALUE
Type of material Fill
Material model Mohr-Coulomb
Material behaviour Drained
Unsaturated unit weight (KN/m3) 18.21
Saturated unit weight (KN/m3) 21.02
Void ratio 0.4
E’ 30.00E3
Cohesion(c) 12
Poisson’s ratio (υ) 0.25
Friction Angle (φ) 15
Angle of Dilatancy (ψ) 0
Groundwater parameter
Data Set Hypres
Model Van Genuchten
Type of soil Coarse
Permeability in Horizontal direction
(m/day), kx
5.0E-6
Permeability in Vertical direction (m/day),
ky
5.0E-6
Interface Reduction Factor (R ) 0.5
Table 3 Parameters used in Levee soil
Parameters reference
Sivakumar et al. (2019)

16. Fig. 4 Mesh view of Model
Fig. 5 Dam with Global Water Table
18 m

17. MODEL VALIDATION
 The results obtained from the numerical
analysis validate with analytical solution and
results are good agreement with Singh et al.
(2006).
 When dam base width is 65 m and height is 20
m, the validation of results of seepage force
are shown in Table 3.
Depth of cut-
off wall
Result of Seepage Force (kN/m)
for unit width of sheet pile cut-off
wall
Singh, et al.
(2006)
PLAXIS 2D
2 35.56 40.83
4 101.09 108.20
6 184.49 213.40
8 283.67 310.40
Table 3 Dam with base width 65 m

18.  When dam base width is 85 m and height is 20 m, the validation results for seepage force are shown
in Table 4.
Depth of cut-off
wall
Result of Seepage Force (kN/m) for
unit width of sheet pile cut-off wall
Singh, et al.
(2006)
PLAXIS 2D
6 161.76 180
8 248.99 267.40
Table 4 Dam with base width 85 m

19. Fig. 6 Seepage Flow through Dam without cut-off wall
RESULT AND DISCUSSIONS

20. Fig. 7 Seepage Flow through Dam by installing Cut-off Wall

21. Different Cases Studies
Case 1: Both side slopes as 1.5
0
50
100
150
200
250
300
350
400
0 2 4 6 8 10 12 14
Seepage
Force
(kN/m)
Penetrated depth of cut-off wall (m)
h1=18m h1=15m
h1=12m h1=9m
Fig. 8 Seepage Force Vs Depth of Cut-off Wall (Slope 1.5)

22. Case II: Side slopes of upstream side and downstream side 2.0
0
50
100
150
200
250
300
350
0 2 4 6 8 10 12 14
Seepage
Force
(kN/m)
Penetrated depth of cut-off wall (m)
h1=18m h1=15m
h1=12m h1=9m
Fig. 9 Penetrated depth Vs Seepage force for slope 2.0

23. Case III: Upstream side slope 2.0 and downstream side slope 2.5
0
50
100
150
200
250
300
350
0 2 4 6 8 10 12 14
Seepage
Force
(kN/m)
Penetrated depth of cut-off wall (m)
h1=18 m
h1=15
h1=12 m
h1= 9 m
Fig. 10 Penetrated Depth Vs Seepage Force for Upstream Slope 2.0 and Downstream Slope 2.5

24. Case IV: Effect of cohesion and angle of internal friction on seepage force
0
50
100
150
200
250
300
350
400
0 2 4 6 8 10 12 14
Seepage
force
(kN/m)
Penetrated depth of cut-off wall (m)
c1 = 2
c1 = 4
c1 = 6
c1 = 8
Fig.11 Penetrated Depth Vs Seepage Force Varying Cohesion and Angle of Internal Friction

25. Case V: Side slopes of upstream side and downstream side 1.5 and varying downstream water level
Depth of cut-off
wall (m)
Seepage force (kN/m) for unit width of sheet pile cut-off wall at
constant upstream water level and varying downstream water
level
h2 = 0 m h2 = 0.5 m h2 = 1.0 m
2 34.76 32.92 28.80
4 120.9 112.04 106.6
6 210.9 201.61 184.9
8 289.0 272.4 267.78
10 345.6 318.7 294.4
12 320.1 292.6 276.64

26. CONCLUSIONS
On the basis of the results and discussion the important conclusions are drawn as follows:
 Seepage force is decreasing with increase in base width of dam and levee for height and water level
constant.
 Effectiveness of depth of sheet pile cut-off wall can be ensured and it can be designed. After certain depth
for given condition, sheet pile cut-off wall is ineffective.
 It is obvious that seepage force acting on sheet pile cut-off wall increases with increase in upstream water
level.
 If head difference decreases then seepage force acting on cut-ff wall also decreases.
 Seepage force is decreasing as the cohesion increases and angle of internal friction decreases of
foundation soil.
 Hence, PLAXIS 2D can be conveniently used for computation of seepage force acting on cut – off wall
and accordingly, analyse and design the rigid sheet pile cut-off wall can be performed.

27. FUTURE SCOPE OF STUDY
On the basis of literature review and analysis through software, the value of seepage
force has been calculated and rigid cut-off wall is designed. This study can be used for
future study for below cases:
 An investigation can be done on multi-layered soil, with different soil parameters
(c & ).
 The effect of Geo- sheet can be used in place of cut-off wall is also a new scope of
study.

28. REFERENCE
1. Athani, S. S., Solanki, C. H. and Mohapatra, B. G. (2016), : “Strains induced around cut-off walls of earth dam
under full reservoir and drawdown conditions”, International Association of Lowland Technology, 297 – 304.
2. Beiranvand, B. and Komasi, M. (2021), : “An Investigation on performance of the cut off wall and numerical
analysis of seepage and pore water pressure of Eyvashan earth dam”, Iranian Journal of Science and
Technology, Transactions of Civil Engineering, https://doi.org/10.1007/s40996-021-00613-y
3. Evans, J. and Ruffing, D. (2021), : “ Design and specification considerations for cut-off walls”, DF-I45
conference.
4. Evans, J. C. and Daniel, D. E. (1993), : “ Vertical cut-toff walls”, Geotechnical Practice for Waste Disposal,
Chapter 17, 430 – 454, Chapman & Hall, London. https://doi.org/10.1088/1757-899X/471/14/04/2021
5. Jesmani, M., Mehdipour, I. and Ajami, A. (2011), : "Comparison between 2d and 3d behaviour of sheet piles by
finite element method", Kuwait Journal of Science and Engineering, Volume 38 (2B), 1–14.
6. Koda, E., Miskowska, A., Sieczka, A. and Osinski, P. (2019), : “Cut-off walls and dewatering system as an
effective method of contaminated sites reclamation process”, Material Science and Engineering, 1 – 8.

29. THANK YOU