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Analysis and simulations of erosion protection designs using the PLAXIS 2D
and Slide programs
Article in Japanese Geotechnical Society Special Publication · January 2016
DOI: 10.3208/jgssp.TC302-10
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Japanese Geotechnical Society Special Publication
The 15th Asian Regional Conference on
Soil Mechanics and Geotechnical Engineering
Analysis and simulations of erosion protection designs using the PLAXIS 2D and Slide programs
N. Chanmeei), D.T. Bergadoii), T. Hinoiii) and L.G. Lamiv)
i) Doctoral Student, Saga University, Saga 840-8502, Japan
ii) Professor, Asian Institute of Technology, Pathumthani 12000, Thailand
iii) Professor, Institute of Lowland and Marine Research (ILMR), Saga University, Saga 840-8502, Japan
iv) Postdoctoral, Institute of Lowland and Marine Research (ILMR), Saga University, Saga 840-8502, Japan
ABSTRACT
Along the zone of interaction between land and water, there are continually changes due to dynamic interaction of
water and land, so lots of problems occur such as Erosion, flooding, etc. Therefore riverbank and flood protection
structures have become useful in the past decades. The National Road NR.01B is built along the mountainous area
below the road is a river which flow parallel to the road alignment in soft shale area. There are 4 different stations
which were investigated at KM90+600, KM 92+125, KM 92+212.5 and KM92+512.5. Unusually heavy monsoon
rains, exacerbated by tropical storms, have caused widespread flooding in more than 60 per cent of the Lao PDR
from late June through August. The monsoon rains continued since, and the country endured almost continuous
heavy rainfall for some ten weeks. The forensic solution for erosion along the National Road is to use
geosynthetic for improving the stability of the erosion protection structures. PLAXIS FEM 2D analysis was
utilized to predict factor of safety for each station in case of low water and high water level. In each station of
erosion protection structure used same soil parameter due to the same locations. The Slide Software was utilized
to predict the value of factor of safety using Bishop, Janbu and Spencer methods in both cases of water level for
each flood and erosion protection structure by using the same soil and support parameters which was used in
PLAXIS FEM 2D Software. Moreover, comparing the best station between each erosion protection structures
were carried out. Furthermore, comparing the results from PLAXIS FEM 2D and Slide Software, the result from
PLAXIS 2D seems to have higher accuracy.
Keywords: Erosion protection, Finite element, Limit Equilibrium, Laos, Geosynthetic, Flood
1 INTRODUCTION
Riverbank area is the zone of interaction between
land and water and continually changes due to
dynamic interaction of water and land. When humans
have settled their residences near or next to those
areas, they have to face with lots of problems such as
Erosion.
Erosion is the process which soil and rock is
removed from the soil or rock surface by natural
phenomenon such as wind, water flow, rainfall,
glacier, etc. Then transported and deposited in other
locations.
For the erosion mechanism, detachment, transport,
and deposition are basic processes that occur on
upland areas. Detachment occurs when the forces of
rainfall drop impact or flowing water exceeds the
soil’s resistance to erosion. Detached particles are
http://doi.org/10.3208/jgssp.TC302-10
1075
transported by the splash of rain drop and flow water.
Deposition occurs when the sediment load of eroded
particles higher than its transport capacity. The
importance of these processes depends on whether the
processes are occurring on inter-rill or rill areas and in
the levels of the controlling variables. Eroded soil
particles mainly move from higher area to lower area
by flowing into rills and gullies. (Choi et al, 2002)
To mitigate the erosion problems, there are many
techniques such as the use of geosynthetics which is
very popular nowadays. Geosynthetics are planar
products manufactured from polymeric materials
which used with soil, rock, or other geotechnicalrelated materials, for the purpose of filtration,
drainage, separation, reinforcement, fluid barrier and
protection. The uses of geosynthetics provide cost
saving benefit but also for the purpose of erosion
control which can increase the resistance of
detachment of soil particles due to wind, water, rain
droplet. Erosion control geomat (ECGM) (Yee, 2012)
is widely use in flood dike which is a rolled groundcovering product that help or prevent or retard the
erosion process.
Vegetation technique also provides a protective
cover to the ground against surface erosion with lower
cost but less effective if compare to geosynthetics.
Moreover the combinations of techniques are also
applicable depending on the design of the dike and
requirement in different location and situation.
are 4 different stations which were investigated at
KM90+600 as shown in Fig 3 and 4, KM 92+125,
KM 92+212.5 and KM92+512.5 as shown in Fig 6 to
8, respectively and for the site in Fig 5.
Soil models and parameters of National Road
NR.01B in Laos are shown in Table 1
Table 1. Soil models and parameters of National Road NR.01B
Materials
γsat
kx = kz
ky
E'ref
(kN/m3)
(m/day)
(m/day)
(kPa)
ν'
c'
φ'
(kPa)
(deg)
2 STUDY AREAS
Shale
22
0.0004
0.0002
5000
0.25
120
60
Phongsali Province in Laos covers an area of
16,270 km2, out of which 77% has forest cover. The
province borders China to the north and west,
Vietnam to the east, Luang Prabang Province to the
south, and Oudomxai Province to the southwest as
shown in Fig 1. It is located high in the mountains,
approximately 450–1,800 m above sea level.
Filled
22
0.004
0.002
3000
0.25
30
31
Fig. 3. Station KM90+600 site
Fig. 1. Location of Phongsali Province, Laos
Unusually heavy monsoon rains, exacerbated by
tropical storms, have caused widespread flooding in
more than 60 per cent of the Lao PDR from late June
through August. The monsoon rains continued since,
and the country endured almost continuous heavy
rainfall for some ten weeks (Disaster Relief
Emergency Fund, 2013). Oudomxay Province, one of
province in northern part of Laos (next to Phongsali
Province) suffered from this situation as shown in Fig
2.
Fig. 4. Design of erosion control at National Road NR.01B in
Pongsali Province, Laos KM90+600
Fig. 5. Station KM92+125 to KM92+512.5 site
Fig. 2. Flooding in Oudomxay Province, Laos
The National Road NR.01B is built along the
mountainous area below the road is a river which flow
parallel to the road alignment in soft shale area. There
1076
structure. Each erosion scheme uses the same soil
parameters which were used in PLAXIS FEM 2D
Software.
4 FACTOR OF SAFETY PREDICTION FOR
EROSION PROTECTION IN LAOS
The prediction the factor of safety for each design
is considered in 2 cases which are low water level and
high water level.
The results in the case of low and high water level
are shown in Table 2 and 3, respectively. The
optimum Lao riverbank erosion protection in case of
low and high water levels simulated by both PLAXIS
FEM 2D and Slide Software was found to be at
KM90+600 as shown in Fig. 9 to 12.
Fig. 6. Design of erosion control at National Road NR.01B in
Pongsali Province, Laos KM92+125
Fig. 7. Design of erosion control at National Road NR.01B in
Pongsali Province, Laos KM92+212.5
Fig. 9. Total displacement and Factor safety from PLAXIS
FEM 2D of Lao riverbank (KM90+600) with low water
level
Fig. 10. Total displacement and Factor safety from Slide
Software of Lao riverbank (KM90+600) with low water level
Fig. 8. Design of erosion control at National Road NR.01B in
Pongsali Province, Laos KM92+512.5
3 FINITE ELEMENT ANALYSIS BY PLAXIS
FEM 2D AND SLIDE PROGRAM
PLAXIS FEM 2D analysis was used to predict the
factor of safety for each design in case of low water
and high water level.
Slide Limit Equilibrium software was utilized to
predict values of factor of safety using Simplified
Bishop, Janbu and Spencer methods in case of low
water and high water level for each erosion protection
1077
Fig. 11. Total displacement and Factor safety from PLAXIS
FEM 2D of Lao riverbank (KM90+600) with high water level
5 CONCLUSIONS
Fig. 12. Total displacement and Factor safety from Slide
Software of Lao riverbank (KM90+600) with high water level
Table 2. Comparative of values of factor of safety between
different stations of erosion protection in Laos with low water
level
Design
KM90+600
PLAXIS FEM 2D
3.76
KM92+125
3.01
KM92+212.5
2.96
KM92+512.5
2.99
Slide Software
Bishop = 4.37
Janbu = 4.68
Spencer = 4.55
Bishop = 3.63
Janbu = 3.44
Spencer = 3.58
Bishop = 3.09
Janbu = 2.94
Spencer = 3.08
Bishop = 3.69
Janbu = 3.46
Spencer = 3.63
Table 3 Comparative of values of factor of safety between
different stations of erosion protection in Laos with high water
level
Design
KM90+600
PLAXIS FEM 2D
4.32
KM92+125
3.29
KM92+212.5
3.26
KM92+512.5
3.30
Slide Software
Bishop = 4.72
Janbu = 4.81
Spencer = 4.84
Bishop = 3.89
Janbu = 3.63
Spencer = 3.75
Bishop = 3.39
Janbu = 3.24
Spencer = 3.31
Bishop = 3.93
Janbu = 3.64
Spencer = 380
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In this study, slope stability factor of safety of each
erosion protection were simulated by PLAXIS FEM
2D and Limit Equilibrium Slide Software.
The factor of safety from Slide Software always
show higher value compare to PLAXIS FEM 2D due
to the over predicted of Limit Equilibrium method.
From all the computed results from PLAXIS FEM 2D
and Slide Software, the result from PLAXIS FEM 2D
has higher accuracy if compared to the result from
Slide Limit Equilibrium Software.
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The Use of Geotextile Container for Shore
Protection Work at East Coast Park and Pasir Ris
Park in Singapore. Proceeding 5th Asian Regional
Conference on Geosynthetics, Bangkok, Thailand.
Disaster
Relief
Emergency
Fund
(2013),
http://reliefweb.int/disaster/fl-2013-000101-lao.
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in Hydraulic Environment. Proceeding 5th Asian
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