Summary of Ph.D thesis: A study on the embankment caculation method reinforced by geotextile in the construction of highway in Vet Nam

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MINISTRY OF EDUCATION AND TRAINING
UNIVERSITY OF TRANSPORT AND COMMUNICATION





Hao Huynh Ngoc



A STUDY ON THE EMBANKMENT CACULATION
METHOD REINFORCED BY GEOTEXTILE IN THE
CONSTRUCTION OF HIGHWAY IN VIETNAM


Major: Construction of hightway and street
Code: 62.58.30.01


SUMMARY OF Ph.D THESIS

Hanoi, June 2014
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This thesis was completed at the university
of transport and communication



Supervisors: Prof. PhD Phung Vu Dinh
PhD Sy Vu Duc


Examiner 1: Prof, Dr.Sc Quang Nguyen Van
Hanoi Architectural University
Examiner 2: Prof, PhD Chuong Do Ba
National University of Civil Engineering
Examiner 3: Ass.Prof, Dr.Sc Can Nguyen Van
Hanoi University of Mining and Geology


This thesis is defended at the university of transport and
communication on h, , 2014.




Thesis can be found at:
1. National Library
2. Library of the university of transport and communication

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Publications

1. Hao Huynh Ngoc MS, Phung Vu Dinh Prof.PhD (2009), “Several
designing measures using geotextiles in order to stabilize weak soil in the
constructing of road and dam, dike”. Bridge and Road Magazine, N
o
.
Nov-2009, Page 8-11.
2. Quang Tran Dinh PhD, Hao Huynh Ngoc MS (2011), “Study of the
improvement for fabrication and construction of prestressed I beam l =
42m with continous thermo slad based on the construction of Hoa xuan
brigde- Danang city“, The Transport and communications magazine, N
o
.
Aug-2011, ISSN 0866-7012, Page 26-29.
3. Hao Huynh Ngoc MS, Phung Vu Dinh Prof.PhD (2013), “Probability of
instability of backfill construction from design perspective“, Bridge and
Road Magazine, N
o
. Aug-2013, ISSN 1859-459X, Page 19-22.
4. Hao Huynh Ngoc MS, Phung Vu Dinh Prof.PhD (2013),“The stability
caculation model of embankment (highways, dikes, dams) reinforced by
geotextile thanks to the finite element method and mention pull behaviors
of geotextile and relationship between stresses and strains of the contact
elements between embankment and geotextile“, Bridge and Road
Magazine, N

o
. Nov-2013, ISSN 1859-459X, Page 8-11.
5. Hao Huynh Ngoc MS, Vu Duc Sy PhD, Phung Vu Dinh Prof.PhD (2014),
“Slide curve analysis results of slope stabilization by finite element
method (HNH_RESS software) in comparison with analytic method “,
Bridge and Road Magazine, N
o
. Jan and Feb-2014, ISSN 1859-459X,
Page 38-41.













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INTRODUCTION
1 - Introduction to the study: Along with the strong growth in the application of
new materials technology in the world , Vietnam’s also very interested in the
study of materials using in geotextile reinforced embankment works roads , dikes
and dams . So that, the research methods completing for calculating results for
reliability problems embankment reinforced by geotextile in the construction of

roads in Vietnam becomes necessary .
Within the scope of this study , the author used the finite element method -
numerical method has several advantages in the present time to apply the
construction algorithm , based on the programming software suit Vietnam and the
conditions for a number of research results stability problems , stress - state
deformation embankment , proposed making calculations and charts used in
utility design .
2 - Reasons for choosing topic : To complete calculation methodology for
problem embankment using geotextiles in the construction of highways
3 - Purpose : Develop computational models roadbed embankment reinforced by
geotextile , contribute to improve the calculation method actually worked closely
with the material and the ability to predict an instability correctly in order to bring
high efficiency , ensure technical requirements designed embankment geotextile
reinforcement
4 - Research Subjects : The land cover using geotextile in road works background
5 - Scope of the Study : Selection , calculation model building problem
embankment geotextile reinforcement . Construction algorithms and computer
programs using the finite element method . Look at the problem embankment
geotextile reinforcement .
6 - The meaning of scientific and practical subjects : geotextiles is a new material
made from synthetic polymer materials or products related to the polymer through
different manufacturing technologies together. Since the 70s of last century
geotextile fabric was born in the western world . Due to the interesting properties
of geotextile Vietnam should have quickly been used to enhance reinforcement
load capacity and stability for the construction, especially the building
embankments in road and bridge construction and irrigation
The early years of the '90s - last century, geotextiles are widely used in many
countries such as France , the Netherlands , the U.S. and Japan , particularly in
Southeast Asian countries like Thailand , Philippines , Indonesia , Malaysia , in
our country , geotextile be put to use building the road since 1993 and more using

widely. According to a study by experts at home and abroad show geotextile used
in the construction of high embankment of earth or embankments on soft soils are
effective economic and technical, easy simple in construction, reduced costs from
15-20%, increase quality of use, the life of the facility .
Thus the complete study methodology , embankment design using geotextile
reinforcement is needed to serve the practical requirements in the integration and
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implementation of industrialization and modernization development of the
country
CHAPTER 1 OVERVIEW ABOUT USING AND CALCULATION METHODS
OF GEOTEXTILE REINFORCEMENT EMBANKMENT
1.1 . The study used calculations and embankment geotextile reinforcement at
home and abroad
1.1.1.Historical development and use of geotextile .
1.1.1.1 . Introduction : geotextile appear first Bidium trade name in the 60s of the
last century in France, but has not been noticed and used very little. Since 1975,
the geotextile is more complete study of water from the development phase,
calculation methods and construction technology. Geotextile is used for rapid
reinforcement enhance the load capacity and stability of the construction work in
general and especially the ground up for work in the construction of roads and
irrigation. In the 80s of the last century geotextile is widely used in many
countries such as France , the Netherlands , the U.S. , Japan , China , India , South
Korea , especially in Southeast Asia : Thailand , the Philippines , Indonesia ,
Malaysia,Brunei
In 1993 our country geotextile was first used in the project to upgrade Highway 5
(Ha Noi - Hai Phong ) by the Design Consultant Company KEI - Japanese design
with over 500,000 m2 of geotextile is to effectively handle embankment on soft
ground . And from 1995 till now, geotextiles have been used a lot with different
functions in various projects such as road construction project to upgrade National
Highway 1, QL10, QL18, NH3, highway 51, QL32, QL38, QL39 and in

construction projects like highways : highways Ho Chi Minh City - Trung Luong
, Thang Long Boulevard ( away from Lang Hoa Lac ) , high speed Hanoi - Hai
Phong Expressway Gie - Ninh Binh , Noi Bai - Lao Cai Highway Long Thanh -
Dau Giay Expressway and Ben Luc - Long Thanh
1.1.1.2. Classification of geotextile [14] , [28] , [29] , [30] Based on the
fabrication technology , geotextiles are classified into two types : woven
geotextile and silk geotechical kind of non-woven .
Some evaluation criteria geotextile : Appendix 1 : Table 1.3 introduces the main
physical and mechanical by application of geotextiles ; Table 1.4 specifications
polyfelt TS nonwovens ; Table 1.5 and Table 1.6 non-woven geotextile HD -
Vietnam [ 50 ] .
1.1.1.3 The function of geotextile [13] , [14] , [27] , [31] , [34] , [35] , [36] , [38] ,
[44], [56], [58], [61], [62], [63], [66], [68] .
1 . functional separation between the layers of material together ( separation )
Geotextile separation layer is made between the buffer layer of sand and mud
below , separated between subgrade below ( subbase ) and the bottom layer of
pavement covered with sand on top .
2 . Functional soft soil reinforcement (reinforcement) For high embankments on
soft ground , it reaches a certain height sliding platform will emerge - the whole
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block sliding , sliding local slope should therefore use geotextile TECHNICAL
reinforcement . Geotextile can also be used in case of reinforced soil need not
weak but the background causeway .
3 . Geotextile reinforcement retaining wall (wall soft key) to increase the ability to
land up tall retaining wall , or steep to 900 degrees , people use geotextile wall
build certainly unsatisfactory medium height wall covering , durability and use
landscaping aesthetics but cheaper from 25 % to half of the reinforced concrete
wall [14] , [19] , [34] , [44] , [45] .
4 . Function filtering , drainage behind the retaining wall ( drainage ) ( or a system
of underground drainage embankment works on traffic , irrigation ) , was

previously used as filter bed material particle counter - with a grading of certain
materials . For the first time in Vietnam , the filtering function , drainage was
used in the retaining wall of the path to the bridge on National Road 1 , Tan Thinh
, Hanoi - Lang Son .
5 . Geotextile to function absorbent They lowered groundwater levels using
geotextile wrap small aggregate materials for drainage , underground drainage
pipe wrap before sanding , enveloping material macadam when no drainage tube ,
which take the form of crushed stone material cut trapezoidal openings no
drainage pipe , make waterproof layer functions to lower groundwater levels .
6 . Protection, erosion control embankment dykes and dams and roof slope
erosion
Geotextile is used for erosion control function [ 31 ] , protecting eroded slopes not
to damage the roadbed , the ditch along the road , slope erosion control line ,
dikes , dams , bottom of the canal , filling the polder areas , riverine lake
embankment , slope areas upstream and downstream river , especially through
space segment of river basin narrow bridge eg erosion in the upper and
downstream of the bridge : Phu Dong bridge ( over the river road) , Nhu Nguyet
bridge ( over the river bridge ) , Suong Giang bridge ( over the River Trade) on
National Highway 1, Hanoi - Lang Son .
7 . Geotextile tubes geotechnical work (Geosolution SI) [35]
Geotextile tubes used are diverse with many different forms : people
unfortunately get into geotextile tubes and fill with sand , lined shore erosion
protection levees , buildings along the coast sea .
1.1.1.4 The construction projects have used geotextiles in Vietnam
1 . With geotextile separation layer functions as project to upgrade Highway 5 in
the year 1993-1994 , expanding the old road surface by 20 meters on the main
embankment . It separates the function of geotextile , road systems in urban areas
Trung Hoa - Nhan Chinh (Hanoi) , before spreading the layer of macadam people
to spread a layer of geotextile Specifications for separating the sand embankment
that separates below the mixed layer between the sand and stone chips easily lead

to unstable surface . With this function geotextile was also used in the upgrade of
Highway 5 , National Highway 1 , QL10 , QL18 and some highways such as
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Highway District. Ho Chi Minh City - Trung Luong ; Gie - Ninh Binh , Noi Bai -
Lao Cai , Ha Noi - Hai Phong , Ha Noi - Thai Nguyen Also geotextile is used
in landfills to make division between land and the class rubbish such as landfill
bottom liner Tam Tan (Cu Chi , Ho Chi Minh City , 2011) , landfill Bo Trach
district (Quang Binh) , landfill Nhon district (Binh Dinh) , Hung Yen city landfill

2 . Geotextile reinforcement function embankment on soft soil : In the years 2000-
2003 , before the construction of embankments online Troi - Vu Oai [ 40 ] , grade
III Delta (Quang Ninh) , chaired set design was used 2 , 3 layers of geotextile
separation layer by doing medium duty reinforcement for embankment on soft
soil . Also in 2002, on National Highway 1 bypass the city of Vinh [ 39 ] design
chair used as geotextile separation layer between the soft soil at a depth of 80cm
and digging up sand poured on . Then continue to use 3 more geotextile layers ,
each layer separated by 40cm to reinforcement training background ( 80cm ) and
section 4 ÷ 5 m high embankment . Two works have exploited so far ( 2013 ) is
more than 10 years , very good quality . This is the process of using geotextiles to
handle embankment on soft soil for the first time in Vietnam , simple construction
, reduced construction costs . Two works make a good premise for the use of
geotextiles for reinforcement of soft soil embankment on many other road
construction projects such as highways , Ho Chi Minh City - Trung Luong , Gie -
Ninh Binh, Ha Noi - Thai Nguyen, Noi Bai - Lao Cai,… .
3 . Geotextile for erosion control functions When slope embankment built to
protect the coastline of Bai Chay - Quang Ninh , geotextiles are used to spread on
the embankment slope surface , then place over the stones deck form concrete
brick cement to prevent erosion of the dam due to heavy pressure waves . Also
geotextile was also used to protect , reinforced slope reservoirs such as reservoir
park Lao Cai city center ( designed in 2000 by the Department of Transportation

as an investor in Lao Cai ) , two lakes Regulators at the National Conference
Center - Hanoi, designed by the German Advisory also used as geotextile layer of
protection against erosion . National Highway 1 Improvement Project paragraph
Hanoi - Lang Son PMU18 represented by the investor , in the period leading to
the Phu Dong Bridge ( River road) , As for the Moon ( The River ) , Xuong Giang
Bridge ( River Trade) , one also used geotextile layer to protect against river
erosion in the upper two side roofs - three downstream of the bridge .
4 . Geotextile material is used instead of filter layer upside down on National
Highway 1 bridge , Tan Thinh - town ( Lang Giang , Bac Giang ) section between
Tan Thinh bridge and railway bridge ( the old National Road 1 ) length of 80m
people built construction of reinforced concrete retaining walls with a height H =
7.2 m in 1998 . At the bottom of the side walls of poured gravel embankment was
then coated with a layer that geotextile before covering background material to
replace the filter bed to the opposite wall at the foot drainage .
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1.1.2 The calculation method geotextile reinforcement embankment: The analytic
methods reinforced embankment calculated to assess stability using limit
equilibrium methods ( force or torque ) and is accompanied by is the use of partial
coefficients, respectively [15], [63] .
1.1.2.1 Methods of analytical calculations have reinforced embankment on soft
ground [ 2 ] , [ 3 ] , [ 7 ] , [ 9 ] , [ 15 ] , [ 16 ] , [ 17 ] , [ 21 ] , [ 32 ] , [ 33 ] , [ 35 ] ,
[37] : Reinforcement is placed in the internal ground and even in body
embankment , to prevent damage due to shear through the embankment itself or in
shear zones soft soil .
1 . Locally stable [7] , [15] , [32] , [33] : Check the local stability of the
embankment slope under the following inequality :

(1.1)
H : height embankment ; Ls : length of horizontal side slope (the slope foot width)
; φ'cv : friction angle of embankment materials at large deformation effective

stress conditions ; fms : partial material factor applied to φ'cv tg ( fms = 1 ) .
2 . Stable circular slide (sliding surface analysis method) : analysis of sliding
surface method is used most commonly in circular sliding stability calculations
for embankment using reinforced embankment placed at the bottom . The torque
caused by the land sliding and load M
D
as :
(1.2)
M
RS
torque by keeping the land :
Torque remains enhanced by keeping M
RR
:

(1.4)
in which: ffs is the partial load factor of unit weight of soil ; wi : the weight of soil
column i ; bi : the ith soil column width ; αi : angle tangential bottom soil column
with the ith lateral Rd : radius circular slip ; fms : partial material factor applied to
tgφ'cv ; φ'cv : friction angle at the base construction material in large deformation
effective stress conditions ; ui : pore-water pressure effects on the ith sliding piece
Troj traction required for 1 meter long embankment at each point along the
bottom of the embankment j is defined as :

(1.5)
Among them : YJ ¬ arm is in the vertical direction of the torque to the dangerous
sliding surface at the center point on the bottom of the embankment j ; MRRj :
largest holding torque by strengthening core at point j on the bottom of
embankment ; MDJ : maximum torque slip at the bottom of the embankment j
(human factor has been) ; M

RS
j : keeping the largest torque generated by the soil
at the bottom of the embankment point j (human factor has been) .
1.1.2.2 Method of computation analysis on reinforced soil embankment good
natural
1 . Where the external stability of one or more results to sabotage occurs,
treatment options may ways , such as reducing roof slope embankment ,
increasing the width column layout , using quality packing material good quality ,
enhanced by the foundation soil reinforcement measures , counter pressure pad ,
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packing material used is lightweight , reinforced combinations in various high
level , more layout drainage system to reduce pressure pore water pressure , or
combined treatment options in [15] , [32] .
2 . Internal stability [ 15] , [32] , [33] , [35] , [57] , [53] , [63] The method of
calculating reinforced embankment on the basis of gender balance method and
use the term partial coefficients corresponding to limit state are calculated .
Includes :
a. Method two wedge blocks ( slip surfaces kinked shape ) [12] , [15]
Driving forces synthesis ( synthetic human disturbance ) in the case of a slope no
more subject to external load is calculated as :

( 1.7 )
Among them : the human R
h
disturbing synthesis of 1m length along the slope ;
ffs is the partial factor applied to the unit weight of the soil , K is the ratio of
stress ( pressure ) horizontal and vertical stress ; ɣ is the unit weight of the soil ;
H is the height of embankment .
To pull off being reinforced , reinforced distance vertically is determined from the
expression:

(1.8)
Among them : Svj gap remains vertical in slope at j ; Tj is the greatest traction in
the 1 m core length in slope at j ; ffs the partial load factor applied to the weight
unit volume of soil , hj is the height of the embankment on the slope j ; f
q
is the
partial load factor applied to the external load , ws is the external load due to
static load ( evenly distributed on the surface at structure [ 15 , p . 10 ] ) .
Paragraph anchor Lej not happen to slip reinforcement is determined from the
limit state vandalism , anchor length remains satisfied [ 15 , p . 118 ] .

(1.9)
Among them : L
ej
is reinforced anchor length minimum calculated at j ; fp : partial
factor control remains pulled slip phenomenon , fn : partial coefficient control
works damaged due cause ; fms : partial factor applied to tgφ'p and c ' , ws :
external load , α ' : interaction coefficient indicates the relationship between
power and ground anchor reinforced with tgφ'p ; φ'p : corner resistance biggest
cut of fill materials ; αbc ' : stickiness factor denotes an anchor link between soil
health - reinforced with c ' c ' : effective cohesion of the packing material .
Comment crease sliding surface method
- The method of calculating " wedge block two " not consider the effects of
horizontal thrust due to the inclination of the upper surface created ( only
considering the vertical force is the weight soil ) . " Block wedge two part " is a
general form of the limit equilibrium method . This method has the advantage of
simplicity , the present destructive potential can determine the approximate
gradually in a wide range . In addition, this method is also easy to set up a loop
calculation program on your computer. Crease sliding surface method is used in

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case of ground sandwiched between soft soil [12] , occurred sliding surface will
follow the crease sliding surface soft soil layer , this case Fsmin safety factor is
determined principle of sliding block fragmentation , applied to heterogeneous
soil types ( sandwiched weak soil layer ) .
b . The method for calculating fragmentation circular slip surfaces [12] , [15] ,
[32] , [33] , [35] , [49] , [65] , [63] The assumptions for the fragmented approach
to circular slip surface properties of the reinforced embankment interaction forces
between the fragments are ignored because of the complex remains influential to
the power and presence of sliding soil core makes little disturbed . In addition, the
method also assumes interaction force between the core is ignored and the core
layer are horizontal ; remains only to be considered at the position sliding surface
intersects with assumptions at each piece separately ; torque to keep the combined
effects of soil aggregate and not less than slipping torque caused by the weight of
soil ( with interest calculated torque rotary sliding blocks ) . Thus equilibrium
conditions need to satisfy to solve the problem :

(1.10)
Where: M
D
sliding torque caused by the weight of the soil itself and external load
; M
RS
: torque due to a shear strength of the soil ; M
RR
: holding torque due to the
presence of aggregates in slope ( 1.11 )
Where: Tj is the greatest traction in core in slope at j ; yj : j distance to the center
core layer sliding Y axis ; ffs : partial factor applied to the unit weight of the soil ;
f

q
: partial factor applied to the external load , Wi : weight of the ith soil column ;
Wsi : external load acting on the piece i c ' : unit cohesion of fill materials
identified in effective stress conditions , ui : pore water pressure exerted on the
sliding surface in pieces i ; φ'p : maximum shear angle of fill materials ; fms : the
partial material factor applied to tgφ'p and c ' ; : adjust the torque coefficient (
limit state damage taken by 1.25 , limit state obtained by using 1.0 ) .
In length it remains to be determined not undermining slip occurs remains is :
(1.14)
L
ej
is reinforced anchor length at least j in slope ; fp : partial coefficient to control
the core is pulled slip phenomenon , fn : partial coefficient to control the
economic consequences caused by damaged buildings cause ; fms : partial factor
applied to tgφ'p and c ' , ws : external load ( due to static load ) , α ' : interaction
coefficients indicate the relationship between power and ground anchor reinforced
with tgφ ' p ; φ'p : maximum shear angle of fill materials ; αbc ' : stickiness
coefficient indicates the relationship between soil anchor strength - reinforced
with c ' c ' : effective cohesion of the packing material .
Slip circle method was developed by [48] : K. Terzaghi , AV Bishop ; G.B. Janbu
; A.A. Nichiprovich ; Theory Method humidity .
Comment circular slide fragmentation methods : Method assuming stable sliding
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surface with a radius R , are commonly used calculations to figure out the most
dangerous slip with a safety factor Fsmin . Slip circle method can calculate the
slope stability is generally different shapes , suitable only for homogeneous soil .
Essence reinforcing factors to be considered tensile strength Tmax .
c . Some other computational methods for reinforced embankments based on
equilibrium torque or force .
i . The method combined stress calculations [15] , [32] , [33] The destructive

method combined stress calculations , is determined on the basis of combined
stress theory and the method of analysis according to Mohr interest . In the final
analysis , this method is somewhat more complex but potentially better analysis
can be reviewed by the local variation of stress .
ii . The method calculates the logarithmic spiral slip surface [15] This method ,
assuming slip surfaces logarithmic spiral has simplified the calculations , can be
directly determined torque causing imbalance . Holding torque ( due to the
presence of aggregates in slope M
RR
) must be greater than the torque cause
imbalance (M
0
), ie, M ≥ M
0
.
Among them : M
RR
is the torque due to a presence of aggregates in slope , Mo :
torque imbalance caused by slope (1.15)
Where: Tj is local tension of the fabric at j ; YJ : the core layer j distance to the
center of the Y -axis slide .
(1.16)
f
fs
is the partial factor for the unit weight of the soil ; f
q
: partial coefficients for
external load ; wi : ith soil column weight ; Wsi : external load acting on the piece
i ; u
i

: Pore water pressure effect on the ith sliding piece ; : torque correction
factor . The length of the anchor reinforcement is also determined by the formula
(1.14)
iii . Gravity method cohesion (Rankin) [15] , [35] , [63] This method of
calculation applied retaining wall is adjusted to calculate the slope remains the
case . In calculating principle applies two wedge blocks but adjusted to determine
how lateral pressure of the soil and the connecting points of greatest traction
corresponding to the tilt of the structure .
Comment analytic methods .
The analytical method based on limit equilibrium , embankment stability analysis
using assumed sliding surface : circular , with every crease assumed sliding
surface found a corresponding safety factor . So should identify numerous slip
surfaces with values different safety factor . Therefore, the ability to find the most
dangerous sliding surface with safety factor hardly accurate fit . Circular sliding
surface method is mainly applied to homogeneous background ; kinked slip
surface applied to multi-layered backgrounds , different physical properties . The
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analytical method applied in the case of computational geometry embankment
sections normal , relatively simple . Not yet reviewed analytical methods to elastic
modulus ( E ) of land , land cover , and reinforcement material stiffness ( EA ) of
the reinforcement material in the background .
1.1.2.3 Numerical methods and computational software
1 . Method extreme Gauss principle and finite difference [8] extreme method
Gauss principle by GS . Prof. Ha Huy Cuong proposed , Hoang Dinh Dam
authors consider the problem in the absence of reinforcement layout and software
problems have reinforced horizontal . This problem is multi-layered elastic
system , relations between state suat_bien application form on the basis of elastic
theory for the case of plane strain problem . In the case of reinforced embankment
, to determine the state of stress - deformation of the embankment below the
horizontal reinforcing effects of vehicle weight ( distributed on a circle with a

radius defined ) is asymmetric problem axis , Hoang Dinh Dam authors have used
finite difference methods to calculate .
2 . Basis of a calculation software program .
a. Geo.Slope Software ( Canada ) [10] , [11] , [12] , [20] , [22]
Stability calculations : Theoretical Foundations of stability calculation in the
program Geo.Slope balance of power and torque to balance safety factor based on
the theory of general limit equilibrium ( General Limit Equilibrium - GLE ) .
As of stress , deformation : finite element method is applied in this problem based
on stability problems limit equilibrium . Variables , the factor of safety obtained
from using limit equilibrium methods . Thus , the factor of safety (Fs) is
calculated by finite element software is regarded as a stable factor in Slope / w , is
defined as the ratio of the total jet cutting along the sliding surface ( ΣSr ) to the
total shear stress along the slip surface that (ΣSm) :


b . Plaxis software (Netherlands) In the stability analysis and slope deformation
problem embankment using geotextile , see Plaxis model stress-strain relationship
of geotextile and contact elements between geotextiles for ground assuming ideal
elastic plastic Mohr - Coulomb as picture 1:27
Finite element method determines stability safety factor method decreased c - φ
read as follows :
,
,
ui
ii
s
r r u r
s
tan c
F

tan c s


  
(1.19)
Among them : , and is the friction angle , unit cohesion and undrained cohesion of
the ground ; , and is the friction angle , cohesion and unit cohesion was not
impaired drainage of land background . The decline in value is calculated as
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
31
E
2sin

3
1-sin
2c cos
1-sin

1
follows
arctan
i
r
s
tan
F







;
i
r
s
c
c
F

and
,
,
ui
ur
s
s
s
F

(1.20)
c . Software phase2 ( Canada ) phase2
software calculates stability analysis and slope
excavation constructed by FEM method , find
the safety factor method decreased by c - φ .
Phase2 Plaxis see similar stress-strain relationship of geotextile and contact
elements with geotextile ground is linear Mohr - Coulomb model in Figure 1.27
Comments calculation methods : The software presented above are considered in
calculating the drag system behavior of geotextile and contact elements geotextile

with elastoplastic ground is ideal , the standard linear Mohr - Coulomb vandalism.
In fact , this relationship is complex includes several different stages according to
Robert M.Koerner model is presented in the next chapter . Therefore, in
calculating not realistically describe the material work .
Compared to other analytical methods mainly solved the problem of slope normal
shaped , circular slip surfaces , kinked hypothesis , based on the limit equilibrium
calculations taking into account the intensity geotextile ART but not considering
the elastic modulus (E) of land , the reinforcement material and stiffness (EA) of
the reinforcement material , the finite element method to calculate all kinds slope
different shapes , which consists of multiple layers embankment complex nature ,
the safety factor is defined as unique and single sliding surface based on the
consideration transferred in the element node . On the other hand , the finite
element method also include many factors affect the elastic modulus of the
ground , elastic modulus , hardness of structural reinforcement material in the soil
; Compared with organic difference method limit approximation problem by
differential equations , applicable only basic rectangular in shape with a simple
relationship , while finite element methods solve approximation results by word
solution of the problem , the background can be applied to any geometric shape
and have complex boundary problem in discrete relationships . From the
comparison presented above shows the finite element method has several
advantages compared to other methods .
1.2 These issues exist which thesis research will focus .
1 . The calculation methodology slope stability embankment with or without
reinforcement geotextile materials , commonly used analytical methods according
calculate equilibrium limit based on the assumption sliding circular , sliding
surface kinked hypothesis . However, numerous studies around the world show
that the slip surface is not sliding round and should be studied by the proposed
calculation methods [15] , [57] , [60] .
2 . Calculations embankment stabilization geotextile reinforcement method
- 11 -

analysis considering only the intensity of the geotextile (Tmax) without
considering the stiffness of geotextile (characterized by elastic modulus eg) .
3 . Relationship stress - deformation of the geotextile is a complex non-linear path
. Therefore need to develop computational models suitable for materials which
have ties pull this complex behavior .
4 . Tension Tmax values of geotextile -reinforced embankment should be studied
to determine the calculated value at each point (location) of the layer of geotextile
-reinforced embankment reaching the limit state intensity .
5 . The study determined the effect of hardness (EAg) geotextile to the safety
factor embankment stability .
6 . The study reinforced embankment geotextile on : the number of necessary
geotextile use , embankment slope coefficient , strength and stiffness of geotextile
reinforcement affect safety fine the embankment , should be studied computation .
From the experimental results calculated to draw the graph using geotextile ,
serving for quick reference in the preliminary design work embankment geotextile
reinforcement .
1.3 Objectives of the study : Select models and algorithms built computer
program problem embankment geotextile reinforcement by finite element method
. From this set , solve real-world problems in construction of reinforced
embankments and suggest that problems exist thesis focused research .
1.4 Contents of Applications Research geotextiles in the construction and
computational models embankment geotextile reinforcement in the world and
Vietnam . Computer model stability problem , embankment reinforcement
permeability of geotextiles by the finite element method . Compared with other
programs , other software in the world and Vietnam to establish algorithms and
computational software program for research .
1.5 Research Methodology : Based on the construction of computational models
using the finite element method , established algorithms and software programs
compare with the calculation methods and programs in and outside the country,
solving accounting and proposed outcomes achieved . Selection and calculation

model building problem embankment reinforcement geotextile material is
presented in the next chapter .
CHAPTER 2 COMPUTATIONAL MODELS OF GEOTEXTILE
REINFORCED EMBANKMENT PROBLEM .
2.1 Purpose and requirements .
2.1.1 Purpose : Selection , calculation model built using reinforced embankment
soft materials describes geotechnical realistic work of structural materials in the
system " soil - core " FEM method study the parameters affecting the stability
analysis and stress states - deformation of reinforced embankment
2.1.2 Requirement calculation model towards working closely with the actual
materials in structural system " + core land " was modeled and selection of
materials characteristic landforms, such that proper reinforcement case .
- 12 -
2.2 Properties of Geotextile [42] , [62] , [63] .
2.2.1 Some properties of the concept of geotextile [62] , [63]
Within the scope of this thesis , the hardness is not used in accordance with the
concept of bending stiffness hardness concept here is understood as : ( EA / L ) is
the stiffness of the unit element bearing axial bar , model chemical element
geotextile in finite element problems . And so EA is called the element stiffness
geotextile , unit is kN .
2.2.2 Road relations stress - deformation of the geotextile
According to the model of Robert M.Koerner in " Designing with Geosynthetics "
, 5th Edition, (USA, 2005) [63] , depending on the geotextile fabricating various
relationships that last curve behavior quite complex . Some types of geotextile
typical path ties stress - deformation characteristic is shown in figure 2.1 .

According to Robert M.Koerner , stress-strain relations of contact elements with
geotextile ground in a laboratory slide relations includes several phases : phase
nonlinear , 0 - 1 , increasing stress and deformation continued slow growth , the
period re- durable (hardened) - paragraphs 1-2 , to increased stress and

deformation increases , and the softening phase - paragraphs 2-3 , to reduce stress
and increase distortion. That relationship is shown in Figure 2.2
2.2.3 Some examples of determining mechanical properties of geotextiles [63]
2.3 Modeling the problem: FEM method in the Plaxis program , Pharse2 are
considered stress - related deformation of the geotextile pull is ideal elastoplastic
Mohr - Coulomb modeled (Figure 1.27) . That is the road slope - related stress as
linear distortion (this slope is characterized by elastic modulus geotextiles) . Then
, when the state of intensity , the geotextile will be destroyed immediately .
However, according to Robert M. Koerner model of the stress - deformation of
the geotextile is a non-linear path consists of several stages (Figure 2.1) . So
depending on the degree of deformation of the geotextile that the stress state will
be different . The following section will build computer model problem
embankment geotextile reinforcement by finite element method . In particular ,
the specific relationship stress - deformation of the geotextile is built in a
- 13 -
nonlinear model of Robert M. Koerner .
2.3.1 Some assumptions : Assumptions ground up n type, the background is one
or more natural soils , each soil layer uniformity . Soft geotextile reinforcement
placed in a soil layer or between two layers of soil . Minutes embankment slope
m1 , m2 , mn . View the soil is elastoplastic multi-layered system , each layer is
characterized by elastic modulus Es , Poisson's ratio ν and intensity characteristics
as unit cohesion c , friction angle  . View reinforced elastic plastic material
resistant traction only , not pressurized , which is characterized by (Eg) elastic
modulus, hardness Eag and tensile strength Tmax.
2.3.2 Develop computational models stability problem of reinforcing soft
embankment according to the finite element method [23]
2.3.2.1 The basic equations of the theory of elasticity [1], [24]
According to Hooke's law , the relationship between the stress-strain response by
the formula:
 

 
 
 
 
 
1
1
1
21
21
21
x x y z
y y x z
z z x y
xy xy
yz yz
zx zx
E
E
E
E
E
E
    
    
    








  


  


  







(2.2)
2.3.2.3 The safety factor method decreased c - φ
The safety factor is calculated as the ratio of the actual resistance and the
minimum resistance as follows : (2.20) or
(2:21)
Among them : , and is the friction angle , unit cohesion and undrained cohesion of
the ground ; , and is the friction angle , cohesion and unit cohesion was not
impaired drainage of land background .
The decline in value is
arctan
i
r
F

tan
S






:
i
r
F
c
c
S

and
,
,
ui
ur
F
s
s
S

(2.22)
Comment calculations by the finite element method taking into account many
factors characteristic of the ground and reinforcing materials such as elastic
modulus ground ; strength , elastic modulus , hardness reinforcement material .

Finite element method to find stability safety factor in the decline of the iterative
solution c - φ .
In the next chapter will focus on building research program algorithm and FEM
- 14 -
calculation method to calculate math embankment reinforced by geotextile . In
particular , the program will build computer algorithm analysis according to the
relational model stresses - deformation of the geotextile by Robert M.Koerner .
This model has not been built in algorithm programs around the world as :
Geo.Slope ; Plaxis or Pharse2 . This is close to the actual model of the kind of
work geotextile material which is related stress - deformation complex is given in
Robert M.Koerner Designing with Geosynthetics , 5th Edition [63] in 2005
previously in this document and in the 1986 version does not have version 1990
or have incomplete model stresses - deformation of materials geotextile.

CHAPTER 3 THE PROGRAM ALGORITHM AND SOFTWARE TO
ANALYSE GEOTEXTILE REINFORCEMENT EMBANKMENT BY FINITE
ELEMENT METHOD
3.1 Develop algorithms .
3.1.1 triangular plate element [18], [24] .
A flat block structure can be divided into three nodes triangular element . Each
displacement element has six degrees of freedom located at the nodes . The
buttons are numbered 1 , 2 , 3 in the opposite direction clockwise . The matrix
elements of the triangle is given by the general equation is rewritten as follows :
              
e
T T T
e
k B E B dV h B E B d Ah B E B

   


(3.2)
3.1.2 Element level parametric triangular plates [18] , [24] , [64] Coordinates any
point in the element coordinates interpolated from nodes: .
1
1
n
e
i
i
N



,
1
n
e
ii
i
x x N



, and
1
n
e
ii
i

y y N



( 3.4 ) displacements at any point in the
element displacements are interpolated according to the button :
1
n
e
x xi i
i
u u N



,
1
n
e
y yi i
i
u u N



(3.5)
The form function of triangular plate element 3 knots written as class parameter
11
N



;
22
N


;
3 3 1 2
1N
  
   
(3.6)
The form function of triangular plate elements are nodes 6:
 
1 1 1
21N


;
 
2 2 2
21N


;
 
3 3 3
21N



;
4 1 2
4N


;
5 2 3
4N


;
6 3 1
4N



Stiffness matrix of triangular plate element written in the local coordinate system
is:
         
1
1
1
21
00
TT
e
K B E B dV h B E B J d d





  
( 3:13 )
The integral in Eq (3:13) can be done by using numerical integration are:
- 15 -
   
1
1
1
1 2 2 1 1 2
1
00
, 0.5 ,
n
i i i
i
f d d W f

     





(3:14)
3.1.3 Mohr - Coulomb model [ 33 ] , [ 54 ] , [ 59 ] , [ 64 ] Mohr - Coulomb model
is the first model included the effects of stress on the intensity of the ground . The
damage occurs when the stress states followed , normal stress on any plane of
material that satisfies the equation:
tan c

  

Mohr - Coulomb model can
be written as a function of stress components main (with the convention that
compressive stress is negative ) as follows (Chen and Mizuno, 1990) [54] :
   
1 3 1 3
11
sin cos
22
c
     
     
(3:16)
3.1.4 Contact Element .
3.1.4.1 Contact element theory [26] , [48] Contact element is used to describe the
phenomenon of slip between two materials with large differences in hardness .
For example, the contact between geotextile and soil. Stress often limited slip
largest by plastic Mohr - Coulomb criteria. Contact elements is characterized by
normal stress and tangential stress, and these two components is related to the
normal deformation and shear strain as follows : .
0
0
n
s
k
k




   

   

   

(3:26) Where:
0
0
n
s
k
D
k




(327)
D is called the elastic matrix , and k
n
; k
s
is the normal stiffness and tangential
Stiffness matrix of contact elements :
    
1
1
T
K B D B t J d





(3.28)
Among them : [B] is a matrix relationship between deformation and displacement
; [D] is the elastic matrix as above , is the determinant of Jacobi matrix and t is the
thickness of the element .
Deformation of the element :
yt yb
xt xb
uu
t
uu
t








   





(3:33)

In that matrix deformation displacement relations in expression ( 3:28 ) takes the
following-form:
 
1 2 3 4
1 2 3 4
0 0 0 0
1
0 0 0 0
N N N N
B
N N N N
t






(3:35)
3.1.4.2 The nonlinear model of contact between the land and VDKT : stress-strain
relationship of the contact elements are often assumed to be ideal elastic plastic
Mohr - Coulomb . However, the actual behavior of the contact between the
geotextile and soil includes several stages as non-linear , re durable and soft goods
. Therefore , depending on the degree of contact between deformation and
geotextile - soil that stress exposure status is different in construction algorithm
- 16 -
calculates loop characteristic way relationship stress - deformation characterized
the relationship as shown in Figure 2.2 .
3.1.5 Geotextile Element .

3.1.5.1 Theory of Computation Element VDKT : VDKT element is modeled with
bar elements have the characteristic stiffness elastic is pulled .
FEM method , displacements at any point within the element can be approximated
by the first two buttons of the displacement element is :
1 1 2 2z x x
u N u N u
(3:36)
3.1.5.2 The nonlinear model of the geotextile element: Conduct of the nonlinear
geotextile element quite complex . Can model the nonlinear behavior of the line
segment , based on the degree of deformation geotextile that can determine the
corresponding stress . The relationship of this behavior is shown in Figure 2.1
3.1.6 Nonlinear Analysis [24] When analyzing structures under nonlinear material
models or nonlinear geometry , stiffness matrix or load vector depends on the
displacement . Typically , the problem is nonlinear solution based on the linear
approximation of . Currently, two methods are the most widely used Newton -
Raphson and Newton - Raphson improvement .
3.1.7 General block diagram program .
3.2 Construction program features :
3.2.1 Introduction to computer interface program hnh_ress V 1:00
Program Name : hnh_ress V 1:00 ( HNH_ Reinforced Embankment Stability
Software - Software calculates reinforced embankment stability ) .

Figure 3.12 Declaring relationship stress – Figure 3.13 Declare hardness (EAG) based
strain of the geotextile on stress-deformation path of geotextile


Fg 3.14 Trails approximately sliding surface Fg 3.15 Approximately the ellipse
running through the most extensive deformation and circle slide

3.2.2 Introduction hnh_ress V1.00 computer program

- 17 -
Hnh_ress program was built by the
finite element method calculation
problem geotextile reinforced
embankment . In this stress-strain
relationship of geotextile are Robert M
Koerner model - described working
closely with the local reality of the
ground fabric . Calculation of
geotextile jet curve behaves as follows :
Jet geotextile in the calculation of load
balancing at each step of the iterative
solution of finite element method is determined by the power curve behavior -
displacement . This curve is constructed from samples geotextile experimental
results ( as shown in the form 3.16 ) . In the first step to finding solutions is the
initial displacement of the system , the stiffness of geotextile to build the stiffness
matrix is the slope of the first straight line from the origin ( if the behavior is
approximately equal to the line segment ) or tangent of the curve ( if the road is
approximately equal to the curve behavior ) at the origin of Ki . After each step
solution , displacement of geotextile be determined Uj and thus determine the
actual jet geotextile was defined as Tj . Secant stiffness is also determined by the
expression : Ktj = Tj / Uj (3.43).
In addition, the program features hnh_ress V1.00 has also established algorithms
to draw lines connecting points shear strain has the largest shear strain in
embankment ( Display > Slip Surface stresses ) , and calculate the sliding surface
to approximately result in the most appropriate form of sliding surface ( Report >
slip line) . Methods and results slip surface approximation is presented in later
chapters . Details of the program are presented in appendix 3 .
Conclusion Chapter 3 : The program geotextile reinforced embankment
HNH_RESS V1.00 software programs are calculated by the finite element

method . This program calculates external functions , stability analysis problems ,
stress condition - deformation of the embankment with conventional finite
element as the other programs , there are also other functions using its specific
programs such as geotextile in reinforced embankment is declared and calculated
stress path relations - including multi-stage deformation of the model Robert M.
Koerner , so the hardness of geotextile also declared properties payment under
this model , the program also displays the results in graphical and text formats on
the dangerous sliding surface of the embankment , and shear strain draw lines
connecting points of maximum shear strain in the soil as well as the result of
calculating the approximate form of text sliding surface and concluded most
logical form of the slip surface . The program can also calculate any problems ,
not limited to changes in the input parameters ( geometrical shapes , materials ,
parameters ) and can edit , write additional computational needs , user research .
- 18 -
The content of research, empirical calculations using the computer program to the
problem of geotextile reinforced embankment load vehicles will be presented in
chapter 4 .
CHAPTER 4 EXPERIMENTAL CALCULATIONS FOR GEOTEXTILE
REINFORCED EMBANKMENT IN HIGHWAYS CONSTRUCTION
In this chapter, the case of soil embankment on soft soil and natural good, is
reinforced and non-reinforced geotextile is calculated according to the finite
element method which uses computer programs to hnh_ress V1.00 perform
analysis. Also some analysis, other studies are also presented in this chapter
contents.
4.1 The natural causeway on good ground
4.1.1 General Data calculated
Table 4.1 Characteristics of good soil embankment
Soil
height up (m)
ɣ (kN/m

3
)
C (kN/m
2
)
φ (
0
)
E (kN/m
2
)
Embankment
6, 8, 10, 12
17.0
15
20
10000
Foudation
-
17.0
20
25
50000
Table 4.2 Characteristics of geotextile under 1m width
T
max
(kN/m)
E (kN/m
2
)

Thickness (m)
EA (kN)
24
486970
0,0033
1607
Table 4.3 Load vehicles
vehicles
n
G
(kN)
B
(m)
L
(m)
q
(kN/m
2
)
q
v
(kN/m
2
)
1
2
130
10
4,2
6,2

15,5
2
2
300
10
6,6
14,3
35,7
3
2
800
10
4,5
35,5
88,75
4.1.2 Analysis of embankment stability: hardness and strength of geotextile
relations with each other through elastic deformation characteristic limits:
max
e
T
EA


(4.4)
4.1.2.1 High embankment 6m
Table 4.4 safety factor of slope
High embankment
factor of slope
Layer number
Distance (m)

Fs
6
1/1
0
0
1,20
So with 6m high embankment safety at a safety factor Fs = 1.2 so in this case
without geotextile reinforcement. In the case of larger embankment slope as 1/0,
75 and at ensuring the safety factor Fs = 1.2, the required geotextile
reinforcement.
4.1.2.2 High embankment 8m
1. The influence of the geotextile layer and the distance between the geotextile
- 19 -
layer to the safety factor of slope
Table 4.5 Effect of number of layers and the distance between the geotextile layer
High
embankment (m)
factor of slope
Layers
number
Distance (m)
Fs
8
1/1
0
0
1,06
8
1/1
1

0
1,07
8
1/1
2
0,5
1,12
8
1/1
3
0,5
1,17
8
1/1
4
0,5
1,21
8
1/1
2
0,3
1,11
8
1/1
3
0,3
1,15
8
1/1
4

0,3
1,19
8
1/1
2
0,4
1,12
8
1/1
3
0,4
1,16
8
1/1
4
0,4
1,20
8
1/1
4
0,6
1,23
8
1/1
3
1,0
1,21
8
1/1
4

1,0
1,27
8
1/1
3
1,5
1,24
8
1/1
4
1,5
1,34
8
1/1
3
2,0
1,27
8
1/1
4
2,0
1,27
2. Determine the tension of geotextile work in embankment
Table 4.6 tension in the geotextile slope vandalized
3. Effect of slope coefficients to the safety factor of slope
Table 4.7 Effect of slope coefficients
High
embankment
(m)
factor of slope

Layers number
Distance (m)
Fs
8
1/1 and 1/1,25
0
0
1,20
8
1/1 and 1/1,50
0
0
1,28
4. Effect of geotextile strength and number of geotextile layers to the safety factor
of slope
Table 4.8 Effect of strength and geotextile layers number
T
max
(kN/m)
factor of slope
Layers number
Distance (m)
Fs
12
1/1
7
0,4
1,20
14
1/1

7
0,4
1,22
16
1/1
6
0,4
1,21
- 20 -
18
1/1
5
0,4
1,19
20
1/1
5
0,4
1,20
22
1/1
5
0,4
1,22
24
1/1
4
0,4
1,20
26

1/1
4
0,4
1,20
28
1/1
4
0,4
1,21
5 . Where embankment roof TCVN 4054-05 [ 5 ] According to the standard
TCVN4054 - 05 8m embankment was covered with a slope coefficient of 1/1 , 75
kinds of land use and land cover as the background for the table 4.1 does not need
reinforced with geotextile .
4.1.2.3 The 10m and 12m high embankment : thesis in full for high embankment
10m , 12m with 5 cases affect the safety embankment stability as covered in
Section 8 meters high . The results of the calculations made in the table .
4.1.3 Building chart investigation geotextile used in high embankment
From the calculated results on high embankment 8m , 10m , 12m recorded in the
table 4.8 ; 4:12 ; 4:16 ; 4:17 table can construct the graph of the relationship
between the intensity and number of geotextile fabric geotechnical engineering .
The chart is used to lookup in the selection of geotextile preliminary design
calculations embankment height as follows :





Fg 4.9 The relationship between the
intensity and number of geotextile
layers slope coefficient of 1/1

Figure 4.10 The relationship between the
intensity and number of geotextile layers
slope coefficients 01/01/25
- 21 -



4.2 The embankment on soft soil





4.3 Identify types of slope slip under the sliding surface approximation method
4.3.1 Method approximately sliding surface (Figure 4.16)
4.3.2 Some examples of shear strain and route calculation is approximately
determined by the form of the slip surface hnh_ress program V1.00

Figure 4:23 approximated result slip surface 12m high embankment, slope 6m on
1/1, 5 and 6 m below the slope 1/1, 5, non-geotextile reinforcement
Some analytical results on record at 4:23 the following table:


Figure 4.11 The relationship between the intensity and number of geotextile
layers, the slope coefficient 1/1.5
Figure 4:15 Elipse shaped slip
embankment on soft soil
Figure 4.16 sliding surface approximation
method