MINISTRY OF EDUCATION AND
TRAINING
MINISTRY OF AGRICULTURE
AND RURAL DEVELOPMENT
THUYLOI UNIVERSITY
MAI THI HONG
RESEARCH ON THE IMPROVEMENT OF THE
ALLUVIAL SOIL IN ORDER TO BUILD, TO UPGRADE
THE EARTH-DAMS IN THE CENTRAL HIGHLANDS
Specialization:
Code No:
Hydraulic Engineering
958 02 02
SUMMARY OF DOCTORAL DISSERTATION
HA NOI, 2019
This scientific work has been accomplished at Thuyloi Univeristy
Supervisor:
Assoc. Prof. Nguyen Trong Tu
of potential water that has not been used for living or manufacturing yet. There
are more than 1000 reservoirs in the Central Highlands. Most of them are earthdams, which was built by the compacted soil since the 80’s - 90’s with the
limitation in construction technology back then. By now, many of the earth-dams
has deteriorated such as the body of the dam is deformed, cracked, sliding, or
infiltration. Moreover, due to the scocial-econimic developing of the Central
Highlands area, it requires a larger comsumption of water. According to, the
water needs for agricutural production will increase 1112%; the water for
industrial use is 1.71.8 times bigger; and the water of human comsumption is
1.92.0 times bigger, in comparison with the present. Although the demand for
water is increasing, the necessary conditions for constructing new reservoirs is
hard. Therefore, the necessity of the repair or upgrade for the earth-dams in the
Central Highland is an urgent need to ensure the capacity of the reservoirs in
order to supply for bigger water consumption.
There are some features that affect the mean of repairing or upgrading those
earth-dams. Firstly, most of the reservoirs are allocated separately in many
places, and the amount of soil needed for upgrading the dams is quite small.
Therefore, the transportation of the soil from a long-distance would be an
uneconomical option. Secondly, the Central Highlands area has been categorized
for some specific uses, such as the area for industrial trees or the area for fruit
trees. It leads to the difficulty in finding the approprioate material source for
reinforcing the earth-dams.
1
In fact, there are some researches that were carried with the aim of using the the
soil in the Central Highlands to construct an earth-dam. However, there is no
study that focuses on using the alluvial soil from reservoirs or rivers to use for
upgrading or repairing the body of earth-dams.
From the above points, research of using local material that can be found in the
5. Scientific and practical significance of thesis
- Scientific significance: The thesis has provided a deeper academical knowledge
about the alluvial soil in the Central Highlands, which is used to improve the
quality of the alluvial soil as the local material for upgrading and constructing
the earth-dams in the Central Highlands area.
- Practical significance: The results from this thesis can be used as a scientific
basis for repairing the old one and constructing the new earth-dams in the Central
Highlands.
CHAPTER 1 OVERVIEW OF DAM USING LOCAL MATERIAL AND
THE EARTH DAMS IN THE CENTRAL HIGHLANDS
1.1
Earth-dam and the requirements in design and construction
Earth-dams is built by the local soil that is near to the location of dams. This type
of dams doesn’t allow the overflow of the water. Its mission is collecting and
keeping the water in the reservoir.
The earth-dams has been used for long-time to reserve the water for human
consumption and agricultural production. In Egypt, the earth-dam has been built
since 4400 BC, and in China, it has been built since 2280 BC. At that time, the
earth-dams was built mainly by hand; using bidding material; construction time
would be quite long (10 15 years); the height of the dam is not over 15m.
1.1.1
The requirements in the dam design
The requirements that has to be followed in designing a earth-dam: The body and
the foundation of the dam must be steady in both construction and utilization
time; The infiltration through the dam’s body and foundation is not significant in
term of losing the water as well as creating the inside erosion; Not allow the water
The characteristics of the reservoirs and the water consumption in the
coming years in the Cetral Highlands
The characteristics of the reservoirs and earth-dams in the Cental
Highlands
At present, there are 2352 irrigation structures in the Cetral Highlands. In which
the reservoirs are 1190, the water-raising dams are 970, pump houses are 130,
other types are 62. The irrigation area in the plan is 289604 ha, while the
irrigation area in real is 215765 ha, and the area that needs to be irrigated is
772189 ha. It means the area of agricultural production that has been provided
with the water is only 27.94%.
Most of the reservoirs in the Cental Highlands are medium and small size, their
volume is amost less than 3 milion m3. Those reserviors are allocated separately
in a huge area where the infrastructure has not yet developed, which would make
transportation is a huge difficulty. The reservoirs were built for 30-40 years.
Therefore the quality of them have been degraded, and they are not capable of
either watering purpose or safety requirements in the flooding case. Since most
of the small and medium-size reserviors are earth-dams, the common
4
degradations are the infiltration through the dam’s foundation or dam’s body, and
breakdown at road-bed slope or dam’s face…etc.
1.2.2
The water consumption in the coming years
According to statistical data from Institute of Water Resources Planning, the total
water demand for the economic-social development of the whole Central
Highlands area are about 11 billion m3 in 2015, and it will increase up to
and it is allocated widely over the Central Highlands area as well as the Southeast
area. The Pham Van Thin’s research showed that the red basaltic soil in the
Central Highlands area has different characteristics. The basaltic soil without
laterite has a maximum dry density in the range 1.281.41 (g/cm3), while the
basaltic soil with laterite has a maximum dry density in the range 1.551.94
5
(g/cm3) that is heavier than first type 2137.8%. Nguyen Van Tho, Tran Thi
Thanh studied the red basaltic soil in the Central Highlands that has a high
content of silty clay, which has a small dry density of 1.01.2 T/m3, and after
standard compaction test its dry density can be increased to 1.31.4 T/m3, and its
maximum dry density is only 1.6 T/m3 by giving more compacting process. The
results from previous studies indicated that if the soil’s dry density has increased
then its shearing resistance is also improved and its compressibility reaches to
medium range, which allows for using this red basaltic soil as filled material. The
resaerch of Nguyen Van Tho, Pham Van Thin and others authors on the
compacting process of red basaltic soil, they found that if the soil moisture is
keeping in proper level during compacting process then it dry density will
increase and the saturated soil has a high shearing resistance; Nguyen Van Tho,
Pham Van Thin, Nguyen Van Chien, Nguyen Cong Man study on the
mineralizable ability, the physico-mechanical properties of basaltic soil that
containt lateritic to use its as filled material. Their research also considered the
effect of the content of coarse grain on the physico-mechanical properties of soil.
They came to the conclusion that the content of coarse grain, the physical
properties of soil, the shape and struture of grain has a remarkable effect on the
constructive ability of the soil; The study of Nguyen Van Tho showed that the
content of coarse grain (N) changed leads to the change of dry density, shearing
resistance, coefficient of permeability. The coefficient of permeability almost
remains when the content of coarse grain N = (0 50)%, but the content of coarse
180÷400kg for one m3 soil in the wet mixing method, while it needs only
90÷180kg cement for for one m3 soil in the dry mixing method. It means the
amount of cement needed in the dry mixing method is only about 50% in
comparison to the wet mixing method. The Law’s research in the Asian
Enigeering Insititute, by mixing 5% cement with low quality clay in Bangkok
(Thailand) has improved the lateral deformation of the soil in 10 times, the
consolidation coefficient of the soil in 10÷40 times; Meei-Hoan Ho và CheeMing Chan has researched the clay that is taken from the Centre of research of
the soft soil at Tun Hussein university in Malaysia (UTHM) from the depth level
from 1.52.0m. After adding the cement, the physical factors of soil has been
improved. Nguyễn Duy Quang studies the muddy ground collected from the
estuarine region of Ariake (Japan) to use as local filled soil.
Hence, the results from the international researchers indicate that the
consolidation of soil by using lime, or lime-cement mix has certainly enhanced
the physical factors of the soil.
1.4.2
The previous research on using cement and lime to consolidate the soil
in Vietnam
There were many studies on using cement and lime to consolidate soil from many
researchers such as Pham Van Huynh; Le Xuan Roanh; Nguyen Quoc Dung. In
conclusion, The national studies on using the inorganic bidding material in
consolidating soil have a common indication that when the increase of cement
proprotion leads to the change in the physico-mechanical properties of the soil,
particularly in term of intensity improvement. The soils that are suitable for
7
consolidating by adding cement are gravel soil, sandy soil, clay sand, clay loam.
When the lime has been added, it helps to reduce the disaggregation of the soil.
the original soil. They are mostly in perspective of using in infrastructure
construction. Therefore, they forcused on enhancing the intensity of the soil,
while using the the binding material to reduce the permeability and
disaggregation of the the alluvial soil has not mentioned yet. ii) The common
construction method used is soil compaction, which aims to improve the dry
density of the soild. However, the effect of soil compaction method depends
8
highly on the grain composition and the soil moisture. Hence, all of the
mentioned issues are going to be considered in this thesis.
CHAPTER 2 SCIENTIFIC BASIS OF THE IMPROVEMENT OF THE
ALLUVIAL SOIL TO MEET THE NEED IN UPGRADING, BUILDING
THE ERATH-DAM IN THE CENTRAL HIGHLANDS AREA
2.1
The filled soild in the Central Highlands area
The soil in the Central Highlands is created from basaltic rock, sedimentary rock,
metamorphosed rock, plutonic rock. Based on the source in creation, the soils in
the Central Highlands can be devided in 2 groups: alluvial soil and residual soil
that is residue on the rock base created from different sources.
2.2
The technical approaches to improve the filled soil
The improvement made to the filled soil to reduce its weak factors, which is in
order to meet the requirement in design, such as: enhancing the bearing capacity;
to reduce the penetrability; to reduce the disintegration; improving the dry
decreased, it is the process of replacing the ion in the soil. Therefore, the efficient
way is to add one of following compoud into the soil: CaO, Ca(OH) 2 or others
material that has a rich Ca content, which basically change the penetrability and
the disintegration of the soil. The amount of adding material depends on the type
of soil, compaction density, the water soluble-salt, the construction
method,…etc. Before choosing the ration of mixing, it is necessary to have a test
to identify the proper mixing ratio. That is the basis for the author’s experiment
study in chapter 3.
2.4
The scientific basis to choose the coarse grain to improve the dry
density of the soil
There are many studies on improving the dry density of the soil by the method
of soil compaction. This method is simple and economical efficiency. However,
the effective of soil compaction is highly depening on the moisture of the soil,
the grain composition of the soil, and compacting equipment. According to
previous research, the method of soil compaction is effective with the soil that
contains the clay content is smaller than 15%. In addition, in the clay (cohesive
soil) is usually existting the air bag, which affects the process of compacting the
soil under the press of external force. To this iusse, it is important to eliminate
the existing of the air bags and to improve the air venting of the soil that depends
on soil’s grain composition and soil porosity.
In particular, the soil’s dry density is calculated by the following equation:
2.5
tm
c
dams, which has been researched by many authors, has been planned for growing
the agricultural production and insutrial plants. Therefore, it is necessary to
research to find the new source of the materials that, in this thesis, is the alluvial
soil. However, this type of soil is normally having some physico-mechanical
properties, as well as some particular factors those are not meet to the
requirement for using in ungrading the earth-dams.
3.2
Choose the soil samples for research
- The soil sample MA, which has been taken in the material yard A near the Tân
Sơn (Gia Lai) water reservoir, is representative for the soil group I that containts
mainly small dimension grains.
- The soil samples MB and MC, which has been taken in the material yard B and
C near the Eamlô and Buôn Sa (Đắk Lăk) reservoir respectively, are
representative for the soil group II that the grains are mainly bigger than 2mm.
3.3
The consolidation of experimental results
The results of the test on soil samples MA, MB, MC revealed that some physicomechanical properties and particular factors of the soils meet the requirements
for constructing, upgrading, repairing the earth-dams, according to TCVN 82162009 and TCVN 8297-2009. However, there are some criteria that the soils have
not yet met the standard as such:
11
- MA soil sample: The dry density is small and the optimum moisture is high,
according to TCVN 8297-2009;
- MB soil sample: the disintegrated time is very short, after 500 seconds the
sample has been completely disintegrated.
The content
of cement
(%)
1
2
3
5
7
The content
of lime (%)
The factor of
percolation k (cm/s)
2
2
2
2
2
9.0710-05
6.3110-05
4.3110-05
2.7210-05
1.2410-05
10
8
of percolation k = 4.3110-05 cm/s.
2/ The second scenario: the proportion of lime content are changed by
1%,2%,3%,5%,7% and the cement content is fixed by 2%
Table 3. 2 The result of percolation test with lime proportion changed and 2% cement
content.
No
The content of
cement (%)
2
2
2
2
2
Coefficient of permeability k (10-5 cm/s)
1
2
3
4
5
The mix of soild
and admixture
MC-2-1
MC-2-2
MC-2-3
MC-2-5
MC-2-7
4
5
6
7
8
The content of lime (%)
Figure 3. 2 The effect of lime content and 2% cement on the factor of percolation
The test’s result indicates that the factor of percolation decrease when the content
of cement and lime increase, as well as lime, is mor effectively in comparison
with cement. The factor of percolation decreases quickly when the content of
lime increase from 13%. With the content of lime is more than 3%, the factor
of percolation keeps going down but with slower speed. Therefore, to enhance
the efficiency of reducing the factor of percolation in regard to the economical
issue, the proposal is using 3% content of lime and 2% content of cement. With
that choice, the factor of percolation of the soil is 2.0510-05cm/s, which is
satisfied TCVN 8216-2009 for using as filled material for constructing or
upgrading the earth-dams.
13
After choosing the content of cement and lime to reduce the soil’s penetrability
6
7
8
MB-0
MB-1
MB-2
MB-3
MB-4
MB-5
MB-7
MB-9
Cement
content
%
0
1
2
3
4
5
7
9
The disintegrated
volume of soil
%
100
100
2
4
6
The content of cement (%)
8
10
Figure 3. 3 The effect of cement content on the disintegrated time of the soil
To be aware that when the content of cement increased the disintegrated time of
the soil significantly increases. In particular, with content of cement is 1% the
disintegrated time of the soil is longer than 1.5 times, with content of cement is
14
3% the disintegrated time of the soil is longer than 4.3 times, and with content
of cement is 9% the disintegrated time of the soil is longer than 14 times.
The disintegrated time increased along with the increase of cement content
because the fine-grain composition in the cement makes the unit surface between
grains increasingly, which lead the surface of reaction between grains also
increasingly. However, in concern to economical factors, it should be noticed
that the disintegrated time of the soil with 5% cement content is quicker than 7.75
times in comparison with no cement content, similarly with 9% cement content
the time for disintegration is 14 times quicker without cement. To this end, the
initial choice of cement content is 5% in regard to both the efficiency of technical
and economical aspects.
3.6.1
The effects of the content of fine gravel on the dry density and the
optimum moisture content
When adding the fine gravel with soil sample will improve the dry density and
reduce the optimum moisture content of original soil. That change is calculaed
by TCVN 4201:2012.
2
40
35
30
1.6
Wop (%)
c (g/cm3)
1.8
1.4
25
20
1.2
mS (%)
10
15
20
25
30
35
40
45
50
55
mS (%)
The effects of the content of fine gravel
on the dry density
3.6.2
0
10
0
5
10
15
20
25
30
35
40
45
50
0
55
5
The effects of the content of fine
gravel on the soil adhesion
The effects of the content of fine gravel on soil deformation and soil
permeability
400
700
350
600
k (10-6 cm/s)
E1-2 (kG/cm2)
300
250
200
150
500
400
300
200
100
100
ms (%)
5
10
15
20
25
30
35
40
45
50
55
ms (%)
The effects of the content of fine gravel
on the modulus of soil deformation
which is in corresponding with fine gravel content ≤ 25%. Therefore, it is
suggested to add the content of fine gravel from 2025% to mix with fine grain
soil in order to improve the characteristics of original soil, which is going to use
for dam banking.
3.7
The conclusion of chapter 3
The research on original characteristics of some filled soil in the Central
Highlands such as gain composition, physico-mechanical properties, and
particular factors has been made, which is the basis for a proper proposal to
improve some physico-mechanical properties of soil in order to use the final mix
for upgrading and constructing the earth-dams. To be specific, the author has
studied 3 types of soils that intend to use for dam banking in the Central
Highlands. Those soils include:
17
- The soils containt a significant fine gravel content: i) If the soild has a marked
penetrability, then the solution is adding 2% cement and 3% lime to reduce the
penetrability; ii) If the soild has a strong disaggregation, the author suggests
adding 35% cement content into original soil.
- The soils with light dry density: the author suggests mixing the fine grave
content from 2025% to improve the mix’s dry density. It also leads to the
reduction of the optimum moisture content and deformability, the increase of
shearing resistance and penetrability but all of the factors are still meet the
applicable requirements to the filled soil of dam banking.
CHAPTER 4 APPLYING THE RESULTS OF THE RESEARCH TO
UPGRADE, TO REPAIR AN EARTH-DAM IN THE CENTRAL
battered upstream/downstream face
Value
463.54 m
463.84 m
461.0 m
3.0 m
12.0 m
3.0
The dam’s present condition and to propose the approach for
upgrading
The investigation of the dam shows its clear degradation; the upstream/
downstream faces are not reinforced, there are luxuriant trees; the dam’s face
18
without reinforcement for years has been disintegrated and not enough
dimensions as designed. The downstream face appears many holes and there is
no drainage water equipment. The downstream face appears many strong
permeable areas, especially at the location of the old river channel.
At present, the dam is being percolated. Therefore, the necessity of repairing to
fix the percolation as well as to ensure the safe utilization of this earth-dam is
urgent. The objective of the repair is to fix the percolation of the dam’s body (at
the location of the old river channel); to expand the outline of dam; to embank
the upstream face by using the local material that has been improved; to build a
new drainage prism in downstream side (in order to improve the stability for
downstream face).
4.2
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
0.1
Cao ®é
460
30
35
40
45
50
55
60
65
70
Kho¶ng c¸ch
Figure 4. 1 The result of permeability calculation with dam crown’s width B = 4.0 m
472
469
0.8
0.40.7
460
442
439
436
-65
-60
-55
-50
-45
-40
-35
-30
-25
-20
-15
65
70
Kho¶ng c¸ch
Figure 4. 2 The result of permeability calculation with dam crown’s width B = 4.5m
472
469
466
0.35
463
0.05
451
448
0.3
0.0
5
0.1
442
0.1
0.2
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
2.799
472
469
466
463
Cao ®é
460
457
454
451
448
445
442
439
436
-65
-60
-55
-50
-45
-40
40
45
50
55
60
65
70
Kho¶ng c¸ch
Figure 4. 4 The result of stability calculation for the upstream face with dam crown’s
width B = 4.0m
2.790
472
469
466
463
Cao ®é
460
457
454
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
469
466
463
Cao ®é
460
457
454
451
448
445
442
439
436
-65
-60
-55
-50
-45
-40
-35
-30
50
55
60
65
70
Kho¶ng c¸ch
Figure 4. 5 The result of stability calculation for the downstream face with dam
crown’s width B = 4.0m
20
1.643
472
469
466
463
Cao ®é
460
457
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
Table 4 2 The calculation’s result of stability coefficient of the dam face
No
1
2
3
Dam crown’s
width
B = 4.0
B = 4.5
m = 5.0
Jmax
0.405
0.351
0.322
Kmin min
in upstream face
2.799
2.790
2.767
Kmin min
in downstream face
1.638
1.643
1.648
CONCLUSION AND RECOMMENDATION
I. The achieved results of this thesis
From the result of research, the main achivements of the thesis are as follow:
The characteristics and the physico-mechanical properties of the soil in the
Central Highlands have been collected and to generalized. Based on that, the
representative soil has been chosen to research, in which the proportion of the
fine-size are the majority as well as containing a marked content of fine-gravel
grain.
Based on the analysis of scientific basis and techincal approaches to improve the
soil characteristics, the author has chosen 3 methods for improving the soil. For
the soil that has s significant permeability, the chosen method is adding cement
and lime to improve the anti-infiltration ability of the soil; For the soil that is
quickly disintegrated, the chosen method is adding cement into the soil; For the
soil that has a light dry density, the chosen method is changing the size grain in
the grain composition, particularly it is adding fine gravel into the soil.
For the soil that has s significant permeability, the solution is adding a proper
content of cement and lime to reduce the permeability. In particular, the author
proposes the content of additives are 3% lime and 2% cement in the thesis.
22
For the soil that is quickly disintegrated, the solution is adding cement to reduce
the soil’s disintegration. In particular, the author suggests using 5% cement to
mix with original soil in this case.
For the soil that has a light dry density, the proposal is to add fine gravel in order
to enhance the dry density of the mix. Together the increase of dry density, the
optimum moisture content decrease and the ability of soil for shearing resistance
and anti-deformability both increase, but the ability in anti-infiltration is quicky
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