MINISTRY OF EDUCATION &
TRAINING
MINISTRY OF AGRICULTURE &
RURAL DEVELOPMENT
THUY LOI UNIVERSITY
TRAN VAN HIEN
SELECTION STUDY OF THE REASONABLE COMPACTING
FACTOR FOR COMPACTED EARTH DAM CONSTRUCTION UNDER
HIGH HUMIDITY CONDITION IN THE NORTH CENTRAL REGION
OF VIETNAM
Specialization:
Hydraulic Engineering
Code No:
62 58 40 01
SUMMARY OF DOCTORAL DISSERTATION
HANOI, 2016
This dissertation has been accomplished at Thuy loi University
Promotor: Assoc. Prof. Ph.D Le Van Hung
Co-promotor: Prof. Ph.D Le Kim Truyen
Reviewer No 1: Assoc. Prof. Ph.D Vu Huu Hai
Reviewer No 2: Assoc. Prof. Ph.D Nguyen Huy Phuong
Reviewer No 3: Assoc. Prof. Ph.D Nguyen Binh Thin
The Doctoral thesis defense will take place at the meeting of the University
Doctoral Committee at Thuy loi University, 175 Tay Son street, Dong Da, Hanoi,
Vietnam
On 16th December, 2016
The dissertation is available at: - The National Library
- Library of Thuy loi University
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INTRODUCTION
1. Problems statement
Earth dams are important structures, which are built across rivers or streams to
let water rise up and form the reservoirs. Earth dams are still widely used in our
country due to the advantageous characteristic of using the local material. They
are cost-efficient through usage of simple construction techniques and simple
foundation treatment... The earth dams construction are always affected by the
flow. After diverting the river the engineers have to solve several issues such as
water drainage in the foundation pit and foundation reinforcement... At the same
time, the construction must be quick to avoid the flood. For that reason, the
construction usually takes place in one dry season.
In recent years, the constructions of earth dams in the North Central region
usually encounter problems, which are cohesive soil in heavy long rain and
humid climate conditions. The key constructions in provinces from Thanh Hoa
to Thua Thien Hue such as: Truoi, Ta Trach, Ngan Truoi, Cam Thuy, Thuy Yen
– Thuy Cam, Da Han, Ban Mong, ... are in the areas that always experience high
humidity in the air and long rainy times in rainy season. The air humidity in many
months is greater than 80%. Therefore, to ensure the design quality such as
cohesive soil compaction achieved K≥0,97 corresponding to the soil moisture
W=Wopt 3% is very difficult. As a result, the construction time lasts longer, and
it does not meet the construction progress or economic and social development
requirements. This reduces the effectiveness of the investment capital and leads
to a long time of capital recovery.
Vietnam has many experiences and achievements on earth dam construction
technologies but also faced many catastrophic failures.
At present and near future, according to the plan and direction of economic
development to 2030 and vision of 2050, North Central region will have to build
many earth dams under high humidity conditions. In order to achieve the goal of
completing these constructions, ensuring the construction quality, following the
construction schedule with a reasonable cost, while minimizing the damages as
well as negative impacts on the society, we need to have proactive solutions
during the design and construction of compacted earth dams under high-humidity
conditions. It urges the authors to find out the in-time solution for the theoretical
and practical issues.
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2. Objectives
This thesis studied the soil and the soil properties in the North Central region and
proposed reasonable and safe solutions for the design and the construction of
compacted earth dams. It meets the requirements for development of economic,
social security and defense of the country.
3. Objects and study areas
This thesis studied the soil and the soil properties for earth dams construction,
solutions for the design and the construction of compacted earth dams in the
North Central region (from Thanh Hoa province to Thua Thien Hue province).
In detail, the study firstly focused on the theories and practicing of earth dam
construction in North Central region, and then the results were applied to select
the reasonable compacting factor and the humidity for compacted earth dam
construction under high humidity condition.
4. Study contents
In order to achieve the main objectives, the author focused on the following
issues:
a) Studying the materials for earth dam construction and natural conditions
of the North Central region (from Thanh Hoa province to Thua Thien
Hue province), assessing the soil characteristics of this area to build the
compacted earth dams;
b) Proposing solutions to reduce soil humidity for the earth dam
construction in the region;
c) Conducting experimental study to select appropriate compacting factor
for the earth dam construction under the high humidity condition of the
study areas;
d) Developing a process to determine appropriate speed for the earth dam
construction with the selected compacting factor and humidity of the
soil;
e) Applying the study results to assess the construction safety of Da Han
dam and Ta Trach dam.
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5. Methodology
- Literature review;
- Studying on the basic theory, inherited the study results on the earth dam
construction using compaction method, which was published in Vietnam and
internationally;
- This study is a combination of experimental testing and theoretical analysis
using some supporting softwares;
- This study also based on the observation, summarizing and analysis the results
from practical experience;
- The study results were reported and discussed in many conferences.
6. Scientific and reality applications
The study results enhance knowledge in studying and practicing of the
compacted earth dam construction.
In theory: This thesis summarized the basic contents of the process to evaluate
and select the materials as well as to identify compacted earth dam construction
solutions, based on summing up, inheriting and developing previous studies on
the earth dams, which were applied in many regions having different or similar
conditions. This process changes with the compacting factor and the humidity of
the soil in the North Central region.
In practice: This thesis built up a basic database, solutions as well as specific
applications for some projects within the study areas from Thanh Hoa province
to Thua Thien Hue province. The author proposes not only a process to choose
reasonable humidity and compacting factor but also an effective solution to
reduce the humidity of the soil for the earth dam construction in the study areas.
7. New contributions
(1) The soils used for the earth dam in this area are mostly sediment on
sedimentary bedrock. In this thesis, the characteristics of cohesive soils
(sediment) in North Central region was evaluated thoroughly, including
non-swelling or weakly swelling soil and non-breakup or weakly
breakup soils;
(2) Compacting factor (K) was selected for the earth dam construction: when
impervious core was sedimentary soil, we selected K≥0,94