As Dam-IT has some effects on reducing seepage flow, therefore it is satisfactory to remediate earthen dam. The result ranges in broad spectrum because applying Dam-IT depends on sample soil layer and its mechanism in different inclined planes on upstream slope.
Trang 1THE POSSIBILITY OF APPLICATION DAM-IT MATERIAL TO
REMEDIATE SEEPAGE ISSUES
FOR SMALL AND MEDIUM RESERVOIRS IN VIETNAM
Nguyen Ha Phuong1, Ho Sy Tam2, Nguyen Phuong Dung2
1
Institute of Civil Engineering, email: nguyenhaphuong@tlu.edu.vn
2
Hydraulic Division - Thuyloi University
1 APPROACH TO SEEPAGE ISSUES FOR
SMALL AND MEDIUM RESERVOIRS
As reported by Directorate of Water
Resources (2012), there are about 6886 dams
in Vietnam, in which over 90% is earthen
dam [1] – nearly 1200/6886 needs to
remediate without delay Although, these
earthen dams have been played an important
role in ensuring water resource security, they
also have been revealed many risks for the
downstream due to dam safety issues,
especially the seepage problems
Seepage is the continuous movement of
water from the upstream face of the dam
toward its downstream face Seepage can
emerge anywhere on the dow nstream face,
beyond the toe Its appearances could range
from a "soft" wet area to a flowing "spring" It
may show up first as an area where the
vegetation is lush and darker green Seepage
can also saturate and weaken portions of the
embankment and foundation, making the
embankment susceptible to earth slides If the
seepage forces are large enough, soil c ould be
eroded from the foundation and be deposited in
the shape of a cone around the outlet
The need for seepage control will depend
on the quantity, c ontent, and location of the
seepage If the seepage has lowered the
reservoir water level or endanger the dam or
appurtenant structures, it is time to take
action over seepage issues although reducing
the quantity of seepage that occurs after
construction is difficult and expensive
Typical methods used to control the quantity
of seepage are grouting or installation of an
upstream blanket; in addition w eep holes and
relief drains c an be installed to relieve water pressure In this research, DAM-IT material was studied its ability to limit – without cease – seepage flow by applying in upstream face of embankment dam For small and medium reservoirs [2] it is essential to promptly handle seepage issues while ensuring rational total investment – DAM-IT material could meet these requirements Technical characteristics of DAM-IT material are discussed below
2 INTRODUCTION AND MECHANISM
OF DAM-IT MATERIAL
In order to withstand with the challenge of climate change as well as other random events and to ensure the safety of people's lives and downstream property, solving safety problem and handling of dam incidents are extremely urgent Due to the time limit for research, this research is mainly focusing
on the seepage issues of the dam and the ability of applying Dam-IT material in the conditions of Vietnam Dam sealer is a new and very effective material in reducing the leak volume and hence diminishing the seepage forces in dam’s body, c onsequently increasing the safety of the dam
Figure 1 The material expanded its size and floated in the water
Shalex indus tries is a specialist manufacturer
of clear sealers and waterproofing compounds
Trang 2that include Dam-IT (or Dam sealer) material to
prevent seepage for dams and ponds [3] The
Dam Sealer was applied in physical models to
evaluate the total reduction volume and from this
point of view the effectiveness of Dam Sealer
was estimated Dam-IT is designed with a
pos itive charge that pulls it down under the water
toward the bottom of the dam or pond
Figure 2 Dimension of the model
The water pres sure (hydrostatic pressure),
which causes the dam or pond to leak, forces
the polymer down into cracks and crevices as it
sinks to the bottom of the pond or dam Once
activated with water, the polymer will expand
in size and bind to other polymer particles to
form larger groups of particles, which
effectively slows and stops the leak The
polymer will continue to expand over s everal
hours and forms a flexible plug that withstands
water pres sure The positive charge of the
particles will also attract any silt and
sus pended matter in the water downward to the
bottom, which acts to embed the polymer
within the soil structure and minimize any
disturbance or movement of the polymer that
may be caused by future water inflows By
attracting the small particle and soil particle in
the water body, Dam Sealer creates a new
cover layer on the top of upstream surface and
then reduce the seepage volume
3 PHYSICAL MODEL AND RESULTS
The model was compacted us ing soil sample
with identified mechanical properties as following:
Wop t based on TCVN 4201:2012 (Wop t=14,52%
and γ= 1,89g/cm3, respectively); = 31,25o, C= 7,95
kN/m2 based on TCVN 4199 : 1995; and
K= 6,04e-6 cm/s based on TCVN 8723 : 2012
The total height of the model was 1,1m with
0,1m for the foundation made of mortal and
1m heigh for retaining water and soil The total
length was 2,5m and the designed width was
0,8m The height of the dam model w as 0,5m
with upstream slope m1=2 and downstream slope m2=1,8 The water column at upstream site was 0,4m compared with the foundation of the dam; the tail water level w as controlled at 0,08m The upstream head was refilled to reach the value of 0,4m after 24 hours Behind the mica plate was a collecting part to measure the seepage volume to the dow nstream site The design dam model w as illustrated in figure 2 and figure 3
Figure 3 Physical model
After constructing physical model and filling w ater, seepage volume w as measured until it reached stable There were 2 cases to carry out experiment: before using Dam-IT material (table 1) and after applying it (table 2), each case was operated in 2 weeks The Dam-IT was mixed with soil sample in order
to increase its efficiency and accelerate the settle speed In the research, the ratio 3% was chosen (30g Dam Sealer/ 1000g soil sample) The time between each measurement period was 24h, 18h, 12h
Table 1 Diary recording before applying
the material
(cm)
DH**
(cm)
3 /s) 3p.m
UH* - Upstream hydraulic Head; DH** - Downstream hydraulic Head
The particular picture used for illustrating the water level at upstream site and
Trang 3downstream site in a particular day because
the phreatic line was stable and the filling
volume of water didn’t change much in the
period of 2 weeks
Figure 4 The water level at upstream site
after 24 hours of observation (10/2-11/2)
In the physical model, the Dam Sealer
layer was settled down under the forces
exerted by the water, besides that the
concentration of Dam Sealer material was
distributed non-uniformly, so this could
reduce the effect of material Dam-IT could
reduce seepage volume in physical model
after 2-day of application
Table 2 Diary recording after applying the
DAMIT material
(cm)
DH (cm)
Dama
3 /s)
Values of discharge through dam’s body
decreased more than 19,2% before and after
applying DAM-IT material (on average results
from table 1 and table 2) It deserves the
effective of Dam Sealer on this physical model
4 CONCLUSION
As Dam-IT has some effects on reducing seepage flow, therefore it is satisfactory to remediate earthen dam The result ranges in broad spectrum because applying Dam-IT depends on sample soil layer and its mechanism in different inclined planes on upstream slope
Since Dam-IT is a new and effective material, further research is needed so that user can deeply understand how to use this material efficiently
Several properties and application should be known, such as the best ratio betw een soil and Dam-IT material, the lifespan of the material and other methods of applying this material, the construction techniques for it and also the ability of applying it on larger scale
The impact of Dam-IT on the environment also needs further research although from data of Shalex company and in our research have observed that it does not harm to the environment Another approach of research on this material is the optimal concentration of Dam Sealer for reducing the seepage volume With the dam model, the effectiveness of Dam Sealer is recommended as about 20% or higher When applying for the real dam, the turbidity of river can increase the efficiency like the mechanism that have been discussing above For embankment dam in Viet Nam, its mechanism can be very effective on reducing the seepage volume in both dam body and foundation However, the method of applying still needs further research to identify the best construction and application method of this material in Vietnam
REFERENCES
[1] Report of Directorate of Water Resources,
2012
[2] QCVN 04-05:2012
[3] https://www.shalex.com.au/damit-dam-sealer [4] TCVN 4201:2012; TCVN 4199:1995; TCVN 8723:2012