original research article geotechnical characteristics … · 2020. 7. 25. · of pegu group at...
TRANSCRIPT
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GLOBAL JOURNAL OF SCIENCE & ENGINEERING Vol. 01 (2020) 22-30
www.knowvel.com
Original Research Article
GEOTECHNICAL CHARACTERISTICS AND
FOUNDATION CONDITION OF PEGU
GROUP IN YANGON AREA KHIN SOE MOE 1, TUN NAING 2, KYAW HTUN 3
ABSTRACT
Yangon is highly dense populated city in Myanmar. Today Yangon area has undergone very rapid
development and expansion because of its socio-economic cum political significance. Therefore
it is required to expand the new satellite town. Therefore, geotechnical site characteristics and
zonation of Yangon area is carry out. In Yangon, three geological rock units such as alluvial
deposits, Irrawaddy Formation and Pegu Group can be found. For this research, geotechnical
characteristics and foundation condition of Pegu Group is investigated. Based on the sample
collected and the laboratory results, foundation condition of Pegu Group are studied. The
purpose of the research is to point out the engineering characteristics and foundation properties
of Pegu Group in the Yangon Area. The Pegu Group consists of three lithostratigraphic units
recognizable from surface geologic characters and subsurface data. They are Besapet
Alternation, Thardugan Sandstone and Hlawga Shale from youngest to old. Besapet Alternation
consists of shales and thinly laminated sandstone which are exposed in the vicinity of Besapet
Lake and also exposed behind the police training school. Besapet Alternation is characterized
by blunish grey to greenish grey, bedded to nonbedded, silty shale with very thin parting of
micaceous sandstones. Thardugan Sandstone consists of blunish grey to brownish grey, fine to
medium grained micaceous and argillaceous sandstone with ferruginous bands. They are
exposed around the Thardukan Pagoda, southwestern and south of Hlawga Lake.It exposes as
massive body sandstone around Thadukan Pagoda and thin bedded sandstone at police
training school. Hlawga Shale consists of shale and laminated clay. They occur at the low land
area at the west of Hlawga Lake beside the Thardugan Sandstone. According USCS
classification, CL, ML, MH, SC, SM and SW soil types are found as residual soil in Pegu Group.
The ultimate bearing capacity of residual soil of Pegu Group is 15 kPa to 600 kPa. The
unconfined compressive strength of Thardugan Sandstone varies from 8 MPa to 61 MPa.
Keywords: Besapet alternation, Geotechnical characteristics, Hlawga shale, Lithostratigraphic
units, Thardugan Sandstone
AUTHOR AFFILIATION
1Associate Professor, Engineering Geology
Department, Yangon Technological University 2Professor and Head, Engineering Geology
Department, Yangon Technological University 3Associate Professor (Retired), Engineering
Geology Department, Yangon Technological
University
Yangon, Republic of the Union of Myanmar
CORRESPONDENCE
Khin Soe Moe, Associate Professor, Engineering
Geology Department, Yangon Technological
University
Email: [email protected] [email protected]
PUBLICATION HISTORY
Received: June 20, 2020
Accepted: June 22, 2020
ARTICLE ID: GJSE-CP-04
1. INTRODUCTION
Yangon is situated between Sittaung River in the east and Ayeyarwaddy
River in the west and it is also the southern extensional rolling region
of Bago Yoma. Yangon City is generally bounded by Hlaing River in the
south and Bago River in the east. The areal extent of Yangon area is
3967.9 square miles (10276.7 km2). Today Yangon area has
undergone very rapid development and expansion because of its socio-
economic cum political significance. It is aware that close interrelation
exists between the natural environment and area development. The
natural factors have exerted strong influence on the development of
urban area. Therefore adequate concerns based on geologic conditions
for future sustainable development of urban planning are necessary.
Geotechnical site characterization and foundation condition of Pegu
Group in Yangon area are needed to take up to ascertain the nature
and properties of rock available at different locations. These studies
also carry out for designing a right type of foundation safely and
economically, a designer must possess sufficient information about the
physical properties and the arrangement of underlying materials .The
combined use of geologic information, natural hazard and urbanization
study have beneficial effect on the development of urban and rural
area.
2. LOCATION AND SIZE
Yangon is located in Lower Myanmar on the eastern margin of the
Ayeyarwaddy delta at the confluence of the Yangon and Bago rivers and
about 30 km away from the Gulf of Martaban. It is located between
North Latitude 16 45' and 17 04' and East Longitude 96 00' and
96 17'.The map index of Yangon area is 94 D/1. There are thirty four
townships and total population is 7.36 million in 2017. The location
map of the Yangon area is shown in Figure 1.
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Figure 1. Location map of Yangon area [1]
3. METHOD OF STUDY
The research is prepared from various points of views such as geology,
engineering geology and environmental geology. The base maps are
geological map, engineering geological map, land use map,
geomorphological map and satellite image. All available data such as
research papers, reports have been studied, and then samples of rock
in the study area had been collected. The results from the laboratory
and field investigation data are analysed for the engineering
characteristics and foundation conditions of Pegu Group in Yangon
area. Based on the sample collected, and the laboratory results,
foundation condition of Pegu Group are studied.
4. PURPOSES OF STUDY
Yangon area has undergone very rapid development and expansion.
The strong growth in population, development of infrastructures and
industry, and the extension of new urban area have resulted in a variety
of competing demands and substantial encroachments upon the
environment. Therefore, adequate planning for the most efficient and
compatible uses of land, engineering characteristics and foundation
properties of soils and rocks are very important in urban planning. Thus
engineering geological and hydrological characteristics of the different
geologic units are needed to investigate in details. It is a reason why
the research title “Geotechnical Characteristics and Foundation
condition of Pegu Group in Yangon Area” is needed to perform. The
purpose of the research is to point out the engineering characteristics
and foundation properties of Pegu Group in Yangon area.
5. RESEARCH WORK
In Yangon, three geological rock units such as alluvial deposits,
Irrawaddy Formation and Pegu Group can be found. The Pegu Group
consists of three lithostratigraphic units recognizable from surface
geologic characters and subsurface data. There are Besapet
Alternation, Thardugan Sandstone and Hlawga Shale from youngest to
old [2]. The outcrop location map of Pegu Group is shown in Figure 2.
Figure 2. Outcrops location map of research area [3]
5.1. Distribution of Pegu Group
This group includes three lithostratigraphic units recognizable from
surface geologic characters and subsurface data. There are Besapet
Alternation, Thardugan Sandstone and Hlawga Shale [2].
5.1.1 Distribution of Besapet Alternation
It consists of shales and thinly laminated sandstone which are exposed
in the vicinity of Besapet Lake and also exposed behind the police
training school. Besapet Alternation is characterized by blunish grey to
greenish grey, bedded to nonbedded, silty shale with very thin parting
of micaceous sandstones. Distribution of Besapet Alternation is shown
in Figures 3, 4 and 5 [2].
5.1.2. Distribution of Thardugan Sandstone
Thardugan Sandstone consists of blunish grey to brownish grey, fine to
medium grained micaceous and argillaceous sandstone with
ferruginous bands. They are exposed around the Thardukan Pagoda,
southwestern [2] and south of Hlawga Lake.It exposes as massive body
Sandstone around Thardugan Pagoda and thin bedded sandstone at
police training school. Distribution of Thardugan Sandstone is shown in
Figures 6-20.
5.1.3. Distribution of Hlawga Shale
Hlawga Shale consists of shale and laminated clay. They occur at the
low land area at the west of Hlawga Lake beside the Thardugan
sandstone. Distribution of Hlawga Shale is shown in Figures 21 and 22.
The distribution of Pegu Group in Yangon Area is shown in Fig. 23.
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24
Figure 3. Besapet Alternation at Besapet Lake
Figure 4. Besapet Lake
Figure 5. Highly weathered Besapet Alternation at roadside of Hlawga
Park
Figure 6. Outcrop at Besapet Alternation and Thadugan Sandstone
boundary at 165849N and 960623E
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25
Figure 7. Massive sandstone body at south of Hlawga Lake
(165850.23N and 960613.43E)
Figure 8. Concretion holes at south of Hlawga Lake
(165850.23N and 960613.43E)
Figure 9. Sandstone body under police station (1) (165849N and
960623E)
Figure 10. Sandstone outcrops on the side of Hlawga Lake
Figure 11. .Sandstone massive body at Kyawe Chay Yar I
Figure 12. Concretion on the sandstone body
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26
Figure 13. Sandstone outcrops at Nat-Nan of Thardugan
Figure 14. Sandstone 0utcrops at Baydar I
Figure 15. Sandstone outcrop at Moe Hein Taung
Figure 16. Sandstone outcrop between No.(3) and No.(4) police
station
Figure 17. Sandstone outcrops at No. (3) Taung
Figure 18. Sandstone outcrops near No.(4) police station
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27
Figure 19. Thin bedded sandstones in police training school
Figure 20. Sandstone outcrop at Tawya Pagoda
Figure 21. Hlawga Shale at the valley of Moe Hein Taung
Figure 22. Hlawga Shale at the west valley of Thardugan Pagoda
Figure 23. Distribution of Pegu Group in Yangon area (modified by Khin
Soe Moe after Win Naing, 1972)
5.2. Geotechnical Characteristics of Pegu Group
Besapet Alternation and Hlawga Shale are highly weathered. So, it is
not possible for taking samples for geotechnical properties of rock. So,
the residual soil of Besapet Alternation and Hlawga Shale are studied
for geotechnical characteristics and foundation condition. Thardugan
Sandstones are reacted with hydrochloric acid for one day and grinded
into powder for sieve analysis. Figures 24, 25, and 26 show sample
preparation for grain size distribution analysis.
Figure 24. Sample preparation for sieve analysis
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28
Figure 25. Sample preparation for sieve analysis
Figure 26. Sieve analysis of Thardugan Sandstone
According USCS classification, CL, ML, MH, SC, SM and SW soil types
are found in Pegu Group. Geotechnical characteristics of residual soil
of Pegu Group at depth 3m, 5m and 10m are shown in Tables 1, 2 and
3.
Table 1. Geotechnical Characteristics of Soil in Pegu Group at 3m
Depth
By using the geotechnical parameters, bearing capacity calculation are
made for the analysis of foundation condition.
The following equations are used for the calculation of bearing capacity
of soil in Pegu Group.
N60 = 1.67 Em Cb Cr N [4]
Where, Em = correction for hammer efficiency (0.6 for a safety hammer,
0.45 for donut hammer)
Cb = correction for borehole diameter (1.0 for 65mm< D < 115
mm,1.05 for D = 150 mm, 1.15 for D = 200 mm)
Cr = correction for drill rod length (1.0 for L > 10m, 0.95 for 6m < L <
10m,0.85 for 4m < L < 6m,0.75 for L < 4m)
N measured SPT blow count
( N1 ) 60 = Cn x N60
where, Cn =
Cn = overburden correction
' = effective overburden pressure [4]
The ultimate bearing capacity is calculated by using the equation:
Qult = ( N1 ) 60 x 12 kPa
The ultimate bearing capacity of residual soil of Pegu Group is 15 kPa
to 600kPa.Some example bearing capacity calculation is shown in
table 4.
Table 2. Geotechnical Characteristics of Soil in Pegu Group at 5m Depth
Soil Type
(USCS)
Wet
unit
wt
(kN/m3)
Dry
unit
wt
(kN/m3)
SPT
N
value
Moist
ure
conte
nt
(%)
Atterberg Limits UCS
Strength
value
(kPa)
Shear Strength
L.L
%
P.L
%
P.I c
(kPa)
()
CL 19.41
-
20.55
16.19
-
17.47
9
-
14
17
-
20.87
36
-
42
20
-
22
16
-
20
74.7
-
116
34.3
-
78.5
12
-
19
ML 18.29
-
18.64
14.95
-
15.29
11
-
12
21.9
-
22.4
42
-
46
22
-
25
20
-
21
105.4
-
107.8
30.6
-
31.1
5
-
7
SM 18.4
-
20.11
15.82
-
17.23
12
-
32
28
-
32
- - - - - 32
-
36
MH 19.16
-
19.68
16.31
-
16.6
10
-
12
17.4
-
20.6
65
-
74
35
-
37
30
-
37
122.1
-
150.9
35
-
44
4
-
8
Table 3. Geotechnical Characteristics of Soil in Pegu Group at 10m Depth
Soil
Type
(USC
S)
Wet
unit
wt
(kN/
m3)
Dry
unit
wt
(kN/
m3)
SPT
N
value
Moist
ure
conte
nt
(%)
Atterberg Limits UCS
Strengt
h value
(kPa)
Shear Strength
L.L
%
P.L
%
P.I c
(kPa)
()
ML 18.2
3
-
18.4
14.6
3
-
14.8
9
-
15
24
-
24.6
36
-
42
20
-
22
16
-
20
86
-
88.5
26
-
27.3
3
-
4
MH 19.2
8
-
19.7
9
16.3
8
-
17.0
4
15
-
21
16.3
-
17.6
65
-
70
32
-
35
30
-
35
143.7
-
170
38.8
-
46
4
-
8
SC 18.6
2
-
19
15
-
15.6
19
-
32
19
-
24
- - - - 88
-
88.3
12
-
20
SM 18.5
6
-
18.6
2
15.3
2
-
15.6
13-
34
20.8
-
21.0
- - - - 3-5 8
-
34
SW 17
-
17.3
14.2
-
14.5
9
30
-
46
23
-
27
- - - - - 30
-
36
Figure 27. Preparation of core sample by core drilling machine
1
'
Soil
Type
(USCS)
Wet
unit
wt
(kN/m3)
Dry
unit
wt
(kN/m3)
SPT
N
value
Moist
ure
conte
nt
(%)
Atterberg Limits UCS
Strength
value
(kPa)
Shear Strength
L.L
%
P.L
%
P.I c
(kPa)
()
CL 18.55
-
19.71
15.02
-
15.92
6
-
9
22.5
-
23.8
36
-
42
20
-
22
16
-
20
62.27
-
105.4
39.2
-
71.6
10
-
18
ML 18.17
-
18.81
14.63
-
15.68
10
-
12
19.8
-
24.6
42
-
46
22
-
25
20
-
21
86.22
-
117.4
25.9
-
35
4
-
12
SC 18.51
-
19.53
14.97
-
15.18
19
-
32
19
-
30.5
- - - - 88.3
-
113
9
-
12
MH 18.56
-
18.9
15.32
-
15.37
13
-
19
20.8
-
21.0
65
-
74
35
-
37
30
-
37
114
-
117
34
-
35
8
-
12
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29
Figure 28. Core samples of Thardugan Sandstone
Table 4. Example bearing capacity calculation of soil in Pegu Group
Depth
(m) Em Cb Cr N N60 CN (N1)60
Qult(kPa)
BH-1
1
0.4
5 1
0.7
5 8 4.5
17.
4
2.0
0 9.02 108.22
2
0.4
5 1
0.7
5 13 7.3 25
1.9
6 14.33 171.98
3
0.4
5 1
0.7
5 16 9.0
32.
9
1.7
1 15.38 184.52
4
0.4
5 1
0.7
5 12 6.8
40.
3
1.5
4 10.42 125.04
5
0.4
5 1
0.8
5 9 5.8
47.
7
1.4
2 8.14 97.69
6
0.4
5 1
0.8
5 16
10.
2
54.
7
1.3
2 13.51 162.18
7
0.4
5 1
0.8
5 16
10.
2
62.
6
1.2
4 12.63 151.60
8
0.4
5 1
0.8
5 16
10.
2
70.
5
1.1
6 11.90 142.85
9
0.4
5 1
0.9
5 16
11.
4
78.
4
1.1
0 12.62 151.40
10
0.4
5 1
0.9
5 16
11.
4
86.
3
1.0
5 12.03 144.31
BH-2
1
0.4
5 1
0.7
5 11 6.2
17.
1
0.2
4 1.50 17.99
2
0.4
5 1
0.7
5 14 7.9
22.
4
0.2
1 1.67 20.03
3
0.4
5 1
0.7
5 15 8.5
29.
9
0.1
8 1.55 18.57
4
0.4
5 1
0.7
5 16 9.0
38.
7
0.1
6 1.45 17.40
5
0.4
5 1
0.8
5 17
10.
9
47.
1
0.1
5 1.58 18.99
6
0.4
5 1
0.8
5 18
11.
5
55.
2
0.1
3 1.55 18.58
7
0.4
5 1
0.8
5 19
12.
1
67.
3
0.1
2 1.48 17.76
8
0.4
5 1
0.8
5 18
11.
5
79.
4
0.1
1 1.29 15.48
9
0.4
5 1
0.9
5 17
12.
1
83.
3
0.1
1 1.33 15.96
10
0.4
5 1
0.9
5 17
12.
1
91.
9
0.1
0 1.27 15.19
Uniaxial compressive test and point load test are performed for
geotechnical characteristics of Thardugan Sandstone. Figures 27 to 30
shows preparation of core sample by using rock core machine and
performance of uniaxial compressive test and point load test.
6. RESULTS & CONCLUSION
Pegu Group consists of Besapet Alternation, Thardugan Sandstones
and Hlawga Shale from surface geologic characters and subsurface
data. Besapet Alternation consists of shales and thinly laminated
sandstone which are exposed in the vicinity of Besapet Lake and
behind the police training school. It is characterized by blunish grey to
greenish grey, bedded to nonbedded, silty shale with very thin parting
of micaceous sandstones.
Figure 29. Performance of Uniaxial compressive strength test
Figure 30. Failure condition of Thardugan Sandstone
Thardugan Sandstone consists of blunish grey to brownish grey, fine to
medium grained micaceous and argillaceous sandstone with
ferruginous bands. They are exposed around the Thardukan Pagoda,
southwestern and south of Hlawga lake. Thardugan Sandstone
exposed as massive body sandstone around Thardukan Pagoda and
thin bedded sandstone at police training school.
Shale and laminated clay comprises in Hlawga Shale. They occur at the
low land area at the west of Hlawga Lake beside the Thardugan
Sandstone.
Well consolidated nature and lithologic character of Pegu Group make
more or less impervious and considered to be non-water bearing.
According to the laboratory results, most of the Thardugan Sandstones
are fine to medium grained and loose to dense. According USCS
classification, CL, ML, MH, SC, SM and SW soil types are found as
residual soil in Pegu Group. Geotechnical characteristics of residual soil
of Pegu Group at depth 3m, 5m and 10m are shown in tables. The
ultimate bearing capacity of residual soil of Pegu Group is from 15kPa
to 600kPa. The unconfined compressive strength of Thardugan
Sandstone is between 8 MPa to 61 MPa. The foundation condition of
Thardugan Sandstone is rated as very good foundation condition than
the Hlawga Shale and Besapet Alternation. SW soil type in residual soil
of Pegu group is excellent to good for road foundation. Shear strength
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30
is excellent and compressibility is neglectable. Excellent drainage
characteristics and low compressibility is found in SM soil type. It is fair
for road foundation. In CL soil, drainage characteristics is impervious
and fair shear strength. It is fair to poor for road foundation.
ACKNOWLEDGEMENTS
The author’s heartfelt thanks to Dr Myint Thein, Rector, Yangon
Technological University for his permission. Special thanks to Dr Day
Wa Aung, Professor and Head of Geology Department, Yangon
University for his help and sharing knowledge and expertise. I would
like to extend thanks to Dr, Htay Lwin, Professor of Geology
Department, YU and Dr. Tun Naing Zaw, Associate Professor of Geology
Department, YU for their valuable advice and guideline. I also thank to
U Kyaw Zin Lat, Associate Professor, U San Oo, Lecturer and Daw Nan
Mo Kham, Assistant Lecturer, YTU for their help and supporting. I also
thank to U Sai Zarni Soe for his microscopic study of rocks. The author’s
deepest thanks are due to all persons for their excellent
encouragements and supporting in carrying out this research
CONFLICT OF INTERESTS
The authors declare that there is no conflict of interest related to the
publication of this article.
REFERENCES
[1 Yangon downtown Map, . [Accessed;
March 2015
[2 W. Naing, Hydrogeology of Greater Yangon, M.Sc.Thesis.
University of Yangon, 1972.
[3 Google Earth Pro 2020, Google Map of Yangon Area. March 2020
[4 V.N.S. Murthy, Principle and Practices of soil Mechanics and
Foundation Engineering, Marcel Dekker Inc, New York, 2003.