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B,^IPUBLICATIONS come4cruaMENDING SECTION11,
BUREAU OF MINGOLOGY AN 3
NA_= NESCDUE3C -ESaaEOPHYMCS
RECORD
BMR Record 1981/25
ROAD GRAVEL INVESTIGATION, BLOCK 64,
TENNANT, ACT
by
G.F. Sparksman
The information contained in this report has been obtained by the Bureau of Mineral Resources, Geology and Geophysics aspart of the policy of the Australian Government to assist in the exploration and development of mineral resources. It may not be -published in any form or used in a company prospectus or statement without the permission in writing of the Director.
BMR Record 1981/25
ROAD GRAVEL INVESTIGATION, BLOCK 64,
TENNANT, ACT
by
G.P. Sparksman
CONTENTS
Page
ABSTRACT
INTRODUCTION^ 1
FIELD INVESTIGATION
SAMPLE ANALYSIS
ALTERNATIVE SOURCES OF MATERIAL^ 2
CONCLUSIONS^ 2
REFERENCES^ 3
TABLE I. SUMMARY OF TEST DATA^ 4
FIGURES
1. LOCALITY MAP
2. LOCATION OF GRAVEL PIT AND BACKHOE TRENCHES
3. PARTICLE SIZE DISTRIBUTION CHART
4. PLASTICITY CHART
APPENDIX I. BACKHOE TRENCH PROFILES
ABSTRACT
Investigation of gravel pit on Block 64, Tennent, ACT by means
of trenching in described. The material - extremely weathered granodiorite -
proved to be too highly plastic for use on unsealed roads. EaLlier reports
of alternative sources of non-plastic gravel in the district are listed.
INTRODUCTION
Late in 1980, the Department of Capital Territory requested
BMR to investigate a disused gravel pit on Block 64, Tennent, ACT.
The purpose of the investigation was to determine the suitability of the
gravel for use on rural roads in the southern part of the ACT. About
1000 m3 per annum is required. The pit is located 9 km from Tharwa,
along the Naas Road and adjacent to the Gudgenby River, (Figs 1 and 2).
FIELD INVESTIGATION
Six backhoe trenches were excavated on 9 December 1980, and
samples were collected from various depths within the trenches and the
gravel pit. Twenty samples were collected, of which twelve were analysed.
Trench profiles are shown in Appendix 1. The gravel consists of in-situ
weathered granodiorite, moderately weathered to a depth of 2.5 - 3.0 m.
The possible working area for a gravel pit is shown in Figure 2. The
reserves of gravel in this area, using a working depth to 2.5 m, are 150, 000
m3
.
SAMPLE ANALYSIS
Testing of samples was undertaken in March 1981. Tests were
carried out according to procedures set out in Australian Standard 1289.
(Standards Association of Australia, 1977). These tests were Grain Size
Analysis, Liquid Limit, Plasticity Index and Linear Shrinkage.
The results of these tests are shown in Figures 3 and 4, and
Table 1 is a summary of the test data. Figure 3 shows graphs of the particle
size of samples. All samples tested lie within the limits specified by the
Department of Housing and Construction for unsealed pavements. All
samples have a low degree of uniformity; samples 1,5, 6, 8 and 11 have
-2-
high plasticity, while samples 2, 3, 4,^7, 9, 10 and 12 have medium plasti-
city. (Table 1).
The Department of Housing and Construction's specifications for
unsealed pavements are: Liquid Limit should not exceed 35%; Plasticity
Index (P.I.) should be between 2% and 10%, and even a less exacting
specification would require a P.I. between 10% and 16%. All the samples
tested, except one, do not conform to these specifications. The one sample
which does conform to even the less exacting specifications, no 7, had a
slightly coarser grain size in the fine sand section.
The gravel, because of its high plasticity is unsuitable for use
on unsealed pavements.
ALTERNATIVE SOURCES OF MATERIAL
There are two locations on the Naas Road just north of the
investigated site, where reserves of non-plastic gravel have been proved
in previous BMR investigations (Hansen, 1970; Bishop, 1973). These
locations are: Grid Reference 6087-2084, Michelago 1:50 000 sheet, where
there is about 100 000 m3 of non-plastic granitic slopewash; and Grid
Reference 6092-2088, Michelago 1:50 000 sheet, where there is about
--26 000 m3 of non-plastic, in-situ weathered granite.
CONCLUSIONS
I.^The material from the investigated pit is too highly plastic
for the proposed use on unsealed roads.
2.^There are alternative sources of non-plastic gravel in the area.
Fis. 1 LOCALITY MAP
148° 50'
•
HALL
V
149°10'
7
4).■ t'A^.--/COTTER
/^-,,..',..- DAM
,.
35 ° 20'
Ma Area Investigated
1.11 Built up Area
-7-- Railway
Highway
Principal Road
^Secondary Road
Vehicle Track
-^Territorial Boundary
• Township
(
CORIM ' DAM
See Fig 2NAAs
I^\7"--/
`.!`,^-aco^_\
az •_cr
"S5°40'
(
12^16^20 Kilometres0^4^81
16/155-16/38Record 1 '81/25
Fi9ure 2 Location of 9r~vel pit and backhoe trenche,
-- ---
M~ 2~~O-+'-+I~I~'~b~-------4----------s~A-o--------~--------~IO~ M~TRcS
__ -:::: TO
¥ ~ >IrIi#1s Rei Il_ -----\:-,)
I \
RFFER£NCE
........ -...... ---I I ---
ROQaI s~led ROQd unsealed
81 oc k bo .... nolary
Grovel pit
Trench) sQrtlple no.
River- , perenn'lCtI Creek, intermittent Area of fDssible
'llJarry; oul-lined +0 calc u late reserves .
- - ---- ----- - ---
C ontol.l" intervQ1 25" Metres
£iJure 3 PARTICLE SIZE DISTRIBUTION CHART
8.S. 51 £ VE
2 -+ 6 \0 20
PARTICLE SIZE -MICRON I CLAY SILT
FINE 1 MEDIUM I COARSE FINE Ru.ord 19&1/25
N-1 3' • 1" - 1 1_ 4 '2
PARTICLE SIZE -MILLIMETRE SA NO GRAVEL
IMED/UM I COARSE FINE IMEOIUM I co ARSE
6" 3G"
16111i~-1& 40 UI/lf(NJ/U
lCOBBLES BOULDERs
)< lu o :z
>I-
bO
50
4-0
30
10
LOW
. _- --- - - --- ----_._ - -
MEC 'UM
i0 3
q V 0 12-
/ l(
HI GH PLA STICITY /'" V
~ V
b' y
0 ,/ // ~
0 b
fb ~ /
71 ._ -- _._ ---_.- ------- - --- - - - - -
o
Rcccord 1961/26
I O · :J. 0 30 4-0
L I QUID
Fi9ure 4- PLASTICITY CHART
50 LIMIT
-- - - - - - -- -- --- . . _- ------ - - _ . - --- - --- - - -
60 70 8'0 qO 100
16/1 SS-16/ 4.1
3
REFERENCES
BISHOP, I.D., 1973 - Gravel for rural roads - seismic refraction surveys
near Tharwa and Williamsdale, A.C.T. Bureau of Mineral Resources,
Australia - Record 1973/40.
HANSEN, R.J., 1970 - Gravel for rural roads, Naas Road, Tharwa area.
Bureau of Mineral Resources, Australia - unpublished report.
STANDARDS ASSOCIATION OF AUSTRALIA, 1977 - Methods of testing soils for
engineering purposes. Australian Standard 1289.
4
TABLE 1. Summary Of Test Data
Sample No.^ 1^2^3^4^5^6^7^8^9^10^11^12
Location (Q, Quarry Wall;^Q^Q^T6^T6 T4^T4^T3 T3 T3 T2 T2 T2T, Trench)
Depth (m)
3
0.7 1.5 0.5 1.4 0.5 1.4 0.2 0.6 1.1 0.3 0.6 1.3
Passing^ INCH sieve/8
% 99 99 100 99 100 99 99 100 99 92 90 92
3 n/16
% 82 72 84 80 97 82 92 81 88 69 73 60
Passing BSS No^7 (2.41 mm) % 56 38 51 45 76 40 65 45 51 39 46 3714^(1.20 mm) % 41 22 32 26 56 21 48 27 29 25 30 2025^(^.60 mm) 7. 31 14 22 16 41 12 38 17 18 16 20 1336 (^.42 mm) % 27 11 19 13 35 10 34 13 15 13 16 1052 (^.29 mm) % 24 9 16 11 29 8 29 10 12 10 13 8100^(^.15 mm) % 19 6 12 8 21 6 23 6 9 7 8 6200 (^.076mm) % 15 4 10 5 16 4 17 4 6 5 6 4
-200 % 15 4 9 5 15 4 16 4 6 5 6 4
Uniformity Coefficient 11 30 12 8 12 15 14 17 12(U=d60
/d10 )
Passing No 36 BSS Material
Liquid Limit % 65 41 44 43 53 56 31 53 40 48 63 38
Plastic Limit % 26 22 22 20 23 24 23 24 20 22 25 20
Plasticity Index % 39 19 22 23 30 32 8 29 20 26 38 18
Linear Shrinkage % 14 11 12 12 12 13 4 11 10 12 12 9
APPENDIX 1
Trench^1
Backhoe trench profiles (depths in metres)
Trench 4
0^- 0.3 Topsoil 0 - 0.1 Topsoil
0.3 - 0.4 Brown silty sand 0.1 - 0.25 Sandy silt
0.4 - 0.5 Brown-yeflow mottled silt . 0.25 - 0.8 EW granodiorite
0.5 -^1.3 HW to MW granodiorite 0.8 -^1.4 HW grabodiorite
1.3 - 1414 granodiorite 1.4 - MW granodiorite
Trench 2 Trench 5
0 -0.15 Topsoil 0 - 0.2 Sandy topsoil
0.15 -.0.4 Light brown gravelly sand 0.2 - 0.35 Silty gravel
0.4 - 0.65 Dark brown-yellow silty clay 0.35 -^1.0 EW granodiorite
0.65 -^1.4 HW granodiorite 1.0 -^1.5 HW granodiorite
1.4 - MW granodiorite 1.5 - MW granodiorite
Trench 3 Trench 6
0 - 0.2 Sandy topsoil 0 - 0.15 Sandy topsoil
0.2 - 0.4 Silty gravel 0.15 - 0.4 Silty gravel
0.4 - 0.8 EW granodiorite 0.4 - 0.6 EW granodiorite
0.8 -^1.5 HW granodiorite 0.6 -^1.4 HW granodiorite
1.5 - MW granodiorite 1.4 - MW granodiorite
Reference
MW = Moderately Weathered: rock is discoloured and noticeably weakened;N-size drill core generally cannot be broken by hand across the rock fabr -
HW = Highly Weathered: rock is discoloured and weakened; N-size drill corecan generally be broken by hand across the rock fabric.
EW = Extremely Weathered: rock is decomposed to a soil, but the originalrock fabric is mostly preserved.