1. science
2. geology

SOME STRENGTH TESTS ON THE
GABBROIC ROCKS FROM THE
NORTH HATTA AREA, UNITED
ARAB EMIRATES
Hasan Arman, Mohamed El Tokhi and Bahaa Eldin Mahmoud Amin
United Arab Emirates University
30 March- 1April, 2015
The Third International Forum for Industrial Rocks & Mining, Expo, Emirates
of Fujairah, United Arab Emirate
Outline of the Presentation
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INTRODUCTION
GEOLOGICAL SETTING
FIELD & LABORATORY STUDIES
RESULTS
CONCLUSIONS & DISCUSSION
ACKNOWLEDGEMENTS
INTRODUCTION
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The study area is located in North Hatta Shear
Zone, at the border between the United Arab
Emirates and Oman.
It is about 95 km north of Al-Ain city and 60 km
southeast of Dubai.
It is located between longitude 24°50'N - 24°60'N
and latitude 55°60'E - 56°17'E (Figure 1).
INTRODUCTION
Figure 1. Simplified
geologic map for the study
area
INTRODUCTION
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The geological features of the proposed region was
restudied through the available literature and field
observations.
During the study, sample locations were identified and
marked on the map (see Figure 1).
INTRODUCTION
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Number of rock samples having different size of at
least 0.30x0.30x0.30 m were collected from selected
sample locations and taken to the laboratory.
Those rock samples were used to prepare rock samples
for different strength types. These are:
o
o
o
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The unconfined compressive strength (UCS),
Brazilian strength (BRS),
Point load strength index (PLSI) and
Schmidt hammer hardness (SHH)
INTRODUCTION
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Those tests were carried out either on the selected rock
block samples or core samples according to suggested
standards.
The main objective of this study is to investigate and
report the strength properties of the gabbroic rocks,
which are important parameters in geology and
engineering applications on/and in rock mass, from North
Hatta area, through in-situ and experimental studies and
discuss their probable influences as foundation and
construction materials.
GEOLOGICAL SETTING
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Field observation revealed that the rock units exposed in
the Hatta zone structurally below the Semail ophiolite,
include platform slope carbonates (Sumeini Group), base
of slope re-deposited sediments (Hamrat Dom Group),
and more distal, deep-sea sediments (Hawasina),
volcanics and metamorphic rocks of the ophiolite sole
(Haybi Complex).
GEOLOGICAL SETTING
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Moreover, Wadi (valley) Hatta consists of highly
deformed imbricate thrust sheets, (allochthonous unit)
which are intact and unconformably overlained by
Maastrichtian sedimentary cover in Jabel (mountain) AlRouda.
The rocks of Hatta area consist predominantly of mafic
and ultramafic rocks, which are considered as units of the
ophiolitic succession.
GEOLOGICAL SETTING
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Hatta area comprises of highly deformed imbricated
thrust sheets of ultramafic rocks.
The ophiolite complex dominates the area around Wadi
Hatta as are relatively continuous belt covering more
than 2/3 area.
Mafic and ultramafic rocks are considered as the major
units of the ophiolitic succession represented by
peridotites, pyroxenites and gabbros (see Figure 1).
GEOLOGICAL SETTING
Figure 1. Simplified
geologic map for the study
area
GEOLOGICAL SETTING
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The gabbroic rocks in the study area form rugged
mountains and rest with tectonic contact against the
underlying mantle sequence.
They occur as faulted blocks to the east and north of
the study area being bounded to the NE and NW by
thrust faults, which have emplaced them over tectonized
peridotite.
The gabbros comprise troctolite, olivine gabbro,
gabbronorite, and normal gabbros.
FIELD & LABORATORY STUDIES
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Number of Schmidt hammer hardness tests were
performed in-situ (approimately1000 readings).
About 40-rock block samples, at least 0.30x0.30x0.30 m
in size, were collected from the field, and were used to
prepare rock samples for different strength tests.
FIELD & LABORATORY STUDIES
o
The unconfined compressive strength (UCS),
o
Brazilian strength (BRS),
o
point load strength index (PLSI) and
o
Schmidt hammer hardness (SHH)
Those tests were carried out either on the selected rock
block samples or core samples according to suggested
standards.
FIELD & LABORATORY STUDIES
FIELD & LABORATORY STUDIES
FIELD & LABORATORY STUDIES
FIELD & LABORATORY STUDIES
FIELD & LABORATORY STUDIES
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All UCS test specimens had a length of diameter ratio of
approximately 2:1.
Both samples ends of the test specimen were kept
perpendicular to the long axis as possible as (ASTM
D4543, 04.02, 1986).
The ASTM standard was used to define UCS of rock
samples (30 core samples) and a constant loading rate
was applied to the test specimen (ASTM D2938, 04.08,
1995).
In general, diagonal shear failure was commonly
observed.
FIELD & LABORATORY STUDIES
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The ITS test samples (37 circular cylinder samples) were
accomplished with reference to procedure described by
Bieniawski and Hawkes (1978) and tested following to
the ISRM procedure (ISRM Suggested methods, 1981).
The PLI tests (24 core samples) were performed following
the procedure described by ASTM (ASTM D5731, 04.0.,
1995).
FIELD & LABORATORY STUDIES
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The SHH of the gabbroic rocks was defined by the rock
hammer test (about 1000 readings in the field and 300
readings in the laboratory). The testing procedure as
recommended by ASTM was followed (ASTM D5873,
04.08., 1996).
RESULTS
SHH
UCS
(MPa)
ITS
(MPa)
PLI
(MPa)
Min.
115
5
5
14
34
Max.
340
19
18
49
49
Mean
209
9
11
36
43
SD*
54
3
3
7
3
Field Test Laboratory Tests
CONCLUSIONS & DISCUSSION
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The UCS of gabbroic rocks in the study area ranges
from high to very high strength with most being high
strength according to Deere and Miller, 1966 .
The ITS was determined by Brazilian and point load
index tests. The strength value obtained by Brazilian
test were more or less same to the strength value
obtained with the point load index test.
The SHH test exhibits quite scattering. This may be due
to rock surface roughness characteristics.
CONCLUSIONS & DISCUSSION
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The strength properties of the Gabbroic rocks are
important parameters in geology and engineering
applications on/and in rock mass.
Nevertheless, generalizing the mechanical properties of
the gabbroic rocks is unreliable due to changes in their
structure, texture and even mineralogical composition.
Therefore, engineers should take extreme precaution
when they use these values in foundation design and as
construction materials.
ACKNOWLEDGEMENTS
This research was financially supported by the Research
Affairs at the UAE University under a contract
#COS/122/156. The authors grateful to the
Department of Geology for encouragements and
support, which led to finalize this research work.
Thanks
The Third International Forum for Industrial Rocks & Mining, Expo, Emirates of Fujairah, United Arab Emirate,
30 March- 1April, 2015