uniaxial compressive strength, dry unit weight and fracture patterns

Transcription

lIEArlo Tr)~ EiJlflVIK~~ rEwAoVIKt'\~ ETOIpia~ TOIJ.
XXXX,
2007
npaKTJKO 11°" lIIEeVOU~ LUVEOpiou. Aet'\va, Malo~ 2007
Bulletin of the Geological Society of Greece vol. XXXX, 2007
Proceedings of the 11'" International Congress, Athens, May,
2007
UNIAXIAL COMPRESSIVE STRENGTH, DRY UNIT WEIGHT
AND FRACTURE PATTERNS OF ULTRABASIC ROCKS IN
OTHRYS MOUNTAIN (CENTRAL GREECE):
CORRELATIONS AND EVALUATION.
Diamantis K.\ Karamousalis Th.!, Antoniou Vas.\ and Migiros G. I
f
Agricultural University ofAthens, Department ofSciences, Division ofGeological Science and
Atmospheric Environment, Laboratory ofMineralogy-Geology, [email protected],
[email protected], [email protected], [email protected]
Abstract
Ultrabasic rocks, taken from the Othrys m!. (Central Greece), are studied in this pa
per. The structural geology and tectonics of the study area are described. Uniaxial
Compressive Strength (UCS) and dry unit weight (y) values are calculated andFac
ture angles are measured The results are statistically assessed and empirical rela
tionships (exponential equations) between UCS and yare presented for the ultra
basic rocks, divided in Peridotites, Serpentinised Peridotites and Serpeminites. Due
to the low correlation coefficient ofthe Serpentinised Peridotites, it was decided that
the Selpentinised Peridotites and Se7peminites should be examined together. The
correlation coefficient of the combined category is much better than the separate
ones.
Furthermore, this paper demonstrates that the majority ofthe ultrabasic rocks tested
were breaking at one angle (rp), which mainly fluctuated between 75° and 90~ The
fracture angles correlate with preViously recognised geological (mainly tectonic)
structures.
The observed deviations are due to petrographic variety, structural complexity, pre
ferred orientation of olivine and orthopyroxene and internal imprinted tectonic de
formation.
Key words: Rock mechanics, ophiolites, laboratOly tests.
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Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
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1. Introduction
Many attempts have been to correlate the Uniaxial Compressive Strength (UCS), which is
undoubtedly the geotechnical property of rocks which is most often quoted, with certain
mechanical and physical characteristics. Nevertheless, only few studies have been concentrated on
ultrabasic rocks (Kournantakis 1982, Paventi et at. 1996, Marinos et at. 2006). An opportunity to
conduct such investigation came up when the Laboratory of Mineralogy-Geology of the
Agricultural University of Athens undertook the geomechanical tests from ERGOSE S.A. for the
construction ofrailway tunnels in Othrys mt.
The study area is located in Othrys (Central Greece) and specifically between the villages of
Lianokladi and Domokos (Fig. 1). It belongs to the Sub-Pelagonian geotectonical unit and it is
mainly comprised of ultrabasic rock masses (Marinos 1974, Migiros 1990).
A number of boreholes were drilled along a narrow N-S zone, from which 138 representative
samples were chosen to be examined.
Uniaxial Compressive Strength and dry unit weight ('1) values were calculated following the
international standards. Photographs were taken before and after each test, fracture patterns were
drawn, the angles were measured and statistically classified.
Within the framework of the present study, the fluctuations ofUCS and "( values and the statistical
analysis of the fracture angles are presented. This paper attempts to derive reliable empirical
equations between UCS and "(, to correlate them with both fracture angles and depth and to outline
the influence of the geological Structure.
2. Materials and methods
Drill core samples from the Othrys mt. were investigated for geotechnical purposes (construction
of railway tunnels by ERGOSE S.A.) in the Laboratory of Mineralogy-Geology of the Agricultural
University of Athens. The boreholes were carried out in a 25 km long N-S direction, from
Lianokladi to Domokos villages, perpendicular to the geological and tectonic structures of the area
and they were drilled at depths up to 300 m from the surface. The wide range of sampte depth
along with the quite large numbers of samples, render our results representative for the Othrys
ultrabasic rock masses.
The initial choice of the samples and the sequence of tests were decided by the supervising rock
mechanics engineer and geologists. At our laboratory a second check was done by taking into
account the isotropy and homogeneity of the samples and some were disqualified as inappropriate
(about 33 %), mainly due to visible discontinuities, i.e. fractures, reducing the number of samples
to 138.
Due to the variable grade of serpentinisation of the peridotite samples, many thin sections were cut
and examined under a polarising microscope and some samples were further analysed by the XRD
method. Three petrologic types of peridotites were distinguished based on their different physical
and mechanical properties.
- 265
The Uniaxial Compressive Strength (UCS) tests were carried out in accordance with the ISRM
(1981) standard. The core samples, whose diameters were 61, 71 and 83 mm, were carefully
prepared keeping an LID ratio between 2,5 and 3,0. The edges of the samples were cut parallel and
smooth. The samples were then oven dried and before every test the samples were weighted with
accuracy in order to calculate the dry unit weight. After each test, the pattern of the fractures was
drawn and the angles of the fractures were measured.
The data was analysed with the Analysis Tool Pack of Microsoft Excel 2003 and the results were
evaluated and then correlated with the geological structures of the area.
3. Geology
The area between the Lianokladi and Domokos villages (Othrys mt.) consists mainly of Alpine
formations (Fig. 1) that belong to the Sub-Pelagonian geotectonic unit (Mountrakis et al. 1983,
Katsikatsos et at. 1986). We can distinguish them, from bottom to top, in the following fonnations
(Marinos 1974, Ferriere 1982, Migiros 1990):
(a) A carbonate sequence of Triassic-Jurassic age which constitutes the basement of the area.
(b) A tectonic nappe, mainly ophiolitic (Katsikatsos et al. 1986)
(c) An unconformable sequence of Cretaceous limestones which passes upward to flysch.
'.."J
':;
c:==:
\~
6
:::~
LIANOKLADJ
Scale
l; <f~
L--J
-------- .~ - -2Jj
d~
-'
LAMIA
l
Figure 1- Geological map of Othrys area (Migiros 1990): 1. Postalpine formations 2. Flysch
(a) Paleocene - Eocene CP) Upper Cretaceous 3. Cretaceous formations of eastern and
central Oth11's 4. Pre-Upper Cretaceous tectonic nappe (n) Undivided (~) Ophiolitic
formations (i) tectonites (ii) cumulates (iii) non-cumulites and volcanic sequence 5. Pre
Cretaceous formations (a) eastern (p) central Othrys 6. Western Oth11's formations
(undivided) 7. Geological boundary 8. Tectonic contact
The ophiolitic formations have thrusted the Triassic-Jurassic carbonate sequence and are consisted
of volcano-sedimentary formations, basaltic lavas, basic rocks and ultrabasic masses. The
- 266
ultrabasic rock masses are mainly represented by the peridotites whose grade of serpentinisation
vanes.
In our study we classified the peridotite samples into the following three rock groups taking into
account petrological and mineralogical studies:
(a) Peridotites: We refer mainly to lerzoliths, hartzbourgites and plagioclastic peridotites with a
grade of serpentinisation less than 30 %.
(b) Serpentised Peridotites: The same rock type but its grade of serpentinisation lies between 30 %
and 70 %.
(c) Serpentinites: Ultrabasic rock types, mainly hartzbourgites, whose grade of serpentinisation is
more than 70 %.
According to Migiros 1990, the tectonic analysis of the geological foonations exhibits the
following prominent tectonic features in the ultrabasic rock masses:
(a) Schistosity: NW-SE direction and NE dip less than 30°
(b) Low thrusts: E-W direction and N dip between 30°-45°.
(c) Thrusts: NW-SE direction and NE dip between 45°_60°
(d) Faults: E-W, NW-SE, NE-SW directions and dips more than 600
4. Laboratory test results
4.1, Dry unit weight (y)
The dry unit weight was calculated for the total number of 138 ultrabasic samples and their values
are illustrated in Figure 2. As seen in Table 1 (statistical analysis), the dry unit weight fluctuates
between 22.99 and 33.77 kN/mJ and the average value is 27.64 kN/m3 .
I-~
_.__ _
..
------..-.-... ---....---------..- .--..-
341
":
i
.. ~
....
I
32 I
I
I
"
~.=. I
o J
30
'.'
i"
1
>-
28
iii
~
!::
5
>
0:
".:
.... .....
......
..
..
26 ,
."."
o
:1
.__. ._. . _.
Figure 2 - Dry Unit weight values of the investigated ultrabasic samples
The ultrabasic rocks, based on their dry unit weight and taking into account their petrological
studies are divided in Peridotites, Serpentinised Peridotites and Serpentinites.
The dry unit weights of Peridotites range from 29.56 kN/m3 to 33.77 kN/m3 , those ofSerpentinites
from 22.99 kN/m3 to 25.98 kN/m 3 and the values of Serpentinised Peridotites vary from 26.00
kN/m J to 29.19 kN/m 3 (Table 2).
- 267
From the above mentioned and taking into account the low standard deviations of the groups that
were formed petrologically, we conclude that there is also a clear differentiation to the dry unit
weight values, as it was expected, which is due to the grade of serpentisation.
Table 1 - Statistical analysis results of the investigated ultra basic samples
ULTRABASIC ROCKS
DRY UNIT WEIGHT (KN/m 3)
MAX
33,77
MIN
22.99
MEAN
27.64
STDEV
2.62
Table 2 - Statistical analysis results of the investigated ultrabasic samples.
DRY UNIT WEIGHT (KN/m 3 )
PERIDOTITES
SERPENTINISED
PERIDOTITES
SERPENTIN ITES
MAX
33.77
MIN
29.56
MEAN
32.04
STDEV
1.52
MAX
29.19
MIN
26_00
MEAN
27.29
STDEV
0.81
MAX
25.98
MIN
22.99
MEAN
25.02
STDEV
0.77
------
60,00%
_·----1
i
52.17%
50,00%
E
~o.OO%
>
z
I
u
~
30,00%
:il
il:
20,00%
10,00% .
0.00%
<26.00
26.00-29,50
>29.50
DRY UNIT wEIGHT (KNlm J )
...._-----,--
Figure 3 - Dry unit weight histogram
Finally based on the results of the dry unit weight statistical analysis for each petrological group
and regarding 29.50 kN/m3 as the minimum value for Peridotites and 26.00 kN/m 3 as the
maximum value for Serpentinites, a histogram was created (Fig. 3). As can be seen the largest
number of samples belong to Serpentinised Peridotites (52.17 %).
4.2. Uniaxial Compressive Strength (UCS)
A scatter diagram of all UCS values is illustrated in Figure 4. The UCS values range from 169.63
to 0040 MPa exhibiting a great fluctuation. Some very uncommon low values of UCS are due to
internal discontinuities, macroscopically undetected. The mean value is 53.62 MPa and the
standard deviation is 35.34 MPa (Table 3). The high value of the standard deviation can be
attributed to the fact that the majority of the samples belong to the Serpentinised Peridotites group
(52.17 %), which exhibit great anisotropy.
- - - - - - - - --------_...._......
180 -'1-- - - - - - - -••••- . - - - .
I
i
I
140 t
160
-:
:IE
I
i" 120 j
~ 1
','
~.
100
CL
80
1
:::E
o
.....
•
~z 40 1
60
'.
.....
.'
..
:>
20·
..
..
"
"
o -"'•..-:.~._-'----_. ----'------...
Figure 4 - Uniaxial Compressive Strength values of the investigated samples
Ta ble 3 - Statistical analysis results of the investigated ultrabasic samples
ULTRABASIC ROCKS
UNIAXIAL COMPRESSIVE
STRENGTH
(MPa)
MAX
169.63
MIN
0040
MEAN
5362
STDEV
35.34
4.3. Fracture Angles (cpO)
Following the ues tests, photographs of the samples were taken and fracture patterns were drawn.
Of the 138 samples, 86.96% had single dipping fractures, while the 13.04 % was broken in two
angles (Fig. 5). These two groups of samples were statistically analyzed separately. After
distinguishing four bins (30°:Scpo<45°, 45°:,:cpo<60°, 60°:':<p°<75°, 75°:,:cp°:,:900), it is shown that both
groups were mainly broken in angles between 75° and 90° (Figs 6, 7). In addition, no fracture
angle values less than 30° were observed. Detailed statistical analysis is shown in Table 4.
Finally, for each sample the dominant angle was identified. A histogram of the prevalent fracture
angles is shown in Figure 8. It is evident that the majority of the samples (60.14 %) had a
prevalent fracture angle between 75° and 90°, while only the 2.17 % broke between 30° and 44°.
100,00% f .
8696%
90,00% . _~~_'_"..."..~
.
70,00%
60,00%
50,00%
40,00%·
30,00%
20,00%
10,00%
0,00% ~'''''''''",,"", .. "'",.1.
I
8' 80,00%
>
u
~
~
w
~
FRACTURE IN ONE
ANGLE
13,04%
0,00%
*"1
I
FRACTURE IN TWO FRACTURE IN MORE
ANGLES
THAN TWO ANGLES
ANGLES OF FRACTURE
Figure 5 - Frequency of the fracture angles
FRACTU RE IN ON E AA G LE
80 00% ~ ---- - - - - - - - - - - - - - _.--------- -- -- - - - - - --- --·~~~:o,~---1
7000%
UifW
tQ
80,00%
~
50,00%
G
ffi 40,00%
::>
o
~
30,00%
19,17'%
20.00%
10,83%
10,00°/0
2.50%
-1::
30-44
[
60-74
45-59
75-90
BINS
Figure 6 - Frequency of one fracture angle
FRACTURE IN TWO ANGLES
::::: 1-------------.--------- ---- ----- -----4-7~k_
-; 3500%
'"
;: 3000%
27,78%
~
25,00%
~ 2500% ,
~
2000%
u. 15,00%
[
=-
%
;::;:;;;::;a;:w
f
I
10,00'%
5,00%
0.00%
i
L
0.00%.
JO-M
I! ,
I
45.09
HI
""
60-74
'W
."
75-90
BINS
Figure 7 " Frequency of two fracture angles
a
Table 4 - Statistical analysis results offracture angles
FRACTURE IN ONE ANGLE
FRACTURE IN TWO ANGLES
BINS
30-44
45-59
60-74
75-90
30-44
45-59
60-74
75-90
FREQUENCY
3
i3
23
81
0
9
10
17
FREQUENCY
(%)
2,50%
10,83%
19,i7%
67,50%
0,00%
25,00%
27,78%
47,22%
MEAN
37,33
55,69
67,48
84,15
0
52,00
67,10
82,41
MODE
42
54
70
85
0
50
64
85
---
-_
•.•...

PREVALENT FRACTURE ANGLES
70,00% - ,- - - - -...--.-----.-.---~~.---.---~---- .. -.----'~ .. ~,.~-,
60.00%
~
~
50))lJ%
>
~ 40.00%
w
=>
a
~
30,OOC'Ai
I
I
W,OO% -\
10.00%
3D-44
45-59
60-74
75-90
BINS
Figure 8 - Histogram of the prevalent fracture angles
5. Results & Discussion
The statistical analysis software used to correlate ues and dry unit weight was the Analysis Tool
Pack of the Microsoft Excel 2003. Figure 9 is a plot diagram ofUeS against 'Y for the total number
of the samples. The relationship gives a good correlation coefficient (R=O.66) and is defined by
the equation UeS=O.0063eo.3117y A closer examination of Figure 9 reveals a discrepancy of the
normally exponential relationship between dry unit weight and ues. This is attributed to the
anisotropic single-crystal elastic properties and the lattice preferred orientation of olivine and
orthopyroxene. Specifically for the Peridotites, the relationship between ues and 'Y gives a high
correlation coefficient (R=O.78) and is represented by UeS=0.2067eo.1892·y (Fig. 10). The same
relationship gives a low correlation coefficient (R=0.26) for Serpentinised Peridotites (Fig. 11) and
a good one (R=066) for Serpentinites (Fig. 12). Thus it is suggested that Serpentinised Peridotites
and Serventinites should be examined together. The new correlation coefficient is 0.74 and the
equation is defined by the UeS=3·1O·7eo.6962·y (Fig. 13). Moreover, the deviations are due to the
varied grade of serpentinisation, the petrographic variety (ha11zburgites, lerzolites, plagioclastic
peridotites) and the internal structural complexity due to the tectonic deformation and alteration.
It can be seen from Figures 5-6, that the majority of the ultrabasic samples broke in one angle,
whicb predominately fluctuated between 75° and 90° When samples fractured in two angles, the
percentage of the bins 45°-59° and 60°-74° increased while the percentage of the bin 75°-90°
decreased (Fig. 7), which is quite reasonable.
From the aforementioned, it is obvious that the fracture angles of the samples deviate from the
expected value of 45° This is mainly attributed to the internal imprint of tectonic structures;
specifically, angles lower than 45° are related to low thrusts, between 45° and 60° to the thrusts and
Βιβλιοθήκη
Θεόφραστος
Τμήμα
Γεωλογίας.
Α.Π.Θ.
those with anglesΨηφιακή
greater than
60° are correlated
to the -faults
and/or
collapse effect.
Finally, there is no obvious relationship between the ues and the fracture angle as in between the
fracture angle and the depth from which the samples were taken. As it is aforementioned, this is
attributed to the petrographic variety and/or to the preferred orientation and the internally
imprinted tectonic structures.
250
i
....
_-"----------
y=O'OO63eO"~""
R =0,66
200
r
....
7l
/.
..
.
'.
.. . ,.
.
it
~ 150
'"
Ii
~ 100
8
~
~
24
26
26
30
I
34
32
CRY UNIT WBGHT (KHIm'j
Figure 9 - DeS against Dry unit weight for the total number of ultrabasic samples
PERIDOTITES
.~
180
j!:
140·
!!
~
<1l
'20
100
80
~
u
60 '
~z
40
20
'"
= O,2067eO 1e,.'lb
R = 0,76
160'1
Ii
0
y
"
·1
0 1
29
29,5
30
30,5
31
31,5
32,5
32
33
33,5
34
DRY UNIT WEIGHT (KNlm',
Figure 10 - DeS against Dry unit weight only for the Peridotites
y =O,3672~o, ,t.Otl~
SERP, PERIDOTITES
;;- 120,00
TI------·
..
i
~
I
100,00
~
~
00,00
ro
60,00
.i!:
.
....... .'
..... .... .
0
~
~
'
40,00
20,00
=0,26
'-~.------l
~
Ii
'<>"
R
'
..
I
I
.
j
0,00
Z5,50
26,00
26.50
27,00
27,50
26,00
28,50
29,00
29,50
DRY UNIT wEIGHT (KNlm')
Figure 11 - ues against Dry unit weight only for the Serpentinised Peridotites
y = 7&13e 1,'(I2.'
SERPENTINITES
R; 0,66
60--------------------_
Lol
:I:
,
I-
'
~ 40
w
....'"
~
• •
I
"'311
'u
• •
'z"'
:=! 10
:::>
••
20
•
o '-'-''1'='=-'=".".':::::O:==::;::!=----*-------i.-----'~---*-----___J
22.5
23
23.5
24
26
25.5
24.5
IKNlm'l
' - - - - - - - - - - - - - _ ...--_._- ... _._.... -...... ---- ----
26.5
mY UNT W8GtfT
-------_.-
Figure 12 -- DeS against Dry unit weight only for the Serpentinites
.. --.------.,
y ; 3E-07e'·"'"
SERPENT1NITES-5ERPEN, PERIDOTITES
R=0.74
-------_._-_.
~ 200
~ 180
~ 160
~
w
~
~
g:
~
i40
120
iDa
GO
u
60
40
'"'
20
~
~
••
0 _ _!'.__=-_~-=:;~7:.~=
22
23
24
....:....-
28
25
30
2\l
[:flY UNIT WBGHT (KNlm'l
' - - - - - - - - - - - _ .. --....
__
._._._----~
-
...- ....
.
Figure 13 - DeS against Dry unit weight combining Serpentinised Peridotites and
Serpelltinites
6.
Conclusions
Due to the petrographic variety, the grade of serpentinisation, prefened orientation of olivine and
orthopyroxene, the structural complexity and the internally imprinted tectonic deformation,
ultrabasic rocks were divided in three groups (Peridotites, Serpentinised Peridotites and
Serpentinites). Each group presents a wide range of geomechanical and physical properties.
This paper demonstrates that for ultrabasic rocks, the relationship between UCS and y gives a good
correlation coefficient (R=0.66) and is defined by the equation UCS=0.0063eo.3117·y. For the
Peridotites only, the relationship between UCS and y gives a high conelation coefficient (R=O.78)
and is represented by UCS=0.2067eo.1892·y. As far as Serpentinised Peridotites are concerned, the
relationship between UCS and y presents a low con'elation coefficient (R=0.26) in contrast to
Serpentinites (R=0.66). It was realized that the examination of Serpentinised Peridotites and
Serpentinites together provides a good correlation coefficient (0.74) and the new equation is
defined by the UCS=3·1O· 7e 0.6962"(. It is obvious that the determination of UCS value with an easy
and economical way (estimation ofy) can provide an important help to the geotechnical engineers.
Furthermore, the majority of the ultrabasic samples were fractured in one angle, which mainly
varied between 75° and 900. The samples broken in two fractures, presented an increase of the
percentage of the bins 45°-59° and 60°-74° while the percentage of the bin 75°-90° got decreased.
Moreover, the fracture angles of 30°-44° were mainly correlated with low angle thrusts, the bin of
45°-59° corresponds
to the Βιβλιοθήκη
thrusts and that
of 60°-90° to- Τμήμα
the faultsΓεωλογίας.
or collapse Α.Π.Θ.
effects.
Ψηφιακή
Θεόφραστος
_ '1'71. _
Finally, there is no apparent relationship between the fracture angle and the depth from which the
sample was taken and between the UCS and the fracture angle.
7. References
Ferriere, J., 1982. Paleogeographies et Tectoniques Superposees dans les Hellenides Internes au
Niveau de l' Othrys et de Pelion (Crece), Univ. des Sciences et Techniques de Lille.
LS.R.M., 1981. Suggested methods for determining the uniaxial compressive strength and deform
ability of rock materials, International Society of Rock Mechanics, Commission on stan
dardization ofLaboratory andfieLd tests, 111-116pp.
Katsikatsos, G., Migiros, G., Triantaphyllis, M., and Mettos, A., 1986. Geological structure of in
ternal Hellenides (E. Thessaly-SW Macedonia, Euboea-Attica-Northern Cyclades islands
and Lesvos). I.C.ME., Ceo!. and Ceoph. Res., Special Issue, 191-212.
Koumantakis, J., 1982. Comportement des peridotites et serpentinites de la Grece en travaux pu
blic. Leur propretes physiques et mechaniques, Bul IAEC, 25, 53-60.
Marinos, G., 1974. Geology of Othrys and issues on its ophiolites, Ann. Ceo!. Des Pays Hell.,
University of Athens, 118-148.
Marinos, P., Hook, E., and Marinos, V., 2006. Variability of the engineering properties of rock
masses quantified by the geological strength index: the case of ophiolites with special em
phasis on tunneling, Bull. Eng. Ceo!. Env. 65, 129-142.
Migiros, G., 1990. The lithostratigraphic-tectonic structure of Othris (Central Greece), BuLl. of the
CeoL. SocietyofCreece, XXVI, 107-120.
Mountrakis, D., Sapountzis, E., Kilias, A., Eleftheriadis, G., and Christofides, G., 1983. Paleo
geographic conditions in the western Pelagonian margin in Greece during the initial rifting
of the continental area, Canadian Journal ofEar. Sc., 20,1673-1681.
Paventi, M., ScobIe, M., and Stead, D., 1996. Characteristics of a complex Serpentinised Ultrama
fic Rock Mass at the Birchtree Mine, Manitoba. In H. Aubertin, Mitri (ed.), North Ameri
can Rock Mechanics Symposium, Rotterdam, 339-346pp.
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