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Four different porous limestone lithotypes were collected from the cellar system of Budapest (Hungary). All lithologies have high porosities ranging from 16 to 30%. The laboratory analyses focused on the mechanical properties testing to assess the strength changes due to water saturation. The density, ultrasonic sound wave propagation, uniaxial compressive strength (UCS) and indirect tensile strength (determined by Brazilian test) test were measured on cylindrical specimens according to EN and ASTM standards in the laboratory. Both dry and water-saturated samples were tested. The results indicate that four lithotypes have distinct strength parameters, and both the UCS and the indirect tensile strength decrease with water saturation. The largest decrease in strength was observed at fine-grained porous limestone and at fine- to medium-grained limestone with a decrease in strength of over 50%. On the contrary, the strength loss of coarse porous limestone is in the order of 16 to 14% of UCS and indirect tensile strength, respectively. Comparing the data set of this study with previous works on various limestones, a good correlation was found between density and Brazilian tensile strength. The presented data set was used as the input parameters for calculating the stability of dry and water inundated cellars. The FEM (Finite Element Methods) calculations of cellar stability indicate that the displacement of water-saturated cellars is nearly triple of the dry ones and that the factor of safety reduced from 1.74 in air-dry condition to 1.07 in water-saturated conditions.
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Acta Montanistica Slovaca, Volume 25 (2020), 3; DOI: 10.46544/AMS.v25i3.7
Stability of Underground Excavation in Porous Limestone:
Influence of Water Content
Jalal ZENAH
1
*, Péter GÖRÖG
2
and Ákos TÖRÖK
3
Authors’ affiliations and addresses:
1
Department of Engineering Geology and
Geotechnics, Budapest University of Technology
and Economics, Budapest, Hungary
e-mail: jalal.zenah@epito.bme.hu
2
Department of Engineering Geology and
Geotechnics, Budapest University of Technology
and Economics, Budapest, Hungary
e-mail: gorog.peter@epito.bme.hu
3
Department of Engineering Geology and
Geotechnics, Budapest University of Technology
and Economics, Budapest, Hungary
e-mail: torokakos@mail.bme.hu
*Correspondence:
Jalal Zenah,
Department of Engineering Geology
and Geotechnics, Budapest University of
Technology and Economics, Budapest, Hungary
e-mail: jalal.zenah@epito.bme.hu
Acknowledgement:
The research reported in this paper and carried
out at BME has been supported by the NRDI
Fund (TKP2020 IES, Grant No. TKP2020 BME-
IKA-VIZ) based on the charter of bolster issued
by the NRDI Office under the auspices of the
Ministry for Innovation and Technology.
How to cite this article:
Zenah, J., Görög, P. and Török, A. (2020).
Stability of Underground Excavation in Porous
Limestone: Influence of Water Content. Acta
Montanistica Slovaca, Volume 25 (3), 337-349
DOI:
https://doi.org/10.46544/AMS.v25i3.7
Abstract
Four different porous limestone lithotypes were collected from the
cellar system of Budapest (Hungary). All lithologies have high
porosities ranging from 16 to 30%. The laboratory analyses focused
on the mechanical properties testing to assess the strength changes
due to water saturation. The density, ultrasonic sound wave
propagation, uniaxial compressive strength (UCS) and indirect
tensile strength (determined by Brazilian test) test were measured
on cylindrical specimens according to EN and ASTM standards in
the laboratory. Both dry and water-saturated samples were tested.
The results indicate that four lithotypes have distinct strength
parameters, and both the UCS and the indirect tensile strength
decrease with water saturation. The largest decrease in strength was
observed at fine-grained porous limestone and at fine- to medium-
grained limestone with a decrease in strength of over 50%. On the
contrary, the strength loss of coarse porous limestone is in the order
of 16 to 14% of UCS and indirect tensile strength, respectively.
Comparing the data set of this study with previous works on various
limestones, a good correlation was found between density and
Brazilian tensile strength. The presented data set was used as the
input parameters for calculating the stability of dry and water
inundated cellars. The FEM (Finite Element Methods) calculations
of cellar stability indicate that the displacement of water-saturated
cellars is nearly triple of the dry ones and that the factor of safety
reduced from 1.74 in air-dry condition to 1.07 in water-saturated
conditions.
Keywords
porous limestone, water saturation, mechanical properties, density,
correlation, FEM modelling, factor of safety
© 2020 by the authors. Submitted for possible open access publication under the terms and conditions
of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Jalal ZENAH et al. / Acta Montanistica Slovaca, Volume 25 (2020), Number 3, 337-349
338
Introduction
Subsurface openings such as human-made cellars or natural caves are common in urban areas worldwide
and can endanger human life and the built environment when these structure collapse (Marschalko et al., 2012).
Cellars are known from France (Al Heib et al., 2015; Smeray et al., 2000), Spain (Fuentes et al., 2010), Italy
(Ciotoli et al., 2015) and from Hungary (Görög et al., 2013; Vamos et al., 2015; Zenah et al., 2019). The
construction period (from Roman times to present) and the excavation methods are different, but in most cases,
these structures are cut in rocks without additional support. Different kinds of rocks host these cellars from
sedimentary rocks: limestone and sandstone (Görög et al., 2013; Siegesmund et al., 2011; Mocsár-Vámos et al.,
2015), to igneous rocks: volcanic tuffs (Aydan and Ulusay, 2003; Kleb and Vásárhelyi, 2003). A similar set of
cellars are found in the cities of Hungary, representing various ages from the Middle Age to the 19th century
(Gálos et al., 1981). These cellars are found at different depth located close to the surface (Görög et al., 2013;
Zenah et al., 2019), or at greater depth (Gálos et al., 1981). The usage of the cellars also varies from agricultural
utilisation like wine storage (Fuentes et al., 2010) and mushroom production, or public spaces hosting social and
cultural events (for example, restaurants) or even smaller openings that are used as water-sewer systems
(Marasović et al., 2014).
Due to the population growth in big cities such as Budapest and intense urbanisation, the extension of the
cities in both horizontal and vertical directions is a rapid process. It requires new building sites that might be
undercut by cellars. The construction activity causes the additional load, and it is especially risky when cellars
are found below the site (Görög et al., 2013; Mocsár-Vámos et al., 2015). In Budapest area, weak rocks,
especially porous limestone host most of these cellars (Görög et al., 2013) and are often found below new
development areas.
The paper presents the results of the laboratory testing of porous limestone collected from the cellar
network of Budapest region and the stability analysis of these human-made cavities due to surface load. It
compares mechanical parameters of this Hungarian highly porous limestone with the data published on testing of
other limestones worldwide (Bednarik et al., 2014; Ghafoori et al., 2018; Ozguven and Ozcelik, 2013). It
emphasises the importance of test conditions and the loss of strength due to water saturation (Vásárhelyi, 2005;
Zenah et al., 2019). These are key issues since the stability of these subsurface openings strongly depend on the
mechanical parameters of the host rock. Namely, when there is a significant loss in strength due to extrinsic
factors occurs, there is a high risk of collapse and surface subsidence. For the calculation of stability and safety
factors of subsurface openings (caves, mines, and cellars) physical parameters of the host rock are essential
(Görög et al., 2013). The obtained mechanical data was used to calculate the stresses around cellars and
subsurface openings that were cut in porous limestone. In the investigation area, there are used and unused
cellars, while the used cellars are ventilated, and the changes in the rock mass quality can be easily detected. The
unused cellars have many times no ventilation and only rarely supervised, which can cause wet rock surfaces.
Therefore, the modelling of the effect of water is essential. Near stability analysis, the different processes such as
mining processes (Janič et al., 2019), weathering processes of the rock masses can be simulated (Ghabezloo and
Pouya, 2006). The FEM calculation in this study tried to determine the effect of water on the stability of the
cellars due to surface loading.
Materials
The studied Hungarian limestone is porous (Rozgonyi, 2002) that was formed during the Miocene period.
The limestone is considered as a shallow marine subtropical carbonate deposited in the Pannonian Basin. It
covers larger areas in and around Budapest (Vásárhelyi, 2005). It was used as a construction material for
centuries, and emblematic buildings of Budapest, such as the Parliament building, Citadella fortress or Mathias
Church was built from this stone (Török et al., 2007). Miocene limestone was used not only in Hungary, but it is
one of the most common building stones in Central Europe. Examples of buildings and structures are known
from Austria (St. Stephan’s Church, Vienna) and Slovakia (Bednarik et al., 2014; Laho et al., 2010), from Czech
Republic (Valtice) also (Přikryl and Přikrylová, 2004; Török et al., 2004). Besides Central Europe, similar stones
are known from Belgium (De Kock et al., 2017), from France (Beck and Al-Mukhtar, 2008; Gibeaux et al.,
2018; Hassine et al., 2018) and from the Mediterranean Region of Italy (Pappalardo et al., 2016), Cyprus
(Modestou et al., 2016) and Malta (Cassar, 2002). Less porous limestones are also known worldwide (Zhang et
al., 2017) and have been used to construct buildings (Smith et al., 2010) and bridges (Ademović and Kurtović,
2018).
The stone was popular since it is highly porous and easy to work with. Therefore, it became one of the key
construction material of the 18th and 19th century (Pápay and Török, 2017). Durable varieties of limestone were
also used for bridge construction such as the limestone bridge in Mostar, Bosnia and Herzegovina (Čorko et al.,
2001).
Jalal ZENAH et al. / Acta Montanistica Slovaca, Volume 25 (2020), Number 3, 337-349
339
The tested porous Miocene limestone is known to be a soft rock with high and variable porosity (14 – 52%),
and consequently, a wide variation in the petrophysical properties was observed (Vásárhelyi, 2005; Zenah et al.,
2019). Its textural variety was also discussed in previous studies (Pápay and Török, 2017; Török et al., 2007).
Laboratory tests were realised on the stone blocks obtained from cellars of Budapest city located at Buda
side of the city (Fig. 1a, 1b). The cellar system has large openings that are currently used for mushroom
cultivation (Fig. 1c, 1d). The studied porous limestone blocks were described in details, and the samples were
divided into four different lithologies: numbered from I to IV.
Type I. Fine-grained porous limestone. It has a few gastropods that form moldic pores. Its micro-fabric is
characterised by very fine carbonate grains with very small pores. Its colour is white, slightly yellowish stain
(Fig. 2I).
Type II. Coarse-grained ooidal porous limestone. It is characterised by fine sand-sized, well-rounded ooids
and has a rough surface with larger but regularly arranged pores. Small grey quartz sand particles are also
observed in this lithotype and broken bioclasts of less than 0.5 cm in size (Fig. 2II).
Type III. Fine- to medium-grained porous limestone. It has a non-uniform microfabric since medium-
grained carbonate particles form irregular patches within the fine-grained, porous limestone. Its fine-grained
parts are coarser than that of Type I, and it contains more bioclasts (Fig. 2III).
Type IV. Cross-laminated fine- and medium-grained porous limestone. The lithotype is not uniform even in
a tests specimen scale; it is visible that it contains fine-grained and medium-grained parts that are alternating and
show cross lamination (Fig. 2IV).
Fig. 1. Map of Hungary (a) with the location of the studied cellar system in Budapest city (b). The cellar was cut into porous limestone and
has large spacing, that is currently used for mushroom cultivation (c, d).
Fig. 2. Textural characteristics of the studied lithotypes (numbered I to IV), scale bar is 1 cm. Their detailed lithological description is in the
text.
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Methods
Cylindrical specimens were drilled (50 mm in diameter) from the limestone blocks by using the core
drilling apparatus in the laboratory. The cores were cut to two sets of sample sizes according to their height
(length-L, diameter-D): for Brazilian tests with L/D 1, and for uniaxial compressive strength tests (UCS) with
L/D in a range from 1.45 to 1.93. In the calculation of UCS, the correction of these values to L/D=2 was made.
The surface of all test specimens was ground to get parallel plane surfaces for uniform stress distribution.
Tests were made according to EN and ASTM guidelines. Dry and saturated apparent densities were
determined according to (EN 1936:2006). The uniaxial compressive strength (UCS) tests and Brazilian tests for
both dry and saturated conditions were made according to ASTM D7012-14e1 and ASTM D 3967-16,
respectively. The water absorption test (EN 13755:2008) was aimed to assess and compare the open porosity and
water uptake of different lithologies. Capillary water absorption was detected based on the measurement of the
masses of specimens after 15 sec in regular intervals till four days. Water absorption capillary curves were also
drawn based on test results. The ultrasonic wave velocity tests were performed on cylindrical test specimens (EN
14579:2004) to analyse internal structure (possibility of micro-cracks) of the rock specimens by measuring wave
velocities in km/sec. Altogether 132 specimens were tested in the laboratory (Tab. 1).
Tab. 1. Test methods and number of tested specimens
Property Code of the test procedure Number of specimens
Dry Saturated
Density EN 1936:2006 132 132
US-wave velocity EN 14579:2004 132 132
UCS ASTM D7012-14e1 31 25
Brazilian strength ASTM D3967-16 31 26
Water absorption EN 13755:2008 132
Capillary water absorption EN 1925:1999 9
The geometry of the cellar was determined by terrestrial laser scanning (TLS), we used a phase-based
terrestrial laser scanner (Faro Focus 120S) with +/- 2mm ranging accuracy and 120 m maximum measurement
range.
The stability calculations have been performed by the Rocscience software package, with the RS2 2019
finite elements code. The used software is a hybrid finite element code, which makes possible the slipping
through joints elements. They can apply the Hoek-Brown material model, so in the modelling, the input
parameters of the modelling programs are: UCS determine in the laboratory as in (Tab.2) and (Tab.3), Young
modulus calculated after the analysis of the lab result (from the stress-strain graph), Hoek-Brown constant (mi) is
calculated based on a lab result, and also it can be calculated by RocLab program (which analyse the laboratory
data, or simply we choose the rock type in the program, and the program will give the value based on the saved
table), and geotechnical strength index for the rock mass (GSI) determined by fieldwork.
According to these values, the software calculates the Hoek-Brown parameters of the rock masses (Hoek et
al., 2002).
Results
Laboratory Tests results
The apparent porosity of tested porous limestone has a range of 10.5 % to 17.7 %, which was calculated
from mass changes as a function of time during capillary water absorption tests (Fig. 3). The absorption curves
have very similar shapes; however, the rate of water absorption and time of full capillary suction saturation
slightly differs. The highest water uptake was observed at Type I lithotype, which has the finest grain size and
smallest pore-sizes The lowest water absorption was measured at specimens of Type IV, where the micro-fabric
is heterogeneous.
The open porosity of the lithotypes can be calculated based on the dry apparent density and saturated
apparent density. The latter one was measured on fully saturated test specimens that were submerged into the
water until full saturation (maximum weight) was obtained. The densities (dry and saturated) as well as strength
parameters of dry and water-saturated test specimens with a minimum, maximum values and averages are given
in Tab. 2 and Tab. 3. The wide range of the results marks the heterogeneity of the lithotypes.
Jalal ZENAH et al. / Acta Montanistica Slovaca, Volume 25 (2020), Number 3, 337-349
341
Fig. 3. The capillary water absorption curves of porous limestone Types I-IV
Tab. 2. Test results of dry specimens
Dry Density [gr/cm
3
] Dry UCS [MPa] Dry Brazilian tensile
strength [MPa]
min max mean min max mean min max mean
Type I 1.51 1.62 1.57 7.90 15.86 10.95 0.18 1.08 0.58
Type II 1.52 1.71 1.62 2.16 13.40 9.57 1.03 2.11 1.56
Type III 1.74 1.85 1.80 15.40 27.77 22.74 1.59 4.65 3.22
Type IV 1.65 1.84 1.77 8.43 26.56 15.12 0.76 2.05 1.16
Tab. 3. Test results of water-saturated specimens
Sat Density [gr/cm
3
] Sat UCS [MPa] Dry Brazilian tensile
strength [MPa]
min max mean min max mean min max mean
Type I 1.81 1.84 1.88 2.85 7.04 5.16 0.07 0.39 0.26
Type II 1.79 1.87 1.95 3.49 12.54 8.06 1.08 1.82 1.35
Type III 1.96 2.02 2.07 5.10 14.57 10.59 0.91 1.42 1.29
Type IV 1.84 1.97 2.06 7.27 17.38 11.91 0.67 1.17 0.89
Densities are plotted in (Fig. 4). The relations between the two measured parameters are generally very
strong, and the correlation coefficient is between 0.5367 and 0.981 (Fig. 4). The highest correlation was found
for Type II, while the lowest for Type I, respectively. The equations and the correlation coefficients are given in
(Tab. 4).
Fig. 4. Relationship between dry and saturated densities of rock Types I-IV
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342
Tab. 4. Calculated relationships between dry and saturated densities of rock Types I-IV
Type Equations R2
I Y=0.5679*X+0.9492 0.5367
II Y=0.8268*X+0.528 0.9814
III Y=0.8214*X+0.5407 0.9212
IV Y=1.1307*X-0.031 0.9444
The relationship between apparent density and ultrasonic waves (US waves) velocity cannot be described
with one equation, (Fig. 5). The various lithotypes from distinct groups of data, and the shift of data set toward
higher values of densities are clear, but in terms of US-wave velocity, the changes are not so uniform (Fig. 5).
Fig. 5. Relationship between apparent density and US wave velocity of rock Types I-IV
According to the measured values, there is a good linear relationship between ultrasonic waves and open
porosity in both dry and saturated conditions (Fig. 6). The differences between dry and saturated samples are
marked by dashed (dry) and continuous lines, and it seems that the distinction of the two test conditions are not
very easy, since there are some overlaps between the fields (Fig. 6).
Fig. 6. Relationship between open porosity and US wave velocity of rock Types I-IV
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343
The relation between density and UCS was plotted in both dry and saturated conditions (Fig. 7). The results
are clearly divided into four distinct groups. Two sets of dry and two sets of water-saturated samples are marked
on (Fig. 7). In the lowest range, the dry specimens of Type I + Type II are found, which is followed by dry
specimens of Type III + Type IV, and water-saturated specimens of Type I + Type II, and water-saturated
specimens of Type III + Type IV, respectively (Fig. 7).
Fig. 7. Relationship between UCS and apparent density of rock Types I-IV (ranges of dry and saturated samples are marked by continuous
and dashed lines, respectively)
A reduction of UCS and tensile strength tests due to water saturation was also determined. The loss in
strength is not uniform. The highest reduction was measured at limestone Type III (over 50%), which is followed
by specimens of Type I, while the least reduction was documented at Type II (Tab. 5). Thus the most sensitive
group to water is Type III, while the least sensitive one is Type II with strength loss of 16 % and 14% in UCS
and in indirect tensile strength, respectively.
Tab. 5. Reduction of strength due to water saturation
Type
UCS, mean value Tensile strength, mean value
Dry
Condition
[Mpa]
Saturated
Condition
[Mpa]
Loss in strength [%] Dry Condition
[Mpa]
Saturated
Condition
[Mpa]
Loss in strength [%]
I 10.95 5.16 52.88 0.58 0.26 55.17
II 9.57 8.06 15.78 1.56 1.35 13.46
III 22.74 10.59 53.43 3.22 1.29 59.94
IV 15.12 11.91 21.23 1.16 0.89 23.27
Stability analysis Results
The 3D geometry of the investigated part of the cellar system is in (Fig. 8). The 2D section, where stability
analyses were made, is 10 m from the main corridor of the cellar system as it is shown in the (Fig.8).
The thickness of the cover layers above the cellar system is around 5 m measured through ventilation shafts.
The model contains two layers the weathered and jointed above the layer of the porous limestone, and the rest of
them, which is massive with only some joints. The input parameters of the calculations are from Tab. 2. The
samples are from the investigated cellar system, but the spatial arrangement of the lithotypes in the cellar are
varied and difficult to include this variation in the model. Therefore, the minimum strength parameters of the
porous limestone types were used in the model (Tab.2, Tab.3). In dry condition: UCS = 2.1 MPa, E = 4110 MPa,
m
i
= 10, GSI = 80. Above the surface, 500 kN/m
2
load was applied to consider further building improvements.
Jalal ZENAH et al. / Acta Montanistica Slovaca, Volume 25 (2020), Number 3, 337-349
344
Fig. 8. 3D view of the investigated part of the cellar system, the geometries were obtained by TLS, red line shows the place of the modelled
cross-section.
The (Fig. 9). shows the total displacements of the calculated sections, both dry and water-saturated
conditions, the increasing displacements are signed with warm colours (yellow, orange and red). The red zone
above the 2. and 3. cellar branches at the top figure shows the highest displacements. The place of the highest
displacements depends on the cover above the cellar branches and the width of the pillar between the branches.
There are only a few joints in the cellar since the rock mass of the porous limestone is massive, but the model
contains these few joints. The effects of the joints to the displacements are given in (Fig. 9), which shows
slightly different displacement at different sides of the joints.
The value of displacements of the different cellar branches between dried and water-saturated conditions is
in (Fig. 10). Under water-saturated conditions, the displacements were almost three times higher compared to
dry conditions. The safety factor was also reduced because of the water-saturated condition from (1.74) in air-
dry condition down to (1.07) in water-saturated conditions.
Fig. 9. Total displacements of the calculated sections both dry and water-saturated conditions
Jalal ZENAH et al. / Acta Montanistica Slovaca, Volume 25 (2020), Number 3, 337-349
345
Fig. 10. Displacements of the different cellar branches
Discussion
The test results of the four lithotypes (Type I-IV) are compared to data on various limestone types published
previously (Tab. 6). The comparison includes the physical parameters such as density, uniaxial compressive and
indirect tensile strength. As shown in the (Tab. 6), the Miocene limestone from Budafok has a relative low UCS
compared to the low porosity limestones of Jordan (Dweirj et al., 2017) or Turkey (Aydan and Ulusay, 2003).
The loss in the UCS due to water saturation is much higher at the Miocene limestone presented in this paper than
that of the Jordanian limestone (Dweirj et al., 2017) (Tab. 6), which strength reduction is except for Zarka
limestone is less than 50%. The Brazilian strength test results of this paper demonstrate the sensitivity of this
limestone types to water saturation. An even higher strength reduction in tensile strength was measured at Zarka
limestone (Dweirj et al., 2017) (Tab. 6).
Previous studies dealing with the effect of water on the strength of porous limestone suggest that there is a
significant loss in strength due to water saturation (Vásárhelyi, 2005; Zenah et al., 2019). The accidental water
saturation or flooding of subsurface openings and mines can also cause significant problems such as sliding or
loss of stability (Polak et al., 2015). It was also noted that not only water but freeze-thaw action also reduces the
strength of this porous Hungarian limestone (Pápay and Török, 2017). Considering all these previous
observations it is necessary to note that important input parameters for the stability calculation of cellar systems
are strength parameters (Görög et al., 2013; Zenah et al., 2019). Thus this observed sensitivity to water clearly
controls the stability of the studied cellar system, namely water saturation or accidental water inundation of
cellars might cause a collapse of the formerly stabile cellar system due to drastic loss in strength of the porous
limestone.
To assess strength parameters with measuring only the density of limestone is possible (Vásárhelyi, 2005)
since there is a correlation between density and strength. It has also been noted that porosity and micro-fabric
strongly influence the durability of such limestones (Scrivano et al., 2018; Török et al., 2007). In the studied
samples Type I has the highest open porosity with the highest water absorption (Fig. 3). Namely, this lithotype
has the highest amount of open pores that can have a negative effect on the loss in strength due to water
saturation (Scrivano et al., 2018). Our results partly confirm this assumption since a high loss in strength (over
50%) was measured on saturated water specimens compared to dry ones (Tab. 5). However, the other lithotype
that is more sensitive to water saturation (Type III), where the loss of strength is larger (Tab. 5), has lower
porosity and lower water absorption (Fig. 3). Here, the higher loss in strength is probably attributed to the pore-
size distribution differences, namely more diverse pores. This feature, the role of pore-size distribution in the
durability and strength loss was already suggested in previous works (Hassine et al., 2018; Pápay and Török,
2017; Přikryl, 2013; Török et al., 2007). The strength and durability of carbonate rocks are negatively influenced
by the clay content, especially when the carbonates (marls) are subjected to cyclic wetting and drying (Vlastelica
et al., 2017).
When Brazilian strength and density of the studied limestone (Type I-IV) are compared with previous
works a fairly good correlation was found, although the data sets of different limestone types were plotted at
various fields in the graph (Fig. 11). It suggests that density is a good indicator of limestone strength, similarly to
previously published data (Martínez-Martínez et al., 2013; Török and Vásárhelyi, 2010; Vásárhelyi, 2005).
Jalal ZENAH et al. / Acta Montanistica Slovaca, Volume 25 (2020), Number 3, 337-349
346
Tab. 6. Physical parameters of limestone, comparative data set from previous work and this study
Place
Density
[kg/m
3
]
UCS
MPa
Brazilian tensile strength
MPa References
Dry Sat Dry Sat Dry Sat
Budafok –Type I
- Hungary
1510 –
1620
1810 –
1840
7.91 -
15.86 2.85 – 7.04 0.18 – 1.08 0.07 –
0.39 this study
Budafok –Type
II - Hungary
1520 –
1710
1790 –
1870
2.16 –
13.40 3.49 – 12.54 1.03 – 2.11 1.08 –
1.82 this study
Budafok –Type
III - Hungary
1740 –
1850
1960 –
2020
15.40 –
27.77 5.10 – 14.57 1.59 – 4.65 0.91 –
1.42 this study
Budafok –Type
IV - Hungary
1650 –
1840
1840 –
1970
8.43 –
26.56 7.27 – 17.38 0.76 – 2.05 0.67 –
1.17 this study
Sóskút -
Hungary
1360 -
2410 1720 - 2460 0.86 - 38.8 0.63 - 27.6 0.07 - 4.16 0.08 -
3.99 (Vásárhelyi, 2005)
Asmari - Iran 2130 -
2570 5.48 -
109.03 (Ghafoori et al., 2018)
Ajlon - Jordan 2640 56.09 49.9 6.08 5.48 (Dweirj et al., 2017)
Zarka - Jordan 2360 48.22 18.4 5.37 1.5 (Dweirj et al., 2017)
Ma’an district
Sateh - Jordan 2610 51.18 45.1 5.61 4.95 (Dweirj et al., 2017)
Dabish - Jordan 2540 64.7 48.3 6.34 4.96 (Dweirj et al., 2017)
Turkey 2640 -
2700 137.2 -
187.4 8.52 - 10.35 (Ozguven and Ozcelik,
2013)
Austria
(different
locations)
3.75 -
115.59
3.32 -
104.89 (Bednarik et al., 2014)
Bratislava,
Slovakia 2210-2600 (Laho et al., 2010)
Fig. 11. Relationship between Brazilian strength and density of limestone, data sources: this study Budafok Types I-IV (B-I to B-IV), J-data
from Jordan (Dweirj et al., 2017) and T-data from Turkey (Ozguven and Ozcelik, 2013).
The stability calculations resulted in a high difference between the maximum displacements in dry 6.45 mm
and saturated 19.10 mm conditions and the safety factor also reduced significantly. The highly water sensitive
material cause significant loss of safety factor. It predicts problems with the stability of the cellars because of the
change in the water content of the rock mass. In reality, the whole rock mass cannot be saturated, but according
to the on-site investigations locally, it can happen, which can cause local stability problems.
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347
Conclusions
The test results presented in this paper indicate that four lithotypes of porous limestone specimens, which
were collected from the same cellar, have a wide range of physical parameters. The open porosity of the studied
specimens is in between 16 to 30%, having the highest value of the fine-grained lithotype (Type I) and the
lowest one of the cross-laminated fine-to medium-grained type (Type IV). Comparing air dry and water-
saturated strength parameters, the reduction in the strength exceeded 50% for Type I and Type III lithologies.
The lowest strength reduction due to water was measured at coarse-grained lithotype (Type II) where the loss is
in the order of 14-16%. The results suggest that water saturation has a less effect on US-wave velocities of
porous limestone with large uniform pores (Type II). Relationships were outlined between the water absorption
and open porosities that are different for each studied lithotype. Comparing the test results of the studied
limestone with the previously published data on limestone indirect tensile strength and density, a good
correlation was found. The stability of dry and water inundated cellars was calculated by using these parameters,
considering that water significantly reduces the strength of this porous limestone and might lead to the collapse
of the cellars.
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... Textural characteristics control the porosity, therefore micritic varieties have lower values than the detritical varieties, which display intergranular voids Ruffolo et al. 2017). Reflecting the textural properties in limestones, a wide range of values of porosity can be found in literature, from values lower than 2% (Hashemi et al. 2018;Majeed et al. 2020;Hu et al. 2020;Korkanç et al. 2021) to values higher than 30% (Turgut et al. 2008;Eslami et al. 2010;La Russa et al. 2013;Szemerey-Kiss and Török 2017;Van Stappen et al. 2019;Zenah et al. 2020). The high variability of the porosity of limestones indicates their durability, because porosity is an excellent indicator of weathering (Tugrul and Zarif 2000) and strength properties (Nasri et al. 2019;Nabawy and El Aal 2019). ...
... The water absorption is connected to the porosity and similar curves can be found in different types of rocks, but the size and connectivity of the pores affect the rate of absorption (Çelik and Kaçmaz 2016;Karagiannis et al. 2016;Feijoo et al. 2017;Sousa et al. 2018;Barroso et al. 2018). Sedimentary layering, stylolites, microfractures and heterogeneous microfabric impact the kinetics of water absorption in limestones (Tomašić et al. 2011;Siegesmund and Dürrast 2014;Zenah et al. 2020). As mentioned for porosity, CWA values show a wide range of values which are according to the published results (Siegesmund and Dürrast 2014;Vásquez et al. 2013Vásquez et al. , 2015Benavente et al. 2015). ...
... The VP depends on the density and elastic properties of the material (Rahman and Sarkar 2021). A good linear relationship between ultrasonic waves and open porosity in both dry and saturated conditions is found (Fig. 7), as observed in several investigations (Nina and Alber 2018;Nasri et al. 2019;Zenah et al. 2020). The UCS values are usually related to VP (Çobanoğlu and Çelik 2008;Rahman and Sarkar 2021), which indicates that low porous samples (CODFV, MCCT, SBM and SBR) will have poor mechanical properties in accordance with the results of similar varieties (the commercial designation is usually different from quarry to quarry) presented in the catalogues of Portuguese ornamental stones (Leite and Moura 2021; Assimagra 2021; ...
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