TY  - JOUR
A1  - Mardoukhi, Ahmad
A1  - Mardoukhi, Yousof
A1  - Hokka, Mikko
A1  - Kuokkala, Veli-Tapani
T1  - Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite
JF  - Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences
N2  - This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates.
KW  - split Hopkinson pressure bar
KW  - rock
KW  - granite
KW  - dynamic loading
KW  - fractal dimension
KW  - surface cracks
Y1  - 2017
U6  - https://doi.org/10.1098/rsta.2016.0179
SN  - 1364-503X
SN  - 1471-2962
VL  - 375
IS  - 2085
PB  - Royal Society
CY  - London
ER  - 
TY  - JOUR
A1  - Mardoukhi, Ahmad
A1  - Mardoukhi, Yousof
A1  - Hokka, Mikko
A1  - Kuokkala, Veli-Tapani
T1  - Effects of heat shock on the dynamic tensile behavior of granitic rocks
JF  - Rock mechanics and rock engineering
N2  - This paper presents a new experimental method for the characterization of the surface damage caused by a heat shock on a Brazilian disk test sample. Prior to mechanical testing with a Hopkinson Split Pressure bar device, the samples were subjected to heat shock by placing a flame torch at a fixed distance from the sample’s surface for periods of 10, 30, and 60 s. The sample surfaces were studied before and after the heat shock using optical microscopy and profilometry, and the images were analyzed to quantify the damage caused by the heat shock. The complexity of the surface crack patterns was quantified using fractal dimension of the crack patterns, which were used to explain the results of the mechanical testing. Even though the heat shock also causes damage below the surface which cannot be quantified from the optical images, the presented surface crack pattern analysis can give a reasonable estimate on the drop rate of the tension strength of the rock.
KW  - SHPB
KW  - Rock
KW  - Granite
KW  - DIC
KW  - Dynamic loading
KW  - Fractal dimension
Y1  - 2017
U6  - https://doi.org/10.1007/s00603-017-1168-4
SN  - 0723-2632
SN  - 1434-453X
VL  - 50
SP  - 1171
EP  - 1182
PB  - Springer
CY  - Wien
ER  -