TY - JOUR
T1 - Micro-mechanics based numerical simulation of NaCl brine induced mechanical strength deterioration of sedimentary host-rock formations
AU - De Silva, V. R. S.
AU - Ranjith, P. G.
AU - Wu, B.
AU - Perera, M. S. A.
PY - 2018/8/14
Y1 - 2018/8/14
N2 - Artificial fracture stimulation in low-grade sedimentary ore deposits is one method to improve mineral extraction efficiency of In-Situ Leaching (ISL) process. Low to moderate saline environments are found in most sedimentary ore deposits that deteriorate intact rock strength over time. It is important to recognize the host rock strength properties prior to artificial fracture stimulation. Therefore, to identify the effect of salinity on the mechanical properties of brine-saturated sandstone, a series of uniaxial compressive strength (UCS) tests and Brazilian tensile strength tests were performed on specimens saturated with water, and with varying NaCl brine concentrations (5.0%, 7.5%,10% and 12.5%). Scanning electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS) tests reveal that increasing salinity deteriorate the mechanical integrity of sandstone by accelerated clay mineral dissolution. Consequently, 12.5% saturation fluid salinity resulted in a 40% reduction in UCS, 22% reduction in Young's modulus and 33% reduction in tensile strength. The strength deterioration observed in the experimental study was then successfully simulated using Particle Flow Code 3D (PFC3D) in consideration of the bond strength deterioration mechanism for sandstone. The calibrated model was used to accurately replicate the damage mechanism of sandstone under the influence of brine saturation. The model forms an accurate intact rock assembly for numerical modelling of saline sedimentary host-rock formations.
AB - Artificial fracture stimulation in low-grade sedimentary ore deposits is one method to improve mineral extraction efficiency of In-Situ Leaching (ISL) process. Low to moderate saline environments are found in most sedimentary ore deposits that deteriorate intact rock strength over time. It is important to recognize the host rock strength properties prior to artificial fracture stimulation. Therefore, to identify the effect of salinity on the mechanical properties of brine-saturated sandstone, a series of uniaxial compressive strength (UCS) tests and Brazilian tensile strength tests were performed on specimens saturated with water, and with varying NaCl brine concentrations (5.0%, 7.5%,10% and 12.5%). Scanning electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS) tests reveal that increasing salinity deteriorate the mechanical integrity of sandstone by accelerated clay mineral dissolution. Consequently, 12.5% saturation fluid salinity resulted in a 40% reduction in UCS, 22% reduction in Young's modulus and 33% reduction in tensile strength. The strength deterioration observed in the experimental study was then successfully simulated using Particle Flow Code 3D (PFC3D) in consideration of the bond strength deterioration mechanism for sandstone. The calibrated model was used to accurately replicate the damage mechanism of sandstone under the influence of brine saturation. The model forms an accurate intact rock assembly for numerical modelling of saline sedimentary host-rock formations.
KW - Brazilian disk tensile strength
KW - Brine saturated sandstone
KW - Compressive strength
KW - Flat-jointed model
KW - Micromechanical structure
KW - PFC3D
UR - http://www.scopus.com/inward/record.url?scp=85047634827&partnerID=8YFLogxK
U2 - 10.1016/j.enggeo.2018.05.005
DO - 10.1016/j.enggeo.2018.05.005
M3 - Article
AN - SCOPUS:85047634827
SN - 0013-7952
VL - 242
SP - 55
EP - 69
JO - Engineering Geology
JF - Engineering Geology
ER -