Damage and Fracture Characteristics of Kimachi Sandstone in Uniaxial Compression

Abstract

ABSTRACT Some of the key concerns regarding the design of underground openings include the implication in potential ground disturbance caused by the excavation method and the redistribution of in situ stress. Both of these factors are related to the extent of brittle fracture damage which could adversely affect the stability of excavation boundary and could possibly change the properties of the near-field host rock. Therefore, the evaluation of deformation characteristics of a damaged rock is very important in analyzing the stability of underground openings. The development of stress-induced micro-cracking in rock samples under uniaxial compression was investigated by using stress-strain data, the moving point regression technique and AE measurements. In addition, damage thresholds and deformation parameters were identified. Finally, empirically modeled deformation behaviors were compared with experimental data. It was shown that crack initiation and crack damage for Kimachi sandstone occurred at 0.578σUCS and 0.822σUCS, respectively. However, it was difficult to find the crack closure threshold due to intrinsic properties of Kimachi sandstone related to its high porosity. The appropriate interval for moving point regression technique should be at least 5% of total data set. Approximately 16% of the total axial strain occurred during crack closure and nearly 40% occurred before crack initiation. In contrast, only 5.6% of the total lateral strains were recorded during the crack closure interval. The largest proportion of total lateral strain was seen to be attributable to the coalescence and unstable crack propagation. Modelled behaviors of Kimachi sandstone coincided well with test data.