Creep Behavior of Rock under Uniaxial Compression
Uniaxial conpression creep tests were conducted under comparatively high stress level (90-95% of strength) on Inada-granite, Tako-sandstone, cement-mortar and Akiyoshi-marble. the following results are obtained;
1) In all samples, the primary creep follows the logarithmic creep law.
2) The secondary creep where strain rate is nearly constant is apparent only for cement-mortar. For other samples, the strain rate continuously decreases at first, and increases after taking its minimum.
3) For Tako-sandtone and Akiyoshi-marble, the value of creep strain at minimum strain rate is nearly equal to half of the width of the complete-stress-strain curve cross-sectioned at corresponding creep stress. In case of granite, the creep strain at minimum strain rate is rather small, whereas, in case of cement-mortar nearly double of the width.
4) Strain rate at an arbitrary time in tertiary creep is inversely proportional to the residual time up to final failure. If this law is applied to rock mass, the failure of underground constructions may be predicted.
5) Except cement-mortar, the creep strain just before final failure (1 sec before failure) is nearly equal to the cross-sectional width of the complete-stress-strain curve. In case of cement-mortar, the creep strain just before funal failure is as much larger than the width.
Key Word: Rock, Uniaxial compression, Creep, Residual time, Complete-stress-strain curve