Fig. 1.
Mine disasters of frozen vertical shaft after thawing:
(a) Concrete protective layer’ deformation and desquamation; (b) Local Rupture and water leakage of shaft lining; (c) Water inrush in frozen shaft; and (b) Sand bursting of freezing shaft wall.
Fig. 2.
(a) Some of sandstone in Luohe Formation; and (b) Specimen dimensions.
Fig. 3.
Experimental flow and instrument:
(a) Intelligent vacuum water saturator instrument and DHG series electric drying oven; (b) The multi-function freeze-thaw testing machine; and (c) RMT-201 rock and concrete mechanics test system.
Table 1..
The mechanical parameters of thawed sandstone under different freezing temperatures.
Fig. 4.
Stress-strain curves of thawed specimen with different freezing temperatures.
Fig.5..
The eventual failure modes of thawed specimens with different freezing temperatures:
(a) 20°C; (b) −10°C; (c) −15°C; (d) −20°C; (e) −25°C; and (f) −30°C.
Fig. 6.
Energy evolution curves of thawed specimens for different freezing temperatures:
(a) 20°C; (b) −10°C; (c) −15°C; (d) −20°C; (e) −25°C; and (f) −30°C.
Fig. 7.
Energy density of thawed specimen under different freezing temperatures:
(a) Total energy; (b) Elastic strain energy; and (c) Dissipated energy.
Table 2..
The energy density of peak point with different freezing temperatures.
Fig. 8.
The variation curve of the energy density at the peak point with different freezing temperature.
Fig. 9.
Sketch map of predicted failure time through linear extrapolation.
Fig. 10.
Energy damage variable, energy damage variable rate and acceleration of thawed sandstone with different freezing temperatures:
(a) 20°C; (b) -10°C; (c) -15°C; (d) -20°C; (e) -25°C; and (f) -30°C.
Fig. 11.
Double-logarithm fitting plots of energy damage rate and time of thawed sandstone at different freezing temperatures.
Table 3..
Power law singularity index (β) of thawed sandstone under different freezing temperatures.
Table 4..
Power law singularity index of (β1) thawed sandstone under unknown β value conditions.
Fig. 12.
Double-logarithm fitting plots of energy damage rate and acceleration of thawed sandstone with different freezing temperatures.
Fig. 13.
Failure time prediction results of thawed sandstone with different freezing temperatures:
(a) 20°C; (b) −10°C; (c) −15°C; (d) −20°C; (e) −25°C; and (f) −30°C. t is the monitoring time corresponding to data point under uniaxial compression; tf p denotes the predicted time of imminent rock failure; tf represents the actual time of rock failure; t/tf represent the ratio of monitoring/ actual failure time; tf p/tf represent the ratio of predicted/ actual failure time.