Experimental Investigation of Unloading-Induced Red Sandstone Failure: Insight into Spalling Mechanism and Strength-Weakening Effect

Table 1

Peak strength of each test at different confining pressures.

Confining pressure (MPa)	5	10	20	30	40	50	60
Peak strength of TCT (MPa)	121.1	158.5	215.3	258.5	296.0	337.7	357.7
Peak strength of BCT (MPa)	70.7	84. 6	104.0	111.4	93.4	88.5	84.9
			95.5	97.9	110. 6	100.7	94.1
Average	70.7	84. 6	99.8	104.7	102.0	94.6	89.5
Peak strength of TLU (MPa)	64.3	76.2		65.9			85.4
			97.9	113.9		110.1
			77.0	68.3	101.5	89.0
			112.3	120.3	105.4	76.5
				110.3
				104.3
Average	64.3	76.2	95.7	97.2	103.5	91.9	85.4
Peak strength of THU (MPa)	68.1	77.2	85.8	78.6	84.0	80.1	84.3
			93.3	97.6	114.3	89.2	60.0
				86.8	73.1
Average	68.1	77.2	89.6	87.7	90.4	84.7	72.2