Energy Release Analysis of a Severe Rockburst in a Headrace Tunnel Crossing a Tectonic Stress Zone

Table 6

Results of unloading confining pressure tests of sandstone.

Initial confining pressure (MPa)	Tests no.	Young’s modulus (GPa)	Poisson’s ration	Peak deviatoric stress (MPa)	Maximum storage elastic energy (kJm^−3)
35	1	40.2	0.26	250	820.0
	2	35.9	0.22	245	866.5
	3	38.3	0.24	246	833.4
45	4	34.2	0.23	269	1114.3
	5	40.3	0.24	282	1053.1
	6	51.7	0.27	283	898.0
55	7	32.1	0.22	267	1363.9
	8	32.8	0.24	286	1445.8
	9	32.7	0.23	285	1434.0
65	10	52.4	0.28	336	1667.5
	11	29.1	0.21	329	1909.8
	12	30.8	0.24	301	1788.8
75	13	28.0	0.23	338	2233.2
	14	35.0	0.25	357	2097.9
	15	38.3	0.25	353	1801.8