Optimal Proportion of Similar Materials and Rockburst Tendency of White Sandstone

Table 2

Factor levels in orthogonal experimental design covered by the study.

Level	(A) Quartz sand (%)	(B) Iron powder (%)	(C) Plaster : cement	(D) Sand size (mm)
1	45	0.5	1 : 1	0.25–0.5
2	50	1	1.5 : 1	0.5–1
3	55	1.5	2 : 1	1-2
4	60	2	3 : 1	2–4