Table 2. Impact Test Parameters.

impact height (m)	coal sample number	impact velocity (m/s)	impulse (kg·m/s)
0.25	X1-1, X1-2, X1-3	2.21	10.21
	Y1-1, Y1-2, Y1-3
	Z1-1, Z1-2, Z1-3
0.4	X2-1, X2-2, X2-3	2.8	12.94
	Y2-1, Y2-2, Y2-3
	Z2-1, Z2-2, Z2-3
0.55	X3-1, X3-2, X3-3	3.28	15.16
	Y3-1, Y3-2, Y3-3
	Z3-1, Z3-2, Z3-3
0.7	X4-1, X4-2, X4-3	3.7	17.1
	Y4-1, Y4-2, Y4-3
	Z4-1, Z4-2, Z4-3
0.85	X5-1, X5-2, X5-3	4.08	18.86
	Y5-1, Y5-2, Y5-3
	Z5-1, Z5-2, Z5-3