Safety Threshold Determination for Blasting Vibration of the Lining in Existing Tunnels under Adjacent Tunnel Blasting

Table 8

The slowest attenuation monitoring data of the PPV for each surrounding rock grade.

No.	Q (kg)	(m)	(cm/s)	Surrounding rock grade
1	36.00	51.28	10.44	III
2	36.00	50.60	9.79
3	36.00	47.74	10.26
4	31.50	49.28	8.64
5	41.50	55.69	7.99
6	18.50	56.88	4.64
7	24.00	41.06	8.55	IV
8	41.00	51.01	7.83
9	30.00	49.09	6.73
10	5.75	47.17	2.29	V
11	5.75	48.63	2.12
12	12.00	55.68	2.14
13	5.75	47.82	1.67
14	18.00	48.02	3.13
15	18.825	38.78	4.46
16	6.00	51.44	1.32