Calculation Model and Influencing Factors of Surrounding Rock Loosening Pressure for Tunnel in Fold Zone

Table 2

and calculated values.

Surrounding rock level	I	II	III	IV	V	VI
(°)	73	60	43	23	12.5	7.5
(°)	>78	67∼78	55∼66	43∼54	31∼42	<30