Optimization for U-Shaped Steel Support in Deep Tunnels under Coupled Static-Dynamic Loading

Table 1

The safety factor of the coupling model between the surrounding rock and U-shaped steel.

Plan		K
A	15	0.8	1/4	10	1	4.5	<0
B	20	1.0	1/3	30	2	4.6	<0
C	25	1.2	1/2	50	3	4.7	<0
D	30	1.5	3/4	70	4	4.8	<0
E	35	2.0	1	90	5	4.9	<0

K is the side stress coefficient, and is the contact area ratio.