An Analytical Calculation Method for Displacement Criterion on Tunnel Surrounding Rock Mass Stability

Table 1

Allowable relative convergence index for tunnel.

Rock class	Tunnel overburden (m)
	＜50	50∼300	300∼500
= 3\ ROMAN III	0.10∼0.30	0.2∼0.5	0.4∼1.2
= 4\ ROMAN IV	0.15∼0.50	0.4∼1.2	0.8∼2.0
= 5 ROMAN V	0.20∼0.80	0.6∼1.6	1.0∼3.0

The relative convergence index unit is %.