Instability Mechanism of Cavity-Bearing Formation under Tunnel Excavation Disturbance

Table 2

Model test plan design.

Working condition	Tunnel diameter D (cm)	Tunnel arch depth H (cm)	Cavity position	Cavity diameter d (cm)	Cavity depth h (cm)
1 (without cavity)	20	40	—	—	—
2 (with cavity)	20	40	Directly above	7.5	12