Study on the Stability of a Transition Section from Soft to Hard Surrounding Rock Based on the Solid-Fluid Coupling Effect

Table 1

Index values of the physical and mechanical properties of the surrounding rock at all grades.

Surrounding rock grade		(GPa)	(MPa)	（°）
III	0.20	8.0	1.2	41.2	3.0
V	0.45	1.5	0.12	24.1	4.5
C25	0.20	30.0	6.00	50	Impermeable
Thin layer	0.25	0.2	8.5	30	—
Anchor rod	0.30	200	—	—	—