Pretreatment for Tunnel Karst Cave during Excavation: A Case Study of Guangxi, China

Table 1

Physical and mechanical parameters.

Material	(kN·m^3)	(GPa)		(MPa)	(MPa)
Surround rock grade IV	22.0	2.4	0.33	85.00	28.00
Second lining (C40)	26	31.5	0.2	2.20	23.40
Initial support (C25）	25	28.5	0.2	1.78	16.70
Fill (C15)	23	22.0	0.16	1.27	10.00

: surrounding rock bulk density; E: elastic modulus; μ: Poisson’s ratio of rock; ƒ_t: tensile strength; ƒ_c: compressive strength.