Experimental Study of Mechanical Characteristics of Tunnel Support System in Hard Cataclastic Rock with High Geostress

Table 1

Support parameters of three test sections.

Test sections	Initial support						Secondary lining	Deformation allowance (cm)
	C25 shotcrete	Bolt			Steel support		Arch wall thickness
	Thickness (cm)	Position	Length (m)	Spacing (m)	Steel support	Spacing (m)
1	27	Arch/wall	4.0	0.8 × 0.8	I20b	0.8	40 cm (reinforced concrete)	40
2	25	Arch/wall	4.0	0.8 × 0.8	I18	0.6	40 cm (reinforced concrete)	40
3	25	Arch/wall	3.5	1.0 × 0.8	I18	0.8	40 cm (reinforced concrete))	30

Notes: (1) according to the data of deformation and stress measurement, support parameters and deformation allowance are adjusted dynamically in time. (2) The advanced support is made of φ42 grouting small pipe, the length is 4.0 m, and the circumferential and longitudinal spacing are 0.4 m and 2.4 m, respectively. Steel mesh: the arch wall adopts φ8 steel bar with mesh size of 20 × 20. 3. The original design is adopted for the section of supporting structure in test sections 1 and 2; only the parameters are changed (the section of Figure 4(b)). The support form of side wall with large curvature is adopted for test section 3 (the section of Figure 4(c)).