Mechanical and Deformation Characteristics and Optimization of Support Parameters for Superlarge-Span Tunnel: A Case Study from Laohushan Tunnel

Table 3

Field test items and measurement methods.

Number	Measurement items	Measurement instrument	Instrument specifications	Measurement frequency
1	Horizontal convergence	TOPCON ES-101 total station	Accuracy: 1 mm	3–15 days	2-3 times/day
				16 days–1 month	1 time/day
				More than 1 month	2-3 times/week
2	Crown settlement	TOPCON ES-101 total station	Accuracy: 1 mm	3–15 days	2-3 times/day
				16 days–1 month	1 time/day
				More than 1 month	2-3 times/week
3	Steel rib stress	Steel string surface strain gauge	2000 με	1 time/day
4	Shotcrete stress	Concrete strain gauge	C25	1 time/day
5	Concrete stress in secondary lining	Concrete strain gauge	C30	1 time/day
6	Steel bar stress in secondary lining	Steel bar stress meter	HRB400	1 time/day