Self-Tuning Inference Model for Settlement in Shield Tunneling: A Case Study of the Taipei Mass Rapid Transit System’s Songshan Line

Table 3

Monitoring setups.

Position of tunnel surface and monitoring section	Monitoring instrument	Monitoring frequency
	Subsidence observation points (SB, SM, and SSI)	d1 > 50 m	Initial value measurement
	Multipoint borehole extensometer (EXM)	d1 ≤ 25 m	Every 5 m
	Inclinometer (TI)
	Crack meter (CG and CM)	d2 ≤ 25 m	Once every 5 m. At least once a day for 3 consecutive days since crossing the observation surface
	Water level observation well and piezometer (OW and PZS)	d2 > 25 m	Once a week
	Soil inclination pipe (SIS)