Shield Tunneling under Railway Station Throats in Soft Soil Areas: A Case Study

Table 6

Monitoring frequency.

Stage	Time period	Monitoring frequency (times per day)
Grouting improvement	One week before improvement	3
Grouting improvement	During grouting	24
Improvement finished	One week	1
Tunneling	20 m before the cutter head reached the railway	4
Tunneling	Crossing	12
Tunneling	50 m after the cutter tail left the railway	4
Tunneling finished	One month	1