Mechanical Responses to Different Excavation Methods of Qichongcun Tunnel in Guiyang City, China

Table 5

Main calculation steps of the three-step method.

Calculation step	Construction conditions
I.S.	Clear the displacement
S1	Excavate the first 1 m of the tunnel for anchor and lining
S2	Excavate 1 m of the first step and the second step for the steel arch and lining
S3	The first step, the second, and third steps are 1 m each for anchor the steel arch and lining
S4	Excavate 1 m of the first, second, and third steps and make the steel arch and initial lining
S5	Repeat the previous step
S6	Repeat the previous step
S7	Repeat the previous step
S8	Repeat the previous step
...	...
S14	Excavate inverted arch
S15	Lay steel for inverted arch
S16	Inverted arch
S17	Second lining