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

Table 3

Main calculation steps for the construction of the double-side guide pit method.

Calculation step	Construction conditions
I.S.	Clear the displacement
S1	Excavate 1 m above the left guide pit
S2	Excavate 1 m above the left guide pit; make the first step of the steel arch and initial lining
S3	Excavate 1 m above the left guide pit; make the second step of the steel arch and initial lining
S4	Excavate 1 m above the left guide pit; make the third step of the steel arch and initial lining
S5	Excavate 1 m above the left guide pit; make the fourth step of the steel arch and initial lining
S6	Excavate 1 m above and below the left guide pit; make the fifth step of the steel arch and initial lining
S7	Excavate 1 m above and below the left guide pit; make the sixth step of the steel arch and initial lining
S8	Excavate 1 m above and below the left guide pit; make the seventh step of the steel arch and initial lining
S9	Excavate 1 m above and below the left guide pit; make the eighth step of the steel arch and initial lining
S10	Excavate 1 m above and below the left guide pit; make the ninth step of the steel arch and initial lining
S11	Excavate 1 m above the right guide pit; make the steel arch and initial lining of previous step
...	...
S16	Excavate 1 m below the right guide pit; make the steel arch and initial lining of previous step
...	...
S21	Excavate 1 m from middle and upper part of the tunnel; make the steel arch and initial lining of previous step
...	...
S26	Excavate 1 m of the middle and lower part of the tunnel; make the steel arch and initial lining of previous step
...	...
S36	Excavate inverted arch
S37	Lay steel for inverted arch and pour inverted arch
S38	Second lining