Table 1 Calculation parameters of twin tunnels.

TD

6 m

6 m

RPT/TD

2/6

2/6

Initial stress field for X orientation (\(\sigma_{{\text{x}}}\))

0.4 MPa

1.0 MPa

Initial stress field for Y orientation (\(\sigma_{{\text{y}}}\))

1.0 MPa

0.4 MPa