## 3 Calculation Results and Influence Factors Analysis
### Transverse Ground Settlement with Different Excavation Intervals
For the staggered double-line tunnels, the maximum ground settlement at 24 m, 48 m, and 75 m longitudinal intervals were 4.73 mm, 4.77 mm, and 4.78 mm, respectively. The land subsidence of these three longitudinal intervals is not very different, and the maximum land subsidence positions of the three are the same, all of which are 1.6 m on the left side of the central axis. The trend of land subsidence in Figure 3b,c is similar to that in Figure 3a. These figures show that, compared with continuous excavation when the distance between the two tunnels is 1.0D and 1.5D, the excavation of the right-line tunnel during the interval excavation will increase the maximum lateral settlement of the ground and make the maximum settlement point deviate from the axis of the double-line tunnel. At the same time, with the increase in excavation interval, the above phenomenon will be more obvious. However, with the increase in the space of the double-line tunnel, the increase in the ground settlement caused by the excavation of the right-line tunnel will be weakened and may even be reversed. In addition, it is surprising that the size of the staggered excavation distance has no significant effect on the final lateral ground settlement of the double-line tunnel. To further study the influence of tunnel spacing on the ground settlement during the excavation of the right-line tunnel, the maximum ground settlement values of the 11 th and 19 th foundation pit steps under different tunnel spaces in Figure 3 are further analyzed. Figure 4 shows the variation in the maximum ground settlement with the change in tunnel space. With the increase in tunnel spacing, the maximum ground subsidence decreases. For the continuous excavation of the double-line tunnel, the change curves of the maximum ground settlement values of the 11 th and 19 th excavation steps are similar, and the difference between the maximum ground settlement between 1.5D and 2.0D is greater than the difference between 1.0D and 1.5D. For the cross-excavated double-line tunnel, the maximum ground settlement curves of the 11 th and 19 th excavation steps are similar, but the settlement difference caused by the change in tunnel spacing does not change much. At the same time, with the increase in tunnel space, the settlement difference between the continuous excavation and 24 m excavation interval double-line tunnel becomes smaller, and the two curves intersect in the 1.8D tunnel space. This shows that with the increase in tunnel space, the effect of the right tunnel excavation on ground subsidence will become weaker. For a certain tunnel space, this effect will turn to the opposite. For the double-line tunnel with continuous excavation and the double-line tunnel with a longitudinal interval of 48 m, the maximum ground settlement difference shows a continuous downward trend with the increase in tunnel spacing. In summary, the ground lateral settlement value of a continuous excavation tunnel and staggered excavation tunnel decreases with the increase in tunnel spacing, and the change rate of settlement in this process is also from small to large. However, the curves of the settlement values of different excavation distances with the change in the tunnel spacing are parallel, and the difference in the rate of change of the settlement is very small. With the increase in tunnel space, the effect of right tunnel excavation on ground subsidence will become weaker. It is worth mentioning that when the excavation interval is 24 m and the tunnel spacing is greater than or equal to a certain value between 1.5D and 2.0D, the effect of increasing land subsidence will even reverse.