proposed double Gaussian model, as shown in Fig. 10. Settlement data
of the array at 2 moments (as shown in Fig. 11) was plotted with different
symbols. Round points indicate the ground settlement records
at moment 1 when the northbound tunnel (i.e. the preceding tunnel)
passed beneath the array whereas square points indicate the ground
settlement records at moment 2 when both tunnels passed through
the array and the ground stabilized. Each group of data was fitted by
the proposed double Gaussian model (i.e. C and F). According to
Eq. (2), both the two curves C and F could be decomposed into two
parts to represent the ground disturbance by each tunnel (i.e. C=
A+B, F=D+E). Descriptions of each curve are illustrated in Table 2.
As shown in Fig. 10, the northbound tunnel (i.e. the preceding tunnel)
passed under the ground array first, while the southbound tunnel
(i.e. the following tunnel) was far away the array. However, the excavation
of southbound tunnel had still made a small disturbance to the
ground (i.e. A). When the southbound tunnel also passed through the
ground array and the ground became stabilized, the ground disturbance
induced by the southbound tunnel had sharply increased from
A to E. Moreover, at this moment, although the northbound tunnel
had passed through for a time, it still enlarged the ground disturbance
from B to D. Finally, D and E made up the overall ground settlement
trough over twin tunnels (i.e. F).
Some other results are shown in Fig. 12. In the Wuhan Metro Project,
in order to speed up the construction progress, the twin tunnels