where, i1 and i2 are the trough width parameters of the two tunnels respectively
(i1 ¼ 1=
ffiffiffiffiffiffiffiffi
2a1
p
,i2 ¼ 1=
ffiffiffiffiffiffiffiffi
2a2
p
). It'sworth noting thatmeter (m)
is used as the unit of i1 and i2, and millimeter (mm) for s1 and s2. Therefore,
the integral results should be divided by 1000 to get the unit ofm2.
Vl is considered as an important safety indicator in spatial dimension.
By combining the spatial analysis with temporal dimension, the
proposed safety-oriented DW facilitates the evaluating the evolution
of Vl. It is found that the derived ground loss Vl is growing in a pattern
that can be well represented by the logistic growth curve (Eq. (15)),
as is shown in Fig. 17..