This research is to grope for a method to reduce high
pore pressure taking place on tunnel shotcrete lining, especially in underwater
tunnels, effectively by utilising a new concept of patternised pin drain.
Accordingly, the patternised pin drain system is investigated numerically in
order to confirm to the effect of reduction of pore pressure by the pin drain
and its effective application. Installation of pin drain shows considerable
reduction in the figure of pore pressure. It is found through 2D numerical
modelling that the change of pore pressure, according to the shape and the
location of pin drain, is sensitive by the sequences of the change of location
> the change of length > the change of angle degree. In the results of
investigation in 3D modelling, the pore pressure is the largest in the centre of
the interval among pin drains, and it is possible to obtain an ideal degree of
longitudinal angle and an interval by investigating pore pressure taking place
on the lining.