Table 3
Maximum equilibrium scour depth data for abutment
The maximum equilibrium scour depth values of the abutment can be
compared with those of Melville (1992), Oliveto and Hager (2002), Dey
and Barbhuiya (2005), and Lim (1997), as shown in Fig 12. The equations
presented by Melville (1992), Oliveto and Hager (2002), Dey and
Barbhuiya (2005), and Lim (1997) are for straight channels. As shown in
Fig. 12, there is no close agreement between previous studies. However,
there is a certain consistency between previous studies and the present
study. One of the most important reasons for this is that the
experiments were performed in different types of channel. In the curved
channels, the flow characteristics are markedly different to those of
straight channels.
Fig. 12. Comparison of maximum scour depth computed using Eqs.
(1-4) with data of the present study
Conclusions
The local scours that occur around the bridge abutments on outer and
inner banks in a curved channel were experimentally examined under
clear-water flow conditions. Based on the findings, the conclusions are
as follows.
- Maximum scour depth increased in line with the increase in flow
intensity.
- The maximum scour depth usually decreased as the abutment length on
the inner and outer banks in a curved channel increased. The abutment
length is thus an important factor for maximum scour depth.
- The maximum scour depth around the abutment located on the outer bank
in the curved channel was greater than the scour depth formed on the
inner bank. The maximum scour depth around the abutments placed on the
outer bank was 1.45 times the scour depth on the inner bank.
- In the curved channel, there were differences in maximum scour depth
at different bend angles. This ranged between 5-15%.
- The location of the maximum scour was at the abutment upstream. The
scour depth at the abutment upstream was higher than the scour depth
at the abutment downstream.
- At the channel entrance, there was less scouring on the first angle of
the curve (at 30°) because the material from the upstream compensated
for the transported material. Therefore, if a bridge is placed in the
first half of the curved channel, there is likely to be less scouring
on the abutments.