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332 RAHMAN, M.M. & HAQUE, M.A. Management (IWEM), Bangladesh University of
(Institute of Water and Flood Management Engineering and Technology (BUET), Dhaka).
(IWFM), Bangladesh University of Engineering Applicability of the Bend Developmemt Theory in
and Technology (BUET), Dhaka). PREDICTION Natural Alluvial River. IWFM Res. Bull., 2004, 5,
OF LOCAL SCOUR AROUND ABUTMENT- 41-49.
LIKE STRUCTURES. IWFM Res. Bull., 2001- The theoretical conditions for the bend
2002, 3, 10-19. development or attenuation have been reviewed
and tested for a study reach of the Meghna river.
Scour depth around abutment-like structures The field observations in the natural alluvial
increases as the value of b/h (b = length of the meander do not support the theories developed for
structure in the lateral direction and h = approach bend development. The limitations of the theory to
flow depth) increases up to certain extent. After apply in the natural meandering river are
that limiting b/h value the observed scour depth discussed.
remains constant both in alluvial rivers and
laboratory channels. This phenomenon is 335 RAHMAN, M.M.; HAQUE, M.A. &
incorporated in an analytical model for the ISLAM, M.S.; (Institute of Water and Flood
prediction of local scour depth for any range of Management (IWFM), Bangladesh University of
b/h. The developed model is closely comparable Engineering and Technology (BUET), Dhaka).
with Melville's formulae that were developed FLOW AND SCOURING AROUND PIERS AND
empirically. The applicability of the developed ABUTMENTS. IWFM. Res. Bull., 2001-2002, 3,
model is tested in the alluvial rivers of Bangladesh. 20-25.
333 RAHMAN, M.M. & HAQUE, M.A. The 2-D flow field at several horizontal planes
(Institute of Water and Flood Management around piers and abutment has been presented
(IWFM), Bangladesh University of Engineering from the results of flume experiments in a fixed
and Technology (BUET), Dhaka). bank straight rectangular channel with both flat
PREDICTION OF LOCAL SCOUR AT bed and erodible bed condition. The experiments
BRIDGE SITE: MODIFICATION AND are conducted in the clear-water scouring.
APPLICATION OF LACEY FORMULA. Previously identified restricted flow concentration
IWFM Res. Bull., 2001-2002, 3, 1-9. region around abutments found to be equally valid
for piers where pier centerline is considered to be
In the recent years, it has been established that b/h the mirror image of the channel wall for
(b = length of the structure in the lateral direction abutments. From the characteristics of the vortex
and h = approach flow depth) is the dominant systems at different horizontal plane, the 3-D flow
factor for the estimation of local scour depth structures are reduced to 2-D and the above
around piers and abutments. One of the major phenomenon has been treated analytically in order
limitations of the lacey formula is that it predicts to develop an integrated scour depth prediction
only one value of the scour depth for a specific method around piers and abutments. The
river because of the absence of the important developed method is then applied to predict the
parameter b/h. Therefore, its application is quite maximum scour depth around piers and abutments
uncertain for the variable b/h. Considering its both against the available laboratory data.
limitations and experimental facts of flow
concentration and shear stress amplification close 336 RAHMAN, M.M.; HUSSAIN, M.A.;
to the above structures, the original Lacey formula ISLAM, G.M.T.; HAQUE, M.A. &
is modified introducing the parameter b/h. The HOQUE, M.M. (Institute of Water and Flood
applicability of the original as well as modified Management BUET, Dhaka). Hydro-
Lacey formula is tested to the data collected from morphological Characteristics around the Meghna
major livers in Bangladesh. Bridge Site in the Meghna River. IWFM Res. Bull.,
2004, 5, 10-16.
334 RAHMAN, M.M.; HAQUE, M.A. &
HOQUE, M.M. (Institute of Water and Flood
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