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ABSTRACT
Sediment deposition in urban open concrete storm drain has caused
many adverse effects to the drainage system such as flash flood and
environmental pollution. This study aimed to provide recommendations
for the purpose of sedimentation mitigation in urban open concrete
storm drain. To understand the physical characteristics of sediment
deposition; sampling was taken from 57 locations in Kuching city,
surrounding towns outside Kuching city and Penang consisting of
residential, commercial and industrial areas and subjected to sieve
analysis. Results showed that the samples were mainly inorganic and
non-cohesive with sand as the major component followed by gravel and
silt and clay for most of the samples. To improve the design
criteria, incipient motion experiments were conducted in a 0.6 m
wide flume for sediment with sizes of 0.81 mm, 1.53 mm 4.78 mm.
Combining the results from the current incipient motion experiments
with the results from an earlier researcher for a 0.3 m wide flume,
multiple linear regression were performed and the best equations for
each of the critical shear stress and critical velocity approach
were developed. A design chart relating the self-cleansing design
relationship between drain minimum slope with the design minimum
flow rate and the respective standard drain size was also developed.
To further improve the self-cleansing capability of open concrete
storm drain, a tipping flush gate was designed and installed on site
at Taman Pekaka, Nibong Tebal, Penang and subjected to monitoring
for four months between 14th November 2012 and 15th March 2013.
Results showed that the tipping flush gate was effective in reducing
the total volume of naturally accumulated sediment in the monitored
drain section. Experiments on the gate characteristics and flushing
performance were conducted in the laboratory with two flumes of
different dimensions. Results from the first flume showed that both
the gate opening angle and duration of flushing have effect on the
flushing performance with the gate opening angle slightly more
significant. Experiments in the second flume generally showed that
the number of flushes required to totally remove the sediment bed
from the 1 m where the bed was initially laid increased by an
average of two times as the sediment bed thickness doubled. An
equation relating the number of flushes required with the angle of
gate opening and sediment deposition thickness was developed.
Guidelines on the design and installation of tipping flush gate on
site have also been presented.
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