Evaluation of Geocomposite filter-drain and possibility of their installation as drain pipes
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Evaluation of Geocomposite filter-drain and possibility of their installation as drain pipes abstract
Shortage of appropriate resources for granular envelopes and environmental
considerations in recent years has been resulted in widespread use of synthetic materials
such as geotextiles and PLM in drainage projects. Different investigations demonstrated
the acceptable efficiency of synthetic envelopes; however, the efficiency of these
envelopes is still lower than granular (mineral) ones. Lower thickness of synthetic
envelopes in comparison with granular ones brings about decline in effective radius of
drainage; consequently, decrease in the efficiency of these envelopes in comparison
with granular ones. One alternative to reduce the effects of decrease in thickness is
increasing open surface of drainage pipes. Since entrance resistance is dependent on
drainage pipes, their shapes and the pores structures, increasing open surface of drains
results in decreasing entrance resistance and also total head loss in drains. Thus,
increase in surface entrance of water into drains can be considerably effective on the
performance of drainage. The purpose of this study was to investigate the efficiency of
geocomposite filter-drains in reducing water table and their application instead of drain
pipes with common envelopes. In this study, to simulate the natural conditions of
drained fields, in laboratory a horizontal sand tank was used that besides regulating
water table at desired head, it could simulate some parts of drainage trenches.
Experimental drains were common drain pipes with diameter of 100 mm (with granular
envelopes), pre-wrapped loose materials of PLM (type of PP450 and geotextile), three
filter-drains with rectangular cross sections (with the same perimeter of drain pipes
using three different kinds of geotextiles), and two circular filter-drains (with diameter
of 100 mm with two different types of geotextiles). The parameters including water
table profile, drainage discharge from drains and entrance resistance at heads of 45, 50,
60, 70, 80, 90, 100 and 110 cm were measured for eight experimental drains with three
replicationsThe results showed that drains with granular envelope, rectangular filterdrains,
and drains with geotextileand PLM envelopes had respectively higher efficiency
in reducing water table and depletion of excessive soil water respectively. The
differences in flow and entrance resistance between circular filter-drains and drains with
granular envelopes were not significant. However, output flow and entrance resistance
of circular filter-drains was 34.9-65.7 and 79.4-90.3 % higher than drains with PLM
envelope, respectively at different heads. The head loss at the center of circular filterdrains
was 0.7-10% lower than drains with granular envelopes but 55.7-77.8% higher
than drains with PLM envelope. The head loss of water table in rectangular filter-drains
was 10.2-51.1% lower than drains with granular envelope but 50.1-52.8% higher than
drains with PLM envelope. Furthermore, output flow in rectangular filter-drains was 42-
46.7% lower than drains with granular envelope but 18.4-52.5% higher than drains with
PLM envelope. The difference in entrance resistance between rectangular filter-drains
and drains with granular envelope was not significant; however, this parameter was
72.2-90.5% lower in drains with PLM envelope compared with rectangular filter-drains.
Geocomposite filter-drains had lower entrance resistance at different heads and they had
acceptable performance in drainage discharge and reduction of water tablein laboratory
conditions.
Evaluation of Geocomposite filter-drain and possibility of their installation as drain pipes Keywords:
Evaluation of Geocomposite filter-drain and possibility of their installation as drain pipes authors