Laboratory comparison of clogging in three types of domestic synthetic envelopes installed in clay‐calcareous soils^*

Abstract

Clogging in subsurface drain envelopes is one of the main issues in drainage systems; changing drainpipes needs a large amount of money and can decrease the profitability of the system, so in this study we tried to select the best envelope according to clogging. This study was conducted to evaluate comparatively the performance of three synthetic envelopes (A, B, C) manufactured in Iran by using a physical permeameter model in the laboratory. The selected envelopes were of PP450 synthetic type. Experiments were performed to examine the changes in drain discharge and hydraulic conductivity of the soil–envelope of each permeameter in each of the three envelopes during a period of 2000 h. Experimental results indicated that at a constant water head, reduction of drain discharge was associated with reduction of hydraulic conductivity of the soil–envelope over time. It was due to the movement of soil particles within the envelopes for each discharge until it reached a constant value or the soil–envelope equilibrium. Comparison of results for the applied envelopes showed that envelope A had a better performance than the other two. Envelope A also had 28% higher drainage coefficient than envelope B and 58% higher drainage coefficient than envelope C, so this property can increase drain distances and save costs. The total hydraulic conductivity of envelope A is 6.5 and 5% higher than those of C and B envelopes, respectively. By comparing envelopes B and C we can see that envelope B presented a better function.