LABORATORY EVALUATION OF LOCALLY MADE SYNTHETIC ENVELOPES FOR SUBSURFACE DRAINAGE IN EGYPT

Permeameter tests have been carried out in two independent laboratorie s to predict the performance of locally made synthetic envelopes to be used for subsurface drainage in Egypt. Both laboratories used four Eg yptian made, voluminous envelopes and compared their drainage performa nce with commercially available thin geotextiles. Two coarse textured Egyptian soils were used, Although both laboratories applied a slightl y different approach, agreement between the outcome of the experiments in both laboratories was obtained. All investigated envelopes prevent ed a massive soil particle movement, Although fine soil particles migr ated to some extent, the likelihood of envelope clogging was limited. The experiments showed that the four Egyptian made, voluminous envelop es do not affect drainage performance negatively in spite of their rat her fine texture, The thin envelopes exhibited however a higher risk t o clogging than the voluminous envelopes, even the thin material with a larger characteristic opening size.