Maka ọnụ ala dị ọnụ ala, geotextiles nwere ike ịgbatị ndụ nke ihe arụrụ arụ kwa ụbọchị site n'igbochi njikọta nke ala subgrade na mkpokọta mkpokọta, yana ime ka obere ala dara ogbenye kwụsị.