A study of soil to geotextile filtration behaviour in conjunction with Berea sand in South Africa

[摘要] ENGLISH ABSTRACT: Geotextiles perform a number of functions in various applications in civil engineering practise. It is often cost effective and more environmentally friendly versus conventionalconstruction methods. One of the main functions of a geotextile is filtration whereby thegeotextile is expected to hold back the soil particles and simultaneously has to allowsufficient water to pass through it. Soils are all different and can be problematic when itcomes to designing geotextile filters. One such problematic soil is encountered in KwaZulu-Natal, situated along the east coast of South Africa. The Berea sand is problematic as it canhighly variable in its engineering properties over a small area.Geotextiles are becoming more and more common practice in South Africa and little isknown about the filtration performance of commercially available geotextiles in conjunctionwith Berea sand. Local guidelines that are available are out of date and do not provideenough information to assist design engineers in decision making. Many internationalguidelines are available and it is difficult to choose which one is best suited to Berea sands.This primary objective of this study is to investigate the filtration performance of four variantsof commercially available geotextiles and three variants of Berea sand. The applicability ofsome of the international filter design criteria will also be assessed. The soil to geotextilecompatibility testing was carried out as per ASTM D5101 (2006) - Standard Test Method forMeasuring the Soil-Geotextile System Clogging Potential by the Gradient Ratio. In total 12permutations were executed. The results showed that only 5 test permutations met thegradient ratio and permeability criteria. The test results also conclude that the permeability isjust as important as the gradient ratio. Thick geotextiles should be considered when used asfilters in Berea sands. The available international geotextile filter design criteria wereassessed and all showed poor correlation between laboratory results and suggested criteria.Designing geotextile filters in conjunction with Berea reds is challenging and it isrecommended that design engineers perform laboratory performance testing in conjunctionwith their designs.

[发布机构] Stellenbosch University