Effective utilization of sand as an additive for the validity of filter design criteria for cohesive soils based on controlling pore size of filters

• Published in: International journal of geotechnical engineering 2014-04, Vol.8 (2), p.205-212
• Main Authors: Dar, A. Q., Lone, M. A., Hussain, B.
• Format: Article
• Language: English
• Subjects: Additives; Base material; Cohesion; Controlling pore size; Criteria; Filter design; Non-uniform particles; Pore channel; Pore size; Porosity; Sand; Silts; Slot test; Soils; Washout
• ISSN: 1938-6362; 1939-7879
• DOI: 10.1179/1939787913Y.0000000024

Often it is necessary to provide a filter for cohesive base materials. The presence of sands in cohesive soils such as silts and clays has a marked influence on the filter behavior, when such soils are used as base materials. Recently a filter design criterion based on controlling pore size of filters was developed to protect cohesive base materials (silts and clays) without addition of sands. This paper describes the applicability of the same filter design procedure for cohesive bases with non-cohesive sands as an additive. Based on laboratory investigations, an attempt has been made to ascertain the maximum content of non-cohesive sands in the base to which the said criterion can be employed. For this purpose cohesive soils were tried with addition of different percentages of sand content (5, 10, 15, 20, 25, and 30%) by weight. The study has shown that the design criterion for cohesive soils on the basis of controlling pore size of filters can be safely adopted up to 25% of non-cohesive content in the base soil. Beyond 25% of non-cohesive content such as sand the behavior of bases in terms of filter requirements changes and filter design is based on design criteria that is based on controlling pore size of filters for non-cohesive base materials.