Mechanically and chemically stabilized bio-solids as embankment fill material

Abstract

A series of laboratory tests (index properties, particle size distribution tests, compaction tests and CBR tests) were conducted on bio-solids to assess whether it could be compacted to be used in embankment fill material. The dry density requirement was not satisfied although the rest of the geotechnical properties were at acceptable level. Therefore, the second phase of study was aimed in investigating how geotechnical properties of bio-solids could be modified through chemical and mechanical stabilization. The second phase of study revealed that chemically and mechanically stabilized bio-solids have improved physical properties than untreated bio-solids. The addition of 30% crushed bricks to stabilize bio-solids was found to be sufficient to achieve the desired level of dry density to be applied as an embankment fill material. To be acceptable for geotechnical reuse, bio-solids must meet the heavy metal contaminant concentration and pathogen limits. It was found that the heavy metal concentration and pathogen limits of biosolids of Biyagama Export Processing zone do not limit the employment of biosolids as geotechnical fill material. Findings suggest that the stabilized bio-solid admixtures with crushed bricks could be potentially used in place of soil as an effective and low cost compacted embankment fill material.