Enhanced Criterion for Selecting Surface Soils for Multi-layered Cover System

The multi-layered cover systems (MLCS) are usually constructed over near surface hazardous landfills to isolate waste from the atmosphere. The existing design and construction criteria of MLCS are predominantly based on the flow or strength characteristics of soil. However, the surface layer of MLCS is subjected to intense soil-atmosphere interaction in the form of precipitation, run off, erosion, infiltration, desiccation, and alternate wetting–drying resulting in the performance deterioration. There are no explicit criteria in literature for accounting all these complex factors while designing the surface layer. This study proposes an enhanced criterion for selecting surface soil and its design compaction state by inclusion of multiple field anticipated performance requisites related to erosion, infiltration, desiccation, and strength characteristics. The main objective of this study is to evaluate these characteristics using simple well-established laboratory tests namely pin hole erosion, disk infiltrometer, volumetric shrinkage, and unconfined compression tests for different soils and different compaction states of good performing soil. Based on the test results, criterion for assessing the suitability of soil as surface layer were evolved. The selected soil was further studied for identifying suitable compaction zone. Results showed that the silty soil with low plasticity, which falls, in ML classification is better suitable for surface layer of MLCS. Compacting soil near optimum moisture content and higher density was found to show enhanced performance with good strength, low permeability, low erodibility, and low shrinkage. The proposed criterion incorporating additional performance markers is a quick method for effective design of surface soil in MLCS.