Laboratory determination of the shear strength of conditioned Water Treatment Sludge for application in daily covers of sanitary landfills

• Grant number: 19/25404-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2019
• End date: June 30, 2020
• Field of knowledge: Engineering - Civil Engineering - Geotechnical Engineering
• Agreement: SABESP
• Principal Investigator: Maria Eugenia Gimenez Boscov
• Grantee: Alexandra Ramos Nardy
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Company: Universidade de São Paulo (USP). Escola Politécnica (EP)

Abstract

The feasibility of using water treatment Sludge (WTS) as daily cover of sanitary landfills aims at reducing environmental impacts consequent of inadequate destination (WTS is generally discarded in rivers), besides substituting and preserving natural soils used for this purpose. However, WTS does not present proper mechanical and hydraulic characteristics for direct utilization in earth works. Even after dewatering in drying beds or centrifuges, high remaining water content makes WTS difficult to compact and spread by equipment usually employed in the field. The low permeability of WTS induces the formation of leachate and gas pockets inside the waste mass, and its low shear strength also creates potential failure surfaces. The objective of this research project is to improve WTS workability characteristics and to promote its use as material for daily cover. Therefore, the performance of WTS conditioned with lime and/or other additive (preferentially also solid waste) in several proportions will be investigated. The general project comprises tests for geotechnical, chemical and mineralogic characterization, compaction, shear strength and hydraulic conductivity. In this particular project, shear strength of WTS-lime (and/or other additive) mixtures will be investigated by unconfined compression, direct shear and triaxial compression tests. Results will indicate the most promising mixtures, and correlations with physical indexes and consistency limits will be searched in order to anticipate field behavior based on simple laboratory tests. (AU)