A review of lateritic soils and their use as landfll liners.pdf

Part 1: Overview

• Topic: This paper reviews the nature and characteristics of lateritic soils and assesses their suitability for landfill lining applications.
• Lateritic soils: These are highly weathered soils found in tropical or sub-tropical regions. They are rich in sesquioxides of iron and aluminium and exhibit various colours, structures, and profiles.
• Landfill liners: These are barriers with low permeability that prevent the migration of leachates from landfills into the environment. They can be constructed from natural, compacted, or geosynthetic soil materials.
• Suitability of lateritic soils: The paper analyses the desirable geotechnical, geological, and geochemical properties of lateritic soils based on existing literature and data. It also explores the leachate attenuation characteristics and discusses methods to improve the properties of lateritic soils by blending them with other materials.

Part 2: Soil properties

• Index and Engineering Characteristics of Lateritic Soils: Authors compiled data on the properties of lateritic soils from 278 locations worldwide and compared them with the standard requirements for landfill liners.
• Grain Size Distribution: The texture of lateritic soils is variable and unpredictable, containing all size fractions from boulders to clay. The particle size distribution varies with the parent rock and the degree of weathering. While most lateritic soils meet the minimum fines and clay content specifications for landfill liners, some are excessively gravely or silty.
• Atterberg Limits: The liquid limits of lateritic soils range from 17% to 135%, and plasticity indexes range from 2% to 73%. The majority of the soils meet the minimum liquid limit and the recommended plasticity index range for landfill liners, but some have high swelling potential and compressibility. The position of the lateritic soils on the Cassagrande plasticity chart indicates the presence of different types and quantities of clay minerals.
• Specific Gravity: The specific gravity of lateritic soils ranges from 2.36 to 3.49, with an average of 2.72. Specific gravity primarily depends on the iron content and the degree of laterization. Most soils meet the minimum specific gravity specification for landfill liners, but one sample does not.
• Compaction Characteristics: The maximum dry density of lateritic soils ranges from 1170 to 2780 kg/m3, with an average of 1800 kg/m3, and optimum moisture contents range from 6.6% to 39%, with an average of 15.9%. The compaction characteristics depend on factors such as grading, clay mineralogy, and compaction energy. About 26.3% of the lateritic soils do not meet the minimum maximum dry density requirement for landfill liners.
• Strength Characteristics of Lateritic Soils: The unconfined compressive strength values of lateritic soils range from 4.23 to 1260 kPa, with an average of 135.3 kPa. Cohesion values range from 5.5 to 153 kPa, with an average of 49.8 kPa. The angle of internal friction values range from 3.2° to 49°, with an average of 24.1°. The shear strength of lateritic soils depends on the friction and cohesion of soil particles, as well as cementation by sesquioxides. Most of the soils do not meet the minimum unconfined compressive strength specification for landfill liners, but the majority meet the minimum cohesion and angle of internal friction specifications.
• Permeability: The permeability of lateritic soils ranges from 2.95×10–12 to 1.22×10–3 m/s, with an average of 7.17×10–5 m/s. The permeability depends on the soil composition and compaction conditions. The average permeability of the soils exceeds all benchmarks for landfill liners. However, individually, a large proportion meet the 1×10–8 m/s minimum requirement, and about half of them meet the 1×10–10 m/s maximum requirement.

Part 3: Mineral Liners

• Mineral liners are layers of natural or processed materials used to reduce or prevent the spread of contaminants from landfills into the environment.
• Types of mineral liners include clay, lateritic, bentonite, and cementitious liners. Each type has distinct properties, advantages, and disadvantages, which depend on soil characteristics, climate, and waste composition.
• Design and performance criteria for mineral liners vary based on factors like hydraulic conductivity, thickness, compatibility, durability, and stability. It's crucial to test and monitor mineral liners to ensure their effectiveness and safety.
• References: This page includes numerous references to previous studies and publications about mineral liners. These cover topics such as geology, geochemistry, mineralogy, geotechnics, and engineering.