Multi-Objective Optimization of Slope Stability Using Wedge Analysis and Genetic Algorithm

Slope stability of different waste containment systems is a matter of serious concern due to its impact on air, land, and water pollution, affecting human and aquatic lives. It has been observed that most of the waste containment slope failures are translational failure. In this chapter, the slope stability analysis of the waste containment is discussed with translational failure (wedge analysis) in single and multi-objective optimization framework using genetic algorithm (GA). Non-dominated sorting genetic algorithm II (NSGA-II) is found to efficient in developing the Pareto front in terms of factor of safety (FOS), height of embankment, and volume of the failed slope. The FOS decreased with increase in height of the slope and the volume of the slope also increased. The optimized slope in terms of different slope angle and with seismic coefficients is also discussed. Such a study will help the professional in deciding the height of the slope as per the FOS in a specified seismic zone.

Evaluation of Lime Treated Oil Contaminated Soils for Use in Waste Containment Applications

This paper presents the results of an evaluation of lime treated oil contaminated soil for use in waste containment systems. Soil samples were treated with up 6 % lime contents. Specimens were prepared at optimum moisture content and compacted using British Standard Light (BSL) or Standard Proctor (relative compaction = 100%) to evaluate its effectiveness when used in waste containment applications. The hydraulic conductivity values increased with higher lime contents but were less than 1 x 10-9 m/s required for a liner material.

Desiccation Induced Shrinkage of Compacted Tropical Clay Treated with Rice Husk Ash

Desiccation studies are an integral part of material selection for waste containment systems. Laboratory studies on compacted tropical clay (with illite as the dominant clay mineral sourced from an excavation site) treated with up to 16% rice husk ash (RHA); an agro-industrial waste to evaluate its desiccation induced shrinkage and hence its suitability as a cover material in waste containment systems were carried out. Soil-RHA mixtures were compacted using three compactive efforts at -2, 0, 2 and 4% of optimum moisture content (OMC). Compacted samples, extruded from the compaction mould were allowed to air dry in the laboratory for a 30 day period after which they were subjected to two cycles of wetting and drying. Results show that changes in mass and volumetric shrinkage strain (VSS) were large within the first five days of drying and were affected by the compactive effort. VSS increased with higher moulding water content, water content relative to optimum and RHA treatments. VSS were affected by the compactive effort. Acceptable compaction planes were obtained for up to 12% RHA treatment. After two cycles of wetting and drying, it was observed that the rate of capillary rise within the compacted soil increased with lower compactive effort and higher rice husk ash treatment. Lower amount of cracking was observed in soil specimen with higher rice husk ash treatment and higher cracking in soils with lower rice husk ash content. Increased compactive effort reduced the effect of swelling during wetting; showing the suitability of the material as a cover in municipal waste containment facility and beneficial reuse of this agro waste product.

Hydraulic Conductivity of Compacted Tropical Clay Treated with Rice Husk Ash

Laboratory study on compacted tropical clay treated with up to 16% rice husk ash (RHA), an agro-industrial waste; to evaluate its hydraulic properties and hence its suitability in waste containment systems was carried out. Soil-RHA mixtures were compacted using standard Proctor, West African Standard and modified Proctor efforts at-2, 0, 2 and 4% of optimum moisture content (OMC). Compacted samples were permeated and the hydraulic behaviour of the material was examined considering the effects of moulding water content, water content relative to optimum, dry density and RHA contents. Results showed decreasing hydraulic conductivity with increasing moulding water content and compactive efforts; it also varied greatly between the dry and wet side of optimum decreasing towards the wet side. Hydraulic conductivity generally decreased with increased dry density for all effort. Hydraulic conductivity increased with rice husk ash treatment at the OMC; but were within recommended values of 1 x 10-7 cm/s for up to 8% rice husk ash treatment irrespective of the compactive effort used. This shows the suitability of the material as a hydraulic barrier in waste containment systems for up to 8% rice husk ash treatment and beneficial reuse of this agro-industrial waste product.