Estimation of the municipal solid waste settlements and the contribution of each of the components are essential in the estimation of the volume of the waste that can be accommodated in a landfill and increase the post-usage of the landfill. This article describes an experimental methodology for estimating and separating primary settlement, settlement owing to creep and biodegradation-induced settlement. The primary settlement and secondary settlement have been estimated and separated based on 100% pore pressure dissipation time and the coefficient of consolidation. Mechanical creep and biodegradation settlements were estimated and separated based on the observed time required for landfill gas production. The results of a series of laboratory triaxial tests, creep tests and anaerobic reactor cell setups were conducted to describe the components of settlement. All the tests were conducted on municipal solid waste (compost reject) samples. It was observed that biodegradation accounted to more than 40% of the total settlement, whereas mechanical creep contributed more than 20% towards the total settlement. The essential model parameters, such as the compression ratio (Cc'), rate of mechanical creep (c), coefficient of mechanical creep (b), rate of biodegradation (d) and the total strain owing to biodegradation (EDG ), are useful parameters in the estimation of total settlements as well as components of settlement in landfill.

Soil Water Characteristic Curves (SWCC) of unsaturated soils have considerable importance in analysis of geotechnical engineering problems. In these analyses, it is necessary to make a distinction between the components of total suction in terms of solute and matric suctions, which is generally ignored in practice. In the present study, suction characteristics of two compacted clayey soils are measured using filter paper method (ASTM D 5298-94), which is useful in this regard. The experimental results show that consideration of only matric suction instead of total suction is conservative as it constitutes about 25 to 60% of total suction in clay soils. Theoretical models were fitted to experimental results, and it is demonstrated that the model parameters are different in terms of total suction and matric suction. The results show that measurement of both the components of suction using the filter paper method is simple and useful in engineering analysis.

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In this paper, an approach for target component and system reliability-based design optimisation (RBDO) to evaluate safety for the internal seismic stability of geosynthetic-reinforced soil (GRS) structures is presented. Three modes of failure are considered: tension failure of the bottom-most layer of reinforcement, pullout failure of the topmost layer of reinforcement, and total pullout failure of all reinforcement layers. The analysis is performed by treating backfill properties, geometric and strength properties of reinforcement as random variables. The optimum number of reinforcement layers and optimum pullout length needed to maintain stability against tension failure, pullout failure and total pullout failure for different coefficients of variation of friction angle of the backfill, design strength of the reinforcement and horizontal seismic acceleration coefficients by targeting various system reliability indices are proposed. The results provide guidelines for the total length of reinforcement required, considering the variability of backfill as well as seismic coefficients. One illustrative example is presented to explain the evaluation of reliability for internal stability of reinforced soil structures using the proposed approach. In the second illustration (the stability of five walls), the Kushiro wall subjected to the Kushiro-Oki earthquake, the Seiken wall subjected to the Chiba-ken Toho-Oki earthquake, the Ta Kung wall subjected to the Ji-Ji earthquake, and the Gould and Valencia walls subjected to Northridge earthquake are re-examined.

Recently, composite reinforcements in which combinations of materials and material forms such as strips, grids, and strips and anchors, depending on requirements, have proven to be effective in various ground improvement applications. Composite geogrids studied in this paper belong to the category of composite reinforcements and are useful for bearing capacity improvement. The paper presents evaluation of results of bearing capacity tests conducted on a composite geogrid, made of composite reinforcement consisting of steel and cement mortar. The study shows that the behavior of composite reinforcements follows the general trends observed in the case of conventional geogrids, with reference to the depth of first layer below the footing, number of layers of reinforcement, and vertical spacing of the reinforcement. Results show that the performance is comparable to that of a conventional polymer geogrid.