Modeling the compaction characteristics of fine-grained soils blended with tire-derived aggregates

This study aims at modeling the compaction characteristics of fine-grained soils blended with sand-sized (0.075–4.75 mm) recycled tire-derived aggregates (TDAs). Model development and calibration were performed using a large and diverse database of 100 soil–TDA compaction tests (with the TDA-to-soil dry mass ratio ≤ 30%) assembled from the literature. Following a comprehensive statistical analysis, it is demonstrated that the optimum moisture content (OMC) and maximum dry unit weight (MDUW) for soil–TDA blends (across different soil types, TDA particle sizes and compaction energy levels) can be expressed as universal power functions of the OMC and MDUW of the unamended soil, along with the soil to soil–TDA specific gravity ratio. Employing the Bland– Altman analysis, the 95% upper and lower (water content) agreement limits between the predicted and measured OMC values were, respectively, obtained as +1.09% and −1.23%, both of which can be considered negligible for practical applications. For the MDUW predictions, these limits were calculated as +0.67 and −0.71 kN/m3, which (like the OMC) can be deemed acceptable for prediction purposes. Having established the OMC and MDUW of the unamended fine-grained soil, the em-pirical models proposed in this study offer a practical procedure towards predicting the compaction characteristics of the soil–TDA blends without the hurdles of performing separate laboratory compaction tests, and thus can be employed in practice for preliminary design assessments and/or soil– TDA optimization studies. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

An objective framework for determination of the air-entry value from the soil–water characteristic curve

The air-entry value (AEV) suction, marking the transition between saturated and unsaturated soil mechanics, is arguably the most important parameter interpreted from the soil–water characteristic curve (SWCC); its accurate determination being essential for the prediction of unsaturated soil properties. The AEV is commonly obtained by a subjective and time-consuming graphical construction. This micro-article proposes an objective framework, developed based on a practical mathematical translation technique, for the AEV determination. Explicit equations for the AEV are derived based on eleven well-established SWCC fitting functions, covering a wide range of functional complexities. In addition to its objective nature (providing unique interpretations of the AEV), the proposed framework complements numerical implementations of unsaturated soil constitutive models. © 2021 The Author(s

Mapping 123 million neonatal, infant and child deaths between 2000 and 2017

Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2—to end preventable child deaths by 2030—we need consistently estimated data at the subnational level regarding child mortality rates and trends. Here we quantified, for the period 2000–2017, the subnational variation in mortality rates and number of deaths of neonates, infants and children under 5 years of age within 99 low- and middle-income countries using a geostatistical survival model. We estimated that 32% of children under 5 in these countries lived in districts that had attained rates of 25 or fewer child deaths per 1,000 live births by 2017, and that 58% of child deaths between 2000 and 2017 in these countries could have been averted in the absence of geographical inequality. This study enables the identification of high-mortality clusters, patterns of progress and geographical inequalities to inform appropriate investments and implementations that will help to improve the health of all populations

Reappraisal of linear shrinkage test for plasticity index determination and classification of fine-grained soils

Among the multitude of alternate plasticity index (PI) estimation proposals, empirical correlations based on the linear shrinkage (LS) test, originally proposed in the 1967 edition of the British BS 1377 standard, seem to be gaining increased attention. This study has two main aims: (i) re-examining LS-based correlations for PI estimation to better understand their true potentials and/or limitations; and (ii) investigating the possibility of employing LS, as a proxy for the standard PI, for fine-grained soil classification. To this end, comprehensive statistical analyses were performed on the largest and most diverse database assembled of its kind, entailing PI:LS measurements for 265 different fine-grained soils [pertaining to the ‘soft’ base percussion-cup liquid limit (LL = 17–134%) and the Australian standard LS = 0.5–32.0%]. It was demonstrated that the LS can generally only provide a rough approximation of the actual PI. At best, only those predictions produced by PI = 1.86 × LS for low-plasticity soils (i.e., L

Converting optimum compaction properties of fine-grained soils between rational energy levels

This study introduces a practical energy conversion (EC)-type modeling framework capable of converting the optimum compaction properties of fine-grained soils between any two rational compaction energy levels (CELs). Model development/calibration was carried out using a database of 242 compaction test results — the largest and most diverse database of its kind, to date, entailing 76 fine-grained soils (covering liquid limits of 16–256%), with each soil tested for at least three different CELs. On establishing the framework, an independent database of 91 compaction test results (consisting of 34 fine-grained soils tested for varying CELs) was employed for its validation. The proposed EC-based models employ measured optimum water content (OWC) and maximum dry unit weight (MDUW) values obtained for a rational CEL (preferably standard Proctor) to predict the same for higher and/or lower compactive efforts (covering 214–5416 kJ/m3). The 95% lower and upper statistical agreement limits between the predicted/converted and measured OWCs were obtained a

Material Flow Cost Accounting Modeling and Life Cycle Analysis of Zinc Smelting Industry Concentrate Unit in Iran to Reduce Environmental Pollution

Introduction: In developing countries, Material Flow Cost Accounting (MFCA) offers numerous benefits, including the identification of hidden costs, waste reduction, improved environmental outcomes, enhanced product quality and competitiveness, and increased process and resource productivity. The zinc mining industry and related activities, such as concentrate production and zinc smelting, require process life cycle analysis due to the extensive pollution they generate, including contamination of surface and underground water from heavy elements in the leachate. Through the use of MFCA modeling, it is possible to accurately evaluate the inputs and outputs of current processes in this field and analyze them for environmental effects.Materials and Methods: This study involved visits to industrial smelting units, expert opinions, and integration with the Sima Pro software database to prepare a life cycle model and network of the product life cycle and its environmental effects. By analyzing the life cycle of Iran's zinc smelting industry, green product productivity was used to calculate the cost-material flow in the selected sample unit, track the material flow, and present a model for the life cycle of zinc. This involved utilizing information from Iran's zinc smelting industry, data from the Sima Pro software database, and the implementation of the MFCA model on information related to zinc smelting and concentrate products. In this model, zinc smelting and zinc concentrate production processes were treated as input and greenhouse gas emissions as output.* Corresponding Author’s email: [email protected]  Results: Based on the material balance relationship, the combination of calcine with sulfuric acid produces leach cake, silver, lead, and air pollution. The research estimates that for the production of one ton of zinc ingot, the amount of air pollution generated is 7 kg. MFCA analysis of the leaching unit of the industrial research complex indicates that the cost of 5070 kilograms of input materials is 12,350,000 Tomans, the cost of the system is 30,000,000 Tomans, and the cost of energy is 1,950,000 Tomans. The study also found that 3549 kg of product is obtained for 9,100,000 Tomans, while 1536 kg of waste is produced at the cost of 3,250,000 Tomans. This highlights the input values, the primary product, and the secondary product.Discussion: Through the provision of comprehensive life cycle models for the zinc smelting process, especially the zinc smelting concentrate process, the inputs and outputs of the production chain were evaluated. By accurately determining the flow cost of these materials, the process of zinc smelting concentrate production can be optimized to minimize losses, reduce environmental pollution, lower direct costs, and increase economic output, thereby leading to the growth and development of the industrial complex

Equilibrium and Kinetic Studies on the Adsorption of Acid Yellow 36 Dye by Pinecone

Background & Aims of the Study: Dyes have significant role in environmental problems, due to their toxic effects on the food chain and sources of water. The purpose of this research was to study the adsorption of acid yellow 36 dye onto pinecone using batch system. Materials & Methods: This research was performed at laboratory scale and batch system. Equilibrium isotherms were modeled using Langmuir, Freundlich, and D-R models. Also kinetic studies were done by three models of pseudo first order, pseudo second order, and intra-particle diffusion. Results: The maximum adsorption was achieved at pH 5.0, adsorbent dose 0.7 g/l and contact time 20 min. The equilibrium adsorption capacity (mg/g) increased with increasing initial dye concentration. The Langmuir model (R2=0.99) provided the best fit for the experimental data. The adsorption kinetics were studied and best fit was achieved by pseudo- second order model (R2= 0.96). Conclusions: According to the results obtained of equilibrium and kinetic studies on the adsorption of acid yellow 36, pinecone can be a suitable and efficient adsorbent in the removal of yellow acid 36 dye from industrial wastewater