Multi-objective optimization of retaining wall using genetic algorithm

The paper investigates the possibility of applying the genetic algorithm NSGA-II to optimize a reinforced concrete retaining wall embedded in saturated silty sand. Multi-objective constrained optimization was performed to minimize the cost, while maximizing the overdesign factors (ODF) against sliding, overturning, and soil bearing resistance. For a given change in ground elevation of 5.0 m, the width of the foundation and the embedment depth were optimized. Comparing the algorithm's performance in the cases of two-objective and three objective optimizations showed that the number of objectives significantly affects its convergence rate. It was also found that the verification of the wall against the sliding yields a lower ODF value than verifications against overturning and soil bearing capacity. Because of that, it is possible to exclude them from the definition of optimization problem. The application of the NSGA-II algorithm has been demonstrated to be an effective tool for determining the set of optimal retaining wall designs.

Urban space change and future prediction of Kangpur Nagar, Uttar Pradesh using EO data

Urban Land use changes, measurements, and the analysis of rate trends of growth would help in resources management and planning, etc. In this study, we analyze the urban change dynamics using a support vector machine model. This method derives the urban and rural land-use change and various components, such as population growth, built-up areas, and other utilities. Urban growth increases rapidly due to exponential growth of population, industrial growth, etc. The population growth also affects the availability of various purposes in its spatial distribution. In this present study, we carried out using multi-temporal satellite remote sensing data Landsat MSS (Multispectral scanner), ETM+ (Enhanced thematic mapper), OLI (Operational land imager) for the analysis of urban change dynamics between years 1980-1990, 1990-2003, 2012-2020 in Kanpur Nagar city in the state of Uttar Pradesh in India. In our study, we used SVM (Support Vector Machine) Model to analyze the urban change dynamics. A support vector machine classification technique was applied to generate the LULC maps using Landsat images of the years 1980, 1990, 2003, and 2020. Envi and ArcGIS software had used to identify the land cover changes and the applying urban simulation model (CA- Markov model) in Idrisi selva edition 17.0 software. The LULC maps of 2003 and 2020 were used to simulate the LULC projected map for 2050 using (Cellular automata) CA- Markov based simulation model.

Dependence of concentration of radon on environmental parameters

Radon (222Ra) is a colourless and odourless natural radioactive element in gaseous state. The concentration of radon in the air is usually low, but it can be very high inside of a living space, because of its possibility to penetrate from a foundation soil over a basement into a building itself. People are daily exposed to a certain concentration of radon that is found in soil, water, air and food. This paper shows a correlation analysis of environmental parameters by using the model of multiple regressions. It defines certain statistical relations between environmental parameters such as temperature, humidity, and atmospheric pressure with measured values of radon concentrations. Measurements were carried out at several locations in various residential buildings in north-western Croatia. The results indicated that individual environmental parameters and radon concentration at individual locations were connected. For example, at one location the concentration of radon was decreasing if atmospheric pressure was increasing. Measurements at another location indicated that the concentration of radon was increasing if air humidity was increasing. Due to large number of different parameters affecting the concentration of radon in residential buildings, a satisfactory statistical model to predict the concentration of radon with environmental parameters is not easy to achieve since it was observed variability of radon concentrations with environmental parameters within different local sites. It is necessary to consider a longer period to determine with certainty a mathematical model that would give the most accurate prediction of radon concentration dependence on environmental parameters which can affect human health and quality of life.

Microbiological quality of well water from Koprivnica-Križevci County in 2018

In this study, microbiological quality of drinking water deriving from the private wells from Koprivnica-Križevci County was investigated. A total of 287 samples from different locations were collected during 2018 and analysed for the following microbiological parameters: total coliforms, Escherichia coli, Enterococcus spp., Clostridium perfringens, Pseudomonas aeruginosa, and the number of aerobic heterotrophic bacteria at 36 °C and 22 °C. The results showed that 24 % of the analysed water samples were of unsatisfactory microbiological quality, with high incidence of faecal contamination. Well water is still the main source of drinking water for many residents of this County, especially in its rural parts, so continuous monitoring and disinfection of drinking water deriving from private wells is of exceptional importance for the public health.

Treatment of wastewater from separators for rainfall runoff using electrochemical oxidation processes

In recent years, industry has increased and with it the amount of oily wastewater, which are considered hazardous waste because they contain various types of heavy metals and oils that endanger the environment and human health. In the last twenty years, there has been increased research on new technologies to treat wastewater as efficiently and environmentally friendly as possible. A recent approach to wastewater treatment is the application of electrochemical processes such as the electro-Fenton process, which belongs to the group of electrochemical advanced oxidation processes and electrocoagulation. The aim of this work was to remove organic contaminants and heavy metals from wastewater originating from oil and grease separators that clean stormwater runoff from traffic areas. The use of stainless steel, iron and aluminum electrodes results in electrooxidation, electroreduction and electrocoagulation. At a current of 15 A the treatment efficiency was 50% for COD and 73% for mineral oil. At a current of 110 A the treatment efficiency was 96% for COD and 90% for mineral oil.

Forest area changes throughout the years in Bjelovarsko-Bilogorska County

The results of forest cover reduction were obtained using raster data and administrative borders for the Republic of Croatia. Examples are taken from other countries to compare the results and show the reduction of cover, both forest and agricultural. The first part of this paper describes the situation in the Republic of Croatia, where Ministry of Environmental Protection provided analysis. The condition of land cover in the Republic of Croatia is presented. The second part of this paper is a description of the task development process in the software package "QGIS". From adding CLC raster data to, the actions performed in the program that were performed until the results arrived. Finally, the interpretation of the obtained data and the conclusion follow.

Composting of fine fraction after mechanical-biological treatment of municipal solid waste

One of most common types of municipal solid waste treatment is mechanical-biological treatment (MBT), which in practice has many variations depending on the method of conducting the technological process and it is possible to get different output fractions. In this paper is analysed waste generated after the MBT with biodrying, where waste after mechanical treatment undergoes process of biodrying, and then is RDF (recovery derived fuel) separated. Fine fraction remains with a high content of organic matter that without additional processing cannot be disposed of on a landfill. The aim of this research was to determine the possibility of fine fraction composting in different conditions – in the open, in the open and covered area, and indoors. In each area are formed three compost piles: 100% fine fraction (KH1, KH4, and KH7), 70% fine fraction and 30% wood chips (KH2, KH5, and KH8), 50% fine fraction and 50% wood chips (KH3, KH6, and KH9). Moisture content, temperature and dissolved organic carbon (DOC) were monitored. Results show that after 13 weeks samples KH1, KH4, and KH7 (100% content of fine fractions) did not achieve DOC value less than 3 000 mg/l. The most effective composting in terms of reducing the DOC is achieved in samples KH3, KH6, KH9. Based on results obtained, it can be concluded that by adding wood chips in fine fraction in ratio 50:50, the most effective and fastest reduction of organic matter is achieved in the analysed samples.

Influence of leachates on geotehnical and geochemical properties of termite mound soils

This study investigated the influence of leachate prepared from Telfairia occidentalis on the geotechnical and geochemical properties of termite mound soil obtained from the premises of the federal university of agriculture, Abeokuta, south-western Nigeria. The termite mound soil samples were collected from three different locations and each sample collected was contaminated by mixing with leachates in percentage increments of 0% 10%, 15% and 20% of dry weight of the air-dried soil. The soil samples were subjected to Atterberg limits and hydraulic conductivity tests for geotechnical observation and X-ray fluorescence tests for geochemical tests. The range of values for the geotechnical analyses were obtained as; plastic limit (9.1% – 14.2%), liquid limit (28.6 % – 61%), plasticity index ((18.2% – 49.5%) and hydraulic conductivity (1.85 – 4.1 x 10-8) cm/sec) with a resultant reduction in the plastic limit, liquid limit and plasticity index values but an increase in the hydraulic conductivity of the samples as the leachate concentration increased. The results from X-ray fluorescence analyses after 20% leachate contamination showed that the major elemental chemical composition for the three samples were comprised of SiO2 (56.25 – 56.5%), Al2O3 (28.42 – 28.50%), Fe2O3 (4.46 – 6.5%), TiO2 (1.08 – 1.23%), CaO (1.45 – 1.60%), P2O5 (0 – 0.04%), K2O (0.9 – 6.1%) and MnO (0.02 – 4.7%). There was a marginal alteration of the indices with the values inferring the presence of a minimum composition of feldspar and a major composition of quartz-rich minerals and thus lending more credence to the presence of silicates as shown from the X-ray fluorescence results. It also infers that the termite mounds are predominantly made from sand materials. The termite soil samples obtained from the aforementioned locations may not be suitable for engineering works unless stabilization procedure is adopted.

Influence of shear rate on the soil's shear strength

One of the most important mechanical properties is shear strength. It is conditioned by the value of the maximum shear stress that the soil can withstand before failure. Exceeding the shear strength causes one particle to slide next to another, causing the failure of soil. The shear strength of the soil for effective stresses is1 a combination of drained strength parameters: internal friction angle (φ) and cohesion (c) defined by the Mohr-Coulomb failure criterion. It is determined “in situ” and by laboratory experiments. Direct shear is the oldest and the simplest laboratory experiment to determine the shear strength of the soil. The first phase of experiment is specimen consolidation under specific vertical stress, and in the second phase specimens are sheared at a given shear rate, depending on the consolidation properties of the soil. Cohesionless soils are sheared at up to 100 times higher shear rate compared to cohesive soils. Shear rate and drainage conditions affect the magnitude of soil strength parameters. The paper is based on the comparison and demonstration of the influence of different shear rates on the peak and residual shear strength in the direct shear device. The tests were performed on two samples of low plasticity clay (CL) and one sample of high plasticity clay (CH).

Indoor air quality in a high school classroom in Rijeka, Croatia (sick classrooms caused by rising CO2 levels)

School’s indoor air quality (IAQ) is very important as it can affect student’s learning abilities and lead to health issues. Therefore, indoor air quality, and in particular the CO2 concentration, was monitored on a daily basis from mid-November till the end of December 2017, by using several low-cost instruments. The measuring was performed in the physics classroom of a grammar school in Rijeka, Croatia. Detailed CO2 generation rates, air exchange rates, and ventilation rates are calculated and reported in this work, from the experimentally obtained data. Very high concentrations of over 4.000 ppm were recorded, indicating that ventilation rates are far below 5 Ls-1 per person, which is the lowest recommended value of ventilation rate according to the European standard EN 13779. The experimentally obtained data are compared with the theoretical models and a strong correlation are achieved. This is one of the first comprehensive studies of this kind in Croatia; therefore, we hope that it will stimulate interest between health workers, scientists, and school management to implement indoor air quality monitoring practices and perhaps introduce automated ventilation systems in classrooms for the benefit of students’ health and their learning abilities.