Construction and calibration of a portable rain simulator designed for the in situ research of soil resistance to erosion | Nikola Živanović, Vukašin Rončević, Marko Spasić, Stevan Ćorluka, Siniša Polovina | Agricultural Journals

One of the prerequisites for the safe exploitation of surface mines is the stability of the working and final slopes of the mine. In order to ensure this, it is necessary to carry out detailed field and laboratory geomechanical tests of the soil and, based on the obtained results, make calculations related to stability analyses. The results obtained in this way are used for dimensioning the slope of exploitation slopes (excavation). Landslides occur when the ultimate shear strength is reached, and therefore, the adequate definition of shear strength parameters is one of the essential prerequisites for successfully solving the stability problem. Unlike earlier tests in Serbia, when the residual shear strength parameters were determined based on the usual conventional methods (direct shear apparatus, triaxial apparatus), this time, in addition to the direct shear apparatus, a ring shear apparatus was also chosen for testing. The paper shows the method of determining the residual shear strength parameters of high plasticity gray clays and siltstones of roof sediments from open pit mine Drmno, using direct and ring shear apparatus. The results show that the residual angle of internal friction for gray clays obtained with the ring shear apparatus is 9.9–10.8°, and for the siltstone, it is 11.8–12.9°, both of which are lower than the values obtained with the direct shear apparatus. In addition, correlations between the residual parameters of soil shear resistance and some physical indicators (plasticity index, clay content) are provided, showing high correlation coefficients. The proposed correlations should be used only when time and financial constraints prevent the execution of actual tests to determine residual shear strength, as concrete experimental procedures provide a much more reliable assessment of the residual strength properties of the soil.

The more economically viable and environmentally sustainable approach for treating the by-products of coal combustion from thermal power plants entails their collective disposal as opposed to individual disposal methods. This aligns with pertinent EU directives and domestic regulations, ensuring compliance with established standards while optimizing resource utilization and minimizing environmental impact. This study evaluated the resistance to wind erosion of the binding properties of a mixture (fly ash (FA), bottom ash (BA), and additives) using an indoor wind tunnel under simulated ambient conditions. Investigations of the mutual impact of ash, bottom ash, and additives (CaO and Ca(OH)₂) with a certain percentage of water were carried out with eighteen samples. The samples consisted of the water at six addition rates 5, 8, 10, 15, 20, and 25% (w/w), and additive at three addition rates (1, 2, and 3% (w/w). Based on the obtained results, the optimal ratios of additives (3% (w/w)) and water (15% (w/w)) were determined. Prior to the wind tunnel experiments, and according to the different addition rates of additives and water, eight samples were prepared with different addition rates of ash. The mass concentrations of suspended particles (PM₁₀) and total suspended particles (TSPs) in these samples were measured at three distinct wind velocities: 1 m/s, 3 m/s, and 5 m/s, respectively. The results indicate that the samples containing the optimal content of additives and water demonstrate a maximum increase in PM₁₀ emission zero values of no more than 1.9 times. This finding can be considered satisfactory from the standpoint of environmental protection.

Typical empirical correlations in geotechnical practice can be useful for estimating the values of necessary parameters to be used in design and geotechnical calculations. For fine-grained soils, undrained shear strength is a key parameter recommended by Eurocode 7 and is strongly influenced by water content. This paper investigates the relationship between water content, fall cone penetration, and undrained shear strength of medium-plasticity silty clays based on an extensive laboratory dataset obtained over a wide range of moisture conditions, including values both below and above natural water content. The analysis is conducted on remoulded soil samples. Power-law relationships between water content and cone penetration were established, and the corresponding parameters were evaluated and compared with values reported in the literature. The undrained shear strength-water content relationship was further analyzed using normalized expressions based on the water content ratio, enabling direct comparison with existing empirical models. A within-sample regression approach was applied to account for repeated measurements on individual soil samples, revealing consistently high coefficients of determination and a narrow range of regression slopes across materials. The results demonstrate that systematic laboratory testing combined with appropriate data normalization and within-sample analysis provides physically meaningful and robust empirical relationships. A site-specific empirical model for estimating undrained shear strength is proposed, offering improved reliability compared to generalized correlations and supporting more accurate site-specific geotechnical assessments.

In this paper, the stability analysis before and after the application of technical solutions was performed on a landslide located on the Stolice-Krupanj route, in the western part of the Republic of Serbia. The landslide also affected part of the road, so the movement of traffic was difficult. Several solutions of the gabion retaining wall and the leveling of the slope affected by the landslide were analyzed. The selection of the optimal solution is based on the fulfillment of two criteria: the stability of the structure and the stability of the entire slope. The stability before the application of technical measures and the general stability of the slope with the applied measures were examined using the Yanbu method, and the local stability using the Bishop method. The stability of the wall was checked in terms of overturning and horizontal movement. These analyzes were performed using GEO5 software (Geotechnical software). Analytical analysis of the load-bearing capacity of the soil under the retaining walls was carried out using the Brinc Hansen method. Two solutions met the set criteria, solution I with a safety factor Fs = 1.81 and solution II Fs = 1.75. The analysis of the bearing capacity of the soil showed that the foundation soil can safely receive the load from the structure in the case of both solutions. Solution II was selected for the optimal solution for landslide rehabilitation.

Pile integrity testing (PIT) is a widely applied and straightforward method for assessing the geometric characteristics and quality of constructed piles. However, its reliability strongly depends on the availability of comprehensive data regarding geological conditions and the construction process. This paper presents a practical case where the absence of information on soil improvement by jet grouting initially led to misinterpretation of pile reflectograms, with piles classified as potentially defective. The heterogeneities introduced by jet grouting significantly affected the reflectograms, creating apparent negative reflections that complicated interpretation. To address this uncertainty, comparative analysis of multiple signals was performed, supported by available geotechnical data. Furthermore, static load tests were conducted on selected piles, confirming their bearing capacity and proving that the initial assessment based solely on reflectograms was misleading.