rss_2.0Geosciences FeedSciendo RSS Feed for Geosciences Feed analysis of mechanical properties on the example of aggregates of Carpathian sandstones<abstract><title style='display:none'>Abstract</title><p>The constantly growing, broadly understood, construction industry requires the use of a large amount of aggregates. The construction of roads, motorways, railway lines and hydrotechnical structures requires the use of aggregates of high quality, which is primarily determined by mechanical properties. The basic parameters describing mechanical properties of aggregates are the Los Angeles (<italic>LA</italic>) fragmentation resistance coefficient and the Micro-Deval (<italic>M</italic><sub><italic>DE</italic></sub>) abrasion resistance coefficient. The <italic>LA</italic> and <italic>M</italic><sub><italic>DE</italic></sub> coefficients depend mainly on the type of rock and its physical and mechanical properties. This has been thoroughly researched and documented as evidenced by the abundant literature in the field. However, the correlation between <italic>LA</italic> and <italic>M</italic><sub><italic>DE</italic></sub> coefficients still gives rise to extensive discussions and some concerns. A number of publications demonstrate dependencies for various types of aggregates. Therefore, research was undertaken to present statistical analysis for one type of aggregate and one geological area.</p><p>This article presents the results of the fragmentation resistance test in the Los Angeles drum and the abrasion resistance test in the Micro-Deval drum of aggregates from Carpathian sandstone deposits. Aggregate samples were divided into three groups according to the location of the deposits and the tectonic unit from which they originated. The obtained results were subjected to static analysis to fit the best mathematical function describing the relationship between the two parameters.</p></abstract>ARTICLE2020-09-24T00:00:00.000+00:00The Use of the Collocation Algorithm for Estimating the Deformations of Soil-Shell Objects Made of Corrugated Sheets<abstract><title style='display:none'>Abstract</title><p>The algorithm presented in this paper is intended for the analysis of deformations of shells in the construction phase of soil-shell objects when strain gauges and geodetic measurements are used. During the construction of such an object, large displacement values occur and the impact of axial forces on the displacement of a corrugated metal sheet is small. Internal forces (strain gauges), as well as the displacements of a selected circumferential band of the shell are determined directly from such observations.</p><p>The paper presents two examples of the analysis of large span shell structures of constructed objects, as well as the assessment of the effectiveness of the finite difference method (FDM) in beam schemes. Good deformation mapping was indicated using the collocation algorithm and the differential approach to the solution when there is a dense mesh and regular distribution of measuring points. In the analysed examples, a significant divergence between the support conditions adopted in the FEM calculation models and the actual static conditions in the objects was indicated. The collocation algorithm is especially designed for such situations. Collocation points in such a solution are used to consider a beam – separated from a structure and without boundary constraints, but with specific changes in curvature – as a reference system, which is determined from the geodetic measurements of two collocation points.</p></abstract>ARTICLE2020-06-26T00:00:00.000+00:00Empirical and theoretical models for prediction of soil thermal conductivity: a review and critical assessment<abstract><title style='display:none'>Abstract</title><p>The paper discusses existing models used to estimate the thermal conductivity of the soil medium. The considerations are divided into three general sections. In the first section of the paper, we focus on the presentation of empirical models. Here, in the case of Johansen method, different relations for Kersten number are also presented. In the next part, theoretical models are considered. In the following part, selected models were used to predict measured thermal conductivities of coarse- and fine-grained soils, at different water contents. Based on these predictions as well as on the authors’ experience, a critical assessment of the existing models is provided. The remarks as well as advantages and disadvantages of those models are summarized in a tabular form. The latter is important from a practical point of view; based on the table content, one can simply choose a model that is suitable for the particular problem.</p></abstract>ARTICLE2020-07-09T00:00:00.000+00:00Risk Reduction of a Terrorist Attack on a Critical Infrastructure Facility of LGOM Based on the Example of the Tailings Storage Facility (OUOW )<abstract><title style='display:none'>Abstract</title><p>This paper identifies the threats and risks of a terrorist attack on a critical infrastructure facility based on the example of <italic>Żelazny Most</italic> Tailings Storage Facility (OUOW). The threat analysis primarily took into account the threats of deliberate human actions. Identification of potential threats concerning the infrastructure surrounding the facility was conducted based on information that is readily available on the Internet. The reasons why it may be a potential target were also justified. Numerical calculations of the stress–deformation scale of the initial state of the reservoir, based on the Biot model with the Kelvin–Voight rheological skeleton, were presented as a starting point for in-depth research on the scale of threats and risks to the reservoir. The presented numerical model can be a starting point for calculating the stability of a reservoir subjected to explosives. The facility constitutes a major element of Lubińsko-Głogowski Okręg Miedziowy (Lubin-Głogów Copper District). OUOW <italic>Żelazny Most</italic> is the biggest such facility in Europe and is utilized to collect tailing waist. When expanded in its southern quarter, the facility will be the biggest in the world.</p></abstract>ARTICLE2020-09-25T00:00:00.000+00:00Vibrations of the Euler–Bernoulli Beam Under a Moving Force based on Various Versions of Gradient Nonlocal Elasticity Theory: Application in Nanomechanics<abstract><title style='display:none'>Abstract</title><p>Two models of vibrations of the Euler–Bernoulli beam under a moving force, based on two different versions of the nonlocal gradient theory of elasticity, namely, the Eringen model, in which the strain is a function of stress gradient, and the nonlocal model, in which the stress is a function of strains gradient, were studied and compared. A dynamic response of a finite, simply supported beam under a moving force was evaluated. The force is moving along the beam with a constant velocity. Particular solutions in the form of an infinite series and some solutions in a closed form as well as the numerical results were presented.</p></abstract>ARTICLE2020-06-29T00:00:00.000+00:00Using Triaxial Tests to Determine the Shearing Strength of Geogrid-Reinforced Sand<abstract><title style='display:none'>Abstract</title><p>Geogrids are widely used in civil engineering projects to reinforce road and railway structures. This paper presents research on the shearing strength of soil samples that have been reinforced with geogrids. The relationship between soil and geogrids is explored and evaluated by modeling the mechanical behavior of heterogeneous materials. For the purposes of this research, data obtained from tests of unreinforced sand samples with triaxial cells were compared with the data obtained from tests of reinforced sand samples. It was found that the shearing strength for reinforced samples was higher (from 9% to 49%) compared to unreinforced samples. Some damage to the geogrid was detected during the experiment, and for this reason, the same tests were numerically simulated for both unreinforced samples and samples reinforced with geogrids. Numerical simulations revealed the main reasons for damage to the geogrids during triaxial testing.</p></abstract>ARTICLE2020-09-25T00:00:00.000+00:00Dynamic Tests in Bridge Health Monitoring<abstract><title style='display:none'>Abstract</title><p>Dynamic tests are one of the most significant diagnostic procedures applied in Bridge Health Monitoring in many countries. The paper presents a proposal of unified classification of the bridge dynamic tests together with review of the testing methods, including tests under designed and controlled loads, arranged short-term tests under normal traffic loads as well as permanent dynamic monitoring by means of built-in gauges mounted on a structure. Classification of bridge dynamic tests is proposed taking into account various types of vibration excitation methods, measured parameters and possible applications of obtained results in the Bridge Health Monitoring. General rules and procedures of bridge dynamic tests are described and discussed.</p></abstract>ARTICLE2020-06-06T00:00:00.000+00:00Analysis of underground stratification based on CPTu profiles using high-pass spatial filter<abstract><title style='display:none'>Abstract</title><p>The issue of the stratification of the underground subsoil is one of the principal geotechnical challenges. The development of the Cone Penetration Tests (CPTu) has resulted in the possibility to record parameters in a quasi-continuous way, which provides a very detailed description of the soil response. Such accurate measurements may therefore be treated as a signal or image and be analysed as such. This paper presents the application of high-pass spatial filters to perform soil stratification on the basis of the static penetration test. The presented algorithm has been tested on the test data set provided by the Organizers of TC304 Student Contest on Spatial Data Analysis (September 22, 2019, Hannover, Germany). It provides reasonable results at negligible computational cost and is applicable to most soils, especially if the contrast between the parameters of the adjacent layers is significant.</p></abstract>ARTICLE2020-09-22T00:00:00.000+00:00The influence of the soil constitutive models on the seismic analysis of pile-supported wharf structures with batter piles in cut-slope rock dike<abstract><title style='display:none'>Abstract</title><p>In coastal regions, earthquakes caused severe damage to marine structures. Many researchers have conducted numerical investigations in order to understand the dynamic behavior of these structures. The most frequently used model in numerical calculations of soil is the linear-elastic perfectly plastic model with a Mohr-Coulomb failure criterion (MC model). It is recommended to use this model to represent a first-order approximation of soil behavior. Therefore, it is necessary to accommodate soil constitutive models for the specific geotechnical problems.</p><p>In this paper, three soil constitutive models with different accuracy were applied by using the two-dimensional finite element software PLAXIS to study the behavior of pile-supported wharf embedded in rock dike, under the 1989 Loma Prieta earthquake. These models are: a linear-elastic perfectly plastic model (MC model), an elastoplastic model with isotropic hardening (HS model), and the Hardening Soil model with an extension to the small-strain stiffness (HSS model).</p><p>A typical pile-supported wharf structure with batter piles from the western United States ports was selected to perform the study. The wharf included cut-slope (sliver) rock dike configuration, which is constituted by a thin layer of rockfill overlaid by a slope of loose sand. The foundation soil and the backfill soil behind the wharf were all dense sand. The soil parameters used in the study were calibrated in numerical soil element tests (Oedometer and Triaxial tests).</p><p>The wharf displacement and pore pressure results obtained using models with different accuracy were compared to the numerical results of Heidary-Torkamani et al.<sup>[<xref ref-type="bibr" rid="j_sgem-2019-0050_ref_028_w2aab3b7d215b1b6b1ab2ac28Aa">28</xref>]</sup> It was found that the Hardening Soil model with small-strain stiffness (HSS model) gives clearly better results than the MC and HS models.</p><p>Afterwards, the pile displacements in sloping rockfill were analyzed. The displacement time histories of the rock dike at the top and at the toe were also exposed. It can be noted that during the earthquake there was a significant lateral ground displacement at the upper part of the embankment due to the liquefaction of loose sand. This movement caused displacement at the dike top greater than its displacement at the toe. Consequently, the behavior of the wharf was affected and the pile displacements were important, specially the piles closest to the dike top.</p></abstract>ARTICLE2020-07-05T00:00:00.000+00:00Testing the rocks loosening process by undercutting anchors<abstract><title style='display:none'>Abstract</title><p>The method of unconventional solid rock loosening with undercutting anchors and the literature analysis of the problem are presented. The tests and test results of the rocks loosening process with a fixed undercutting anchor are described. The tests were carried out within the RODEST project, OPUS 10 competition No. 2015/19/B/ST10/02817, financed by the National Science Centre. Numerical modeling process as well as a series of laboratory and in situ tests were carried out. The test stand equipment and methodology for the in situ tests are presented. The tests were conducted in four mines, which allowed to obtain and determine the following characteristics: <list list-type="order"><list-item><p>loosening force as a function of anchoring depth (for a given type of rock),</p></list-item><list-item><p>the range of rock loosening in a function of anchoring depth (for a given type of rock), and</p></list-item><list-item><p>loosened rock volume as a function of anchoring depth (for a given type of rock).</p></list-item></list></p><p>The in situ test results are compared with the concrete capacity design (CCD) model used for the calculation of anchor load capacity in concrete.</p></abstract>ARTICLE2020-07-09T00:00:00.000+00:00Analysis of the Collapse Gradient of Deep Water Horizontal Wellbore and the Effects of Mud Chemical Activity and Variation in Water Depth<abstract><title style='display:none'>Abstract</title><p>Wellbore collapse is an instability-event that occurs at low mud density and leads to unfavorable economic project, reaching billions of US dollars. Thus, it is important to accurately determine its value, especially in deepwater horizontal wellbores. The main reasons for nontrivial problems with such wellbores are evident: the shale encountered are anisotropic in nature and possess planes of weakness; they react with water-based mud, generate osmotic stresses, swell, and fall unto the wellbore bottom, thereby increasing the non-productive time. To this end, salts are added to reduce the collapse tendency, but it is not currently known what amount of salt addition maintains stability, and does not lead to wellbore fracture; in deepwater, the current trend in global warming means there is a future concern to the industry. As the climate temperature increases, more ice melts from the polar region, the seawater expands and the sea level rises. How to incorporate the corresponding effect on collapse gradient is scarcely known. This study captures the major concerns stated above into wellbore stability analysis. Following the classical approach for geomechanical analysis, Mogi-Coulomb criterion was combined with a constitutive stress equation comprising contributions from mechanical and osmotic potentials of mud and shale. A sophisticated industry model was used to consider the deepwater effect. The results show significant reduction in collapse gradient as the water depth increases, also, larger difference between the mud and shale chemical activities represents higher complexities in the wellbore. In addition, the reduction in the chemical activities of mud limited to 37.5% of the initial value can be practically safe.</p></abstract>ARTICLE2020-04-09T00:00:00.000+00:00Heave analysis of shallow foundations founded in swelling clayey soil at N’Gaous city in Algeria<abstract><title style='display:none'>Abstract</title><p>The design of shallow foundations on swelling soils needs a thorough study to evaluate the effect of swelling potential soil on the final foundation heave. For this reason, a simple analytical approach based on the soil stress state under the foundation can be used to calculate the foundation heave. This paper reports a set of analytical and numerical analysis using the finite-difference code (FLAC 3D), performed on an isolated shallow foundation founded on a swelling soil mass at N’Gaous city in Batna Province, Algeria, subjected to distributed vertical loads. Further, the influence of some parameters on total heave was analyzed, such as the embedded foundation and soil stiffness. The analysis results from the proposed 3D modelling was compared and discussed with analytical results. The numerical results obtained show a good agreement with the analytical solutions based on oedometer tests proposed in the literature, and deliver a satisfactory prediction of the heave of the shallow foundations.</p></abstract>ARTICLE2020-07-07T00:00:00.000+00:00Influence of the heterogeneity of a dump soil on the assessment of its selected properties<abstract><title style='display:none'>Abstract</title><p>This article concerns the assessment of selected physical and mechanical properties of a dump soil. The dump soil is a specific soil with a very heterogeneous internal structure. Next to each other, there may be lumps and crumbs of cohesive soils mixed with non-cohesive soils accompanied by a very diverse admixture of organic substance. In addition, the soil in the waste dump, in spatial terms, may significantly differ in consistency and density. This is the result of the process of forming a dump soil, which takes place in three stages: excavation, transport and dumping. A heterogeneous soil deposited within the waste dump is subject to further processes: consolidation, compaction and creeping. Changes occurring in the course of these processes have a significant impact on the development of the properties of the dump soil.</p><p>Due to the large diversity of the tested soils, the results of their properties were divided into two groups, based on type and consistency of soil. This allows us to estimate the selected properties of the dump soil only on the basis of their macroscopic analysis.</p></abstract>ARTICLE2020-09-30T00:00:00.000+00:00Application of non-classical operational calculus to indicate hazards in numerical solutions of engineering problems<abstract><title style='display:none'>Abstract</title><p>The article addresses the application of non-classical operational calculus to approximative solutions of engineering problems. The engineering-sound examples show that a continuous–discrete problem transformation from differential unequivocal problem to a differential wildcard problem, triggering a change in solution quality. A number of approximative methods are capable to alter both quantitative and qualitative solution effects.</p></abstract>ARTICLE2020-06-26T00:00:00.000+00:00Supervised probabilistic failure prediction of tuned mass damper-equipped high steel frames using machine learning methods<abstract><title style='display:none'>Abstract</title><p>In this study, firstly, the behavior of a high steel frame equipped with tuned mass damper (TMD) due to several seismic records is investigated considering the structural and seismic uncertainties. Then, machine learning methods including artificial neural networks (ANN), decision tree (DT), Naïve Bayes (NB) and support vector machines (SVM) are used to predict the behavior of the structure. Results showed that among the machine learning models, SVM with Gaussian kernel has better performance since it is capable of predicting the drift of stories and the failure probability with <italic>R</italic><sup>2</sup> value equal to 0.99. Furthermore, results of feature selection algorithms revealed that when using TMD in high steel structures, seismic uncertainties have greater influences on drift of stories in comparison with structural uncertainties. Findings of this study can be used in design and probabilistic analysis of high steel frames equipped with TMDs.</p></abstract>ARTICLE2020-09-30T00:00:00.000+00:00Model experiments to assess effect of cavities on bearing capacity of two interfering superficial foundations resting on granular soil<abstract><title style='display:none'>Abstract</title><p>The objective of this paper is to describe the effect of cavities on the bearing capacity of two interfering footings based on granular soil using an exclusively experimental approach with a test model designed in the laboratory. The experimental protocol was carried out based on the variation of several parameters such as the spacing (<italic>x</italic>) (axis to axis) between the footings, and the distance (H) between the footings and cavities and between the cavities axes (L). The results highlight the effect of cavities and the interference of two strip footings on the bearing capacity factor (<italic>q</italic>) and efficiency factor (EF). Moreover, the results revealed that, in the case wherein the distance between the footings and the cavity is greater than 3, the cavity impact is eliminated.</p></abstract>ARTICLE2020-06-13T00:00:00.000+00:00Modelling the time-dependent behaviour of soft soils<abstract><title style='display:none'>Abstract</title><p>Time dependence of soft soils has already been thoroughly investigated. The knowledge on creep and relaxation phenomena is generally available in the literature. However, it is still rarely applied in practice. Regarding the organic soils, geotechnical engineers mostly base their calculations on the simple assumptions. Yet, as presented within this article, the rate-dependent behaviour of soft soils is a very special and important feature. It influences both the strength and the stiffness of a soil depending on time. It is, thus, significant to account for time dependence in the geotechnical design when considering the soft soils. This can result in a more robust and economic design of geotechnical structures. Hence, the up-to-date possibilities of regarding creep in practice, which are provided by the existing theories, are reviewed herein.</p><p>In this article, we first justify the importance of creep effects in practical applications. Next, we present the fundamental theories explaining the time-dependent behaviour of organic soils. Finally, the revision of the existing constitutive models that can be used in numerical simulations involving soft soils is introduced. Both the models that are implemented in the commercial geotechnical software and some more advanced models that take into account further aspects of soft soils behaviour are revised. The assumptions, the basic equations along with the advantages and the drawbacks of the considered models are described.</p></abstract>ARTICLE2020-06-30T00:00:00.000+00:00Deformations and stability of granular soils: Classical triaxial tests and numerical results from an incremental model<abstract><title style='display:none'>Abstract</title><p>This article presents a modified incremental model describing pre-failure deformations of granular soils under classical triaxial conditions. The original shape of equations has been proposed by Sawicki and Świdziński [<xref ref-type="bibr" rid="j_sgem-2019-0039_ref_040_w2aab3b7d272b1b6b1ab2ac40Aa">40</xref>, <xref ref-type="bibr" rid="j_sgem-2019-0039_ref_041_w2aab3b7d272b1b6b1ab2ac41Aa">41</xref>]. A new form of equations that are consistent with the proposed definitions of deviatoric loading and unloading is suggested. Triaxial tests necessary for calibrating the proposed model have been performed. The modified model is used to simulate the deformations and stability of sand for every pre-failure loading path and makes it possible to describe the behaviour of granular soil under both drained and undrained conditions.</p><p>A comparison of experimental and numerical results is presented. All investigations were performed in a classical tri-axial apparatus.</p></abstract>ARTICLE2020-06-30T00:00:00.000+00:00Determination of the Atterberg Limits of Eemian Gyttja on Samples with Different Composition<abstract><title style='display:none'>Abstract</title><p>The paper presents the results of laboratory tests of plastic limit <italic>w<sub>P</sub></italic> and liquid limit <italic>w<sub>L</sub></italic> of Eemian gyttja characterized by different organic matter content <italic>I</italic><sub>om</sub> and calcium carbonate content CaCO<sub>3</sub>. Comparison of the liquid limit <italic>w<sub>L</sub></italic> determined with the use of the Casagrande apparatus <italic>w<sub>LC</sub></italic> and a cone penetrometer with cones having apex angles of 60° <italic>w<sub>L</sub></italic><sub>60</sub> and 30° <italic>w<sub>L</sub></italic><sub>30</sub> is shown. Based on statistical analysis of the test results, single- and two-factor empirical relationships for evaluating the plastic limit <italic>w<sub>P</sub></italic> and liquid limit <italic>w<sub>L</sub></italic> of Eemian gyttja depending on the organic matter content <italic>I</italic><sub>om</sub> and/or calcium carbonate content CaCO<sub>3</sub> are presented in this study.</p></abstract>ARTICLE2020-06-30T00:00:00.000+00:00An influence of track stiffness discontinuity on pantograph base vibrations and catenary–pantograph dynamic interaction<abstract><title style='display:none'>Abstract</title><p>In this article, the computational methodology of the catenary–train–track system vibration analysis is presented and used to estimate the influence of vehicle body vibrations on the pantograph–catenary dynamic interaction. This issue is rarely referred in the literature, although any perturbations appearing at the pantograph–catenary interface are of great importance for high-speed railways. Vehicle body vibrations considered in this article are induced by the passage of train through the track stiffness discontinuity, being a frequent cause of significant dynamic effects. First, the most important assumptions of the computational model are presented, including the general idea of decomposing catenary–train–track dynamic system into two main subsystems and the concept of one-way coupling between them. Then, the pantograph base vibrations calculated for two train speeds (60 m/s, 100 m/s) and two cases of track discontinuity (a sudden increase and a sudden decrease in the stiffness of track substrate) are analyzed. Two cases of the railway vehicle suspension are considered – a typical two-stage suspension and a primary suspension alone. To evaluate catenary–pantograph dynamic interaction, the dynamic uplift of the contact wire at steady arm and the pantograph contact force is computed. It is demonstrated that an efficiency of the two-stage suspension grows with the train speed; hence, such vehicle suspension effectively suppresses strong sudden shocks of vehicle body, appearing while the train passes through the track stiffness discontinuity at a high speed. In a hypothetical case when the one-stage vehicle suspension is used, the pantograph base vibrations may increase the number of contact loss events at the catenary–pantograph interface.</p></abstract>ARTICLE2020-06-30T00:00:00.000+00:00en-us-1