Selección y diseño de las medidas de corrección de un talud inestable

[SPA] La sobre-excavación de un talud de grandes dimensiones, con problemas de estabilidad, aparece como la medida más utilizada para corregir esta situación. En un proceso de rotura a gran escala los taludes buscan de forma natural el equilibrio trasladando parte de sus materiales a la zona anterior al pie, como si establecieran una barrera de tierras, eliminando además peso de la parte superior, de la que proceden estos materiales. Al haberse superado los valores pico, la superficie de rotura ya solamente colabora al equilibrio con la resistencia residual. Una de las medidas que reproduce ese comportamiento es la de rellenar el pie del talud creando una barrera natural de tierras en esa posición y descargando o sujetando parte de la masa superior. La ventaja, en relación con la situación de rotura, se encuentra en la conservación de la resistencia intacta de los materiales, lo que proporciona una mayor seguridad. En este trabajo, apoyado en un conjunto de ejemplos prácticos, se plantea una metodología para seleccionar una variedad de medidas que pueden utilizarse, sobre la condición de que la situación final de diseño cumpla con las garantías de seguridad. Tal como se plantea en la minería en muchas ocasiones, se puede asumir cierta movilidad de los bloques que constituyen el macizo de roca, y remodelar las tierras inestables para buscar la geometría del talud más adecuada y evitar los riesgos de deslizamientos o desprendimientos sobre el área de trabajo.[ENG] The re-excavation of a large slope, with stability problems, appears as principal measure used to correct its instability. In a large slope failure, terrain naturally seek balance by transferring part of it mass to the foot slope area, establishing a land barrier, also eliminating the weight of the upper part, where these materials come from. Once the peak shear strength values have been overtaken, the breaking surface only contributes with its residual resistance. One of the measures that can reproduce this behavior is the filling of the slope’s foot creating a natural barrier of lands in that position and unloading or holding part of the upper mass too. The advantage, in relation to the breaking situation, lies in the preservation of the intact strength of the materials, which provides greater security. In this paper, supported by a set of practical examples, the methodology proposed is to select among a variety of measures that can be used, searching that the final design situation complies with the security guarantees. As is usually suggested in mining, it is possible to assume a certain mobility of the blocks that make up the rock mass, and to remodel the unstable lands in order to find the most appropriate slope geometry to avoid the risks of landslides or rock falls on the work area

Numerical simulation of density-driven flow and heat transport processes in porous media using the network method

Density-driven flow and heat transport processes in 2-D porous media scenarios are governed by coupled, non-linear, partial differential equations that normally have to be solved numerically. In the present work, a model based on the network method simulation is designed and applied to simulate these processes, providing steady state patterns that demonstrate its computational power and reliability. The design is relatively simple and needs very few rules. Two applications in which heat is transported by natural convection in confined and saturated media are studied: slender boxes heated from below (a kind of Bénard problem) and partially heated horizontal plates in rectangular domains (the Elder problem). The streamfunction and temperature patterns show that the results are coherent with those of other authors: steady state patterns and heat transfer depend both on the Rayleigh number and on the characteristic Darcy velocity derived from the values of the hydrological, thermal and geometrical parameters of the problems.The first author acknowledges the support of the Universidad Politécnica de Cartagena through a pre-doctoral scholarship and the economic support of the Universidad Católica del Norte to cover the costs to publish in open access

Statistical and kinetic study for leaching of covellite in a chloride media

Covellite is a relatively rare copper sulfide with slow dissolution kinetics. The present investigation used the surface optimization methodology to evaluate the effect of three independent variables (time, chloride concentration and sulfuric acid concentration) on the rate of extracting Cu from covellite. The effects of chloride concentration and temperature over time were also studied. An ANOVA indicated that the linear variables of time and chloride concentration have the greatest influence, this being highly representative (R2 = 0.9945). The highest copper extraction rate (71.23%) at room temperature, was obtained with a high chloride concentration (100 g/L), a low concentration of sulfuric acid (0.5 M), and a leaching period of 600 h. The dissolution is described by the model of the unreacted core, the rate of leaching of the covellite is controlled by the chemical surface reaction at temperatures between 50 and 90°C, with concentrations of 0.5 M of H2SO4, 100 g/L of chloride, and a leaching period of up to 6 hours, where an activation energy of 72.36 kJ/mol was obtaine.The authors are grateful for the contribution of the Scientific Equipment Unit-MAINI of the Universidad Católica del Norte for aiding in generating data by automated electronic microscopy QEMSCAN® and for facilitating the chemical analysis of the solutions. We are also grateful to Marina Vargas Aleuy and Carolina Ossandón Cortés of the Universidad Católica del Norte for supporting the experimental tests

Optimization of parameters for the dissolution of Mn from manganese nodules with the use of tailings in an acid medium

Manganese nodules are an attractive source of base metals and critical and rare elements and are required to meet a high demand of today’s industry. In previous studies, it has been shown that high concentrations of reducing agent (Fe) in the system are beneficial for the rapid extraction of manganese. However, it is necessary to optimize the operational parameters in order to maximize Mn recovery. In this study, a statistical analysis was carried out using factorial experimental design for the main parameters, including time, MnO2/Fe2O3 ratio, and H2SO4 concentration. After this, Mn recovery tests were carried out over time at di_erent ratios of MnO2/Fe2O3 and H2SO4 concentrations, where the potential and pH of the system were measured. Finally, it is concluded that high concentrations of FeSO4 in the system allow operating in potential and pH ranges (0.2 to 1.2 V and 1.8 to 0.1) that favor the formation of Fe2+ and Fe3+, which enable high extractions of Mn (73%) in short periods of time (5 to 20 min) operating with an optimum MnO2/Fe2O3 ratio of 1:3 and a concentration of 0.1 mol/L of H2SO4.The authors are grateful for the contribution of the Scientific Equipment Unit- MAINI of the Universidad Católica del Norte for aiding in generating data by automated electronic microscopy QEMSCAN®, and for facilitating the chemical analysis of the solutions. We are also grateful to the Altonorte Mining Company for supporting this research and providing slag for this study, and we thank Marina Vargas Aleuy, María Barraza Bustos and Carolina Ossandón Cortés of the Universidad Católica del Norte for supporting the experimental tests

An educational software for teaching soil consolidation

[EN] The educational tool SICOMED_3D has been created to simulate problems of soil consolidation by prefabricated vertical drains. Thanks to its nice interface of windows, the introduction of data is very fast and easy for the students, while providing users with simple handling and powerful calculations. Its graphical environment allows to get representations of the excess pore pressure, local settlements and total surface settlement. SICOMED_3D can also generate an animation that recreates the evolution of the surface settlement during the consolidation process. The software presents, like commercial softwares, the most common options (e.g., save and open cases files, save animations and representations, etc.). Although the program is created to be used in several fields, among others as an engineering or research tool, the main use of interest for this work is for educational purposes. Another important application is as low-cost laboratory practices, as students can experiment by modifying the soil properties, including the depth of penetration of the vertical drain, in a quick, simple and intuitive way.García Ros, G.; Alhama Manteca, I.; Cánovas Vidal, M.; Sánchez Pérez, JF. (2017). An educational software for teaching soil consolidation. En Proceedings of the 3rd International Conference on Higher Education Advances. Editorial Universitat Politècnica de València. 865-872. https://doi.org/10.4995/HEAD17.2017.5447OCS86587

Self-learning of the direct soil tomography problem using a specific educational software

[EN] The educational tool DITPRO has been created to simulate problems of direct soil tomography problem. The introduction of data is very easy for the students, because the software has an interactive grid window. Moreover, provides to the users an easy handling and powerful calculations. Its graphical environment allows access to a graphical representation of potential functions. The software presents, like commercial softwares, the most common options (e.g., save and open cases files and representations, etc.). Although the program is created to be used in several fields, among others as investigation tool, the mainly use of interest for this work is as educational tool. Another important use is as low-cost laboratory practices. The student has the possiblity to obtain system information of the Spice code text file, whose rules are well known by students with knowledge of electrical circuit theory. The student must to design and implement several sceneries and explain it to check his/her understanding of the problem.http://ocs.editorial.upv.es/index.php/HEAD/HEAD17Sánchez Pérez, JF.; Alhama Manteca, I.; García Ros, G.; Cánovas Vidal, M. (2018). Self-learning of the direct soil tomography problem using a specific educational software. Editorial Universitat Politècnica de València. 1-8. https://doi.org/10.4995/HEAD17.2017.5451OCS1

Leaching of pure chalcocite in a chloride media using sea water and wastewater

Chalcocite is the most important and abundant secondary copper ore in the world with a rapid dissolution of copper in an acid-chloride environment. In this investigation, the methodology of surface optimization will be applied to evaluate the e_ect of three independent variables (time, concentration of sulfuric acid and chloride concentration) in the leaching of pure chalcocite to extract the copper with the objective of obtaining a quadratic model that allows us to predict the extraction of copper. The kinetics of copper dissolution in regard to the function of temperature is also analyzed. An ANOVA indicates that the linear variables with the greatest influence are time and the chloride concentration. Also, the concentration of chloride-time exerts a significant synergic e_ect in the quadratic model. The ANOVA indicates that the quadratic model is representative and the R2 value of 0.92 is valid. The highest copper extraction (67.75%) was obtained at 48 h leaching under conditions of 2 mol/L H2SO4 and 100 g/L chloride. The XRD analysis shows the formation of a stable and non-polluting residue; such as elemental sulfur (S0). This residue was obtained in a leaching time of 4 h at room temperature under conditions of 0.5 mol/L H2SO4 and 50 g/L Cl.The authors are grateful for the contribution of the Scientific Equipment Unit- MAINI of the Universidad Católica del Norte for aiding in generating data by automated electronic microscopy QEMSCAN® and for facilitating the chemical analysis of the solutions. We are also grateful to the Altonorte Mining Company for supporting this research and providing slag for this study, and we thank to Marina Vargas Aleuy and María Barraza Bustos of the Universidad Católica del Norte for supporting the experimental tests

Study of the application of PCM to thermal insulation of UUV hulls using Network Simulation Method

The Unmanned Underwater Vehicles (UUV) designed for the detection and neutralization of naval mines are characterized by their high requirements regarding the reduction of the signatures of a vessel (thermal, acoustic, magnetic, etc.), all of them must be reduced in order not to be detected by the mines during the mission. This research work focuses on the reduction of the thermal signature transmitted by the UUV hull, where the use of phase change materials (PCM) is proposed as thermal insulation, placing it between the internal heat source of the UUV and the pressure hull, with the aim of drastically increasing the time in which the external face of the hull of the UUV is within a range of 3 °C and 5 °C temperature increase, allowing it to perform its mission without being detected by the thermal sensors of current naval mines. The simulation will be carried out using the Network Simulation Method for the resolution of the governing equations, which will allow the optimization of the necessary insulation thickness according to the required mission profile. In addition, it is proposed an expression that relates the PCM thickness and the time needed to reach a certain temperature increase

Leaching manganese nodules in an acid medium and room temperature comparing the use of different Fe reducing agent

The deposits of Fe-Mn, in the seabed of the planet, are a good alternative source for the extraction of elements of interest. Among these are marine nodules, which have approximately 24% manganese and may be a solution to the shortage of high-grade ores on the surface. In this investigation, an ANOVA analysis was performed to evaluate the time independent variables and MnO2/reducing agent in the leaching of manganese nodules with the use of different Fe reducing agents (FeS2, Fe2+, Fe-0 and Fe2O3). Tests were also carried out for the different reducing agents evaluating the MnO2/Fe ratio, in which the Fe-0 (FeC) proved to be the best reducing agent for the dissolution of Mn from marine nodules, achieving solutions of 97% in 20 min. In addition, it was discovered that at low MnO2/Fe ratios the acid concentration in the system is not very relevant and the potential and pH were in ranges of -0.4-1.4 V and -2-0.1 favoring the dissolution of Mn from MnO2.The authors are grateful for the contribution of the Scientific Equipment Unit- MAINI of the Universidad Católica del Norte for aiding in generating data by automated electronic microscopy QEMSCAN®and for facilitating the chemical analysis of the solutions. We are also grateful to the Altonorte Mining Company for supporting this research and providing slag for this study, and we thank to Marina Vargas Aleuy of the Universidad Católica del Norte for supporting the experimental tests. Pedro Robles thanks the Pontificia Universidad Católica de Valparaíso for the support provided

How Did the COVID-19 Lockdown Pandemic Affect the Depression Symptomatology in Mediterranean Older Adults with Metabolic Syndrome?

Background and Aims. To control the COVID-19 spread, in March 2020, a forced home lockdown was established in Spain. In the present study, we aimed to assess the effect of mobility and social COVID-19-established restrictions on depressive symptomatology in older adults with metabolic syndrome. We hypothesize that severe restrictions might have resulted in detrimental changes in depressive symptomatology. Methods. 2,312 PREDIMED-Plus study participants (men = 53:9%; mean age = 64:9±4:8 years) who completed a COVID-19 lockdown questionnaire to assess the severity of restrictions/lockdown and the validated Spanish version of the Beck Depression Inventory-II (BDI-II) during the three established phases concerning the COVID-19 lockdown in Spain (prelockdown, lockdown, and postlockdown) were included in this longitudinal analysis. Participants were categorized according to high or low lockdown severity. Analyses of covariance were performed to assess changes in depressive symptomatology across lockdown phases. Results. No significant differences in participant depression symptomatology changes were observed between lockdown severity categories (low/high) at the studied phases. During the lockdown phase, participants showed a decrease in BDI-II score compared to the prelockdown phase (mean (95% CI), -0.48 (-0.24, -0.72), P < 0:001); a nonsignificantly larger decrease was observed in participants allocated in the low-lockdown category (low: -0.59 (-0.95, -0.23), high: -0.43 (-0.67, -0.19)). Similar decreases in depression symptomatology were found for the physical environment dimension. The post- and prelockdown phase BDI-II scores were roughly similar. Conclusions. The COVID-19 pandemic lockdown was associated with a decrease in depressive symptomatology that returned to prelockdown levels after the lockdown. The degree of lockdown was not associated with depressive symptomatology. The potential preventive role of the physical environment and social interactions on mental disorders during forced home lockdown should be further studie