Prediction of the mechanical behavior of the Oporto granite using data mining techniques

The determination of mechanical properties of granitic rocks has a great importance to solve many engineering problems. Tunnelling, mining and excavations are some examples of these problems. The purpose of this paper is to apply Data Mining (DM) techniques such as multiple regressions (MR), artificial neural networks (ANN) and support vector machines (SVM), to predict the uniaxial compressive strength and the deformation modulus of the Oporto granite. This rock is a light grey, two-mica, medium-grained, hypidiomorphic granite and is located in Oporto (Portugal) and surrounding areas. Begonha (1997) and Begonha et al. (2002) studied this granite in terms of chemical, mineralogical, physical and mechanical properties. Among other things, like the weathering features, those authors applied correlation analysis to investigate the relationships between two properties either physical or mechanical or physical and mechanical. This study took the data published by those authors to build a database containing 55 rock sample records. Each record contains the free porosity (N48), the dry bulk density (d), the ultrasonic velocity (v), the uniaxial compressive strength (σc) and the modulus of elasticity (E). It was concluded that all the models obtained from DM techniques have good performances. Nevertheless, the best forecasting capacity was obtained with the SVM model with N48 and v as input parameters.Fundação para a Ciência e a Tecnologia (FCT

Indicators of acid mine drainage in an affected system: the case of the mine Santo António de Penedono

O presente estudo descreve os efeitos da evolução geoquímica e mineralógica dos resíduos mineiros acumulados na escombreira de Santo António de Penedono, Penedono. Mediante a aplicação de diferentes tipos de indicadores: físico-químicos, ecológicos e mineralógicos, descrevem-se as propriedades do ambiente de drenagem superficial. Os resultados demonstram o caráter ácido do efluente e sugerem a eficácia de algas acidófilas como indicadoras de contaminação mineira. A análise mineralógica põe em evidência o papel dos precipitados de drenagem ácida no controle da mobilidade de poluentes, em especial do arsénio.The present study describes the effects of geochemical and mineralogical evolution of Penedono mine waste-dumps by applying different types of indicators: physical-chemical, ecological and mineralogical. The results obtained demonstrated the typical sulfated nature of acid mine drainage (AMD) and suggested the effectiveness of acidophilic algae as indicators of mining pollution. Mineralogical analysis by X-ray diffraction and transmission electron microscopy highlights the role of AMD-precipitates controlling the mobility of pollutants, in particular of arsenic.(undefined

Metals and arsenic enrichment processes in sulfide-rich waste dumps - the role of the clay size fraction

[Extract] 1. Purpose Abandoned mines pose some of the most outstanding environmental risks, namely related with potentially toxic metals and metalloids in mining soils. Mobilization or fixation of these elements in the soil particles can be regulated by the interactions between several biogeochemical and mineralogical processes. In this context, the present study is focused on the detection of metals and arsenic enrichment processes in different particle size fractions of two distinctive sulphide-rich waste dumps. Furthermore, the study evaluates the role of typical clay size minerals, such as oxyhydroxides and clay minerals in the retention of toxic elements...info:eu-repo/semantics/publishedVersio

Manganese oxides as biominerals in a granitic subterranean environment

Black coatings were detected on granite surfaces in groundwater catch work tunnels from Porto city (NW Portugal). XRD, FTIR, Micro-Raman, ICP-MS, TEM-EDS, SEM-EDS and SEM-FIB were the analytical procedures carried out to investigate the origin of the black coatings. In this subterranean environment, the enrichment in metals and other trace elements, such as Mn and Fe, and clay minerals characterize the black microbial mats, mainly composed of Mn/Fe-oxidising bacteria.Fundação para a Ciência e a Tecnologia (FCT

Laboratory-induced endolithic growth in calcarenites: biodeteriorating potential assessment

This study is aimed to assess the formation of photosynthetic biofilms on and within different natural stone materials, and to analyse their biogeophysical and biogeochemical deterioration potential. This was performed by means of artificial colonisation under laboratory conditions during 3 months. Monitoring of microbial development was performed by image analysis and biofilm biomass estimation by chlorophyll extraction technique. Microscopy investigations were carried out to study relationships between microorganisms and the mineral substrata. The model applied in this work corroborated a successful survival strategy inside endolithic microhabitat, using natural phototrophic biofilm cultivation, composed by cyanobacteria and algae, which increased intrinsic porosity by active mineral dissolution. We observed the presence of mineral-like iron derivatives (e.g. maghemite) around the cells and intracellularly and the precipitation of hausmannite, suggesting manganese transformations related to the biomineralisation.Fundação para a Ciência e a Tecnologia (FCT

Enrichment of trace elements in the clay size fraction of mining soils

Reactive waste dumps with sulfide minerals pro- 14 mote acid mine drainage (AMD), which results in water and 15 soil contamination by metals and metalloids. In these systems, 16 contamination is regulated by many factors, such as mineral- 17 ogical composition of soil and the presence of sorption sites 18 on specific mineral phases. So, the present study dedicates 19 itself to understanding the distribution of trace elements in 20 different size fractions (<2-mm and <2-μm fractions) of min- 21 ing soils and to evaluate the relationship between chemical 22 and mineralogical composition. Cerdeirinha and Penedono, 23 located in Portugal, were the waste dumps under study. The 24 results revealed that the two waste dumps have high degree of 25 contamination by metals and arsenic and that these elements 26 are concentrated in the clay size fraction. Hence, the higher 27 degree of contamination by toxic elements, especially arsenic 28 in Penedono as well as the role of clay minerals, jarosite, and 29 goethite in retaining trace elements has management implica- 30 tions. Such information must be carefully thought in the reha- 31 bilitation projects to be planned for both waste dumps

Mineralogical attenuation for metallic remediation in a passive system for mine water treatment

Passive systems with constructed wetlands have been consistently used to treat mine water from abandoned mines. Long-term and cost-effective remediation is a crucial expectation for these water treatment facilities. To achieve that, a complex chain of physical, chemical, biological, and mineralogical mechanisms for pollutants removal must be designed to simulate natural attenuation processes. This paper aims to present geochemical and mineralogical data obtained in a recently constructed passive system (from an abandoned mine, Jales, Northern Portugal). It shows the role of different solid materials in the retention of metals and arsenic, observed during the start-up period of the treatment plant. The mineralogical study focused on two types of materials: (1) the ochre-precipitates, formed as waste products from the neutralization process, and (2) the fine-grained minerals contained in the soil of the wetlands. The ochre-precipitates demonstrated to be poorly ordered iron-rich material, which gave rise to hematite upon artificial heating. The heating experiments also provided mineralogical evidence for the presence of an associated amorphous arsenic-rich compound. Chemical analysis on the freshly ochre-precipitates revealed high concentrations of arsenic (51,867 ppm) and metals, such as zinc (1,213 ppm) and manganese (821 ppm), indicating strong enrichment factors relative to the water from which they precipitate. Mineralogical data obtained in the soil of the wetlands indicate that chlorite, illite, chlorite–vermiculite and mica–vermiculite mixedlayers, vermiculite, kaolinite and goethite are concentrated in the fine-grained fractions (<20 and <2 μm). The chemical analyses show that high levels of arsenic (up to 3%) and metals are also retained in these fractions, which may be enhanced by the low degree of order of the clay minerals as suggested by an XRD study. The obtained results suggest that, although the treatment plant has been receiving water only since 2006, future performance will be strongly dependent on these identified mineralogical pollutant hosts.Fundação para a Ciência e a Tecnologia (FCT

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p&lt;0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p&lt;0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised