Luís Fernando Martins Ribeiro

Analytical Slope Stability Analysis Based on Statistical Characterization of Soil Primary Properties

The role of statistical tools in the modeling of slope stability has been increasingly studied in the last decades. Mainly, this growth can be related to the availability of fast computational routines which enable massive-repetition numerical algorithms such as Monte Carlo simulations. On the other hand, analytical approaches to this problem, in the majority of cases, rely on considering the random variables of interest being normally distributed. This latter assumption tends to provide incorrect results while dealing with skewed data since normal distribution is symmetric about its mean value. In order to address this issue, a complete statistical study of a set of porosities data is undertaken. A total of seven well-known statistical distributions are adjusted to such data, showing that normal distribution is the worst possible fit for the considered data set. By means of an empirical correlation between strength properties and porosity, the probability density function of the factor of safety of a hypothetical slope is analytically derived based on a Mohr-Coulomb failure criterion. This way, it is shown that the probability of failure can be explicitly obtained by means of solely the distribution of a primary property of the material in study, namely, its porosity. Also, the results obtained by considering the porosity data normally distributed are compared to the ones hereby developed showing considerable differences.

Experimental and Physical Modeling of Bed Load Heterogeneous Sediment Transport

AbstractThe hydraulic deposition process linked to tailings dams normally presents some technical deficiencies mainly because of the lack of control of hydraulic parameters. Problems of instability in tailings dams usually arise from poor management practices, such as poor decant pond control, in addition to the material being placed randomly. Hydraulic parameters, such as the flow rate and concentration of the slurry, play an important role in the formation of hydraulic fills. Grain size, distribution, segregation, and density, and slope inclination are the main characteristics of tailings dams, which are affected by the hydraulic parameters of the slurry. To investigate these factors, an experimental apparatus [hydraulic deposition simulation test (HDST)] was used to simulate the hydraulic deposition process in the laboratory, where all variables that could affect the phenomenon could be controlled carefully. The HDSTs using different flow rates and concentrations were carried out using the iron waste f...

Comportamento geotécnico de rochas brandas na mina Córrego do Sítio, Santa Bárbara (MG)

Abstract In this work the characterization of phyllites in theCorrego do Sitio Mine, Santa Barbara, MG, is discussed,as well as some factors that influence the shear strengthalong the foliation surface. Results of mineralogicdescription, physical indices and direct shear tests ofthree areas in this mine are presented. Weathering actson the variability of some properties, such as theporosity, void ratio, dry specific gravity, and also on theshear strength, with considerable reduction of thecohesion after alterability tests. In addition, theroughness observed on the foliation surface in the rocksof Crista pit influences the rock mass behaviour,increasing its shear strength. Keywords : Weak rocks, alterability, shear strength. Mineracao Comportamento geotecnico de rochasbrandas na mina Corrego do Sitio, SantaBarbara (MG) (Geotechnical behavior of weak rocks in Corrego do Sitio mine,Santa Barbara (MG)) Manoel da Conceicao Lopes Mestre em Engenharia Mineral,DEMIN/UFOP. E-mail: manoellopes@uai.com.br

Interference Factors on Tests of Asphalt Biding Agents Destinated to Paving Works Using a Statistic Study

The asphalt binder characterization tests, with the purpose of being used in paving works, consist an excellent instrument of quality evaluation for these asphalt binders in order to guarantee the construction of higher durability works. However, it is possible observing innumerous factors during the tests which can affect, in a significant way, a more specific evaluation by each one of the proposed tests. Based on this context, the present paper presents an analysis of the principal factors that can interfere directly in the results of the characterization tests of asphalt binder, and, which can harm the performance and durability of asphaltic paving. The methodology adopted is based in a sampling of results obtained for the main characterization tests, petroleum asphaltic cement - CAP 50/70, accomplished by 08 different work teams, where a study formulated by statistic tools was applied, highlighting the main trusted results to an effective qualitative evaluation of the binders tested in paving works. In the end of this paper, the possible interference which can compromise the analysis of binders in significant ways will be shown.

Condutividade hidráulica saturada de um rejeito de minério de ferro

Nowadays the increased tailing volume, generated by the utilzation of minerals with low iron, has been motivating mining companies to adopt the technique hydraulic fill structures with upstream method as the main solution for tailings disposal. This methodology is influenced by the appearance of uncertainties related to the deposition process for the beach and to the tailing that is launched randomly and without control of the discharge variables that influence this process. As such, high iron concentration areas are formed in the dam, tending to influence the geotechnical properties of this material. Thus, the objective was to study tailing behavior in function of the percentage of iron and silica present and to verify their influence in the saturated hydraulic conductivity of this tailing through laboratory and field tests.