Waldyr Lopes de Oliveira Filho

Use of the DCP test for compaction control of staged dikes in mining tailings dams

An alternative method for quality control of earthworks in mining tailing dams is described in this article. It is composed by a penetrometer, known by the acronym DCP (Dynamic Cone Penetrometer), and is used primarily in road construction (quality assessment of pavement layers). With this apparatus, strength measurement of superficial layers of natural and compacted soils can be performed, including mine sand tailings, in a fast and efficient manner. The instrument was successfully used in the construction control of an iron ore mining tailings staged dam in the Quadrilatero Ferrifero, in Minas Gerais State, and the results showed distinctly effective densification of the embankment compacted layers, but with a sort of irregularity in their spatial distribution. In addition, field control using the traditional core-cutter method was also performed for comparison between both techniques.

Numerical simulation of hillside mine waste dump construction

In activities involving disposal of mine waste in a dump, it is necessary to carry out a preliminary study of the mechanical behavior of both dump and the foundation materials. Due to the complexity of this problem, numerical techniques are essential for providing an approximate answer to the problem. Thus, the finite element method (FEM) was used to evaluate the stress-strain-strength behavior of a hillside waste dump built on a deformable foundation by the ascending method; the results of which are herein presented. The dump material is considered to be Morh-Coulomb nonlinear elastic perfectly plastic while the foundation material is considered to be linear elastic. The numerical simulation of mine waste dump construction is carried out by the “gravity turn on” technique and the dynamic mesh procedure. Different geometric configurations are analyzed and it is concluded that some requirements established by law should be reviewed and refined.

Dimensionamento estrutural de estradas de mina a céu aberto

An unpaved mine haul road, based on CBR and DNER empirical methods, was designed using materials which are typical in current Brazilian iron ore mining. By means of the mechanistic-empirical structural ELSYM5 software, the results obtained by previous methods were compared and an optimization of the DNER design was proposed. The results demonstrate that the total thickness of the pavement calculated by the two methods is basically the same and that the base layer thickness calculated by the DNER method is superior to the one obtained by the CBR method, whereas the opposite occurs in relation to the sub-base. Both designs show through the application of ELSYM5 software that they are not the most appropriate, since the strain of some layers, especially in the CBR case, is above the acceptable limit of 2000 µe. Analyzing the variation of the layers thickness, it was possible to obtain an adequate design, which led to the reduction of the total pavement layer thickness from 1.97 m to 1.40 m. The reduction of the layers strain in which the elastic modulus was submitted to variation, demonstrates the importance of performing tests for the physical characterization of materials.

Estudos experimentais do processo de ressecamento de um rejeito fino de mineração

Desiccation studies of fine mining tailings under natural climatic conditions and resting under a drainage bottom in a test site are presented in this paper. A test section, loaded with several instruments, was implemented in the area to monitor a desiccating layer of the fine tailings especially deposited in the area. A weather station and considerations of a hydrologic model for potential evaporation were very important to characterize the top boundary condition. In monitoring soil variables, an innovative technique was introduced to measure volumetric water content: the time domain reflectometry. Data generated in this research can be used to determine constitutive properties related to the desiccation phenomenon and also be used to calibrated a numerical model to describe soil behavior under desiccation.

Determination of the Soil Water Retention Curve Using the Flow Pump

Reliable measurements of the Soil Water Retention Curve, SWRC, are necessary for solving unsaturated flow problems. In this sense, a method to obtain the SWRC of a silty sand using a flow pump, as well as details about procedures and some results, are herein presented. The overall conclusion is that the new method is very convenient, fully automated, and produces reliable results in a fast and easy way, making the technique very promising.

Waste disposal using a spreader and conveyor belt method

In the search for opportunities to decrease operational costs in iron ore mining, waste disposal by conveyor belt has been considered as an alternative. In this work, this form of waste dump is investigated by means of the construction of a test pile and the assessment of geotechnical characteristics such as shear strength and in situ densities. Results were compared with two other dumps built by the traditional methods of bench and layer. The overall conclusion of this research shows that densities are 10% lower and shear strengths measured by a penetrometer are ten times lower in comparison with the other dumps. Therefore, a good understanding of this method and a thorough discussion of the project parameters are suggested before construction.

Diagnosis about iron ore mine haul roads in the Quadrilátero Ferrífero: Itabira Complex case

Although mine haul roads only provide support for mining activities, their role can be quite significant in any effort to optimize transportation with trucks in open pit mining. In 2009, an inventory about the design, construction and maintenance conditions of these structures in mines in the Quadrilatero Ferrifero was undertaken through a partnership between a large mining company and UFOP. Although the conditions of the roads could be considered broadly satisfactory, several points with potential for improvement were observed. This partnership was recently resumed on enlarged bases for an upgrade, but with a quantitative approach and in a representative mine. The report of this mine haul road diagnosis with a feedback on how we can do more and better for mine haul roads are presented in this work.

Monitoramento de poropressões construtivas.

In earthworks where construction porepressures are a conditioning design factor, field instrumentation becomes essential in order to avoid incidents or risks to the structures safety. In this context, this article presents the laboratory and field tests performed with a piezometer probe known as Levelogger®, originally developed for fluid pressure measurement in tanks and which was modified for use in soils. This device was then used with success in a practical geotechnical application. Both tests were conducted in an innovative manner and the Levelogger® proved to be an excellent alternative for measuring porepressures in events which require quick response and easy operation.

Classificação de pilhas de estéril na mineração de ferro

In this paper a Canadian proposal for waste dumps classification according to their physical stability is presented. The method is based on a semi-quantitative evaluation of key factors affecting the stability of a waste dump, and the result allows assigning a certain class of dump according to their instability potential. These classes define a recommended level of effort for investigation, design, construction and monitoring of the dumps. To check the effectiveness of the classification a case study was carried out in face of the iron ore mining reality, in Nova Lima City, Minas Gerais State. The implementation of this work involved a documentation search followed by field work and analyses in order to apply the collected information about the dumps in the classification. The work also shows innovations introduced by the Authors about the use of the classification system as a means of assessing the quality of the dumps management and also makes it possible to identify main aspects of a project. The proposed classification system showed that it is a very useful tool for both planning and evaluation of all stages of a waste dump life.

Análise numérica do processo de ressecamento de um rejeito fino da mineração de ferro

To obtain analytical solutions for desiccation analyses of soft soil such as mine tailing slimes is difficult because of the non-linearity of the material constitutive relationships and complexity of the problem boundary conditions. Thus, it is more attractive to use of numerical models to address the desiccation phenomenon. This paper presents a numerical model for desiccation of a fine mine tailings produced by milling processes of iron ore. The modeling is based on the theory proposed by Abu-Hejleh (1993) and uses a finite difference computer code associate to that theory. This model was calibrated using field data from a previous work and results from laboratory tests. Good agreement was found between simulation results and field observations suggesting applicability of the numerical model in future designs to enhance effectiveness of the desiccation process.