Andrei Andras

• PhD
• Professor at University of Petroșani

Open-pit mining generates significant amounts of waste material, leading to the formation of large waste dumps that pose environmental risks such as land degradation and potential slope failures. The paper presents a stability analysis of waste dump slopes in open-pit mining, focusing on the Motru coalfield in Romania. To assess the stability of th...

Microwave treatment is one of the research topics to solve cutting problems of hard rocks such as low cutting rate and high tool wear. Microwave irradiation creates fractures in the rock body and decreases its strength. Numerous studies have been conducted to ascertain how microwaves affect the strength of rocks. Ten carbonate rocks are examined in...

Electrical contacts are important circuit components with diverse industrial applications, and their failure can lead to multiple unwanted effects. Hence, the behavior of electrical contacts is a widely studied topic in the scientific literature based on various approaches, tools, and techniques. The present study proposes a new approach to numeric...

Electrical contacts are important circuit components with diverse industrial applications, and their failure can lead to multiple unwanted effects. Hence, the behavior of electrical contacts is a widely studied topic in scientific literature based on various approaches, tools, and techniques. The present study proposes a numerical modeling and simu...

Anthropogenic activities related to mining generate both progress and a vast amount of waste that is responsible for environmental degradation. The Jiu Valley is one of the areas of Romania where mining has affected large areas of land, used to build mines and tailings ponds. The former Coroiesti coal processing plant (CCPP) is such a location with...

Thermostats operate alongside intelligent home automation systems for ensuring both the comfort of the occupants as well as the responsible use of energy. The effectiveness of such solutions relies on the ability of the adopted control methodology to respond to changes in the surrounding environment. In this regard, process disturbances such as sev...

In this study, the fatigue usage factors for Findley and Matake stress-based criteria were determined in the case of an MK5×2 mine hoist drum brake system subjected to cyclic maneuver braking. The study was conducted for this type of brake system, because the majority of mine hoists in Romanian mines are equipped with this brake type, being in oper...

The paper studies the effects of a damping device linking the seat of the operator to the cabin floor of an operating bucket-wheel (BW) excavator. The effects of vibrations on humans were briefly presented first, based on a relevant literature review. Next, to a previously developed and validated model of the BW arm, a cabin model was attached, and...

This paper studies both the thermal and mechanical behavior of brake system models in the case of the emergency braking of a mine hoist model. Using a step-by-step approach inspired by studies conducted on small brake systems with high rotation speeds specific to road and rail vehicles, a comparative analysis using a computer simulation was perform...

The paper deals with theoretical bases of the implementation in mining equipment design of up-to-date methods using modelling and simulation, supported by examples of personal research. This has become necessary due to the structural complexity of this equipment, and the variety and aggressiveness of their operating environment. The presented examp...

Breakdown of stackers and excavators in opencast mines is possible because of operating, manufacturing and structural causes, and it produces high financial losses. These can be prevented by using various measures, including analyses and strength tests, with computerized modeling and simulation using FEA or other techniques being implemented in the...

The paper presents the state-of-the-art on the microwave assisted mechanical rock cutting by presenting actual findings and tendencies in the field in international literature, and the activities performed during the intermediate stage and the results obtained by the team from the University of Petroşani as partner within the ERAMIN-ERANET-MIWACUT...

This paper presents an investigation of the temperature variation of the two most important components of the braking system of a mine hoist, the disk and the pads respectively. Based on the complete model of the brake system created at 1:1 scale in SolidWorks, by taking into consideration only the disk, it’s mounting surface and the brake pads, th...

Starting from the general principles of material cutting, with applicability to coal and overburden excavation using bucket wheel excavators (BWEs), this paper proposes another method for calculating the drive power of the bucket wheel excavator by computer modeling. This approach required two steps. In the first step, the volume of the excavated m...

The sustainable exploitation of raw materials, with improved safety and increased productivity, is closely linked to the development of mechanical mining installations. Mine hoists are designed for the transport of material, equipment and personnel between the mine surface and the underground. The mine hoist braking system is of paramount importanc...

The paper deals with an overview of the state of art on using microwaves for assist hard rock cutting with mechanical means. The information provided consist on actual findings from the literature review, and the results of researches performed in this field by the team of the University of Petroșani. Tests have been carried out to determine the ph...

The technologies for trenchless execution of mini and microtunnels for an installation of municipal infrastructure in urbanized sites, used at present, are described in the article. The emphasis is laid on uncontrolled methods, in the case of the diameters of installations which do not exceed 200-250 mm and their length not bigger than 30-40 m. Som...

Over the past twenty years, the increasing significance of virtual spaces created by the internet, GPS and multimedia communication networks has played a major role in the growing interest attributed to the study of space. The promises and the menaces of globalization, the political and economic events which have reshaped the world in the last deca...

The paper deals with the modal analysis and frequency response analysis of a bucket wheel excavator (BWE) boom, obtained by simulation, based on a virtual model of an existing BWE boom. The boom, which generally is realized as a spatial truss, is the most vulnerable subsystem of the BWE, being submitted to severe operational loads characterized by...

For the ERc 1400-30/7 type bucket wheel excavator (BWE) used in various Romanian open pit mines, a virtual model of the boom was constructed in SolidWorks. On this model, the variable in time forces acting during the excavation process were simulated, and the time history analysis (time response) was performed. This dynamic time response analysis w...

The sustainability of lignite production requires, among other factors, cost reduction, high efficiency, as well as the increase of the production capacity. In order to rationalize and increase the efficiency of lignite mines, the optimization of the production process is necessary. In this respect, equipment revitalization and modernization is a k...

The bucket wheel excavator (BWE) is a complex continuous digging machine, used to excavate material using a layout of buckets installed on a rotor (bucket wheel), and at the same time, using the conveyor system installed on its boom, transferring this material to the main conveyor. The bucket wheel is the operating equipment, and it rotates in the...

The paper deals with the calculation of the operational reliability for the cutting-teeth mounted on bucket wheel excavators used in lignite extraction in the Oltenia Basin. Based on the data recorded for three types of cutting-teeth used in production, a reliability study has been carried out which determines the main reliability indicators of the...

Operation of vertical transport installations is based on adjustable electrical drive systems which must ensure the technical conditions regarding the variation in time of the speed, the current of the main motors and the accelerations at start and brake phases. Electric drives are part of the fast process of automation equipment. In the case of a...

The quality of bucket wheel excavators (BWEs) operations is largely influenced by the physical-mechanical (structure, mineralogical composition, plasticity, anisotropy, degree of fracturing etc.) and technological properties (compressive strength, tensile strength, shear strength, compaction, consolidation, cutting resistance etc.) of the rocks. If...

One of the frequent problems that needs to be addressed when mining coal deposits is the presence in the working face of cohesive materials having high mechanical strength in relation to the average rock to be excavated. These are generally called "hard formations" or "hard inclusions" and are in the form of either continuous layers or boulders. Th...

The paper deals with the study of Powered roof support analysis, taking into account the interaction with surrounding rocks. In this respect, an analytical model of kinematics and load of the shield, a differential model of the shield-rock system equivalent stiffness and a Fuzzy logic based analysis of the parameters variation are presented. In the...

The performances of the excavation machines depend largely on the tool and overall machine characteristics and on the other hand on physical mechanical characteristics of the excavated rock. There were more theories based on analytical deductions to explain the main cutting parameters on the basis of basic physical mechanical properties of the exca...

The paper deals with a case study for carried out in order to justify the installation of a gas cogeneration system fitted with an internal combustion engine, system used to supply electricity and heat to the users of an energy user which exceeds 1000 toe/year. 2 scenarios were therefore compared based on the energetic analysis: -the actual scenari...

The paper deals with a comprehensive reliability analysis of the conveyor belts belonging to an underground coal mine in the Jiu Valley, Romania. As resulted from the mine management reports, the transportation system is responsible for many downtimes and is a real bottleneck in the constant and adequate production, and the suspicion is the weak st...

The optimization of the coal winning process using different mechanical and alternative cutting techniques using appropried mathematical models is an up to date reserch methodology. In the paper, two kind of such models are presented, first using deterministic analytical relations evaluated by numerical calculus, and the second using Monte-Carlo si...