Browse

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. This problem is of particular importance in Europe where lignite deposits are exploited in large opencast mines utilizing Bucket Wheel Excavators (BWEs) as the main means ...

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 the excavated materials are relatively homogenous, without intercalations with excessive cutting resistance, it is not difficult to conduct the technological process. I...

The solving of the project of the Ministry of Agriculture of the Czech Republic dedicated to sustainable agricultural management in the North Western Bohemia is under way from 2015 to 2018. The Brown Coal Research Institute is the main participant of the project. This article briefly summarises new results of the research of the Most Basin localities restoration problems. The main attention is devoted to the research of experimental areas founded in different dump localities with different dump rocks and different...

The specific energy consumption is mainly influenced by kinematics and dynamic measures of vertical transport installations as well as by the compatibility of different composing parts and their subcomponents. The optimisation of kinematics and dynamic parameters characterising a transport cycle is decisive considering the energy consumption. Also considering the operation of the vertical transport installations, as well as the character of the variation of kinematics and dynamic parameters during a race, it has b...

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 first two models, the classical approach of shield mechanics, the loading scheme was modified by taking into account the horizontal force acting between the roof and th...

In the present work for the first time in the world practice 430322 occultations of stars by the Moon are analyzed. The relevance of the work is that the accuracy analysis of stars' proper motion in modern star catalogues can only be conducted using either observations of small planets or occultations, since only those observations are longterm and homogenous in time. When making the occultation database a comparative analysis has been used to study types and accuracy of occultation. For photoelectric observations...

The scientific paper proposed deals with the reliability analysis of the average usage time of the brake pads as components of the braking system of the industrial front-end loader and transporter machinery used in mining operations in Romania. The research was conducted at the request of several mining companies in Romania, that are using the front-end loader and transporter machinery in their daily operations. The study is based on the empirical information and the preliminary reliability results that were recor...

The article shows features of a soil, illustrated with cracks. These cracks are natural detail of a soil, which more humified and less dense, than the rest part of the soil. Author highlights frequency and depth of these cracks in a soil profile, which essentially affects on the functions of the soil at the disclosure. On the mastered for an agriculture soil, cracks come from surface, in spite of that top horizons of the soil were homogenized in processing. Cracks go through the most humified part of the soil, whi...

The paper deals with the theoretical and practical analysis of the influence that the cutting direction of the bucket wheel excavator has on the digging forces acting on the wheel. Usually, when the terrace cut technology is applied, the bucket wheel of the excavator cuts vertical chips where mainly the perpendicular to stratification digging method is predominant. All the laboratory trials - done on the test rig - were conducted mainly for this type of vertical chip cutting. In cases when the drop cut method is a...

The scientific paper deals with the multi-criterion optimization of the teeth that are used on the buckets of bucket wheel excavators. From past theory and practice, it is known that geometry of the tooth greatly influences the cutting parameters and the endurance and the strength of the tooth itself. The dependencies between the cutting forces, the penetrating forces, the specific energy on the rake angle and the relation between this last one and the robustness of the tooth are somewhat contradictory, so in the ...

Pesticides alter the biological properties of the soil, leading to a complete loss of their fertility. Chestnut soils (meadow brown, light brown) are resistant to contamination by pesticides and by fertilizers in particular. We have carried out studies on the effect of the examined soil pollution with high doses of fertilizers and pesticides on the soil mesofauna representatives. The work is based on studying influence of anthropogenic impacts on soil biological activity in comparison with its main indicators, whi...

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 excavated rock. In this paper we use a new methodology, based on reliable laboratory data, which make possible to obtain correlation and regression formulas in order to pred...