The progress of wear associated with the compound and diffusion layers of nitrided samples was studied by employing laboratory tests at low, medium and high contact pressures, simulating the conditions occurring during the hot extrusion of aluminium. It was found that with increasing of contact pressure also wear rates increase that indicates on predominately frictional removal of compound layer which was confirmed by scanning electron microscopy and back-scattered electron micrographs as well as energy-dispersive spectroscopy analysis of tested surfaces. Testing at medium contact pressures reveals some common features observed at testing at lower as well as at higher contact pressures. The essential difference between the testing at medium and low contact pressures is in the density of the obtained micro-craters and appearance of their extension in sliding direction at medium contact pressures. At higher contact pressure, removal of compound layer is already preferentially oriented in sliding direction in the first stage, while at medium contact pressure, this is observed only in later stages of degradation progress.
COBISS.SI-ID: 1452895
This paper presents a new, mathematical expression for describing the soil-water characteristic curve (SWCC) over a range of water contents where finegrained soils exhibit plastic properties. The finding that the relationship between the soil suction and the water content can be expressed in terms of the specific surface area of soils was based on experimentally determined relationships between the water content and the soil's specific surface area, as well as between the thickness of the adsorbed water layer on the external surfaces of clay minerals and the quantity of free-pore water for the water content between the liquid and plastic limits. The double-porosity model for the pore-space geometry was considered, as well as that all the water in the clay-aggregates is adsorbed, and that the adsorption mechanism is dominated by the van der Waals forces. The validity and applicability of the proposed equation for the SWCC estimation was verified on three samples in which the SWCC was measured, as well as the specific surface area, the mineralogical and chemical compositions, the grain size distribution, and the Atterberg limits. Despite the fact that good correlations were found between the calculated parts of the SWCC and the measured, the practical applicability of the proposed equation remains problematic due to the values of Hamaker constant, which are not yet well defined for different minerals.
COBISS.SI-ID: 18331670
Site investigation has to be effective and must be carried out in a systematic way. The purpose of this article is to evaluate the number of investigation points, field tests, and laboratory tests for a description of a building site. Such an assessment depends on many parameters based on experiences which cannot be physically evaluated. The guidance on spacing is available from many sources, and such guidance provides a starting point for the extent of investigation. The recommendations were examined and used for building of the model to predict the optimal number of investigation points. Several parameters with the biggest influence on the number of investigation points were considered. The influence of each parameter was determined on the basis of recommendations and engineering judgment. Increments of the minimum number of investigation points for a different building site conditions were used to construct the model with adaptive network fuzzy inference system (ANFIS). The formed ANFIS-SI model was applied on reference cases. There is a good agreement between the model and the reference cases. Additionally, the recommendations for the type and frequency of tests in each stratum are provided to optimize the soil investigation. The ANFIS-SI model, with integrated recommendations, can be used as a systematic decision support tool for engineers to evaluate the number of investigation points for a description of the building site.
COBISS.SI-ID: 17886998
The use of underground space for various needs has seen a significant growth in recent year. This possibility is also reflected in the concept of construction underground nuclear facilities. Based on previous experience, success in the future might be bound to such as smaller nuclear facilities by some named as Small Modular Reactors (SMRs). Suitable locations at appropriate depth taking advantage of the natural barrier properties afforded by the good quality bedrock have important influence on providing appropriate natural circumstances for SMRs. Underground sitting can provide superior protection compared to that of a surface serviced sitting in many critical situations and subsequent devastating consequences for the operation of a nuclear facility. Complicated underground complex needed for a nuclear power system need special attention calling for dedicated investigations and also research on such as issues as earthquake hazard, although the latter seems to be documented being advantageous already. The paper will present a case that clearly shows the obvious advantages of the use of underground space for current available nuclear technologies and assessments of seismic loads influences on nuclear underground structures.
COBISS.SI-ID: 1487199
In the deep sections of the mine shaft where underground facilities should be interconnected, the design procedure still pays attention to time dependant processes and stress strain changes that influence the existing permanent mine roadways. During the progress of excavation and primary support installation in underground construction, the behaviour of highly faulted grounds in greater depths requires appropriate yielding elements. Analyses should be taken into account as well as the possibility that rock pressures could reduce the excavation profile of the mine’s permanent construction. The construction of underground facilities in highly faulted grounds leads to big radial displacements towards excavation space not only during the time of construction but also later, when the inner lining is installed. In addition to the presentation of part of the excavation and support methods in such ground conditions the calculations results showed that the installation of the yielding elements have an effect on support elements and prevent shotcrete damage during the curing stage. The calculation results of ground loads and displacements on designed supports system are presented with a three dimensional(3D) numerical geomechanical model adopted for highly faulted ground surrounding deeper complex underground structures, have shown real application in the praxis.
COBISS.SI-ID: 1495903