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Abstract

The paper discusses existing models used to estimate the thermal conductivity of the soil medium. The considerations are divided into three general sections. In the first section of the paper, we focus on the presentation of empirical models. Here, in the case of Johansen method, different relations for Kersten number are also presented. In the next part, theoretical models are considered. In the following part, selected models were used to predict measured thermal conductivities of coarse- and fine-grained soils, at different water contents. Based on these predictions as well as on the authors’ experience, a critical assessment of the existing models is provided. The remarks as well as advantages and disadvantages of those models are summarized in a tabular form. The latter is important from a practical point of view; based on the table content, one can simply choose a model that is suitable for the particular problem.

Abstract

The method of unconventional solid rock loosening with undercutting anchors and the literature analysis of the problem are presented. The tests and test results of the rocks loosening process with a fixed undercutting anchor are described. The tests were carried out within the RODEST project, OPUS 10 competition No. 2015/19/B/ST10/02817, financed by the National Science Centre. Numerical modeling process as well as a series of laboratory and in situ tests were carried out. The test stand equipment and methodology for the in situ tests are presented. The tests were conducted in four mines, which allowed to obtain and determine the following characteristics:

  1. loosening force as a function of anchoring depth (for a given type of rock),
  2. the range of rock loosening in a function of anchoring depth (for a given type of rock), and
  3. loosened rock volume as a function of anchoring depth (for a given type of rock).

The in situ test results are compared with the concrete capacity design (CCD) model used for the calculation of anchor load capacity in concrete.

Abstract

In the present work, we study the rotations of the polarization of light propagating in right and left-handed films and layered structures. Through the use of complex values representing the rotations we analyze the transmission (Faraday effect) and reflections (Kerr effect) of light. It is shown that the real and imaginary parts of the complex angle of Faraday and Kerr rotations are odd and even functions for the refractive index n, respectively. In the thin film case with left-handed materials there are large resonant enhancements of the reflected Kerr angle that could be obtained experimentally. In the magnetic clock approach, used in the tunneling time problem, two characteristic time components are related to the real and imaginary portions of the complex Faraday rotation angle . The complex angle at the different propagation regimes through a finite stack of alternating right and left-handed materials is analyzed in detail. We found that, in spite of the fact that Re(θ) in the forbidden gap is almost zero, the Im(θ) changes drastically in both value and sign.

Abstract

The design of shallow foundations on swelling soils needs a thorough study to evaluate the effect of swelling potential soil on the final foundation heave. For this reason, a simple analytical approach based on the soil stress state under the foundation can be used to calculate the foundation heave. This paper reports a set of analytical and numerical analysis using the finite-difference code (FLAC 3D), performed on an isolated shallow foundation founded on a swelling soil mass at N’Gaous city in Batna Province, Algeria, subjected to distributed vertical loads. Further, the influence of some parameters on total heave was analyzed, such as the embedded foundation and soil stiffness. The analysis results from the proposed 3D modelling was compared and discussed with analytical results. The numerical results obtained show a good agreement with the analytical solutions based on oedometer tests proposed in the literature, and deliver a satisfactory prediction of the heave of the shallow foundations.

Abstract

In coastal regions, earthquakes caused severe damage to marine structures. Many researchers have conducted numerical investigations in order to understand the dynamic behavior of these structures. The most frequently used model in numerical calculations of soil is the linear-elastic perfectly plastic model with a Mohr-Coulomb failure criterion (MC model). It is recommended to use this model to represent a first-order approximation of soil behavior. Therefore, it is necessary to accommodate soil constitutive models for the specific geotechnical problems.

In this paper, three soil constitutive models with different accuracy were applied by using the two-dimensional finite element software PLAXIS to study the behavior of pile-supported wharf embedded in rock dike, under the 1989 Loma Prieta earthquake. These models are: a linear-elastic perfectly plastic model (MC model), an elastoplastic model with isotropic hardening (HS model), and the Hardening Soil model with an extension to the small-strain stiffness (HSS model).

A typical pile-supported wharf structure with batter piles from the western United States ports was selected to perform the study. The wharf included cut-slope (sliver) rock dike configuration, which is constituted by a thin layer of rockfill overlaid by a slope of loose sand. The foundation soil and the backfill soil behind the wharf were all dense sand. The soil parameters used in the study were calibrated in numerical soil element tests (Oedometer and Triaxial tests).

The wharf displacement and pore pressure results obtained using models with different accuracy were compared to the numerical results of Heidary-Torkamani et al.[] It was found that the Hardening Soil model with small-strain stiffness (HSS model) gives clearly better results than the MC and HS models.

Afterwards, the pile displacements in sloping rockfill were analyzed. The displacement time histories of the rock dike at the top and at the toe were also exposed. It can be noted that during the earthquake there was a significant lateral ground displacement at the upper part of the embankment due to the liquefaction of loose sand. This movement caused displacement at the dike top greater than its displacement at the toe. Consequently, the behavior of the wharf was affected and the pile displacements were important, specially the piles closest to the dike top.

Abstract

The crystal structures of various types of perovskite halide compounds were summarized and described. Atomic arrangements of these perovskite compounds can be investigated by X-ray diffraction and transmission electron microscopy. Based on the structural models of basic perovskite halides, X-ray and electron diffractions were calculated and discussed to compare with the experimental data. Other halides such as elemental substituted or cation ordered double perovskite compounds were also described. In addition to the ordinary 3-dimensional perovskites, low dimensional perovskites with 2-, 1-, or 0-dimensionalities were summarized. The structural stabilities of the perovskite halides could be investigated computing the tolerance and octahedral factors, which can be useful for the guideline of elemental substitution to improve the structures and properties, and several low toxic halides were proposed. For the device conformation, highly crystalline-orientated grains and dendritic structures can be formed and affected the photo-voltaic properties. The actual crystal structures of perovskite halides in the thin film configuration were studied by Rietveld analysis optimizing the atomic coordinates and occupancies with low residual factors. These results are useful for structure analysis of perovskite halide crystals, which are expected to be next-generation solar cell materials.

Abstract

The microstructure and texture in pure nickel were investigated during multi-step cross cold rolling (CCR) and subsequent annealing. It was found that the deformation texture in the CCR nickel was dominated by Brass and rotated Brass about normal direction (ND) (BsND) texture components, along with marginal cube textures. The resulted deformation textures had a significant effect on the recrystallization behavior. Annealing of the CCR nickel at 550°C for 1 h led to the formation of dominant <012> // ND fiber accompanied by minor rotated cube textures, rather than strong cube texture. Increasing the annealing temperature up to 800°C resulted in further enhancement of <012> // ND fiber textures. The possible reasons for recrystallization behavior in annealed CCR sample were discussed based on in-situ annealing experiments from two aspects of oriented nucleation and oriented growth theories.

Abstract

This article presents the methodology and results of single shear tests of bolt rods under dynamic impact loading generated by means of a drop hammer. Comparative analysis was also performed for bolt rod load capacity, stress and shear work under static and dynamic (impact) loading. The developed method of single shear testing of bolt rods under impact loading makes it possible to obtain repeatable test results concerning maximum bolt rod shearing force, shear stress and shear work values.

Comparative shear tests of four types of bolt rods under static and impact loading showed that the APB-type bolt rods made of AP770 steel, which was characterised by having the highest strength, exhibited the greatest shear work. AM22-type bolt rods exhibited a very similar work value. Though the AM22-type bolt rods made of A500sh steel demonstrated lower strength than the APB-type bolts, as well as a smaller diameter and cross section, they dissipated the impact energy better thanks to their higher plasticity. This could indicate the direction of optimisation for bolt rods in order to increase their impact strength.

Mathematical relationships were also formulated for selected tests, describing the real single shear courses F d =f(t) of bolts under impact loading. The obtained relationships could be applied in the load assessment process of bolt rods intended for use under roof caving, tremor and rock burst conditions.

Abstract

This article presents a modified incremental model describing pre-failure deformations of granular soils under classical triaxial conditions. The original shape of equations has been proposed by Sawicki and Świdziński [, ]. A new form of equations that are consistent with the proposed definitions of deviatoric loading and unloading is suggested. Triaxial tests necessary for calibrating the proposed model have been performed. The modified model is used to simulate the deformations and stability of sand for every pre-failure loading path and makes it possible to describe the behaviour of granular soil under both drained and undrained conditions.

A comparison of experimental and numerical results is presented. All investigations were performed in a classical tri-axial apparatus.

Abstract

The paper presents the results of laboratory tests of plastic limit wP and liquid limit wL of Eemian gyttja characterized by different organic matter content I om and calcium carbonate content CaCO3. Comparison of the liquid limit wL determined with the use of the Casagrande apparatus wLC and a cone penetrometer with cones having apex angles of 60° wL 60 and 30° wL 30 is shown. Based on statistical analysis of the test results, single- and two-factor empirical relationships for evaluating the plastic limit wP and liquid limit wL of Eemian gyttja depending on the organic matter content I om and/or calcium carbonate content CaCO3 are presented in this study.