- Détails du magazine
- Format
- Magazine
- eISSN
- 2083-831X
- ISSN
- 0137-6365
- Première publication
- 09 Nov 2012
- Période de publication
- 4 fois par an
- Langues
- Anglais

#### Chercher

Accès libre

#### On the Onset of Thermal Convection in a Layer of Oldroydian Visco-Elastic Fluid Saturated by Brinkman–Darcy Porous Medium

Pages: 3 - 10

#### Résumé

Thermal instability in a horizontal layer of Oldroydian visco-elastic fluid in a porous medium is investigated. For porous medium the Brinkman–Darcy model is considered. A linear stability analysis based upon perturbation method and normal mode technique is used to find solution of the fluid layer confined between two free-free boundaries. The onset criterion for stationary and oscillatory convection is derived analytically. The influence of the Brinkman–Darcy, Prandtl–Darcy number, stress relaxation parameter on the stationary and oscillatory convection is studied both analytically and graphically. The sufficient condition for the validity of PES has also been derived.

#### Mots clés

- thermal instability
- Oldroydian visco-elastic fluid
- Brinkman–Darcy number
- Prandtl–Darcy number

Accès libre

#### Numerical Simulations of Blast Loads from Near-Field Ground Explosions in Air

Pages: 11 - 18

#### Résumé

Numerical simulations of air blast loading in the near-field acting on the ground have been performed. A simplified blast model based on empirical blast loading data representing spherical and hemispherical explosive shapes has been simulated. Conwep is an implementation of the empirical blast models presented by Kingery and Bulmash, which is also implemented in the commercial code LS-DYNA based on work done by Rahnders-Pehrson and Bannister. This makes it possible to simulate blast loads acting on structures representing spherical and hemispherical explosive shapes of TNT with reasonable computational effort as an alternative to the SPH and Eulerian model. The CPU time for the simplified blast model is however considerably shorter and may still be useful in time consuming concept studies. Reasonable numerical results using reasonable model sizes can be achieved not only for modelling near-field explosions in air but most areas of geotechnical. Calculation was compared with blast SPH and Eulerian model.

#### Mots clés

- near-field
- blast load
- numerical simulation
- high explosive

Accès libre

#### Reliability Analysis of Bearing Capacity of Square Footing on Soil with Strength Anisotropy Due to Layered Microstructure

Pages: 19 - 28

#### Résumé

The paper deals with reliability analysis of square footing on soil with strength anisotropy. The strength of the soil has been described with identified anisotropic strength criterion dedicated to geomaterials with layered microstructure. The analysis assumes dip angle

#### Mots clés

- layered microstructure
- square footing
- strength anisotropy
- reliability analysis
- probability of failure
- factor of safety

#### Résumé

The considerable influence of the soil backfill properties and that of the method of compacting it on the stiffness of soil-steel structures is characteristic of the latter. The above factors (exhibiting randomness) become apparent in shell deformation measurements conducted during construction and proof test loading. A definition of soil-shell structure stiffness, calculated on the basis of shell deflection under the service load, is proposed in the paper. It is demonstrated that the stiffness is the inverse of the deflection influence function used in structural mechanics. The moving load methodology is shown to be useful for testing, since it makes it possible to map the shell deflection influence line also in the case of group loads (concentrated forces), as in bridges. The analyzed cases show that the shell’s span, geometry (static scheme) and the height of earth fill influence the stiffness of the structure. The soil-steel structure’s characteristic parameter in the form of stiffness

#### Mots clés

- soil-steel structure
- numerical analysis
- stiffness of structure
- proof test

Accès libre

#### Moisture Content Impact on Mechanical Properties of Selected Cohesive Soils from the Wielkopolskie Voivodeship Southern Part

Pages: 37 - 46

#### Résumé

Results of investigations of shearing resistance and compressibility of fine-grained cohesive soil from the southern part of the wielkopolskie voivodeship in relation to the increasing moisture content are presented. The analysis of two series of samples, using soil paste for the consistency index of 0.9 and 0.4–0.3 was carried out. The results imply that the increasing moisture content causes a decrease in the angle of shearing resistance and cohesion and is also reflected in the higher compressibility of the soil. It was observed that regardless of the soil consistency, the angle of shearing resistance decreases and the cohesion value and the oedometric modulus of primary (consolidation) and secondary compressibility grows with the increase in the clay fraction.

#### Mots clés

- soil consistency
- shearing resistance
- compressibility

Accès libre

#### Analysis of the Foundation Slab Settlement of the “Africa Pavilion” Facility in Wrocław

Pages: 47 - 55

#### Résumé

This article presents the results of numerical calculations of soil consolidation underneath the “Africa Pavilion” structure in Wrocław Zoo, Poland. To determine the deformations of the baseplate of the “Africa Pavilion” and deformations of the subsoil, Biot’s consolidation theory for two-phase medium was applied. The calculations were carried out using the professional program FlexPDE v.6, which is based on the Finite Element Method. Numerical calculations performed were used to evaluate the design assumptions allowing for the laying of hydraulic conduits under the slab.

#### Mots clés

- soil consolidation
- numerical calculations
- settlement
- hydraulic conduits

Accès libre

#### Analysis of Prognosis of Lowland River Bed Erosion Based on Geotechnical Parameters

Pages: 57 - 63

#### Résumé

The river erosion is a complex process, the dynamics of which is very difficult to predict. Its intensity largely depends on hydraulic conditions of the river channel. However, it is also thought that natural resistance of the subsoil has a great influence on the scale of the erosion process. Predicting the effects of this process is extremely important in the case of constructing a piling structure (for example, artificial reservoirs). The partition of the river channel causes significant lowering of the river channel bed downstream the dam which threatens the stability of hydro technical and engineering (bridges) buildings. To stop this unwanted phenomenon, stabilizing thresholds are built. However, random location of thresholds significantly reduces their effectiveness. Therefore, taking under consideration natural geotechnical conditions of the subsoil appears to be extremely important.

In the light of the current development of in-situ tests in geotechnics, an attempt to use results from these tests to predict the bed erosion rate was made. The analysis includes results from CPTU and DPL tests, which were carried out in the Warta River valley downstream the Jeziorsko reservoir. In the paper, the general diagrams for the procedure of obtaining and processing the data are shown. As a result, the author presents two multidimensional bed erosion rate models built based on hydraulic data and results from CPTU or DPL tests. These models allow taking more effective actions, leading to the neutralization of the effects of the intensive bed erosion process.

#### Mots clés

- CPTU
- relative density
- bed erosion
- river flow

Accès libre

#### Numerical Modelling of the Mining Induced Horizontal Displacement

Pages: 65 - 73

#### Résumé

The paper presents results of numerical calculations and modeling of mining-induced surface deformation based on Finite Element Method (FEM). Applying the numerical method discussed to calculations allows us to assume a larger number of factors, such as rock mass structure, fracture network, rock properties, etc., which essentially affect the results obtained. On the basis of an elastic transversely isotropic model, an analysis of horizontal displacement distribution and surface subsidence was carried out for two sample regions of mines. The results of numerical calculations were later compared with the measured values. Such an analysis proved that the applied numerical model properly described distribution and values of subsidence and slope of subsidence trough, though there were serious differences in the values of calculated horizontal displacement, especially in areas of far influence range. In order to improve the matching, the influence of boundary conditions of the model on the value of calculated horizontal displacement was analyzed. The results are presented in graphs.

#### Mots clés

- Finite Element Method
- horizontal displacements
- mining excavation

Accès libre

#### Some Considerations on Horizontal Displacement and Horizontal Displacement Coefficient B

Pages: 75 - 82

#### Résumé

Mining-induced deformations of the ground surface and within the rock mass may pose danger not only for surface constructions but also for underground objects (e.g., tunnels, underground storages, garages), diverse types of pipelines, electric cables, etc. For a proper evaluation of hazard for surface and underground objects, such parameters as horizontal displacement and horizontal deformations, especially their maximum values, are of crucial importance. The paper is an attempt at a critical review of hitherto accomplished studies and state of the art of predicting horizontal displacement

#### Mots clés

- horizontal displacement coefficient
- horizontal displacement
- minig exploitation

#### Résumé

The article is a review of the current problems of the foundation pile capacity calculations. The article considers the main principles of pile capacity calculations presented in Eurocode 7 and other methods with adequate explanations. Two main methods are presented:

#### Mots clés

- pile load capacity calculation
- Eurocode 7
- α – method and β – method
- direct methods based on CPTu data

Accès libre

#### Comparison Between Two Methods for Estimating the Vertical Scale of Fluctuation for Modeling Random Geotechnical Problems

Pages: 95 - 103

#### Résumé

The design process in geotechnical engineering requires the most accurate mapping of soil. The difficulty lies in the spatial variability of soil parameters, which has been a site of investigation of many researches for many years. This study analyses the soil-modeling problem by suggesting two effective methods of acquiring information for modeling that consists of variability from cone penetration test (CPT). The first method has been used in geotechnical engineering, but the second one has not been associated with geotechnics so far. Both methods are applied to a case study in which the parameters of changes are estimated. The knowledge of the variability of parameters allows in a long term more effective estimation, for example, bearing capacity probability of failure.

#### Mots clés

- scale of fluctuation
- spatial variability