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

#### Chercher

- Accès libre

Ultrasonic Waves and Strength Reduction Indexes for the Assessment of the Advancement of Deterioration Processes in Travertines from Pamukkale and Hierapolis (Turkey)

Pages: 3 - 9

#### Résumé

In constructions, the usefulness of modern technical diagnostics of stone as a raw material requires predicting the effects of long-term environmental impact of its qualities and geomechanical properties. The paper presents geomechanical research enabling presentation of the factors for strength loss of the stone and forecasting the rate of development of destructive phenomena on the stone structure on a long-time basis. As research material Turkish travertines were selected from the Denizli-Kaklık Basin (Pamukkale and Hierapolis quarries), which have been commonly used for centuries in global architecture. The rock material was subjected to testing of the impact of various environmental factors, as well as European standards recommended by the author of the research program. Their resistance to the crystallization of salts from aqueous solutions and the effects of SO_{2}, as well as the effect of frost and high temperatures are presented. The studies allowed establishing the following quantitative indicators: the ultrasonic waves index (I_{Vp}) and the strength reduction index (I_{Rc}). Reflections on the assessment of deterioration effects indicate that the most active factors decreasing travertine resistance in the aging process include frost and sulphur dioxide (SO_{2}). Their negative influence is particularly intense when the stone material is already strongly weathered.

#### Mots clés

- travertine
- deterioration
- geomechanical properties
- ultrasonic diagnosis
- strength

- Accès libre

Ground Penetrating Radar Investigations of Landslides: A Case Study in a Landslide in Radziszów

Pages: 11 - 18

#### Résumé

The article presents the results of research of the activated landslide in Radziszów in 2010. The study focused on the evaluation of engineering geology conditions, preceded by geophysical surveys. It mainly focused on the GPR method using the IDS georadar equipped with antennas in the frequency range of 100 MHz. Antenna selection was based on archival research which showed that the depth of occurrence of clays, where the roof can be a potential slip surface, ranges between 3-10 m below the surface.

GPR method applied allowed the course of the potential slip surface to be determined and the results obtained significantly correlated with the results of engineering geology tests carried out.

#### Mots clés

- geophysical methods - GPR
- geohazards
- landslide

- Accès libre

An Analysis of Excavation Support Safety Based on Experimental Studies

Pages: 19 - 29

#### Résumé

The article presents the results of inclinometric measurements and numerical analyses of soldier-pile wall displacements. The excavation under investigation was made in cohesive soils. The measurements were conducted at points located at the edge of the cantilever excavation support system. The displacements of the excavation support observed over the period of three years demonstrated the pattern of steady growth over the first two months, followed by a gradual levelling out to a final plateau. The numerical analyses were conducted based on 3D FEM models. The numerical analysis of the problem comprise calculations of the global structural safety factor depending on the displacement of the chosen points in the lagging and conducted by means of the φ/c reduction procedure. The adopted graphical method of safety estimation is very conservative in the sense that it recognizes stability loss quite early, when one could further load the medium or weaken it by further strength reduction. The values of the M_{sf} factor are relatively high. This is caused by the fact that the structure was designed for excavation twice as deep. Nevertheless, the structure is treated as a temporary one.

#### Mots clés

- soldier-pile wall
- inclinometer measurements
- φ/c reduction procedure

- Accès libre

Evaluation of Bearing Capacity of Strip Footing Using Random Layers Concept

Pages: 31 - 39

#### Résumé

The paper deals with evaluation of bearing capacity of strip foundation on random purely cohesive soil. The approach proposed combines random field theory in the form of random layers with classical limit analysis and Monte Carlo simulation. For given realization of random the bearing capacity of strip footing is evaluated by employing the kinematic approach of yield design theory. The results in the form of histograms for both bearing capacity of footing as well as optimal depth of failure mechanism are obtained for different thickness of random layers. For zero and infinite thickness of random layer the values of depth of failure mechanism as well as bearing capacity assessment are derived in a closed form. Finally based on a sequence of Monte Carlo simulations the bearing capacity of strip footing corresponding to a certain probability of failure is estimated. While the mean value of the foundation bearing capacity increases with the thickness of the random layers, the ultimate load corresponding to a certain probability of failure appears to be a decreasing function of random layers thickness.

#### Mots clés

- random field theory
- reliability
- bearing capacity
- random layers concept
- kinematic approach

- Accès libre

Recognition of Anhydrite Intercalated Salt Deposit from Seismic Dataset Distorted by Noise

Pages: 41 - 48

#### Résumé

Acoustic inversion is useful to extract information from seismic data. Inhomogeneities of salt deposits should be predicted before the decision of underground storage location is made. The work concerns the possibility of detecting anhydrite intercalation in the rock salt from seismic dataset. The resolution strongly depends on signal to noise ratio. The synthetic pseudoacoustic impedance sections are generated for efficiency test of predictive and minimum entropy deconvolution process, when random noise distorts the seismic traces.

#### Mots clés

- underground storage
- acoustic impedance
- salt deposit
- inhomogeneity detection
- noise

#### Résumé

Ordinary pile bearing capacity tests are usually carried out to determine the relationship between load and displacement of pile head. The measurement system required in such tests consists of force transducer and three or four displacement gauges. The whole system is installed at the pile head above the ground level. This approach, however, does not give us complete information about the pile-soil interaction. We can only determine the total bearing capacity of the pile, without the knowledge of its distribution into the shaft and base resistances. Much more information can be obtained by carrying out a test of instrumented pile equipped with a system for measuring the distribution of axial force along its core. In the case of pile model tests the use of such measurement is difficult due to small scale of the model.

To find a suitable solution for axial force measurement, which could be applied to small scale model piles, we had to take into account the following requirements:

- a linear and stable relationship between measured and physical values,

- the force measurement accuracy of about 0.1 kN,

- the range of measured forces up to 30 kN,

- resistance of measuring gauges against aggressive counteraction of concrete mortar and against moisture,

- insensitivity to pile bending,

- economical factor.

These requirements can be fulfilled by strain gauge sensors if an appropriate methodology is used for test preparation (Hoffmann [1]). In this paper, we focus on some aspects of the application of strain gauge sensors for model pile tests. The efficiency of the method is proved on the examples of static load tests carried out on SDP model piles acting as single piles and in a group.

#### Mots clés

- screw displacement piles
- CFA piles
- deep foundation
- model tests
- group of piles

- Accès libre

Experimentally Validated Nonlinear Analysis of Bridge Plate Girders with Deformations

Pages: 53 - 61

#### Résumé

Comprehensive methodology of numerical nonlinear analysis of the consecutive phases in the structural behaviour of bridge plate girders with deformations is presented. The analysis concerns all stages of structure loading until failure and especially determination of the ultimate shear load capacity. Verification and validation of the numerical procedures proposed is based on comparison of the calculated results with effects of experimental laboratory shear capacity tests of plate girders carried out at the University of Ljubljana.

#### Mots clés

- FEM analysis
- experimental tests
- bridge plate girders
- deformations
- load capacity

- Accès libre

Analysis of Harmonic Vibration of Cable-Stayed Footbridge under the Influence of Changes of the Cables Tension

Pages: 63 - 71

#### Résumé

The paper presents numerical analysis of harmonically excited vibration of a cable-stayed footbridge caused by a load function simulating crouching (squats) while changing the static tension in chosen cables. The intentional synchronized motion (e.g., squats) of a single person or group of persons on the footbridge with a frequency close to the natural frequency of the structure may lead to the resonant vibrations with large amplitudes. The appropriate tension changes in some cables cause detuning of resonance on account of stiffness changes of structures and hence detuning in the natural frequency that is close to the excitation frequency. The research was carried out on a 3D computer model of a real structure - a cable-stayed steel footbridge in Leśnica, a quarter of Wrocław, Poland, with the help of standard computer software based on FEM COSMOS/M System.

#### Mots clés

- cable-stayed footbridge
- FEM model
- harmonic vibration
- vibration reduction

- Accès libre

On Unsaturated Soil Mechanics – Personal Views on Current Research

Pages: 73 - 84

#### Résumé

This paper presents the authors’ personal views on current research being conducted by various research groups around the world in the broad area of mechanics of unsaturated geomaterials in general and soils in particular. The topic is of interest to a wide spectrum of scientists and engineers working in diverse areas such as geology and geophysics, powder technology, agricultural, petroleum, chemical, geotechnical, civil, environmental and nuclear engineering. Even if we restrict ourselves to civil, geotechnical and environmental engineering, it is noted that a plethora of hypotheses as well as a number of empirical and semi-empirical relations have been introduced for describing the mechanics of unsaturated porous media. However, many of these proposed advances as well as methods of testing may lack sound theoretical basis.

#### Mots clés

- unsaturated soil
- suction
- microstructure of saturation
- constitutive relation

- Accès libre

Influence of Structural Features and Fracture Processes on Surface Roughness: A Case Study from the Krosno Sandstones of the Górka–Mucharz Quarry (Little Beskids, Southern Poland)

Pages: 85 - 93

#### Résumé

The paper presents the results of analysis of surface roughness parameters in the Krosno Sandstones of Mucharz, southern Poland. It was aimed at determining whether these parameters are influenced by structural features (mainly the laminar distribution of mineral components and directional distribution of non-isometric grains) and fracture processes. The tests applied in the analysis enabled us to determine and describe the primary statistical parameters used in the quantitative description of surface roughness, as well as specify the usefulness of contact profilometry as a method of visualizing spatial differentiation of fracture processes in rocks. These aims were achieved by selecting a model material (Krosno Sandstones from the Górka-Mucharz Quarry) and an appropriate research methodology. The schedule of laboratory analyses included: identification analyses connected with non-destructive ultrasonic tests, aimed at the preliminary determination of rock anisotropy, strength point load tests (cleaved surfaces were obtained due to destruction of rock samples), microscopic analysis (observation of thin sections in order to determine the mechanism of inducing fracture processes) and a test method of measuring surface roughness (two- and three-dimensional diagrams, topographic and contour maps, and statistical parameters of surface roughness). The highest values of roughness indicators were achieved for surfaces formed under the influence of intragranular fracture processes (cracks propagating directly through grains). This is related to the structural features of the Krosno Sandstones (distribution of lamination and bedding).

#### Mots clés

- anisotropy
- rock cracking
- fracture processes
- flysch
- geomechanics
- Krosno Sandstones
- surface roughness

- Accès libre

Technical Note: Example of the Application of Jet Grouting to the Neutralisation of Geotechnical Hazard in Shaft Structures

Pages: 95 - 99

#### Résumé

The article presents a geotechnical hazard neutralisation technology for shaft structures. The diagnosis of problems with uncontrolled subsidence of the ventilation duct provided by the authors enabled the development of a schedule of works required for the protection and reinforcement of foundation soil in the shaft area. The technology of protection works was selected after the analysis of the technical condition of shaft structures as well as hydrological and geomechanical conditions. Due to the closeness of the shaft lining, it was necessary to form grout columns using jet grouting and low-pressure grouting technologies. The article presents the issues related to the selected technology and its application to the neutralisation of the emergent geotechnical hazard. The method of performance of recommended works was also described together with their impact on the technical condition of structures discussed as well as their functionality and usage.

#### Mots clés

- jet grouting
- shaft
- mining construction
- structure diagnostics

- Accès libre

Technical Note: Outlays on Construction of Airport Runways with Prestressed and Dowelled Pavements

Pages: 101 - 111

#### Résumé

For two variants of runways with abrasive concrete pavements in the prestressed and dowelled technologies, analyses have been presented regarding labour, materials, use of machinery, and financial outlays, together with the necessary technological-organisational analyses and assessment of work execution cycles, by the example of construction of a runway at the Katowice Airport.

#### Mots clés

- dowelled runway
- prestressed concrete
- technology and organization of construction