Fractured rocks extend over much of the world, cropping out in shields, massifs, and the cores of major mountain ranges. They also form the basement below younger sedimentary rocks; at depth; they represent a continuous environment of extended and deep regional groundwater flow. Understanding of groundwater flow and solute transport in fractured rocks is vital for analysis of water resources, water quality and environmental protection, geotechnical and engineering projects, and geothermal energy production. Book chapters include theoretical and practical analyses using numerical modelling, geochemistry, isotopes, aquifer tests, laboratory tests, field mapping, geophysics, geological analyses, and some unique combinations of these types of investigation. Current water resource and geotechnical problems in many countries—and the techniques now used to address them—are also discussed. The importance of geological interpretation is re-emphasised in analysing the hydrogeology of fractured, mostly crystalline rocks and in how critical this is for understanding their hydrology and the wise utilisation of resources. This is indeed hydrogeology in its broadest sense. The importance of, but great difficulty in, extending or upscaling fractured rock hydraulic properties is also made clear.
This book is aimed at practicing hydrogeologists, engineers, ecologists, resource managers, and perhaps most importantly, students and earth scientists not yet familiar with the ubiquity and importance of fractured rock systems.
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There have been stability theories developed for beams, plates and shells the most significant elements in mechanical, aerospace, ocean and marine engineering. For beams and plates, the theoretical and experimental values of buckling loads are in close vicinity. However for thin shells, the experimental predictions do not conform with the theory, due to presence of small geometric imperfections that are deviations from the ideal shape.
This fact has been referred to in the literature as 'embarrassing', 'paradoxical' and 'perplexing'. Indeed, the popular adage, "In theory there is no difference between theory and practice. In practice there is", very much applies to thin shells whose experimental buckling loads may constitute a small fraction of the theoretical prediction based on classical linear theory; because in practice, engineers use knockdown factors that are not theoretically substantiated.
This book presents a uniform approach that tames this prima-donna-like and capricious behavior of structures that has been dubbed the 'imperfection sensitivity' thus resolving the conundrum that has occupied the best minds of elastic stability throughout the twentieth century.
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The goal of the Detailed Analysis is to use all available tools to develop accurate projections of potential ground-borne vibration impact and, when necessary, to design mitigation measures. This is appropriate when the General Assessment has indicated impact and the project has entered the final design and engineering phase. It may also be appropriate to perform a Detailed Analysis at the outset when there are particularly sensitive land uses within the screening distances. Detailed Analysis will require developing estimates of the frequency components of the vibration signal, usually in terms of 1/3-octave-band spectra. Analytical techniques for solving vibration problems are complex and the technology continually advances. Consequently, the approach presented in this chapter focuses on the key steps usually taken by a professional in the field.
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REVIEW OF VIBRATION ANALYSIS METHODS FOR GEARBOX DIAGNOSTICS AND PROGNOSTICS
Author: Mitchell Lebold, Katherine McClintic, Robert Campbell, Carl Byington, and Kenneth Maynard Applied Research Laboratory The Pennsylvania State University | Size: 455 KB | Format:PDF | Quality:Unspecified | Publisher: Proceedings of the 54th Meeting of the Society for Machinery Failure Prevention Technology, Virginia Beach, VA, May 1-4, 2000, p. 623-634. | pages: 12
Vibration analysis for condition assessment and fault diagnostics has a long history of application to power and mechanical equipment. The interpretation and correlation of this data is often cumbersome, even for the most experienced personnel, and thus automated processing and analysis methods are sometimes sought. As such, statistical features are commonly used to provide a measure of the vibration level that can be compared to a threshold value indicative of a failed cond ition.
Many feature vectors have been developed over the years and are well documented in the literature. What is not clear from the literature is the details associated with each feature so that the results are consistent among users. Preprocessing is vaguely stated and terms, such as “residual signal”, are commonly used yet can mean different techniques. An attempt has been made to define the terms, establish the preprocessing needed for each feature, and provide the details needed to produce consistent results.
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The vibration response of piled foundations to inertial and underground railway induced loadings
Author: Pieter COULIER | Size: 5.1 MB | Format:PDF | Quality:Unspecified | Publisher: ENGINEERING DEPARTMENT MECHANICS, MATERIALS AND DESIGN DYNAMICS AND VIBRATION TRUMPINGTON STREET CB2 1PZ CAMBRIDGE UK | pages: 123
Vibrations and re-radiated noise in buildings induced by (underground) railway traffic are a major environmental concern. Vibrations are generated at the wheel-rail interface and propagate through the soil into buildings, where they cause annoyance to inhabitants. During the last decades, a lot of research has been performed to search for efficient and cost-effective vibration countermeasures. This dissertation is concerned with the dynamic behaviour of piled foundations. A model for piled foundations which accounts for the fundamental behaviour of each pile and the interaction between neighbouring piles, through wave propagation in the soil, is developed. It is a boundary element
model, formulated in the frequency domain, based on an existing single pile model.
The model is used to validate the Pipe-in-Pipe (PiP) model for piles, a computationally efficient model
for piled foundations based on the homonymic model for vibrations from underground railways. The
models are found to be in good agreement, which offers great perspectives to use the PiP model as an
engineering tool.
The influence of adjacent piles on the response of a certain pile is investigated by means of a power
flow analysis. It will be demonstrated that the effect is strongly dependent on the relative positions
of the piles compared to the position of the load applied. Moreover, a tendency to wave scattering is
revealed when the wavelength approaches the distance between piles and load.
Ultimately, the response of piled foundations to underground railway induced loadings is investigated.
Uncoupling of source (railway track) and receiver (piled foundations) is assumed, resulting in a two-step approach. The model is once more used to validate the PiP model for piles. Several aspects, such as the effect of the foundation design, the contribution of horizontal and rotational motion, the importance of pile-soil-pile interactions and the isolation performance of base isolation are examined. Results suggest that steel springs are preferred to rubber bearings, as the isolation frequency can be lowered more significantly. Moreover, it will become clear that the current boundary element model has the ability to reveal the complexity of the situation, which cannot be achieved by means of simplified
models.
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Size: 3.4 MB | Format:PDF | Quality:Unspecified | Publisher: SP Swedish National Testing and Research Institute Acoustics SP REPORT 2000: 25 Borås 2000 | Year: 2000 | pages: 103
Field measurements were carried out at two sites in southwest Sweden. Three, 3-directional accelerometers were used at three different distances from the middle of the railway track. All the accelerometers were mounted 50cm below the ground surface. Each accelerometer for the three directional accelerometers was mounted to represent one direction, the X direction is perpendicular to the railway track, the Y direction is parallel to the railway track and the Z direction is the vertical direction on the ground. The signal generated due to the passing trains were recorded by Sony Digital Recorder (DAT). Due to the fact that, this DAT has eight input channels and we used three 3-directional accelerometers, which
means nine accelerometers, one channel had to be omitted.
MATLAB was used to analyse the signals. The vibration levels were analysed using time weighting Sand the acceleration values were converted to velocity values. These measurements were carried out on three different types of trains: X2000, intercity, and freight trains.
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VIBRATION SERVICEABILITY OF FOOTBRIDGES UNDER HUMAN-INDUCED EXCITATION: A LITERATURE REVIEW
Author: STANA ŽIVANOVIĆ, ALEKSANDAR PAVIC and PAUL REYNOLDS | Size: 854 MB | Format:PDF | Quality:Unspecified | Publisher: Živanović, S., Pavić, A. and Reynolds, P. (2005) Vibration serviceability of footbridges under human-induced excitation: a literature review. Journal of Sound and Vibration, Vol. 279, No. 1-2, pp. 1-74. ( | pages: 69
Increasing strength of new structural materials and longer spans of new footbridges, accompanied with aesthetic requirements for greater slenderness, are resulting in more lively footbridge structures. In the past few years this issue attracted great public attention. The excessive lateral sway motion caused by crowd walking across the infamous Millennium Bridge in London is the prime example of the vibration serviceability problem of footbridges. In principle, consideration of footbridge vibration serviceability requires a characterisation of the vibration source, path and receiver. This paper is the most comprehensive review published to date of about 200 references which deal with these three key issues.
The literature survey identified humans as the most important source of vibration for footbridges. However, modelling of the crowd-induced dynamic force is not clearly defined yet, despite some serious attempts to tackle this issue in the last few years. The vibration path is the mass, damping and stiffness of the footbridge. Of these, damping is the most uncertain but extremely important parameter as the resonant behaviour tends to govern vibration serviceability of footbridges. A typical receiver of footbridge vibrations is a pedestrian who is quite often the source of vibrations as well. Many scales for rating the human perception of vibrations have been found in the published literature. However, few are applicable to footbridges because a receiver is not stationary but is actually moving across the vibrating structure.
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Seismic wave propagation in granular soils can induce large strain amplitudes in case of strong earthquakes. Seismic motions are irregular in frequency content and in amplitude, and have three different components in orthogonal directions. In this context, the main objective of this PhD research deals with nonlinear effects observed in granular soils under such complex loadings. The assumptions and simplifications usually considered for representing seismic loadings are evaluated, focusing on two main aspects: (i) cyclic stress frequency applied to the sample (ii) superposition of two
independent stresses. For that purpose, the nonlinear behaviour of two different sands, Leman Sand and Fonderie Sand, is explored with cyclic and seismic triaxial tests. These tests are performed with
unidirectional or bidirectional loadings, at medium to high strain amplitude, and in the earthquake frequency range. A dynamic triaxial press was developed to perform such tests, with dry and undrained saturated sand
samples. Axial and lateral stresses can be applied independently with large amplitudes for various loading shapes. An innovative non-contact measurement technique was developed to continuously
monitor the sample radius; this testing equipment is based on three laser sensors, set up around the triaxial cell, which detect the position of the sample surface thanks to optical triangulation. The obtained data are processed through a complex calibration system to provide the radial strain evolution at mid-height of the sample. The mounting structure supporting the sensors allows precise positioning and is equipped for manual vertical scanning of the sample profile.
The first triaxial tests are performed with classical cyclic loadings, to characterize the behaviour of the two sands in pseudo-dynamic conditions. These dry and undrained saturated tests allow to describe the
decrease of stiffness which leads to failure of the sand sample. Failure of undrained saturated sand occurs by liquefaction. Dry and undrained cyclic tests performed on Leman Sand at various frequencies from 0.1 to 6.5 Hz
show that the behaviour of this granular material is frequency-dependent at medium to large strains.
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A Dynamic Response Study on Optimal Piling Depth with respect to Ground Vibrations
Author: ERIK OLSSON Department of Civil and Environmental Engineering Division of Applied Acoustics Vibroacoustics Group | Size: 1.3 MB | Format:PDF | Quality:Unspecified | Publisher: CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2014 | Year: 2014 | pages: 74
Dynamic response of a piled foundation in soil has lately received much attention in research areas such as civil engineering and seismic engineering. The goal of this thesis is to learn more about the dynamic response of a single pile in clay and in particular to study if there is an optimal piling depth. The clay types investigated are an idealized isotropic clay and a case-specific for Gamla Ullevi, Gothenburg, Sweden. The motion and forces are small and the soils are considered as linear elastic materials. A solid finite element model is built in one case-specific and one idealized version. The idealized version is validated by mechanical response theory of a elastic half-space and also by comparison to a semi-analytical wavenumber model published 2013 by Kuo & Hunt. The response results show perfect agreement with half-space response theory and good agreement with the wavenumber model. The point mobility of a vertically loaded pile, and the transfer mobility at surface and in depth, are studied for different pile lengths for frequencies below 20 Hz. The results from both finite element model and the wavenumber model show convergence piling
depth at about 30 meters for both soil types. The transfer function results are reciprocal which allows to consider the foundation as the recipient of ground vibrations.
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