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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Feldspar dissolution during the weathering of granite under tropical conditions

Mdyusoff, Zainuddin January 2008 (has links)
Much of Malaysia is composed of granite. Samples ranging from unweathered granite to surface soils from newly exposed cut slopes and drill-holes were analysed using Quantitative X-ray Powder Diffraction (QXRPD), X-ray Fluorescence spectrometry (XRF), Inductively-coupled plasma mass spectrometry (ICP-MS), Scanning Electron Microscopy (SEM) and Optical microscopy. Samples were also sent to commercial laboratories for the determination of geotechnical engineering index and strength properties. The analyses have brought about a categorization of the weathering profiles into 4 ‘zones’: top soil, saprolite, weathering boundary and unweathered granite zones. The reactions within the active weathering boundary zone dictate the formation of secondary minerals. The findings in each different zone have enlightened the understanding of the development of secondary minerals especially clays in a deep weathering profile. The study also confirms and furthers understanding of the way chemical weathering occurs on the K-feldspar grains and is followed by the mechanical collapse of the grains leading to the reduction in the geotechnical strength of the material. The major element mobility study did not show any relation to the degree of weathering within the saprolite. Trace element study did not give conclusive results. However, a rare earth element (REE) study shows that the mobility of REE depends on the degree of weathering. The presence of clay minerals and feldspar grains are related to the geotechnical engineering properties, especially the strength properties which are responsible to the stability of slopes.
2

Experimental and theoretical investigation of the behaviour of brickwork cladding panel subjected to lateral loading

Ng, Chee Liang January 1996 (has links)
This thesis deals mainly with the resistance of single leaf brickwork cladding panels subjected to uniform lateral pressure. Such panels when supported on three or four sides bend like thin plates and are subjected to bi-axial bending. A bi-axial failure criterion for brickwork, which shows both strength and stiffness orthotropies, is required to predict the strength of the cladding panels. A systematic investigation was undertaken to establish the failure criterion of brickwork in bi-axial bending using a novel test method. A total number of 33 cross-beams in which both vertical and horizontal moments can be applied simultaneously was tested to define the failure criterion. From the tests, it appears that the strength in the weaker direction is enhanced in biaxial bending. In most cases, the load was shed from the weaker to the stronger direction after cracking. Once the section cracks, it is not capable of carrying any moment, which indicates the brittle nature of masonry. A conventional plate bending finite element program was modified incorporating the bi-axial failure criterion which takes into account the load-shedding observed in the tests. A smeared crack modelling technique was used to model the progressive cracking in bi-axial bending. Once the material properties in bi-axial bending were established and numerical modelling was carried out to predict the behaviour, it was essential to apply the theoretical model to walls subjected to lateral loading. A total number of 15 walls with different aspect ratios and boundary conditions was tested for comparison with the numerical method. Good agreement was obtained between the theoretical model and experimental results. All walls were tested under ideal boundary conditions so that rotational restraint at the supports could be avoided. Similar observations of load shedding from the weaker vertical direction to the stronger horizontal direction were observed also in the wall tests. This was confirmed by measuring the drop and increase in the reactions in the weaker and stronger directions. This was also confirmed from strain measurements in two orthogonal directions before and after cracking. These results also indicate without doubt that a cracked section cannot support any moment. This modified finite element program using the bi-axial failure criterion developed in this thesis was also used to compare the results with the wall test carried out by other researchers. A good agreement between the theoretical and the experimental results of wall with and without openings and subjected to lateral loading was also obtained. Hence, this finite element program using the bi-axial failure criterion can be used for the design of laterally loaded brickwork panels with confidence.
3

A study of the strength and behaviour of concrete blockwork masonry under eccentric loads with special reference to reinforced columns

Naghoj, Nart M. January 1994 (has links)
This thesis presents a comprehensive experimental and theoretical investigation carried out to study the behaviour and to determine the ultimate compressive strength, f<SUP>1</SUP><SUB>m</SUB>, of blockwork masonry prisms. The enhancing effect of strain gradient on f<SUP>1</SUP><SUB>m</SUB> caused by eccentricity was studied using two different eccentricities. The thesis also presents the results of an experimental and theoretical investigation carried out to study the strength and behaviour of reinforced blockwork masonry built with different percentages of vertical reinforcement and subjected to different eccentricities in order to establish the load-moment strength interaction diagrams. On the basis of the test results gathered from the experimental part of this study and the basic assumptions used in the design of reinforced concrete columns using ultimate limit state principles, a theoretical method was suggested to predict the ultimate strength of reinforced blockwork masonry columns subjected to axial and eccentric loads.
4

The consolidation behaviour of soft clays

Tonks, David M. January 1978 (has links)
Increased understanding of engineering behaviour of soil requires sophisticated interplay between observation, theory and analysis. Interactive Graphics programs are presented to handle numerical extensions to Terzaghi Consolidation Theory, permitting multi-layer analysis, time-dependant loading, and governing parameters varying with effective stress. The capabilities of such analysis are explored. Problems arise with non-linear stress-strain behaviour and there is considerable evidence that strain rate is also a significant variable for soft clays. A model proposed by Bjerrum is investigated in detail. This suggests skeletal behaviour may be constituted of two relationships, termed Instantaneous Consolidation - comprised of stress-strain functions only, and Delayed Consolidation - relating only strain and time. These processes may be considered independent, but progress simultaneously. The mathematical model of such consolidation, and its solution, has been developed by Garlanger. Improved numerical solution techniques are presented. Some minor theoretical inconsistencies are resolved, and some major ones identified. Later work establishes the theoretical validity of the scheme. After clarification and modification this is rather better than originally claimed. The major modification is in treatment of the critical pressure, PC. It is suggested that a discontinuity of stress-strain function is superfluous; the phenomenon is adequately defined by inclusion of a compatible strain-time function. Experimental evidence for this and the general acceptability of Garlanger's scheme is based on some 30 consolidation tests of varying type, pressure, and prior delayed consolidation, on Grangemouth silty-clay. Other cases of laboratory and field behaviour are also considered. It is concluded that the modified Garlanger theory is the most satisfactory approach currently available, and is potentially of considerable value for analysis of the Consolidation of Soft Clays.
5

Earth embankments reinforced with fabric

El-Hadi, Kamel Mohd January 1979 (has links)
In the first part of the study, consideration is given to the possible use of continuous sheet fabric reinforcement in embankments with non-vertical sides. A hypothesis for how the reinforcement functions is advanced, and design procedures are developed. In the second part of the study, the problem of cracking of earth and earth-rockfill dams has been studied. It has been recognized that the tensile strains and stresses which develop within the embankment are the main cause of cracking. This makes the knowledge of the behaviour of soil in tension necessary for adequate design and construction. Hence, a simple laboratory technique for tensile testing of soils has been developed. Furthermore, an alternative defensive measure against cracking and hydraulic fracturing by using fabric reinforcement is proposed and discussed. Laboratory work has been conducted, through shear box tests and triaxial tests, to study the feasibility of reinforcing cohesive soils (ie, clays) with fabric. Using a standard finite element program, the analysis of cracking and stability is presented in Chapter 9. This includes a study of the influence of the inclusion of reinforcing fabric sheets on the internal stability of earth embankments.
6

Analysis and assessment of masonry arch bridges

Robinson, Justin January 2000 (has links)
The importance of masonry arch bridges to the transport infrastructure throughout Europe is unquestionable. However with the ever increasing axle loads present on today's roads, and new European directives increasing the required load carrying capacity, the need for an accurate and reliable method of arch bridge assessment has never been more important. The current methods of arch bridge assessment have been shown to be conservative resulting in unnecessary and costly repair work or replacement of structures. The research described in this thesis is an element of an on-going study into soil-structure interaction, a very important factor for the accurate assessment of arch bridges. This overall investigation, continuing study into the effects of soil-structure interaction, is undertaken with a variety of methods and techniques. These include model bridge testing investigating different load types and fill heights, monitoring of full scale structures and subsequent analysis investigating thermal effects, comparison of the present arch bridge assessment methods linked with an actual arch bridge assessment program and the development of new numerical modelling models of arch assessment. Thus an investigation using discrete element analysis methods has been conducted, with comparison with finite element methods and physical models.
7

Soil-structure interaction in arch bridges

Fairfield, Charles Alexander January 1994 (has links)
European Community directives now insist upon the imposition of 11.5t axle weights for the assessment of highway bridges and structures. This need for heavier loads arises from the Community wide harmonisation of transport policy. Its successful implementation requires the urgent assessment of our bridge stock of some 75000 masonry arches. The analysis of arch bridges has long lacked an accurate method of assessing the loads transmitted to the arch ring by the surrounding soil. This thesis proposes pressure distributions suitable for use in the analysis of arch bridges. It examines, by way of instrumented small scale and <i>in-situ</i> tests, the soil-structure interaction effects arising from the backfill material. Observations of zones of soil displacement around a loaded arch are made in order to better describe the interactive effects. A finite element analysis of the instrumented tests was done and a parametric study was used to assess the effects of various material properties upon the system's behaviour. The inclusion of the interactive effects observed, and modelled, intends to lead to cost savings in the arch bridge assessment programme by reducing the conservatism inherent in the most common assessment methods. Design curves incorporating soil-structure interaction effects are presented where significant capacity increases can be seen compared with analyses ignoring the effects.
8

Anisotropy in granite and the effects of tunnel excavation in a controlled source shear-wave experiment

Holmes, Gordon Murray January 1995 (has links)
Observations of shear-wave splitting in signals from a controlled seismic source have never previously been used to parameterise a rockmass in a mine environment. In developing the necessary processing and modelling techniques and interpreting the final results, I demonstrate the usefulness of such a controlled-source shear-wave experiment to parameterise non-destructively a granite rockmass <I>in situ</I> and monitor non-destructively the effects of excavation. A Schmidt Hammer is used to pulse the free end of a nylon rod inserted down a 40cm borehole to create the seismic signals. I show the resulting seismograms to be highly reproducible, with cross-correlation coefficients of 0.90 or greater resulting for repeated raypaths, and that the shear-wave motion produced matches that due to an infinitesimal, isotropic, directional point source. I demonstrate that the use of multiple source orientations of a known source for repeated raypaths greatly improves the reliability of picking shear-wave polarisations and time delays. Thus the use of multiple source orientations of a known source is highly desirable in any controlled source shear-wave experiment. I demonstrate the use of cross-correlation to be effective in detecting temporal changes and that particle motions need only be displayed on the planes perpendicular to the source-receiver directions when interpreting changes in shear-wave particle motions, which is convenient for large datasets. I identify temporal changes due to the advancement of the zone of excavation disturbance, which suggests that Extensive-Dilatancy Anisotropy is at least partially responsible for the <I>in situ </I>anisotropy. An increase in the strength of anisotropy suggests that excavation creates an anisotropic fabric of dry cracks with orientations governed by either the <I>in situ</I> stress field or mineral alignment. These results suggest that shear waves may be used to remotely monitor a rockmass.
9

An appraisal of the geotechnical aspects of multi-span masonry arch bridges

Prentice, David James January 1996 (has links)
The importance of the masonry arch in Britain's infrastructure has never been more significant especially at the present time under ever increasing axle loads. It is estimated that there are over forty thousand highway arch bridges in the UK alone of which the majority were constructed between the 17<SUP>th</SUP> and 19<SUP>th</SUP> centuries. As a result of recent European Community directives, a significant proportion of these are required to be reassessed to ascertain their load carrying capacity. The bridge assessment program in the UK is therefore urgent. Current methods of assessment are conservative and often result in unnecessary repair work. Improvements to these methods are now urgently required. This thesis therefore details a continuing study of the effects of the interaction of the soil and the structure on the overall strength of a multi-span arch bridge. The research involves testing of both small and large scale models in an attempt to quantify the effect of the pier on the overall failure load. Both instrumentation and image analysis are used to monitor the dispersal of stress throughout the various models. An assessment of the suitability of using finite element analysis to predict these stresses is also carried out. Finally, the results of a long term monitoring program of a new arch bridge using instrumentation installed during the construction is presented and the effects of seasonal temperature variations are investigated. A new technique for the assessment of arches is subsequently derived which is based on the regression analysis of the tests undertaken for this thesis. It is hoped that the results of this research can be quantified with the long term view of incorporating them in updated assessment methods.
10

Non-destructive and geotechnical testing of railway track bed ballast

Clark, Max January 2001 (has links)
This thesis examines two techniques to identify the condition of rail track ballast: ground penetrating radar (GPR) and infra-red thermography. Basic work was undertaken on ballast durability using the slake durability test. Laboratory work using (GPR) was undertaken and the dielectric properties of rail track bed ballast were evaluated, using clean and spent ballast with various moisture contents. This was the first study of its kind. These results were examined and verified on a prototype track bed at The University of Edinburgh, where the conditions were known. This showed that GPR could be used to characterise the composition of in-situ railway track bed ballast. GPR was then used in a full-scale working track situation and different areas of clean and spent ballast successfully identified. Similar laboratory work was also undertaken using infrared thermography on samples of clean and spend ballast. It was found that clean and spent ballast changed temperature at different rates. Which agreed with theoretical models. The work undertaken on the prototype track bed and the full-scale working track confirmed these findings. Also the areas of clean and spent ballast identified with GPR were confirmed with infra-red thermography. This research has shown that GPR and infra-red thermography are appropriate techniques to obtain the characteristics of the composition of railway track bed ballast.  Both techniques found the same anomaly on the full-scale working track: a patch of spent ballast within an area of clean ballast. These techniques are faster and more cost effective than current methods of ballast investigation.

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