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This research aims at developing a novel vibration-based damage identification technique that can efficiently be applied to real-time large data for detection, classification, localisation and quantification of the potential structural damage. A complete testing procedure of the Experimental Modal Analysis (EMA) in freely supported beam based on impact hammer, as a relevant excitation source for field measurements, was established and the quality of its measurements was ensured. The experimental data in this research was collected from five laboratory-scale reinforced concrete beams modelled with various ranges of common defects. Reliable finite element beam models for the five beams in their normal conditions were developed correlated and updated using the results of the experimental tests. As a first round of investigation of the damage identification methods, the results of the modal parameters along with a number of their formulations and combinations were evaluated as model-based damage characterisation systems. Different ways for the representation and visualisation of the measurements in the time- or frequency-domain in a format pertinent for pattern identification were assessed. A two-stage combination between principal component analysis and Karhunen-Loéve transformation (also known as canonical correlation analysis) was proposed as a statistical-based damage identification technique. The suggested technique attempts to detect features regarding outliers or variation in the structural dynamic behaviour. In addition, it is used to serve as an unsupervised classification tool for data representing different structural conditions. Vibration measurements from time- and frequency-domain were tested as possible damage-sensitive features in an effort to avoid the expensive prolonged calculations of the modal parameters. In the first stage of the algorithm, principal component analysis is conducted on data from frequency response functions or response power spectral density functions in order to reduce the size of the data. The first prominent principal components that account for a reasonable percentage of the variance in the original data are preserved. In the second stage, the important principal components are provided as inputs to Karhunen-Loéve transformation to constitute the new transformed space. Within-class and between-class covariance matrices are exploited for maximising the discriminant capacity between subgroups. The new generated sets of data are analysed as a typical mathematical eigenproblem to account for the first two or three principal components that retain the major part of the variance. These components are next being employed for significant visualisation of the original data. The proposed system would provide unsupervised means that is capable to process, compare and discriminate between different periodically-collected immense data without considerable unnecessary effort for computations and modelling. The results of this statistical system help in distinguishing between normal and damaged patterns in structural vibration data. Most importantly, the system further dissects reasonably each main group into subgroups according to the levels of damage. The performance of this technique was credibly tested and verified on real measurements collected from the five beams with various detailed damage states. Its efficiency was conclusively proved on data from both frequency response functions and response-only functions. The outcomes of this two-stage system show realistic detection and classification and outperform results from the rival principal component analysis-only.

This thesis presents new methods for predicting pile response under different loading and soil conditions. The new methods offer practs engineers with a simple, quick and reliable tool for designing piles and ensuring that both safety and serviceability requirements are satisfied. In this thesis, an energy-based analytical approach for determining the dynamic response of piles subjected to dynamic loads is presented. The kinematic and potential energies of the pile-foundation system are minimized by a variational principle to obtain the governing equations of the pile-foundation system, along with the appropriate boundary conditions. Comparison with field data demonstrates the success of the new approach for predicting the resonant frequencies of laterally loaded piles. Energy-based methods are also developed for piles subjected to combined static loading. These methods are formulated for different constitutive models: linear-elastic, non-linear elastic and elasto-plastic models. In addition to energy-based methods, simple similarity methods have been developed to predict pile displacements. In the similarity methods, the load-displacement curve of a pile foundation can be obtained directly by scaling the stress-strain response obtained from a triaxial test on a representative soil sample. Linear scaling factors are presented and extensive verification is carried out against field data, centrifuge models and nonlinear finite element analysis.

This thesis develops a novel understanding of the fundamental issues in characterising and propagating unpredictability in rock engineering design. This unpredictability stems from the inherent complexity and heterogeneity of fractured rock masses as engineering media. It establishes the importance of: a) recognising that unpredictability results from epistemic uncertainty (i.e. resulting from a lack of knowledge) and aleatory variability (i.e. due to inherent randomness), and; b) the means by which uncertainty and variability associated with the parameters that characterise fractured rock masses are propagated through the modelling and design process. Through a critical review of the literature, this thesis shows that in geotechnical engineering – rock mechanics and rock engineering in particular – there is a lack of recognition in the existence of epistemic uncertainty and aleatory variability, and hence inappropriate design methods are often used. To overcome this, a novel taxonomy is developed and presented that facilitates characterisation of epistemic uncertainty and aleatory variability in the context of rock mechanics and rock engineering. Using this taxonomy, a new framework is developed that gives a protocol for correctly propagating uncertainty and variability through engineering calculations. The effectiveness of the taxonomy and the framework are demonstrated through their application to simple challenge problems commonly found in rock engineering. This new taxonomy and framework will provide engineers engaged in preparing rock engineering designs an objective means of characterising unpredictability in parameters commonly used to define properties of fractured rock masses. These new tools will also provide engineers with a means of clearly understanding the true nature of unpredictability inherent in rock mechanics and rock engineering, and thus direct selection of an appropriate unpredictability model to propagate unpredictability faithfully through engineering calculations. Thus, the taxonomy and framework developed in this thesis provide practical tools to improve the safety of rock engineering designs through an improved understanding of the unpredictability concepts.

Further investigations are described in the development of a biaxial glass inclusion gauge as a practical instrument for internal stress determinations in concrete. With this technique the magnitudes and directions of the required host stresses are interpreted from the induced stresses in the gauge by photoelastic methods. Before discussing the new work the concepts and principal features of earlier stress gauges are described and existing knowledge of the photoelastic stress meter is summarised. Some elementary aspects of concrete shrinkage effects on the gauge readings are then discussed; the experimental evidence includes the problem of inclusion stresses produced by shrinkage and superposed external loads. The discussion continues with an assessment of stressmeter behaviour under the action of two-dimensional stresses of opposite sign. Experimental evidence is compared with a theoretical solution and other indirect stress measurements using conventional strain gauge techniques. The experimental results from both the shrinkage and compression-tension tests reveal significant anomalies in the inclusion stress distribution. Then comparisons are made with calculated conditions. This feature, which has not been considered by previous investigations, is discussed with reference to the assumptions implicit in the theoretical solutions. An explanation is proposed for the observed behaviour. Finally a practical application of the stressmeter in a buttress Jam is described and the readings are compared with calculated stress conditions for the buttress. Recommendations are made for the benefit of similar applications in the future. The thesis concludes by discussing the implications of the present results to the photoelastic stressmeter method of determining stresses in concrete and suggestions are made for topics of further study.

Bond degradation is an irreversible phenomenon that, experimentally, appears to be controlled by plastic strain accumulation. Conventional constitutive soil models do not capture the effects of small strain non‐linearity, recent stress history as well as material structure and its consequent reduction due to bond degradation. The aim of this thesis is to investigate the behaviour of a constitutive model that describes the initial structure, on various geotechnical problems. The kinematic hardening structured constitutive model (Rouainia and Muir Wood, 2000) ,formulated within a framework of kinematic hardening and bounding surface plasticity, was implemented into the PLAXIS Finite Element Analysis software package and was used to simulate a variety of boundary value problems. The implementation of the model was validated through a number of single finite element analyses of laboratory tests on natural clay from the Vallericca valley in Italy. The model was further adopted in the finite element analyses of geotechnical problems. The first of these simulated the Self Boring Pressuremeter test in London Clay, with the main focus being the characterisation of the degree of initial structure of London clay, as well as identifying the effect of structure related parameters. The premise that the SBPM is installed without damage was also investigated. The second boundary value problem involved the 2D and 3Danalysis of an embankment situated on soft structured clay in Saint Alban, Canada. The numerical predictions of pore‐water pressures and settlements are also compared with field measurements. The model developed in this work was then adopted in the study of the behaviour of a deep excavation located in Boston, Massachusetts, USA. The numerical simulations were aimed to demonstrate that the added features of the model implemented in this work such as small strain stiffness, structure and anisotropy are vital components to give a good prediction. Comparison of the predicted wall profiles, time dependent dissipation of excess pore water pressures and associated ground heave with field data are provided.

Classical soil mechanics as presented by Karl Terzaghi assumed that the soil is in a fully saturated state. However, in tropical areas of the world residual and colluvial soil slopes exist in an unsaturated condition and the traditional theories and methods of slope stability analysis cannot be readily applied. However, situations may arise when unsaturated soils rapidly become saturated during rainstorms and the traditional theories do apply. The quick response of pore water pressure to rainfall intensity in a multi-layered residual soil and colluvium has been studied and reported in this research project. The effect of infiltration into a slope of variable saturated hydraulic conductivity values on stability was also examined. It was found that for a multi-layered residual soil the rapid infiltration of water into the more permeable soil layer causing saturation had a relatively quick impact on pore water pressure increase and hence the stability of the slope even though the overlying residual soils of lower saturated hydraulic conductivity remained unsaturated. In tropical areas which experience heavy rainfall periods during the wet season followed by very dry spells for several months of the year the infiltration process particularly in multi-layered unsaturated residual soil slopes is not fully understood. This thesis attempts to address this problem with the objective of contributing to the understanding of the hydrological processes taking place in a multi-layered unsaturated residual soil slope and a colluvial slope and to demonstrate how quickly the unsaturated soils become saturated and unstable during a 24-hour rainstorm event. The study includes the use of field instrumentation, laboratory testing and finite element numerical analysis to determine the changes in pore water pressure and instability in the two slopes due to infiltration during rainstorms. The sites selected for the study are located on the Caribbean island of Saint Lucia in the West Indies. Both sites experienced land slippage during heavy rainfall events. A study of the cause of the slope failures of a colluvial soil slope derived from weathered basalt and a residual soil slope from weathered parent andesite rock. The effect of the hydrological process induced by variable rainfall patterns and their effect on the stability of the two slopes unstable are examined. Pore water pressure and matric suction were measured in the field at both sites with tensiometers manufactured by Soil Moisture Equipment Corporation, Santa Barbara, California, and were installed at variable depths at specified locations on the slopes. Slope inclinometers, standpipe piezometers and rainfall gauges were also used for field instrumentation. The combined seepage and limit equilibrium slope stability analyses were conducted using the soil properties from the field and laboratory testing programs. The software Slope/W and Seep/W from Geo-Slope International Ltd, Calgary, Alberta, Canada were used for modeling the slope failures. The results of the study indicate the sensitivity of the relationship between variable pore water pressures, suction and the degree of saturation as expressed by the Soil Water Characteristic Curve (SWCC).The effect of these stress variables on the stability of the two slopes are also presented. Several areas are highlighted where additional research work is required such as the need to accurately identifying soil parameters for unsaturated residual soils and colluvium both in the field and laboratory. Of particular concern is the accurate measurement of the saturated hydraulic conductivity and suction of these materials which contribute to the frequent occurrence of catastrophic landslides during the rainy season on the Caribbean island of Saint Lucia.

This study has investigated the feasibility and advantages of using ternary blended binders containing limestone powder (LP), i.e. Portland-limestone cement (PLC), with fly ash (FA) or ground granulated blastfurnace slag (GGBS) in three types of high-consistence concrete i.e. self-compacting concrete (SCC), flowing concrete (FC) and underwater concrete (UWC), concentrating on the hardened mechanical and durability properties. Initially, mix design methods, tests, target fresh properties and constituent materials were selected for each concrete type. In the first stage of the study SCC mixes were formulated with binary and ternary binder blends with up to 80% cement replacement (by volume). The hardened properties of these, i.e. compressive and tensile strength, sorptivity and rapid chloride penetration resistance, were measured and the relationships between these investigated. Optimum replacement levels of GGBS and FA were estimated (40 and 20% respectively), and were used in the subsequent stages of the study on FC and UWC. The main outcomes were: -It is feasible to produce high-consistence concrete using ternary blended binders with LP and GGBS or FA. -It is possible to achieve similar or higher long-term compressive strengths with ternary binder mixes than with binary binder mixes for concrete with low water/cement ratio (<0.4). -A good relationship was obtained between the sorptivity results and the compressive strength which was independent of the concrete type, age and powder composition. -No relationship between the rapid chloride penetration test results and the compressive strength was obtained; the results had a high degree of scatter. There were reductions in the total embodied carbon contents of the concrete mixes with the incorporation of additions. There is scope for further investigating the synergistic effect between limestone powder and ggbs and fly ash to further reduce the Portland cement content leading to greater potential economic and environmental advantages.

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