The work described in this thesis was firstly concerned with developing and evaluating automated soil testing equipment and associated instrumentation. The equipment consists principally of a triaxial stress path cell of the Bishop-Wesley type, a microcomputer and two pressure controllers. Inductive displacement transducers have been mounted inside the cell to measure axial and radial strains locally on the specimen boundary and axial strains between the end caps. The local axial strain measurements have proved superior to the end cap measurements which can be adversely affected by bedding errors and misalignment of the transducers relative to the loading axis. Following the development, the system was used to investigate the stress-strain behaviour of Cowden Till, particularly at small strains (0.01 - 0.10%). Cylindrical blocks of 250mm diameter were retrieved from the site and stored under isotropic stress. Eight specimens of 100mm diameter were trimmed from these blocks and subjected to either a drained or undrained compression test under load-controlled conditions. Cowden Till has been shown to exhibit strongly non-linear stress strain behaviour, even at small strains, and most of the shear strain is irreversible. The stress-strain characteristics were in acceptable agreement with those derived from a 865mm diameter plate loading test with under-plate instrumentation. Although the interpretation of the plate test is still being investigated, it is concluded that plate tests provide no better information about the stiffness of the material than triaxial tests of the type described in this thesis. The experimental stress-strain behaviour during compressive loading has been compared with the predictions of some mathematical models. The nonlinear elastic model of Atkinson (1973) appears to be applicable to Cowden Till, for which the behaviour is approximately isotropic. Simple stiffness predictions on the basis of critical state soil mechanics are inadequate at small strains. However, the model of Pender (1978) predicts the behaviour reasonably well. (ii) An attempt has been made to analyse the compression (bedding error) which occurs at the end of a triaxial specimen as the axial strain is increased. A quantification of the compression is hindered by the random nature of surface variations and by the limitations of present theories.

This study has demonstrated that the phenomenon of acoustic emission can be used to detect and monitor first time deformation characteristics in stiff, heavily-overconsolidated clay soils. The results from two field studies are presented and discussed with the aim of identifying the mechanisms responsible for the generation of acoustic emission. The first study, conducted at the Building Research Establishment's test site at Cowden (Humberside), was a section of cliff, naturally eroded by sea action. The second study, conducted in a 'moth-balled' brick-pit in Arlesey (Bedfordshire), was a large scale test in which instability was induced in a cut slope (in the Gault Clay) by cutting away at the toe. A number of different designs of wave guide were installed at both sites in order to determine the relative performance of each and, also, to provide further insight into the generation mechanisms. Some consideration has also been given to the effect of alternative data processing techniques. The results obtained indicate that the active wave guide model is the more appropriate in explaining the occurrence of acoustic emission and this finding is supported by the results of laboratory tests designed to replicate the perceived role of the wave guide in the field. In itself, identification of the generation mechanism is a result but, more importantly, understanding of the mechanics enables the design of monitoring systems which are suited to particular geotechnical conditions. Some comparison is also made between acoustic emission and standard methods of deformation monitoring. It is observed that acoustic emission can detect and clearly indicate disturbances at the same time as standard methods record such small magnitudes of movement as to be indistinguishable from instrument error. Additionally, a number of triaxial shear tests were conducted on a selection of soils which illustrates that different soils do exhibit different acoustic characteristics. Finally, this study demonstrates the feasibility of envelope processing using analogue to digital signal conversion both in the field and laboratory. Four published papers pertaining to work described within this thesis are appended.

The re-evaluation of pesticide use patterns is a high priority internationally. The process has led to a reduction in the numbers of pesticides allowed for use in many countries. This withdrawal of pesticides is aimed at consumer and environmental protection. Pesticide mobility and persistence is of major importance especially when considering the protection of water sources. In order to evaluate the suitability of a pesticide for use it is essential that its environmental behaviour is understood and predictable. In this thesis several case studies in which damage to crops may have been caused as a result of herbicides migration are described. Pesticide adsorption and persistence determinations showed that the adsorption coefficients do not differ from those published. Pesticide half lives are however likely to be prolonged in South African soils. Field migration studies show that pesticides are vertically and horizontally mobile in South African soils, seemingly independent of soil type. Both migration as well as upward movement was found, due to the mobility of the pesticides in the test soils. Mobility evaluation was identified as an aspect of importance for registration of pesticides under local conditions. To this end a system is proposed whereby migration can be incorporated into the existing pesticide evaluation framework. The system proposed used the migration model PESTAN as a predictive tool for pesticide migration in the evaluation process. The model is used for the evaluation of pesticides, according to Proposed Pesticide Migration Categories (PPLC). Migration evaluation should be conducted in conjunction with GPS systems to aid in determining potential risk areas where certain pesticide should not be used. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2009.

The re-evaluation of pesticide use patterns is a high priority internationally. The process has led to a reduction in the numbers of pesticides allowed for use in many countries. This withdrawal of pesticides is aimed at consumer and environmental protection. Pesticide mobility and persistence is of major importance especially when considering the protection of water sources. In order to evaluate the suitability of a pesticide for use it is essential that its environmental behaviour is understood and predictable. In this thesis several case studies in which damage to crops may have been caused as a result of herbicides migration are described. Pesticide adsorption and persistence determinations showed that the adsorption coefficients do not differ from those published. Pesticide half lives are however likely to be prolonged in South African soils. Field migration studies show that pesticides are vertically and horizontally mobile in South African soils, seemingly independent of soil type. Both migration as well as upward movement was found, due to the mobility of the pesticides in the test soils. Mobility evaluation was identified as an aspect of importance for registration of pesticides under local conditions. To this end a system is proposed whereby migration can be incorporated into the existing pesticide evaluation framework. The system proposed used the migration model PESTAN as a predictive tool for pesticide migration in the evaluation process. The model is used for the evaluation of pesticides, according to Proposed Pesticide Migration Categories (PPLC). Migration evaluation should be conducted in conjunction with GPS systems to aid in determining potential risk areas where certain pesticide should not be used. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2009.

No description available.

No description available.

In Sweden, it is common to use the CPT - Cone Penetration Test when probing in loose soils. This is mainly because the method is suitable for further assessment of soil layer sequences, pore pressure and forming an estimate of the geotechnical properties in-situ. Evaluation of a CPTu sounding in Sweden today takes in most cases place through the computer software CONRAD, which is based on semi-empirical relations. This study evaluates different methods for determining soil layer and classification as well as the density of materials based on results from CPTu surveys. P. K Robertson's methods for soil classification has been compared with CONRAD and verified soil layer sequences through laboratory protocols. A method for in-situ density estimation has also been studied and evaluated. Previous studies have shown that by using signal processing on CPTu data, it is possible to identify changes in soil layer sequence. Thus, a wavelet transform has in this study been used on the SBT index to find positions in which the layer sequence changes. The purpose of the study has been to investigate the validity of the evaluation methods, but also to see if additional information can be obtained without changing either the performance or sounding equipment. The study is based on CPTu data taken from already performed and completed preliminary investigation projects in Central Sweden, which means that no field investigations linked to this work has been carried out. The main conclusions from this study are: • Application of signal processing to CPTu data has potential to evaluate and interpret stratigraphic layers in a soil profile and has in this study identified silt layers • The wavelet transform is efficient to sort out interesting properties in soil based on CPTu results and has the potential to be successfully applied to sounding results performed in coarser soils • Robertson's SBT method for soil interpretation works well as an evaluation method in homogeneous, loose soils • Robertson's density evaluation method works well in homogeneous, loose soils but has problems handling clays with crust characteristics and soils with a high organic content.

Amostras indeformadas de um solo residual foram coletadas na zona oeste da cidade de São Paulo com o intuito de caracterizar o solo e estudar seu comportamento mecânico. Sua composição mineralógica é apresentada, assim como um estudo microscópico que identifica alguns destes minerais e evidencia sua microestrutura. Desse modo, é discutido como sua mineralogia e microestrutura influenciam em seu comportamento mecânico, estudado por meio de ensaios edométricos e de ensaios triaxiais convencionais de carregamento axial. Analisou-se sua compressibilidade, permeabilidade, seu grau de estruturação, suas relações tensão-deformação e envoltórias de escoamento, de ruptura e de Estados Críticos. O solo foi caracterizado como saprolítico, proveniente de um biotita-gnaisse milonitizado. A partir dos resultados obtidos a respeito do comportamento do solo, três modelos constitutivos escolhidos para estudo foram calibrados: elástico linear, elasto-plástico perfeito (Mohr-Coulomb) e elasto-plástico com endurecimento (Hardening-Soil). Com esta modelagem matemática, foi concebida uma modelagem numérica tridimensional de elementos finitos, a fim de simular a escavação de um túnel e de obter as trajetórias de tensões atuantes ao seu redor devidas a sua escavação. Outros ensaios triaxiais foram executados, desta vez seguindo-se as trajetórias de tensões obtidas numericamente. Os parâmetros elásticos dos três modelos constitutivos foram determinados para cada trajetória de tensões e o maciço envolvente à escavação foi modelado como sendo mecanicamente heterogêneo. Ou seja, limitaram-se zonas ao redor do túnel com diferentes propriedades mecânicas em função da trajetória de tensões atuante. Por fim, são comparados os parâmetros geotécnicos determinados com diferentes trajetórias de tensões, assim como os resultados obtidos com ambas as modelagens numéricas. / Undisturbed samples of a residual soil had been collected from the west zone of São Paulo city, in order to characterize the soil and study its mechanical behaviour. Its mineralogical composition is presented, as well as a microscopic study which identifies some of these minerals and evinces its microstructure. Thus, how the soil mineralogy and microstructure influence its mechanical behaviour is discussed, which was studied by means of oedometer tests and conventional axial loading triaxial tests. One analysed the soil compressibility, permeability, structuring degree, stress-strain relations and yielding, rupture and Critical State envelopes. The soil had been characterized as saprolite, derived from a biotite-gneiss. Based on the results concerning the soil behaviour, three constitutive models were calibrated: linear elastic, elastic perfectly plastic (Mohr-Coulomb), and elastic-plastic with hardening (Hardening Soil). With this mathematical modelling, a three-dimensional numerical model with finite elements was designed, for the purpose of simulating a tunnel excavation and obtaining the stress paths around it due to its excavation. Other triaxial tests were carried out, this time by following the stress paths numerically obtained. The elastic parameters of the three constitutive models had been determined for each stress path and the ground surrounding the excavation had been modelled as a mechanically heterogeneous media. I.e., zones around the tunnel had been limited by its different mechanical properties, as a function of the actual stress path. Finally, the geotechnical parameters determined by different stress paths are compared, as well as the results obtained for both numerical models.

Amostras indeformadas de um solo residual foram coletadas na zona oeste da cidade de São Paulo com o intuito de caracterizar o solo e estudar seu comportamento mecânico. Sua composição mineralógica é apresentada, assim como um estudo microscópico que identifica alguns destes minerais e evidencia sua microestrutura. Desse modo, é discutido como sua mineralogia e microestrutura influenciam em seu comportamento mecânico, estudado por meio de ensaios edométricos e de ensaios triaxiais convencionais de carregamento axial. Analisou-se sua compressibilidade, permeabilidade, seu grau de estruturação, suas relações tensão-deformação e envoltórias de escoamento, de ruptura e de Estados Críticos. O solo foi caracterizado como saprolítico, proveniente de um biotita-gnaisse milonitizado. A partir dos resultados obtidos a respeito do comportamento do solo, três modelos constitutivos escolhidos para estudo foram calibrados: elástico linear, elasto-plástico perfeito (Mohr-Coulomb) e elasto-plástico com endurecimento (Hardening-Soil). Com esta modelagem matemática, foi concebida uma modelagem numérica tridimensional de elementos finitos, a fim de simular a escavação de um túnel e de obter as trajetórias de tensões atuantes ao seu redor devidas a sua escavação. Outros ensaios triaxiais foram executados, desta vez seguindo-se as trajetórias de tensões obtidas numericamente. Os parâmetros elásticos dos três modelos constitutivos foram determinados para cada trajetória de tensões e o maciço envolvente à escavação foi modelado como sendo mecanicamente heterogêneo. Ou seja, limitaram-se zonas ao redor do túnel com diferentes propriedades mecânicas em função da trajetória de tensões atuante. Por fim, são comparados os parâmetros geotécnicos determinados com diferentes trajetórias de tensões, assim como os resultados obtidos com ambas as modelagens numéricas. / Undisturbed samples of a residual soil had been collected from the west zone of São Paulo city, in order to characterize the soil and study its mechanical behaviour. Its mineralogical composition is presented, as well as a microscopic study which identifies some of these minerals and evinces its microstructure. Thus, how the soil mineralogy and microstructure influence its mechanical behaviour is discussed, which was studied by means of oedometer tests and conventional axial loading triaxial tests. One analysed the soil compressibility, permeability, structuring degree, stress-strain relations and yielding, rupture and Critical State envelopes. The soil had been characterized as saprolite, derived from a biotite-gneiss. Based on the results concerning the soil behaviour, three constitutive models were calibrated: linear elastic, elastic perfectly plastic (Mohr-Coulomb), and elastic-plastic with hardening (Hardening Soil). With this mathematical modelling, a three-dimensional numerical model with finite elements was designed, for the purpose of simulating a tunnel excavation and obtaining the stress paths around it due to its excavation. Other triaxial tests were carried out, this time by following the stress paths numerically obtained. The elastic parameters of the three constitutive models had been determined for each stress path and the ground surrounding the excavation had been modelled as a mechanically heterogeneous media. I.e., zones around the tunnel had been limited by its different mechanical properties, as a function of the actual stress path. Finally, the geotechnical parameters determined by different stress paths are compared, as well as the results obtained for both numerical models.

[Truncated abstract] Characterising the behaviour of calcareous sediments that possess some degree of bonding between their constituents has attracted worldwide research interest in recent years. Although many recent studies have made significant contributions in delineating the behaviour of these sediments, there is still paucity of information particularly on the cyclic behaviour of cemented calcareous soils. This thesis describes in detail the characteristic features of cemented calcareous soils and proposes methods for characterising their cyclic behaviour. Two different calcareous soils Goodwyn (GW) and Ledge Point (LP) soils representing extreme depositional environments were examined in this study. Artificially cemented sample were created using the CIPS (Calcite Insitu Precipitation Systems) technique, considering its superiority over other most commonly available cementation techniques in replicating the natural pattern of cementation, and the behaviour of natural calcarenite under monotonic loading conditions. The experimental program involved triaxial testing of both uncemented and calcite-cemented calcareous soils under different loading conditions, i.e. isotropic compression tests to high-pressure (16 MPa), monotonic shearing tests, undrained cyclic shearing tests and undrained monotonic post-cyclic shearing tests. Significant emphasis has been placed on the cyclic behaviour of these soils. Internal submersible LDVTs were used for the accurate and continuous measurement of strain down to about 10-5