Land filling provides a major, safe, and economical disposal route for biosolids and sludges. With an expanding world, the demand for larger and higher capacity landfills is rapidly increasing. Proper analysis and design on such fills have pushed the boundaries of geotechnical engineering practice, in terms of proper identification and assessment of strength and deformation characteristics of waste materials. The engineering properties of Municipal Solid Waste (MSW) with co-disposal of biosolids and sludges with regards to moisture characteristics and geotechnical stability are of utmost importance. Significant changes in the composition and characteristics of landfill may take place with the addition of sludges and biosolids. In particular, the stability of waste slopes needs to be investigated, which involves the evaluation of the strength properties of the mixture of the waste and biosolids. This thesis deals with impact of the addition of biosolids on the geotechnical properties of class I landfill as determined from field investigations. The geotechnical properties are evaluated using an in-situ deep exploration test, called the Cone Penetration Test (CPT). CPT provides a continuous log of subsurface material properties using two measuring mechanisms, namely, tip resistance and side friction. The areas receiving biosolids are compared with areas without, to evaluate the effect of landfilling of biosolids. The required geotechnical shear strength parameters (angle of internal friction and cohesion) of MSW and biosolids mixture are determined by correlation with CPT results similar to the procedure followed in evaluating soil properties. The shear strength parameters obtained from the CPT data are then used to study the stability of different slope configurations of the landfill. The slope stability analysis is conducted on the various landfill models using the computer software SLOPE/W. This software was designed for soils but was found to be suitable for modeling landfills, as the waste is assumed to act similar to a cohesionless soil. Based on the field investigations, the angle of internal friction was found to be about 29° and the determination of any cohesion was not possible. It was concluded that the most suitable practical solution to adding biosolids into the landfill was in the form of trenches. From the slope stability study, it was found that the factor of safety reduces significantly with the introduction of biosolids due to a reduction in shear strength and increase in the overall moisture content. From a parametric study, the stability of a 1:2 side slope with an angle of friction lower than about 20° was found to be less than the safe limit of 1.5. In addition, the factors of safety for landfills with trenches extending close to the edges of the slopes were also found to be unsafe and this situation needs to be avoided in practice.

To acquire deeper understanding and insights into the mechanical behaviour of fibre reinforced saturated/unsaturated cohesive soils, a programme of work was designed and included. 1) Conducting standard Consolidation Undrained (CU) tests to investigate mechanical behaviour of non-reinforced fully saturated soil. 2) Studying the strength of fibre reinforced clay though unconfined compression tests. 3) Testing the behaviour of unsaturated reinforced soil in unsaturated triaxial tests. 4) Determining the soil-water characteristic curves (SWCC) on soil sample with different fibre content. The investigation was undertaken on a clay of low plasticity index. Samples tested with addition of 1, 3 and 5 % fibre content and different values of matric suction of 50, 100 and 200 kPa, one of the challenges that were encountered in this research are how to prepare homogenous samples. A method for prepared compacted fibre reinforced soils with improved fibre distribution and density profile has been proposed and examined. The test results indicated that waste carpet fibres increase the shear strength of unsaturated clay soils. It was also found that relative increase in strength is also a function of applied suction. An increase in waste carpet fibres was found to reduce the hysteresis of soil. A data analysis conducted on the results of unsaturated tests as a function of fibre content and matric suction. The behaviour modelled was shown to be a perfect fit with the experimental data.

The shear stress in an unsaturated soil increases rapidly with limited shear strain to a peak value and then drops gradually with a further increase in the shear strain until a residual value is reached. In other words, there is a significant strain-softening behavior under large shear deformation. A variety of geotechnical structures (e.g., slopes, foundations, retaining walls and piles) associated with unsaturated soils typically undergo a large progressive deformation prior to reaching failure conditions due to the influence of environmental factors (e.g., rainfall infiltration and wetting-drying cycles). As a result, the shear strength of soils in sliding zones typically reduces from a peak to a residual value with the progressive development of large shear deformation, while the shear strength of soils in other zones are still at the peak level. In other words, in many scenarios the strain-softening behavior of unsaturated soils can significantly influence the mechanical behavior of geo-structures. Therefore, a thorough understanding of the shear strength behavior of unsaturated soils during strain-softening is required to reliably interpret the mechanical behavior of geo-structures that undergo large shear deformation. Significant advances have been made during the last thirty years to understand and model the strain-softening behavior of unsaturated soils. Most of these studies however focus on the strain-softening behavior within a relatively small shear deformation due to the limitations of the experimental apparatuses. Only limited experimental studies under large shear deformation were reported based on the modified suction-controlled ring shear apparatus. Therefore, more investigations are still required to provide a comprehensive understanding of the shear strength behavior of unsaturated soils during strain-softening under large shear deformation. Studies presented in this thesis are directed towards investigating the shear strength behavior of unsaturated soils during strain-softening and its application in geotechnical engineering practice. The following studies have been conducted: (i) A state-of-the-art review of the strain-softening behavior of unsaturated soils published in the literature during the past three decades is summarized. The physical mechanisms and modelling methods of the strain-softening behavior and the peak, critical and residual shear strength of unsaturated soils are investigated. (ii) A disturbed state concept model is proposed to predict the variation of shear stress in unsaturated soils during strain-softening process under drained condition. Five sets of experimental data gathered from the literature on unsaturated soils varying from coarse- to fine-grained soils are used to verify the proposed model. The proposed model can provide reasonable predictions for the strain-softening stress-strain relationships of various types of unsaturated soils. The model is simple in concept and all the required parameters can be obtained from conventional saturated and unsaturated shearing tests and pressure plate tests. (iii) Two sets of suction-controlled multistage ring shear tests are conducted on unsaturated SP-SM soil and Indian Head till (IHT), respectively. The variation of the shear stress, void ratio, and water content of specimens during shearing (the shear displacement reaches 100 mm) under multi levels of net normal stress and matric suction are described and discussed. The influence of matric suction and net normal stress on the residual shear strength envelops of unsaturated soils are critically discussed. (iv) A model for predicting the residual shear strength for a wide range of unsaturated soils comprising coarse- to fine-grained soils is developed in terms of two stress state variables (i.e., the net normal stress and matric suction) by using the soil water characteristic curve as a tool. The model is formulated and validated based on experimental data in a series of suction-controlled ring shear tests using the axis-translation technique, including the two sets of tests (SP-SM and IHT) conducted in this research and another three sets of tests (SM, SC-SM and CH) gathered from the literature. The fitting parameters are related to the plasticity index (Iₚ); thus, only four basic parameters (i.e., cᵣ', φᵣ', Sᵣ and Iₚ) are included in this approach. (v) A series of slope stability analyses of a landslide in unsaturated condition are conducted using Geoslope software based on the peak and residual shear strength parameters. The analyses results highlight the role of residual shear strength in the slope stability of unsaturated soils. In summary, the mechanical behavior of unsaturated soils under large shear deformation is comprehensively investigated in this thesis. The experimental results of the suction-controlled ring shear tests reported in this research contribute towards understanding the fundamental shear strength behavior of unsaturated soils during strain-softening under large shear deformation. The models proposed in this research provide simple tools to predict the shear strength of unsaturated soils under different levels of shear deformation.

The flexural behavior of a light-weight wood-based composite system was studied through destructive experiments. The composite panel system consisted of profiled dimensional lumber, which makes up the surface layers, and 1"-thick boards running across the surface layers. Considering the changes in cross-sections along the panel due to the presence of the embedded boards, classical theories such as the Euler-Bernoulli beam and Kirchhoff-Love plate could not be implemented. Instead, the deflections and maximum failure loads of the composite system under full- and short-span bending tests were measured during their destructive bending testing, and were compared against the mechanical properties of the conventional three-ply CLT panel with the same thickness as the panel with embedded cross-laminations. According to maximum failure loads and deflections, it was concluded that full-span panels with embedded cross-laminations exhibited higher strength and stiffness, whereas short-span panels exhibited higher strength and lower stiffness properties compared to conventional CLT panels.

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[pt] Uma extensa campanha de ensaios de cisalhamento direto foi realizada na Areia da Praia de Ipanema, inspirado em Simões (2015). Os ensaios foram realizados em corpos de prova na condição seca, moldados em seis diferentes domínios de compacidade relativa (CR), desde muito fofo até muito compacto. Para cada domínio de CR, foram realizados ensaios sob dez diferentes valores de tensão normal nominal, variando de 25 a 1250 kPa. Em todos os ensaios, foi utilizado um dispositivo desenvolvido para impedir a rotação do top cap. A grande quantidade e variedade de ensaios permitiu uma análise detalhada de como as características das curvas tensão cisalhante sobre tensão normal versus deslocamento horizontal relativo e deslocamento vertical do top cap versus deslocamento horizontal relativo variaram com as variações de CR e de tensão normal, especialmente o ângulo de atrito de pico e o deslocamento vertical do top cap na ruptura, mostrando contração ou dilatação na ruptura. O ângulo de atrito a volume constante da Areia da Praia de Ipanema parece estar situado entre 30 e 32 graus. Uma curva que relaciona índice de vazios crítico e tensão normal nominal crítica foi obtida a partir dos ensaios de cisalhamento direto na Areia da Praia de Ipanema, sendo análoga à linha de estado crítico proposta por Lee e Seed (1967). Ademais, a alta frequência de aquisição de dados tornou explícito o fenômeno conhecido como stick-slip nas curvas obtidas, mostrando que a amplitude do fenômeno é tanto maior quanto menor a tensão normal nominal. / [en] A comprehensive research program of direct shear tests was carried out on Ipanema Beach Sand, inspired by Simões (2015). The tests were carried out on specimens in dry condition, prepared in six different domains of relative density (Dr), from very loose to very dense. For each Dr domain, tests were performed under ten different values of nominal normal stress, ranging from 25 to 1250 kPa. In all tests, a device developed to prevent the rotation of the top cap was used. The large number and variety of tests allowed a detailed analysis of how the characteristics of the Shear stress over normal stress versus relative horizontal displacement curves and top cap vertical displacement versus relative horizontal displacement curves varied with CR and normal stress variations, especially the peak friction angle and the vertical displacement of the top cap at failure, showing contraction or dilation at failure. The angle of friction at constant volume of the Ipanema Beach Sand seems to be situated between 30 and 32 degrees. A curve relating critical void ratio and critical nominal normal stress was obtained from the direct shear tests run on Ipanema Beach Sand, being analogous to the critical state line proposed by Lee and Seed (1967). Moreover, the high frequency of data acquisition made explicit the phenomenon known as stickslip in the obtained curves, showing that the amplitude of the phenomenon is greater the smaller the nominal normal stress.

The aim of this study is to determine if the mini block sampling technique couldoffer a complement to the Swedish standard StII piston sampler for achieving higherquality samples. The principle is that having a greater diameter the sample is meticulouslytrimmed to the usual geometry, so that the periphery of the sample is not disturbedby the sampling procedure and the same testing equipment can be employed.Hence, the test would provide higher and more accurate values of deformation andshear strength properties.The testing campaign executed for this study includes routine analysis with fallcone tests, CRS oedometer tests, DSS tests, CAUC triaxial tests and sedimentationtests. All of them have been performed on East-Sweden varved clay from Barkarby,Stockholm. Afterwards, the results and the sampling procedure were analysed toevaluate the performance of the mini block sampler.The mini block sampler provided more pronounced preconsolidation pressureson CRS tests as well as higher values of the quality index Mi=ML. DSS tests presenthigher values of undrained shear strength but no difference in shear strain at failure.In addition, the values of shear modulus show stiffer behaviour for block samplesas a prove of better clay structure preservation. Regarding triaxial results, theundrained shear strength values are higher for block samples with higher stresspeaks and lower strain to failure in the stress-strain graphs. Finally, several qualityindex were analysed obtaining better results for block sampling in most of them.It can be concluded that mini block sampler generally presents better qualitysamples than piston sampler for East-Swedish clay. Additionally, it is highlyfavourable for commercial projects due to each block provides up to 8 standard 50mm samples

This thesis evaluates the commonly used geotechnical probing method CPTu, on how different probe configurations impact the resulting evaluated undrained shear strength in soft clay deposits, in comparison to each other and laboratory methods. This is done by performing field investigations on Lindefältet, Södermanlands län, Sweden. Comparison is done on the two Swedish manufacturers of CPTu probes, by different calibration limits, filter types and whether overloading the probe over the calibration limit affects the evaluated undrained shear strength registered. The main conclusions are that one of the manufacturers’ probes registers deviating results in one configuration, that calibration limit has a noticable impact on the results, and that overloading on the probe and filter choice has negliable impact on the results. / I detta examensarbete utvärderas den vanligt förekommande geotekniska sonderingsmetoden CPTu, på hur olika konfigurationer av sonder påverkar den resulterande utvärderade odränerade skjuvhållfastheten i lösa leravlagringar, 9i jämförelse med varandra och med laboratoriemetoder. Detta är genomfört genom fältundersökningar på Lindefältet, Södermanlands län. Jämförelsen gjordes på de två svenska CPTu-tillverkarnas sonder. Detta är gjort med hänsyn till olika kalibreringar av konspetstryck, filtertyper, och huruvida sonden har varit överlastad påverkar den utvärderade skjuvhållfastheten som registreras. De huvudsakliga slutsatserna är att en av tillverkarnas sonder registerar udda värden i en konfiguration, att kalibreringar av konspetstryck har en märkbar påverkan på de resulterande värdena på utvärderade odränerade skjuvhållfastheten, samt att överlastning av sonder och val av filtertyp har liten till omärkbar påverkan på resultatet.