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För att förnya och förbättra den spårbundna trafiken inom Sverige är stambanor för höghastighetståg ett alternativ som utreds då det skulle innebära förkortade transporttider både för person- och godstrafik. Innan höghastighetsbanor kan etableras i Sverige finns det många faktorer som måste utredas. Eftersom tågen går med betydligt högre hastigheter än de tåg som redan används blir känsligheten för problem som kan uppstå i undergrunden betydligt högre och toleransen för sättningar och tjällyft är i princip lika med noll. På grund av klimatet som råder i Sverige finns det mycket att reda ut angående tjälproblematiken. Förutom låga temperaturer och vatten i jorden kan en trumma påverka hur tjälen utvecklas i järnvägsbanken. I den här studien analyseras påverkan som en trumma i järnvägsbanken har på tjälutvecklingen. Inverkan har analyserats utifrån ett tvärsnitt inuti järnvägsbanken för två olika köldmängder, -500 graddagar och -1300 graddagar. Innertemperaturen i trumman har antagits variera längs med trummans längd. Temperaturen har varierats inne i trumman att vara från 10 % upp till 75 % av köldmängden i uteluften. Förutom att analysera hur olika temperaturer påverkar tjälutvecklingen har den mängd material som behöver schaktas bort och ersättas med ett isoleringsmaterial för att förhindra att tjälproblem uppstår beräknats. Oberoende av trummans storlek och temperatur kommer trumman inte att kunna placeras direkt på terrassnivån utan att tjälfronten når det tjälfarliga materialet och risk för att tjälproblem ska uppstå. När temperaturen inne i trumman är 75% av köldmängden utomhus, och därmed nära temperaturen utomhus, blir tjälfronten även brantare än för lägre innertemperaturer. En brant tjälfront kan inducera större och mer ojämna tjällyft. För att undvika att problem uppstår måste ett isoleringslager av ett tjälpassivt material anläggas. Mängden material som måste ersättas ökar med trumdiameter och ökar betydligt beroende på om temperaturen inne i trumman är 10% eller 75% av utomhusköldmängden. Exempelvis ökar mängden under en trumma med 30 centimeters diameter från 1 m3 till 35,5 m3 respektive från 10,1 m3 till 58,4 m3 för en 150 centimeters diameter. Ökade mängder medför högre kostnader i både material och transporter, vilket är något som tillsammans med övriga faktorer senare måste analyseras vidare för att få mer kunskap och underlag inför en möjlig etablering av höghastighetsbanor.

Suffusion, also called internal instability, is an internal erosion mechanism that occurs in embankment dams when fine-grained particles are washed out of the core soil matrix by seepage. Initiation of internal erosion depends mainly on three major factors: grain size distribution of the soil, stress conditions and hydraulic load; whilst its continuation depends of the filter properties. Broadly graded moraines, as glacial tills, are more susceptible to internal erosion by suffusion than other types of soils used in dams. Most embankment dams in Sweden consist of a central core of glacial till built more than 50 years ago. At the time of its construction, the available guidelines did not include specific grain size boundaries for the core and the filter related to internal erosion susceptibility. Today, several Swedish embankment dams have experienced incident of internal erosion such as leakages and sinkholes, making internal erosion an important safety issue. This circumstance allows raising the questions: How safe are the Swedish embankment dams and what conditions are needed for internal erosion by suffusion to initiate? This research aims to contribute to the assessment of dam safety by giving inputs regarding the characterization of internal erosion by suffusion and the relation among the main factors involved on its occurrence (geotechnical characteristics of soil material, degree of compaction and hydraulic load). This in order to increase the knowledge regarding the critical hydraulic gradient needed to develop suffusion in a given till material with a known degree of compaction. The research includes a laboratory program consistent on suffusion tests, which is an extension of the standard permeability test, and considers post-test examination and diagnosis of the samples. Two main groups of tests were performed: small and large suffusion tests. The small tests serve as a reference of the expected behaviour of soil samples under different boundary and test conditions, which allows optimizing the number of test to be performed in large tests. Results show that suffusion mechanism can be classified as internal suffusion (or filtration) and external suffusion (loss of soil particles from the soil matrix). The influence of compaction degree on the initiation of suffusion is limited in internally stable soils. However, poorly compacted specimens exposed to high hydraulic gradients could develop both internal and external suffusion if the filter is not capable to retain the eroded particles. The hydraulic conductivity of specimens with internal suffusion tends to decrease with a step wise increase of the hydraulic gradient. Such tendency is the result of the matrix of soil reaching equilibrium with the new seepage stresses. The hydraulic conductivity of specimens with external suffusion tends to increase with the increase of the hydraulic gradient.

Granular materials have a “discrete” nature whose global mechanical behaviors are originated from the grain scale micromechanical mechanisms. The intriguing properties and non-trivial behaviors of a granular material pose formidable challenges to the multiscale modeling of these materials. Some of the key challenges include upscaling of coarse-scale continuum equation form fine-scale governing equations, calibrating material parameters at different scales, alleviating pathological mesh dependency in continuum models, and generating unit cells with versatile morphological details. This dissertation aims to addressing the aforementioned challenges and to investigate the mechanical behavior of granular materials through multiscale modeling. Firstly, a three-dimensional nonlocal multiscale discrete-continuum model is presented for modeling the mechanical behavior of granular materials. We establish an information-passing coupling scheme between DEM that explicitly replicates granular motion of individual particles and a finite element continuum model, which captures nonlocal overall response of the granular assemblies. Secondly, a new staggered multilevel material identification procedure is developed for phenomenological critical state plasticity models. The emphasis is placed on cases in which available experimental data and constraints are insufficient for calibration. The key idea is to create a secondary virtual experimental database from high-fidelity models, such as discrete element simulations, then merge both the actual experimental data and secondary database as an extended digital database to determine material parameters for the phenomenological macroscopic critical state plasticity model. This expansion of database provides additional constraints necessary for calibration of the phenomenological critical state plasticity models. Thirdly, a regularized phenomenological multiscale model is investigated, in which elastic properties are computed using direct homogenization and subsequently evolved using a simple three-parameter orthotropic continuum damage model. The salient feature of the model is a unified regularization framework based on the concept of effective softening strain. The unified regularization scheme is employed in the context of constitutive law rescaling and the staggered nonlocal approach to alleviate pathological mesh dependency. Lastly, a robust parametric model is presented for generating unit cells with randomly distributed inclusions. The proposed model is computationally efficient using a hierarchy of algorithms with increasing computational complexity, and is able to generate unit cells with different inclusion shapes.

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Numerical modelling is often needed as a tool to predict the behaviour and assess the safety of dam structures. Embankment dam structures analyses are quite complex and potential failures are hazardous. Predictions of dam behaviour by numerical modelling rely on knowledge about the mechanical properties of the materials the dam is constructed with. The materials included in a dam vary significantly because zones in the dam have different functions. In order to conduct reliable modelling, parameter values defining the stress-strain relationship of the materials are needed to be assigned.  Obtaining information about the mechanical behaviour in already existing embankment dams is usually challenging. As many dams are old, there might be a limited amount of information available of the materials used, construction methods and mostly about the stress-strain relationship of the soil. Traditionally, field sampling is performed in order to obtain such information. However, conventional field sampling might negatively affect the dam body and thereby the performance as well as the safety of the dam. This is of special importance if sampling is performed in the impervious (core) part. Since traditional sampling might harm the dam body, use of non-destructive methods would be advantageous to utilise for obtaining information about the stress-strain relationship and the strength in a dam structure.  An option for a non-destructive method is parameter identification by inverse analysis. The idea of inverse analysis is to calibrate finite element models towards field measurements. In the calibration process, the input for a stress-strain relationship (constitutive model) is modified until the discrepancy between the output of the numerical model and the associated chosen field measurement is minimised. The agreement between output from the numerical model and reality is measured by an objective function that will calculate the error. In order to automatically search for the minimum a search algorithm is utilised in the optimisation process. When the objective function is minimised, the calibration of the material parameters is done.  In previous research at Luleå University of Technology, the method of inverse analysis was applied to an embankment dam. The finite element program PLAXIS was used in combination with an optimisation code. The optimisation code includes an objective function (for error evaluation) and a search algorithm. The genetic algorithm was employed as search algorithm, since it is known for its robustness and efficiency as well as the fact that it provides a set of solutions instead of one unique answer. This is beneficial from a geotechnical point of view, since engineering judgement can be included in the final choice of solution.     The first study in the present thesis deals with a case study of an embankment dam, where a simple model calibration was performed. This was a part of a larger study, at the ICOLD Benchmark Workshop in 2017, where the work presented here was forming one of the contributions. In order to have a model response similar to reality, the contributors were asked to choose constitutive models and calibrate them. The calibration was done by manually changing the input for the constitutive model chosen. While the response of the numerical finite element model was capturing the trends of measured total stresses and pore pressure in the dam quite well, there were difficulties in capturing the long term deformations of the dam. This was a challenge for all contributors. An idea for improving the model response, is to run a more advanced calibration by inverse analysis.  In the second study in the thesis, predictions are presented for the embankment dam that inverse analysis was previously conducted for at LTU. Strengthening actions in form of a new berm were performed at the dam. With identified material parameter values from the inverse analysis, predictions were conducted both before and after the strengthening measures. The predicted deformations were compared to deformation data from inclinometer measurements.  A reasonably well agreement was obtained with the real deformations. The trend of the deformations was replicated and the magnitudes of the deformations were in the right order. The study is indicating that predicting future dam behaviour based on results from inverse analysis can be done reasonably well.  In the third and final study in the thesis, effects of random measurement error on the performance of the genetic algorithm for soil parameter identification are assessed. Also here, with the application to the embankment dam used in previous research at LTU. Optimisations were performed against inclinometer measurements. To be sure that the constitutive model can find the correct solution, synthetic (i.e. numerically generated) inclinometer data was utilised. Perturbations were randomly generated within chosen intervals of error and added to the numerically generated deformations.  The genetic algorithm showed its robustness, by continuing to search for solutions without breaking down even if the field data was substantially perturbed. Considering usual errors for inclinometer measurements, the genetic algorithm can deliver good solutions. The inclinometer errors used were taken from literature, and thereafter related to the perturbations of the numerically generated data. Dealing with errors that are becoming gradually larger than what can be considered as usual, problems are faced by the genetic algorithm. In this cases it is difficult to find a solution, and if solutions are found they might significantly deviate from the unperturbed optimum solution.  The three studies handled in this thesis are treating aspects of back analysis of embankment dams; from a simple calibration, to predictions based on material parameters from advanced inverse analysis and finally effects of errors on the genetic algorithm. It been shown that using inverse analysis for already existing embankment dams is very beneficial for the material characterisation and is forming a step towards better predictions of future dam behaviour.

Contact erosion is a type of  internal erosion which develops at the boundary between two varying soil layers inside a dam body under the condition of tangential water flow inside the coarser soil parallel to the boundary. As the behaviour of foundation is unknown as the grout curtain starts eroding after a couple of years. This zone between the embankment and foundation also leads to contact erosion.  Laboratory methods are a fast method of assessing the conditions for contact erosion to initiate as they do not involve a large investment like field testing methods. They also give an insight of the filter designs and long term stability of the dam core due to erosion.

The selection of a landfill site is considered as a complicated task because the whole process is based on many factors and restrictions. This study shows the present status of solid waste management, solid waste sources, staffing for solid waste collection, machinery and equipment used in the waste collection process, finance and financial management at Babylon Governorate and its Qadhaa. The management of collection and disposal of waste in Babylon Governorate and its Qadhaa is done through open dumping of waste and the quality of the collection process is poor. This is the case in Al-Hillah Qadhaa, which is located in the central part of the governorate, Iraq and Al-Qasim Qadhaas, which is situated in the southern part of the Babylon Governorate, Iraq. These sites do not conform to the scientific and environmental criteria applied in the selection of landfill sites.  In the first part of the current study, to find out how much solid waste will be produced in the future; two methods were used to calculate the population growth in Al-Hillah and Al-Qasim Qadhaas to the year 2030. The results showed that the total waste in 2030 according to the first and second methods respectively will be 394,081 tonnes and 472,474 tonnes in Al-Hillah Qadhaa, and (54,481 tonnes and 76,374 tonnes) in Al-Qasim Qadhaa. The cumulated quantity of solid waste expected to be produced between 2020 and 2030 according to the first and second methods respectively was 3,757,387 tonnes and 4,300,864 tonnes in Al-Hillah Qadhaa, whilst in Al-Qasim Qadhaa it was 519,456 tonnes and 695,219 tonnes. The generation rate in 2020 will be (0.88 and 0.62) kg/ (capita. day) in Al-Hillah and Al-Qasim Qadhaas respectively; in year 2030, the generation rate will be (0.97 and 0.69) kg/ (capita. day) based on method 2 and an expected incremental increase in generation rate of 1 kg/ (capita. day) per year.  The second part of this study aims to find the best sites for landfills in Al-Hillah and Al-Qasim Qadhaas. For this reason, 15 criteria were adopted in this study (groundwater depth, rivers, soil types, agricultural land use, land use, elevation, slope, gas pipelines, oil pipelines, power lines, roads, railways, urban centres, villages and archaeological sites) using GIS (geographic information system), which has a large capacity for managing input data. In addition, the AHP (analytical hierarchy process) method was used to derive the relative weightings for each criterion using pairwise comparison. The suitability index map for candidate landfill sites was obtained. Two suitable candidate landfill sites were found to fulfill the scientific and environmental requirements in each Qadhaa, with areas of 9.153 km2 and 8.204 km2 respectively in Al-Hillah Qadhaa, and with areas of 2.766 km2 and 2.055 km2 respectively in Al-Qasim Qadhaa. The area of these sites can accommodate solid waste from 2020 until 2030 based on the required areas, which were 4.175 km2 and 4.778 km2 (Ali-Hillah Qadhaa) and 0.577 km2 and 0.772 km2 in (Al-Qasim Qadhaa) according to the first and second methods respectively.