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Aiming at modelling the mechanical behaviour of soil-rock mixtures accurately and efficiently, a coupled MPM-DEM formulation combining the material point method (MPM) and the discrete element method (DEM) is proposed. It is solved concurrently via the contact force linking the two individual methods. Specifically, the soil is modelled with MPM as continuums to avoid handling the contacts between fine particles. The rocks are modelled by DEM to capture the contact characteristics of rocks. This method is validated with ball impacting and block sliding tests first for the contact between material points and DEM particles. Its capability in describing the mechanics of soil-rock mixtures is thereafter proved by comparing the simulation results with pure DEM simulations of binary mixtures and laboratory tests of soil-rock mixtures. It is demonstrated that MPM-DEM can reproduce the stress–strain response of soil-rock mixtures and capture the influence of rock contents and rock sizes. In addition, a coarse-graining modelling scheme is implemented, i.e., representing the soil particles with fewer material points, which significantly increases the efficiency compared with pure DEM. Our proposed method provides a novel way to model soil-rock mixtures with reasonable computational efforts, which sheds light on simulating large-scale soil-rock mixtures in nature or engineering., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Geo-engineering

Element testing of soft soils is challenging due to the large strains attained in the pre-failure range. Besides the heterogeneity of natural samples, the set-up configuration is the main driving factor for non-homogenous response. Stress, strain and pore pressure non-uniformities induced by the loading system affect the observed behaviour and complicate proper interpretation of the results. Among the difficulties encountered in the interpretation of laboratory data, the unexpected decrease of the stress ratio frequently observed on Dutch organic soft clays on the wet side of critical state is investigated by numerically back-analysing the triaxial test set-up. A 3D finite element simulation using an advanced constitutive model for soft clays developed at TU Delft was performed to clarify the nature of the response. The results indicate that a decrease in the deviatoric stress up to critical state may be interpreted as a true feature of the soil response. However, the response at large strains is very much influenced by the triaxial shear apparatus, in particular, by the rotation of the top cap which triggers geometrical instability. Practical recommendations are given to limit the effects of the set-up configuration on the determination of the undrained shear strength to be used for field applications., Geo-engineering

Predictions of the unsaturated shear strength with generalized effective stress-based approaches disregard the non-uniform microstructure of remolded fine-grained soils. The study aims at investigating the adequacy of microstructurally-based effective stress to predict the unsaturated shear strength of remolded fine-grained soils over a wide range of suctions. For that purpose, shear strength data are acquired on a silty clay soil compacted at two different dry densities through suction-controlled triaxial tests and unconsolidated triaxial tests at constant water content. The microstructure of the soil at the as-compacted state is determined with Mercury Intrusion Porosimetry and is directly incorporated in different expressions of microstructurally-based effective stress available in the literature. The experimental data suggest that compared to the generalized effective stress, microstructurally-based effective stress expressions provide better predictions of the unsaturated shear strength, especially at high suctions. Also, the use of microstructurally-based effective stress is particularly relevant for remolded fine-grained soils compacted at high dry densities, i.e. with a low proportion of macropores., SCOPUS: ar.j, info:eu-repo/semantics/published

Numerical modelling in Geo-Engineering is used to solve complex problems by simulating, analysing, or predicting soil behaviour under certain loading and boundary conditions. The soil behaviour is simulated by constitutive models that describe the relationship between stresses and strains through a mathematical formulation. Model parameters are used to calibrate model behaviour to physical soil behaviour measured during in-situ testing (e.g. CPT) or laboratory testing (e.g. triaxial testing). The selection of model parameters is challenging as it needs to cope with aspects as, constitutive model limitations, laboratory test limitations, sample disturbance, soil heterogeneity and many other. This study shows how these model parameters can be determined, optimised and selected by using over 3000 triaxial test results performed on dutch soils (stored in text files) and machine learning tools., Geo-Engineering

Die dynamische Bodenverdichtung ist eine in der Baubranche sehr häufig zur Anwendung kommende Bodenverdichtungsmaßnahme. Mit dem technischen Fortschritt der letzten Jahrzehnte geht eine zunehmende Automatisierung einher. Auch bei den Bodenverdichtungsverfahren ist eine arbeitsintegrierte und flächendeckende Kontrolle der Verdichtungswirkung gefragt. Um die versuchstechnisch entwickelten Kontrollverfahren in Hinblick auf den vorgeschlagenen „Verdichtungskennwert“ zu verifizieren, kommen numerische Simulationen zum Einsatz. Für die theoretischen Untersuchungen muss das Verhalten des Bodens mit geeigneten Stoffgesetzen beschrieben und programmiertechnisch in die jeweilige Software implementiert werden. In dieser Arbeit wird ein hypoplastisches Stoffgesetz ohne und mit intergranularen Dehnungen in Form einer UMAT in die FEM-Software ABAQUS implementiert. Dabei werden zwei Varianten für die numerische Lösung der Materialtangente (Konsistente Tangente und Kontinuumstangente) programmiert. Die Implementierung wird anhand von Elementtests in Form des Ödometer- und Triaxialversuchs sowie durch Vergleich mit Versuchs- und Simulationsergebnissen aus publizierter Literatur überprüft. Die dabei durchgeführten Parameterstudien zeigen den aus publizierten Unteruschungen bekannten großen Einfluss des Kompressionsexponenten auf das Verhalten des Bodens. Außerdem zeigt der Vergleich von Simulationsergebnissen des Ödometertests mit jenen des Triaxialversuchs eine unterschiedliche Sensitivität bezüglich des kritischen Reibungswinkels. Die praktische Anwendbarkeit und numerische Stabilität wird anhand der numerischen Simulation der dynamischen Bodenverdichtung mit dem Tiefenrüttler an einem vereinfachten, dreidimensionalen Rüttler-Boden-Interaktionsmodell überprüft. Die verschiebungsgesteuerten Simulationen mit dem hypoplastischen Stoffgesetz können die Ausbreitung der Druckwelle und die mit der Zeit zunehmende Reichweite der Verdichtung qualitativ abbilden. Die ausgewählten Parameterst, Dynamic soil compaction is a common soil compaction measure in civil engineering. Technical progress in recent decades has been accompanied by increasing automation. Work-integrated and continous control of the compaction effect is required for soil compaction methods. In order to verify the experimetally developed control procedures with regard to the proposed „compaction parameter“, numerical simulations are used. For the theoretical research, the behavior of the soil must be described with a suitable constitutive model and implemented in the used software package. In this Master thesis, a basic and extended (interganular strains) hypoplastic constitutive model in the form of a UMAT is implemented in the FEM software ABAQUS. Two variants are coded for the numerical solution of the material tangent (consistent tangent and continuum tangent). The implementation is verified by element tests in the form of the oedometer and the triaxial test as well as by comparison with experimental and simulation results from published literature. The parameter studies performed show the large influence of the compression exponent on the behavior of the soil, which is already known from previous studies. Furthermore, the comparison of the simulation results of the oedometer test with those of the triaxial test shows a different sensitivity with respect to the critical friction angle. Practical applicability and numerical stability are verified by numerical simulation of dynamic soil compaction with the vibratory compactor on a simplified, three-dimensional vibrator-soil interaction model. The displacement controlled simulations with the hypoplastic constitutive model can qualitatively represent the propagation of the pressure wave and the increasing range of compaction over time. The selected parameter studies (vibrator amplitude, initial soil density) are numerically stable up to 100 cycles., Thomas Wolf, BSc, Masterarbeit Universität Innsbruck 2022, Kurzfassung deutsch und englisch

Die dynamische Bodenverdichtung ist eine in der Baubranche sehr häufig zur Anwendung kommende Bodenverdichtungsmaßnahme. Mit dem technischen Fortschritt der letzten Jahrzehnte geht eine zunehmende Automatisierung einher. Auch bei den Bodenverdichtungsverfahren ist eine arbeitsintegrierte und flächendeckende Kontrolle der Verdichtungswirkung gefragt. Um die versuchstechnisch entwickelten Kontrollverfahren in Hinblick auf den vorgeschlagenen „Verdichtungskennwert“ zu verifizieren, kommen numerische Simulationen zum Einsatz. Für die theoretischen Untersuchungen muss das Verhalten des Bodens mit geeigneten Stoffgesetzen beschrieben und programmiertechnisch in die jeweilige Software implementiert werden. In dieser Arbeit wird ein hypoplastisches Stoffgesetz ohne und mit intergranularen Dehnungen in Form einer UMAT in die FEM-Software ABAQUS implementiert. Dabei werden zwei Varianten für die numerische Lösung der Materialtangente (Konsistente Tangente und Kontinuumstangente) programmiert. Die Implementierung wird anhand von Elementtests in Form des Ödometer- und Triaxialversuchs sowie durch Vergleich mit Versuchs- und Simulationsergebnissen aus publizierter Literatur überprüft. Die dabei durchgeführten Parameterstudien zeigen den aus publizierten Unteruschungen bekannten großen Einfluss des Kompressionsexponenten auf das Verhalten des Bodens. Außerdem zeigt der Vergleich von Simulationsergebnissen des Ödometertests mit jenen des Triaxialversuchs eine unterschiedliche Sensitivität bezüglich des kritischen Reibungswinkels. Die praktische Anwendbarkeit und numerische Stabilität wird anhand der numerischen Simulation der dynamischen Bodenverdichtung mit dem Tiefenrüttler an einem vereinfachten, dreidimensionalen Rüttler-Boden-Interaktionsmodell überprüft. Die verschiebungsgesteuerten Simulationen mit dem hypoplastischen Stoffgesetz können die Ausbreitung der Druckwelle und die mit der Zeit zunehmende Reichweite der Verdichtung qualitativ abbilden. Die ausgewählten Parameterst, Dynamic soil compaction is a common soil compaction measure in civil engineering. Technical progress in recent decades has been accompanied by increasing automation. Work-integrated and continous control of the compaction effect is required for soil compaction methods. In order to verify the experimetally developed control procedures with regard to the proposed „compaction parameter“, numerical simulations are used. For the theoretical research, the behavior of the soil must be described with a suitable constitutive model and implemented in the used software package. In this Master thesis, a basic and extended (interganular strains) hypoplastic constitutive model in the form of a UMAT is implemented in the FEM software ABAQUS. Two variants are coded for the numerical solution of the material tangent (consistent tangent and continuum tangent). The implementation is verified by element tests in the form of the oedometer and the triaxial test as well as by comparison with experimental and simulation results from published literature. The parameter studies performed show the large influence of the compression exponent on the behavior of the soil, which is already known from previous studies. Furthermore, the comparison of the simulation results of the oedometer test with those of the triaxial test shows a different sensitivity with respect to the critical friction angle. Practical applicability and numerical stability are verified by numerical simulation of dynamic soil compaction with the vibratory compactor on a simplified, three-dimensional vibrator-soil interaction model. The displacement controlled simulations with the hypoplastic constitutive model can qualitatively represent the propagation of the pressure wave and the increasing range of compaction over time. The selected parameter studies (vibrator amplitude, initial soil density) are numerically stable up to 100 cycles., Thomas Wolf, BSc, Masterarbeit Universität Innsbruck 2022, Kurzfassung deutsch und englisch

This article presents a model for the permanent deformation (PD) behavior of unbound granular materials (UGMs) used in the base and subbase layers of pavement struc- tures. The model was developed based on multistage (MS) repeated load triaxial (RLT) test- ing. This is essentially a modified version of a previously developed model to better suit to field conditions in a simple and effective manner. The model was calibrated for eight com- monly used UGMs using MSRLT tests with a range of moisture contents. For validation, the calibrated models were used to predict the PD behavior of three of the UGMs in MSRLT tests with stress levels and moisture contents different from those used during the calibrations. This model showed better quality of fit when compared with another widely used PD model. The model was further tested successfully for field conditions by capturing the PD behavior of an instrumented pavement test section in a controlled environment using a heavy vehicle simu- lator (HVS) based accelerated pavement testing (APT). Inputs for calibrating the model were based on the readings from the instrumentations. The parameters of the model were adjusted to match the measured data with the predictions. Based on these results for various design conditions, some ranges of values of the material parameters of the model were suggested., Optimization of particle size distribution for unbound granular materials

Under hösten 2019 har Vattenfall Research & Development byggt en experimentell jordfyllningsdamm i Älvkarleby med dimensionerna 20x15x4 meter. Delar av experimentdammen är konventionellt konstruerade och har installerats med geoteknisk utrustning som utgörs av bland annat inklinometrar och portrycksgivare. Andra delar av experimentdammen har byggts in med defekter som ska representera åldersrelaterade skador eller utförandefel vid konstruktion. Experimentdammen ger möjlighet att under realistiska och kontrollerade förhållanden studera det mekaniska beteendet i samband med fyllning av vatten och vidare drift med hjälp av den geotekniska instrumenteringen samt med stöd av numerisk modellering. I detta examensarbete, som utgör en del av Luleå tekniska universitets forskningsprojekt mot experimentdammen, har experimentdammens beteende i form av deformationer och portryck studerats under uppfyllnad och drift fram till sommaren 2021. Detta har utförts genom simuleringar i det finita elementprogrammet PLAXIS 2D 2019 för en tvärsektion av experimentdammen i plant-deformationstillstånd. Mätpunkterna i modellen har baserats på faktisk placering av den geotekniska instrumenteringen. Den finita elementmodellen av experimentdammen har konstruerats och fyllts med vatten enligt dokumentation från fält. En flödes-deformationsanalys, med den konstitutiva modellen Hardening Soil och den hydrauliska modellen van Genuchten, har tillämpats för att modellera den simultana utvecklingen av portryck och deformationer under uppfyllnad. Materialparametervärden för den finita elementmodelleringen har erhållits från Vattenfall R&D, relevant litteratur och från fält- och laboratorieförsök. I fält har vattenvolymeterförsök utförts på tätkärnan och i laboratoriemiljö har modifierad proctorpackning, dränerade konventionella triaxialförsök, permeabilitetsförsök och övertryckskapillarimeterförsök utförts på tätkärnans material. Resultatet från övertryckskapillarimeterförsök har anpassats mot den h, During the autumn of 2019, Vattenfall Research & Development constructed an experimental embankment dam in Älvkarleby with the dimensions 20x15x4 metres. Parts of the experimental dam are conventionally constructed and have been equipped with geotechnical instrumentation which consist of, among other things, inclinometers and pore pressure transducers. Other parts of the experimental dam have built in defects to represent age-related damages or execution errors during construction. The experimental embankment dam provides the opportunity to, under realistic and controlled conditions, study the mechanical behaviour during filling of water and operation by means of the geotechnical instrumentation and the use of numerical modelling. In this master’s thesis, which forms part of Luleå University of Technology’s research project towards the experimental dam, the behaviour of the experimental dam in terms of deformations and pore pressures have been studied during filling and operation until the summer of 2021. This has been performed by simulations in the finite element program PLAXIS 2D 2019 for a cross section of the experimental dam under plane-strain conditions. Measuring points in the model have been based on the actual location of the geotechnical instrumentation. The finite element model of the experimental dam has been constructed and filled according to documentation from field. A fully-coupled flow deformation analysis, with the constitutive model Hardening Soil and hydraulic model van Genuchten, has been utilised to model the simultaneous development of pore pressure and deformations during filling. Values of material parameters for the finite element modelling have been received from Vattenfall R&D, relevant literature and from field- and laboratory tests. In the field, balloon tests have been performed on the core material. In laboratory environment, modified proctor compaction tests, drained conventional triaxial tests, permeability tests and pressure plate tes

Models that introduce rolling resistance at the contact are widely employed in simulations using the discrete element method (DEM) to indirectly represent particle shape effects. This approach offers substantial computational benefits at the price of increased calibration complexity. This work proposes a method to simplify calibration of rolling resistance. The key element is an empirical relation between a contact parameter (rolling friction) and a 3D grain shape descriptor (true sphericity). Values of true sphericity can be obtained by image analysis of the grains, either directly by 3D acquisition or by correlation with simpler-to-obtain 2D shape measures. Evaluation of rolling friction is thus made independent from that of other model parameters. As an extra benefit, the variability of grain shape in natural sands can be directly mapped into the discrete model. A mapping between rolling friction and true sphericity is calibrated using specimen-scale and grain scale results from two triaxial compression tests on Hostun sand and Caicos ooids. The mapping is validated using different triaxial tests from the same sands and from other reference sands (Ottawa, Ticino). In the case of Ticino grain-shape acquisition is made in 2D, using an ordinary table scanner. The results obtained support this direct calibration procedure., The support of EU through 645665 - GEO-RAMP - MSCA-RISE and of the Ministry of Economy of Spain through research Grant BIA2014-59467-R is gratefully acknowledged. Laboratoire 3SR is part of the LabEx Tec 21 (Investissements d’Avenir - grant agreement n_ANR-11-LABX-0030)., Peer Reviewed, Postprint (author's final draft)

Shallow and deep seated landslides in natural slopes are often induced by rainfall. The cause of the failure is usually considered to be due to the decrease in effective confining stress due to a suction loss by water infiltration. However, rainwater infiltrates into the slope surface resulting in a reduction of shear strength of soil and deformation and failure may occur even without significant change in effective stress. It is thus essential to examine the deformation and failure characteristics of the soil induced by wetting. This study investigates on the wetting-induced deformations under isotropic compression condition and triaxial shearing condition using a triaxial test apparatus for unsaturated soils. Two soil samples collected from the active landslide sites from Pakistan were used to examine both the shear strength and deformation behavior during water infiltration at different levels of deviatoric stress by keeping the deviatoric stress constant during the water infiltration stage. The test results showed that, even though the deviatoric stress is kept constant during water permeation at different stress levels, the distortional deformation was exhibited due to wetting by a significant amount for both samples. The effect of water infiltration on the deformation behavior of unsaturated soil regarding the change in the degree of saturation and void ratio was also observed. There was a decrease in the void ratio for both specimens during increasing the degree of saturation at different level of deviatoric stress ratio. Under higher deviator stress, more decrease in void ratio and an increase of the degree of saturation were observed. Therefore, it can be said that deformation of soil due to water infiltration is a critical phenomenon and it should be considered while analyzing the soil behavior due to water infiltration by rainfall or rise in groundwater level, even if the slope is not failed, significant deformations may hinder the performance of natural

The triaxial compressive response of bituminous mixes with volume fractions of aggregate in the range 52 to 85% was investigated over a wide range stresses and strain rates. The types of loadings considered include triaxial monotonic constant stress and constant applied strain rate, as well as creep recovery, continuous cyclic, and stress pulse train loadings. The mixes with a "fully dense" aggregate skeleton were found to dilate under all loading conditions and the creep response of the mixes was dependent on both the deviatoric and hydrostatic stresses. By contrast, recovery was found to occur under zero applied deviatoric stresses with the recovery rate only dependent on the "recoverable strain" and independent of any superimposed hydrostatic stress. Continuous and pulse loading cyclic stress-controlled tests showed that the response of the mixes was governed by the mean applied deviatoric stress in the continuous cyclic tests while strain recovery was important in the pulse loading tests. A phenomenological constitutive model was proposed to fit the measured triaxial response of the bituminous mixes and shown to capture the measurements over all the triaxial stress states and loading time histories investigated here. Furthermore, the model was extended to capture the temperature dependence of the mixtures which is governed by the temperature dependence of the bitumen binder. © 2010 ASCE.

Under hösten 2019 har Vattenfall Research & Development byggt en experimentell jordfyllningsdamm i Älvkarleby med dimensionerna 20x15x4 meter. Delar av experimentdammen är konventionellt konstruerade och har installerats med geoteknisk utrustning som utgörs av bland annat inklinometrar och portrycksgivare. Andra delar av experimentdammen har byggts in med defekter som ska representera åldersrelaterade skador eller utförandefel vid konstruktion. Experimentdammen ger möjlighet att under realistiska och kontrollerade förhållanden studera det mekaniska beteendet i samband med fyllning av vatten och vidare drift med hjälp av den geotekniska instrumenteringen samt med stöd av numerisk modellering. I detta examensarbete, som utgör en del av Luleå tekniska universitets forskningsprojekt mot experimentdammen, har experimentdammens beteende i form av deformationer och portryck studerats under uppfyllnad och drift fram till sommaren 2021. Detta har utförts genom simuleringar i det finita elementprogrammet PLAXIS 2D 2019 för en tvärsektion av experimentdammen i plant-deformationstillstånd. Mätpunkterna i modellen har baserats på faktisk placering av den geotekniska instrumenteringen. Den finita elementmodellen av experimentdammen har konstruerats och fyllts med vatten enligt dokumentation från fält. En flödes-deformationsanalys, med den konstitutiva modellen Hardening Soil och den hydrauliska modellen van Genuchten, har tillämpats för att modellera den simultana utvecklingen av portryck och deformationer under uppfyllnad. Materialparametervärden för den finita elementmodelleringen har erhållits från Vattenfall R&D, relevant litteratur och från fält- och laboratorieförsök. I fält har vattenvolymeterförsök utförts på tätkärnan och i laboratoriemiljö har modifierad proctorpackning, dränerade konventionella triaxialförsök, permeabilitetsförsök och övertryckskapillarimeterförsök utförts på tätkärnans material. Resultatet från övertryckskapillarimeterförsök har anpassats mot den h, During the autumn of 2019, Vattenfall Research & Development constructed an experimental embankment dam in Älvkarleby with the dimensions 20x15x4 metres. Parts of the experimental dam are conventionally constructed and have been equipped with geotechnical instrumentation which consist of, among other things, inclinometers and pore pressure transducers. Other parts of the experimental dam have built in defects to represent age-related damages or execution errors during construction. The experimental embankment dam provides the opportunity to, under realistic and controlled conditions, study the mechanical behaviour during filling of water and operation by means of the geotechnical instrumentation and the use of numerical modelling. In this master’s thesis, which forms part of Luleå University of Technology’s research project towards the experimental dam, the behaviour of the experimental dam in terms of deformations and pore pressures have been studied during filling and operation until the summer of 2021. This has been performed by simulations in the finite element program PLAXIS 2D 2019 for a cross section of the experimental dam under plane-strain conditions. Measuring points in the model have been based on the actual location of the geotechnical instrumentation. The finite element model of the experimental dam has been constructed and filled according to documentation from field. A fully-coupled flow deformation analysis, with the constitutive model Hardening Soil and hydraulic model van Genuchten, has been utilised to model the simultaneous development of pore pressure and deformations during filling. Values of material parameters for the finite element modelling have been received from Vattenfall R&D, relevant literature and from field- and laboratory tests. In the field, balloon tests have been performed on the core material. In laboratory environment, modified proctor compaction tests, drained conventional triaxial tests, permeability tests and pressure plate tes

This paper describes the geotechnical behavior of the Blue Marls from the Guadalquivir River Basin in Southern Spain, defined as high-plasticity clays that behave as a stiff, over- -consolidated clayey soil. These Blue Marls are, in general, classified as an inadequate material for reuse in various earthworks. In this study the comparison between the geotechnical properties of its natural and compacted remolded state, with and without additives, is studied based on different laboratory tests. A great variety of laboratory tests were performed, including triaxial tests under consolidated undrained conditions. Three types of samples were tested in triaxial tests to define different stress-strain behaviors: undisturbed and remolded samples of the in-situ clay material, as well as remolded clay samples mixed with lime. Lime stabilization is frequently used to improve the geotechnical properties of clayey soils for application in different earthworks. The back-analysis of the slope stability is performed for a comprehensive assessment of the condition of the slopes consisting of these remolded materials mixed with lime as well as without lime. The results of the retrospective analysis of man-made slopes permit an analysis of the operational geotechnical strength parameters necessary in the design of slopes as well as its comparison with the results of the triaxial consolidated undrained tests. The improvement of the strength parameters for the slope-stability analysis is confirmed under remolded conditions with and without the addition of the small amount of lime., Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

In this report, an experimental investigation of the influence of currents on submarine slope stability is presented for the Eastern Scheldt storm surge barrier case. Slope instabilities, including liquefaction failures, have been observed in the scour hole slopes near this barrier. The currents above the sloping bed are expected to initiate the liquefaction slope failures. The effects of the excess pore water pressure increase, that is generated by the currents, on the soil response are investigated by triaxial tests. Multiple excess pore water pressure rates are applied on a loose soil sample. The triaxial tests show that higher excess pore water pressure rates result in earlier developments of strains at lower stress ratios. This research is intended as a step towards a better understanding of the initiation mechanism of the liquefaction slope failures near the barrier.

Recycled granular materials such as Recycled Concrete Aggregate (RCA) and Recycled Crushed Masonry (RCM) are widely used in The Netherlands as base layers in asphalt pavements. The lack of natural resources and the growing amounts of demolition waste made that the Dutch industries in the early 1980s started to explore the possibilities to use construction debris in road construction. Recently, the application of recycled materials in pavement structures has also found traction in South Africa. Due to differences in pavement design, however, the mechanical and environmental exposure of these materials will be more severe than in the Netherlands. This results in different challenges with respect to (long term) performance and material durability. Understanding the potential durability issues and the way durability affects pavement performance is crucial to successfully implement these materials in South African pavements. This research, conducted at Stellenbosch University, South Africa, involves laboratory testing to investigate the performance and durability aspects of recycled aggregates. By means of triaxial testing before and after durability simulation, it is aimed to address the extent of potential material breakdown and the influence this has on performance. Tests are conducted on RCA, RCM, MG65 and MG30. The latter two refer to a mixture of RCA and RCM, with a mass percentage RCA of 65% and 35%, respectively. In addition to the recycled materials, a commonly used crushed rock of G2 quality is tested as well to serve as benchmark. Monotonic triaxial tests, to obtain the shear parameters, are performed on all materials except the pure RCM. Permanent deformation triaxial tests, to gain understanding of the long term response to cyclic loading, are performed on RCA and MG65. Specimens are tested under different confinement and deviator stress levels. For the durability simulation, the South African Durability Mill (DMI) is used. The DMI enables durability tes, Civil Engineering | Structural Engineering

In this report, an experimental investigation of the influence of currents on submarine slope stability is presented for the Eastern Scheldt storm surge barrier case. Slope instabilities, including liquefaction failures, have been observed in the scour hole slopes near this barrier. The currents above the sloping bed are expected to initiate the liquefaction slope failures. The effects of the excess pore water pressure increase, that is generated by the currents, on the soil response are investigated by triaxial tests. Multiple excess pore water pressure rates are applied on a loose soil sample. The triaxial tests show that higher excess pore water pressure rates result in earlier developments of strains at lower stress ratios. This research is intended as a step towards a better understanding of the initiation mechanism of the liquefaction slope failures near the barrier.

Recycled granular materials such as Recycled Concrete Aggregate (RCA) and Recycled Crushed Masonry (RCM) are widely used in The Netherlands as base layers in asphalt pavements. The lack of natural resources and the growing amounts of demolition waste made that the Dutch industries in the early 1980s started to explore the possibilities to use construction debris in road construction. Recently, the application of recycled materials in pavement structures has also found traction in South Africa. Due to differences in pavement design, however, the mechanical and environmental exposure of these materials will be more severe than in the Netherlands. This results in different challenges with respect to (long term) performance and material durability. Understanding the potential durability issues and the way durability affects pavement performance is crucial to successfully implement these materials in South African pavements. This research, conducted at Stellenbosch University, South Africa, involves laboratory testing to investigate the performance and durability aspects of recycled aggregates. By means of triaxial testing before and after durability simulation, it is aimed to address the extent of potential material breakdown and the influence this has on performance. Tests are conducted on RCA, RCM, MG65 and MG30. The latter two refer to a mixture of RCA and RCM, with a mass percentage RCA of 65% and 35%, respectively. In addition to the recycled materials, a commonly used crushed rock of G2 quality is tested as well to serve as benchmark. Monotonic triaxial tests, to obtain the shear parameters, are performed on all materials except the pure RCM. Permanent deformation triaxial tests, to gain understanding of the long term response to cyclic loading, are performed on RCA and MG65. Specimens are tested under different confinement and deviator stress levels. For the durability simulation, the South African Durability Mill (DMI) is used. The DMI enables durability tes, Civil Engineering | Structural Engineering

An exponential equation is introduced to predict the nonlinear variation of shear strength with matric suction for unsaturated soils. The proposed equation involves three constant parameters, two of which are effective shear strength parameters (i.e., ′ and c′). The third parameter is the maximum capillary cohesion, c″max, which is the maximum possible increase in shear strength due to matric suction. A procedure for the determination of c″max from the soil-water characteristic curve (SWCC) is devised. The proposed equation is validated through a series of constant-suction consolidated drained triaxial tests conducted on specimens reconstituted by isotropic consolidation from the slurry state. In addition, the validity of the equation is investigated by applying it to the test results of five other soils that were available in the literature for the low-suction range (i.e., up to 1,500 kPa). A comparative study on the prediction of shear strength was carried out between the proposed equation and six other shear strength equations found in the literature. The results show that the proposed equation provides reliable predictions of the shear strength of unsaturated soils when the shear strength converges to an asymptotic value at the residual water content.

A new procedure for the preparation of low-plasticity silt specimens that are isotropically reconstituted from slurry is developed for use in both saturated and unsaturated soil testing. Spatial variations of the water content and grain size distribution were examined to confirm the uniformity of the specimens (regarding void radio and segregation). The new preparation method results in a homogeneous specimen, which has a simple stress history. The repeatability of the proposed method in preparing identical specimens was verified for both saturated and unsaturated soil testing. The strength and volumetric behavior of specimens prepared by the introduced method are compared with those of moist-tamped compacted specimens and one-dimensionally reconstituted slurry specimens by performing consolidated drained triaxial tests. The microstructure of the specimens prepared with different methods was examined using Scanning Electron Microscopy and Mercury Intrusion Porosimetry. The test results indicate that silt specimens could exhibit either dilative or contractive behavior at normal consolidated conditions, depending on the microstructure.

A proper representation and understanding of the mechanical response of the sediment is a prerequisite for successful future gas production from gas hydrate bearing sediments, in view of the geotechnical issues encountered in recent field trials. Recent investigations have indicated that the increase of sediment strength, due to hydrate existence, is of frictional nature and associated with changes in the kinematic response, and not necessarily due to cementation. Following this idea, this paper presents a non-cohesive micro model for methane-hydrate bearing sediments, where the hydrate is represented as solid particles precisely positioned between sand particles, contributing to the skeleton response even for small strains. Analytical expressions relating between the geometry, interparticle properties, and the mechanical response of the hydrate bearing sediment are developed in the paper. Global stress strain response is evaluated under simulated triaxial loading, exhibiting stiffer, stronger and more dilative response compared to pure sand samples. It is shown that a trade-off exists between the particle size and the inter-particle friction, which can be unifed using a participation factor related to the pore size distribution. As observed in recent experimental investigations, the suggested model results in a cohesionless response when analyzed using Rowe's stress dilatancy theory.

A large triaxial testing cell (for specimens of 30 cm diameter) has been recently commissioned for the laboratory of geotechnical engineering. The student will help in the set-up and proofing of this unique apparatus and will perform triaxial test in gravels with and without fines, eventually reinforced with geogrids.

The construction and conservation of new roads requires many natural and economic resources, so the recycling is one of the most used techniques currently, so it is important to understand the mechanical properties of the type of application to be used. The present paper focuses on the evaluation of the mechanical properties of a stabilized base with foamed asphalt (cold recycled). The study analyzed the influence of two design variables such as the type of active filler (lime and cement) and the content of foamed asphalt (2.2 to 2.4%). The parameters used in the evaluation were indirect tensile strength, friction angle and cohesion (triaxial test) and resilient modulus (MR). The results indicate that the addition of lime improves the mechanical properties of the stabilized base. Regarding mechanical parameters, it was observed that the stabilized mixtures with foamed asphalt show an increase in their resistance compared to a granular base, being the loss of cohesion the failure mode of this type of stabilization., La construcción y conservación de nuevas carreteras requiere de muchos recursos tanto naturales como económicos, ya que el reciclado de materiales es una de las técnicas más utilizadas en la actualidad, por lo cual es importante conocer las propiedades mecánicas del tipo de aplicación a utilizar.El presente trabajo se enfoca en la evaluación de las propiedades mecánicas de una base estabilizada con asfalto espumado (reciclado en frio). El estudio analizó la influencia de dos variables de diseño como son el tipo de filler activo (cal y cemento portland) y el contenido de asfalto espumado (2.2 a 2.4%). Los parámetros utilizados en la evaluación fueron la resistencia a la tensión indirecta, el ángulo de fricción interna y cohesión (ensayo triaxial) y el módulo resiliente.Los resultados muestran que la inclusión de cal mejora las propiedades mecánicas de la base estabilizada. En lo referente a los parámetros mecánicos se observó que las mezclas estabilizadas con asfalto espumado presentan un aumento de su resistencia en comparación con una base granular tradicional, siendo la pérdida de cohesión el modo de falla de este tipo de estabilización

The construction and conservation of new roads requires many natural and economic resources, so the recycling is one of the most used techniques currently, so it is important to understand the mechanical properties of the type of application to be used. The present paper focuses on the evaluation of the mechanical properties of a stabilized base with foamed asphalt (cold recycled). The study analyzed the influence of two design variables such as the type of active filler (lime and cement) and the content of foamed asphalt (2.2 to 2.4%). The parameters used in the evaluation were indirect tensile strength, friction angle and cohesion (triaxial test) and resilient modulus (MR). The results indicate that the addition of lime improves the mechanical properties of the stabilized base. Regarding mechanical parameters, it was observed that the stabilized mixtures with foamed asphalt show an increase in their resistance compared to a granular base, being the loss of cohesion the failure mode of this type of stabilization., La construcción y conservación de nuevas carreteras requiere de muchos recursos tanto naturales como económicos, ya que el reciclado de materiales es una de las técnicas más utilizadas en la actualidad, por lo cual es importante conocer las propiedades mecánicas del tipo de aplicación a utilizar.El presente trabajo se enfoca en la evaluación de las propiedades mecánicas de una base estabilizada con asfalto espumado (reciclado en frio). El estudio analizó la influencia de dos variables de diseño como son el tipo de filler activo (cal y cemento portland) y el contenido de asfalto espumado (2.2 a 2.4%). Los parámetros utilizados en la evaluación fueron la resistencia a la tensión indirecta, el ángulo de fricción interna y cohesión (ensayo triaxial) y el módulo resiliente.Los resultados muestran que la inclusión de cal mejora las propiedades mecánicas de la base estabilizada. En lo referente a los parámetros mecánicos se observó que las mezclas estabilizadas con asfalto espumado presentan un aumento de su resistencia en comparación con una base granular tradicional, siendo la pérdida de cohesión el modo de falla de este tipo de estabilización

Coral gravel soils are composite soils comprised of large fragments of finger coral and fine particles from silt matrixes. When the amount of coral fragments is small, the mechanical behavior of the coral gravel soil is mainly governed by the silt matrixes, and when the amount of coral fragments is large, the mechanical behavior is mainly governed by the coral fragments. Undisturbed samples, called high-quality samples in the present study, were collected at large-scale coastal construction sites in Okinawa Prefecture and Kagoshima Prefecture, Japan. A series of triaxial CD-tests was conducted in the laboratory to evaluate the mechanical characteristics of coral gravel soils. The test results were examined from various viewpoints to find a common governing parameter for the mechanical behavior of coral gravel soils. It was anticipated that it would be difficult to interpret the mechanical behavior of the high-quality samples in a uniform manner because undisturbed coral gravel soils, in the form of natural sediments, are generally very heterogeneous. To provide a reference for the parametric interpretation of the test results showing the remarkable features of coral gravel soils, such as interlocking and particle crushing, the test data newly obtained for the high-quality samples were compared to the previous test results obtained for reconstituted mixtures having various volumetric percentages of coral fragments. It was found that an intergranular void ratio corresponding to 0.075 mm, in which particles finer than a grain size of 0.075 mm (i.e., particles of clay and silt) are regarded as voids, can be employed as a useful parameter in evaluating the shear strength of both reconstituted and undisturbed coral gravel soil samples.

Proper choice of a constitutive model is an essential part of any successful application of numerical methods in geotechnical engineering. In most cases, attention is paid to the soil constitutive model. For structural elements, such as tunnel linings, retaining structures etc. elastic constitutive models are often used. These material models however do not involve many aspects of a real structural behavior such as limited tensile and compressive strength, strain softening and time dependent behavior during service life of a construction. In the proposed paper, an application of the novel constitutive model for shotcrete (Schädlich, Schweiger, 2014) is presented. The paper is focused at the process of determination of input parameters values of this model based on performed laboratory test. Section of the primary collector network in Brno was chosen for the purpose of obtaining shotcrete lining samples.

Proper choice of a constitutive model is an essential part of any successful application of numerical methods in geotechnical engineering. In most cases, attention is paid to the soil constitutive model. For structural elements, such as tunnel linings, retaining structures etc. elastic constitutive models are often used. These material models however do not involve many aspects of a real structural behavior such as limited tensile and compressive strength, strain softening and time dependent behavior during service life of a construction. In the proposed paper, an application of the novel constitutive model for shotcrete (Schädlich, Schweiger, 2014) is presented. The paper is focused at the process of determination of input parameters values of this model based on performed laboratory test. Section of the primary collector network in Brno was chosen for the purpose of obtaining shotcrete lining samples.

Proper choice of a constitutive model is an essential part of any successful application of numerical methods in geotechnical engineering. In most cases, attention is paid to the soil constitutive model. For structural elements, such as tunnel linings, retaining structures etc. elastic constitutive models are often used. These material models however do not involve many aspects of a real structural behavior such as limited tensile and compressive strength, strain softening and time dependent behavior during service life of a construction. In the proposed paper, an application of the novel constitutive model for shotcrete (Schädlich, Schweiger, 2014) is presented. The paper is focused at the process of determination of input parameters values of this model based on performed laboratory test. Section of the primary collector network in Brno was chosen for the purpose of obtaining shotcrete lining samples.

Coral gravel soils are composite soils comprised of large fragments of finger coral and fine particles from silt matrixes. When the amount of coral fragments is small, the mechanical behavior of the coral gravel soil is mainly governed by the silt matrixes, and when the amount of coral fragments is large, the mechanical behavior is mainly governed by the coral fragments. Undisturbed samples, called high-quality samples in the present study, were collected at large-scale coastal construction sites in Okinawa Prefecture and Kagoshima Prefecture, Japan. A series of triaxial CD-tests was conducted in the laboratory to evaluate the mechanical characteristics of coral gravel soils. The test results were examined from various viewpoints to find a common governing parameter for the mechanical behavior of coral gravel soils. It was anticipated that it would be difficult to interpret the mechanical behavior of the high-quality samples in a uniform manner because undisturbed coral gravel soils, in the form of natural sediments, are generally very heterogeneous. To provide a reference for the parametric interpretation of the test results showing the remarkable features of coral gravel soils, such as interlocking and particle crushing, the test data newly obtained for the high-quality samples were compared to the previous test results obtained for reconstituted mixtures having various volumetric percentages of coral fragments. It was found that an intergranular void ratio corresponding to 0.075 mm, in which particles finer than a grain size of 0.075 mm (i.e., particles of clay and silt) are regarded as voids, can be employed as a useful parameter in evaluating the shear strength of both reconstituted and undisturbed coral gravel soil samples.

A novel procedure was developed to measure the total volume change of the unsaturated soils in triaxial testing. The principle of the proposed method was based on cell fluid volume measurements corrected by the assumption of viscoelastic behavior for the triaxial setup. Calibration and parameter determination procedures of the model are devised, and the presented model is implemented into a MATLAB code. The proposed method was validated through a series of consolidated drained triaxial tests on saturated specimens, by comparing the changes in volume measurement of proposed method and conventional measurement (pore fluid). The accuracy in volume measurement during consolidation and shear stages of these tests was between 0.09 and 0.32 cm3, which is on par with or better than more complex and expensive alternatives found in the literature. Repeatability of the proposed technique in measurement of the volume change was also investigated through a series of suction controlled unsaturated soil tests.

The triaxial test measures the mix stability in the form of shear strength and gave better information for the prediction of field performance. The stresses acting on the laboratory specimen during the test simulate the state of stresses existing in the pavement. The Stone Matrix Asphalt mixtures (SMA)were investigated using triaxial shear strength testing at 50.8 mm/min ram rate loading at 60°C to investigate the effect of additive, coir fibre on the strength properties by varying  the percentages of fibre. SMA without fibre  is taken as the control mixture. The test was conducted at 0, 50, 75 and 100kPa confinements. The Mohr-Coulomb failure theory was used to analyze the test data and the analysis shows that the SMA stabilized mixtures had highest cohesion and shear strength as compared to the control mixture, but almost similar angle of internal friction value. The higher values of cohesion and shear strength can be associated to a fibre content of 0.3% and the percentage increase in cohesion is about 53% with respect to the control mixture. This shows that the mixture has greater resistance to shearing stresses than the control mixture. There is a trend that the strain at failure increases with increasing confinement pressure, indicating their stress dependent behaviour. The stress-strain curves indicate that the peak stress developed and the time of its occurrence is higher in stabilized mixtures when compared to those of the control mixture. For stabilized mixtures, it is observed that the shape change of the stress-strain curves is more gradual with increase in fibre content and brittle type failure does not seem to occur as in the case of control mixture.&nbsp

The triaxial test measures the mix stability in the form of shear strength and gave better information for the prediction of field performance. The stresses acting on the laboratory specimen during the test simulate the state of stresses existing in the pavement. The Stone Matrix Asphalt mixtures (SMA)were investigated using triaxial shear strength testing at 50.8 mm/min ram rate loading at 60°C to investigate the effect of additive, coir fibre on the strength properties by varying  the percentages of fibre. SMA without fibre  is taken as the control mixture. The test was conducted at 0, 50, 75 and 100kPa confinements. The Mohr-Coulomb failure theory was used to analyze the test data and the analysis shows that the SMA stabilized mixtures had highest cohesion and shear strength as compared to the control mixture, but almost similar angle of internal friction value. The higher values of cohesion and shear strength can be associated to a fibre content of 0.3% and the percentage increase in cohesion is about 53% with respect to the control mixture. This shows that the mixture has greater resistance to shearing stresses than the control mixture. There is a trend that the strain at failure increases with increasing confinement pressure, indicating their stress dependent behaviour. The stress-strain curves indicate that the peak stress developed and the time of its occurrence is higher in stabilized mixtures when compared to those of the control mixture. For stabilized mixtures, it is observed that the shape change of the stress-strain curves is more gradual with increase in fibre content and brittle type failure does not seem to occur as in the case of control mixture.&nbsp

The triaxial test measures the mix stability in the form of shear strength and gave better information for the prediction of field performance. The stresses acting on the laboratory specimen during the test simulate the state of stresses existing in the pavement. The Stone Matrix Asphalt mixtures (SMA)were investigated using triaxial shear strength testing at 50.8 mm/min ram rate loading at 60°C to investigate the effect of additive, coir fibre on the strength properties by varying  the percentages of fibre. SMA without fibre  is taken as the control mixture. The test was conducted at 0, 50, 75 and 100kPa confinements. The Mohr-Coulomb failure theory was used to analyze the test data and the analysis shows that the SMA stabilized mixtures had highest cohesion and shear strength as compared to the control mixture, but almost similar angle of internal friction value. The higher values of cohesion and shear strength can be associated to a fibre content of 0.3% and the percentage increase in cohesion is about 53% with respect to the control mixture. This shows that the mixture has greater resistance to shearing stresses than the control mixture. There is a trend that the strain at failure increases with increasing confinement pressure, indicating their stress dependent behaviour. The stress-strain curves indicate that the peak stress developed and the time of its occurrence is higher in stabilized mixtures when compared to those of the control mixture. For stabilized mixtures, it is observed that the shape change of the stress-strain curves is more gradual with increase in fibre content and brittle type failure does not seem to occur as in the case of control mixture.&nbsp

The triaxial test measures the mix stability in the form of shear strength and gave better information for the prediction of field performance. The stresses acting on the laboratory specimen during the test simulate the state of stresses existing in the pavement. The Stone Matrix Asphalt mixtures (SMA)were investigated using triaxial shear strength testing at 50.8 mm/min ram rate loading at 60°C to investigate the effect of additive, coir fibre on the strength properties by varying  the percentages of fibre. SMA without fibre  is taken as the control mixture. The test was conducted at 0, 50, 75 and 100kPa confinements. The Mohr-Coulomb failure theory was used to analyze the test data and the analysis shows that the SMA stabilized mixtures had highest cohesion and shear strength as compared to the control mixture, but almost similar angle of internal friction value. The higher values of cohesion and shear strength can be associated to a fibre content of 0.3% and the percentage increase in cohesion is about 53% with respect to the control mixture. This shows that the mixture has greater resistance to shearing stresses than the control mixture. There is a trend that the strain at failure increases with increasing confinement pressure, indicating their stress dependent behaviour. The stress-strain curves indicate that the peak stress developed and the time of its occurrence is higher in stabilized mixtures when compared to those of the control mixture. For stabilized mixtures, it is observed that the shape change of the stress-strain curves is more gradual with increase in fibre content and brittle type failure does not seem to occur as in the case of control mixture.&nbsp

Studying the wetting-induced softening behavior of unsaturated soils is important for understanding rain-induced slope failures in unsaturated soils. However, experimental studies on expansive soils are limited. This study investigates the wetting-induced softening characteristics of an unsaturated expansive clay via suction-controlled triaxial tests on recompacted and natural specimens. It was found that the wetting-induced swelling of the soil included a significant component of plastic strain and its magnitude decreased with the net confining stress. When a soil specimen was subjected to wetting at a constant deviator stress, a threshold value of soil suction was identified after which the axial strain increased greatly. This value tended to increase with the applied net stress ratio. After the threshold suction, the wetting process for recompacted specimens could be divided into a yielding process associated with volumetric strain hardening/softening and a failure process in which the volumetric behavior depended on the applied net stress ratio. The natural specimens exhibited a brittle failure like a heavily overconsolidated soil during wetting at a constant deviator stress and continuous volumetric dilation occurred after the threshold suction. The wetting-induced softening soil behavior revealed from the present study could interpret the rain-induced progressive slope failure in unsaturated expansive soils.

Studying the wetting-induced softening behavior of unsaturated soils is important for understanding rain-induced slope failures in unsaturated soils. However, experimental studies on expansive soils are limited. This study investigates the wetting-induced softening characteristics of an unsaturated expansive clay via suction-controlled triaxial tests on recompacted and natural specimens. It was found that the wetting-induced swelling of the soil included a significant component of plastic strain and its magnitude decreased with the net confining stress. When a soil specimen was subjected to wetting at a constant deviator stress, a threshold value of soil suction was identified after which the axial strain increased greatly. This value tended to increase with the applied net stress ratio. After the threshold suction, the wetting process for recompacted specimens could be divided into a yielding process associated with volumetric strain hardening/softening and a failure process in which the volumetric behavior depended on the applied net stress ratio. The natural specimens exhibited a brittle failure like a heavily overconsolidated soil during wetting at a constant deviator stress and continuous volumetric dilation occurred after the threshold suction. The wetting-induced softening soil behavior revealed from the present study could interpret the rain-induced progressive slope failure in unsaturated expansive soils.

By signing the Valletta Treaty, several countries have obliged themselves to save archaeological heritage sites and fund relevant research. UNDERSTRESS is a proposal for funding which does research and provides data to predict damage done to such archaeological site by construction of linear infrastructure. As a preliminary study this BSc thesis is carried out in the framework of UNDERSTRESS. Although research has been done on archaeological artefacts embedded in sand, charred organic seeds have not been investigated thoroughly yet. The sand, which comes from a depot near Dronten in the Netherlands, has been used because multiple archaeological artefacts have been found in that sand layer. As analogue for the charred organic seeds coco pops, the cereal, have been used. The characteristics of the sand as well as of the coco pops have been investigated. A falling height of fifty centimetres has proven to create a reproducible density. To test the damage to the coco pops samples have been triaxial tested with a vacuum pressure applied of 80 kPA. This vacuum pressure create an effective confining pressure of 80 kPA as well. With the falling height and the confining pressure, a sample configuration in which two layers of coco pops are placed, the damage to those coco pops is zero when applied to a strain of five millimetres. The damage is made visible by using 3D visualising software called Avizo. The grain have not been damage during that test and they have not reallocated as well. For another configuration the coco pops did not react the same. The entire sample was filled with coco pops and sand as supporting material and this time the strain was 15 millimetres. Three scans made at three different times during the loading show that the coco pops are not damaged until after the sample has reached its maximum stress. All the damage to the coco pops as well as the reallocation of the coco pops happens between the peak stress and the unloading. At the slice where the radia, Geo-Engineering, Geoscience & Engineering, Civil Engineering and Geosciences

Luxembourg is geologically divided into two parts: Oesling in the North and Gutland in the Middle and South. Oesling is part of the Ardennes plateau. Gutland was formed in the Triassic and Jurassic ages and is much younger than Oesling. It consists mainly of sedimentary rocks. Luxembourg has a variety of interesting, weak or problematic soils, such as the swelling gypsum layers, the layered schists of Wiltz and especially the weak Keuper-Rhaetian-clay. The Rhaetian clay layer is mostly rather thin and is found at a relatively constant altitude and the band where it comes to the surface is identified by the varying erosion erratically found throughout Gutland. Approximately two third of all landslides are found along this line. Hence it was decided to investigate the Rhaetian clay in the geotechnical laboratory of the University of Luxembourg. Samples were taken from a pit at Rue de Mühlenbach on the north side of the city of Luxembourg and from a sliding slope of a building pit in Schutrange. The friction angle was found to be phi = 8° at Mühlenbach and phi = 13° at Schuttrange, which are both record low friction angles, which explains the high number of landslides in Luxembourg.

Luxembourg is geologically divided into two parts: Oesling in the North and Gut-land in the Middle and South. Oesling is part of the Ardennes plateau. Gutland was formed in the Triassic and Jurassic ages and is much younger than Oesling. It consists mainly of sedimentary rocks. Luxembourg has a variety of interesting, weak or problematic soils, such as the swelling gypsum layers, the layered schists of Wiltz and especially the weak Keu-per-Rhaetian-clay. The Rhaetian clay layer is mostly rather thin and is found at a relatively constant altitude and the band where it comes to the surface is identified by the varying erosion erratically found throughout Gutland. Approximately two third of all landslides are found along this line. Hence it was decided to investigate the Rhaetian clay in the geotechnical laboratory of the University of Luxembourg. Samples were taken from a pit at Rue de Mühlenbach on the north side of the city of Luxembourg and from a sliding slope of a building pit in Schutrange. The friction angle was found to be 8° at Mühlenbach and 3° at Schuttrange, which are both record low friction angles, which explains the high number of landslides in Luxembourg.

Luxembourg is geologically divided into two parts: Oesling in the North and Gutland in the Middle and South. Oesling is part of the Ardennes plateau. Gutland was formed in the Triassic and Jurassic ages and is much younger than Oesling. It consists mainly of sedimentary rocks. Luxembourg has a variety of interesting, weak or problematic soils, such as the swelling gypsum layers, the layered schists of Wiltz and especially the weak Keuper-Rhaetian-clay. The Rhaetian clay layer is mostly rather thin and is found at a relatively constant altitude and the band where it comes to the surface is identified by the varying erosion erratically found throughout Gutland. Approximately two third of all landslides are found along this line. Hence it was decided to investigate the Rhaetian clay in the geotechnical laboratory of the University of Luxembourg. Samples were taken from a pit at Rue de Mühlenbach on the north side of the city of Luxembourg and from a sliding slope of a building pit in Schutrange. The friction angle was found to be phi = 8° at Mühlenbach and phi = 13° at Schuttrange, which are both record low friction angles, which explains the high number of landslides in Luxembourg.

Luxembourg is geologically divided into two parts: Oesling in the North and Gut-land in the Middle and South. Oesling is part of the Ardennes plateau. Gutland was formed in the Triassic and Jurassic ages and is much younger than Oesling. It consists mainly of sedimentary rocks. Luxembourg has a variety of interesting, weak or problematic soils, such as the swelling gypsum layers, the layered schists of Wiltz and especially the weak Keu-per-Rhaetian-clay. The Rhaetian clay layer is mostly rather thin and is found at a relatively constant altitude and the band where it comes to the surface is identified by the varying erosion erratically found throughout Gutland. Approximately two third of all landslides are found along this line. Hence it was decided to investigate the Rhaetian clay in the geotechnical laboratory of the University of Luxembourg. Samples were taken from a pit at Rue de Mühlenbach on the north side of the city of Luxembourg and from a sliding slope of a building pit in Schutrange. The friction angle was found to be 8° at Mühlenbach and 3° at Schuttrange, which are both record low friction angles, which explains the high number of landslides in Luxembourg.

Studying the wetting-induced softening behavior of unsaturated soils is important for understanding rain-induced slope failures in unsaturated soils. However, experimental studies on expansive soils are limited. This study investigates the wetting-induced softening characteristics of an unsaturated expansive clay via suction-controlled triaxial tests on recompacted and natural specimens. It was found that the wetting-induced swelling of the soil included a significant component of plastic strain and its magnitude decreased with the net confining stress. When a soil specimen was subjected to wetting at a constant deviator stress, a threshold value of soil suction was identified after which the axial strain increased greatly. This value tended to increase with the applied net stress ratio. After the threshold suction, the wetting process for recompacted specimens could be divided into a yielding process associated with volumetric strain hardening/softening and a failure process in which the volumetric behavior depended on the applied net stress ratio. The natural specimens exhibited a brittle failure like a heavily overconsolidated soil during wetting at a constant deviator stress and continuous volumetric dilation occurred after the threshold suction. The wetting-induced softening soil behavior revealed from the present study could interpret the rain-induced progressive slope failure in unsaturated expansive soils.

By signing the Valletta Treaty, several countries have obliged themselves to save archaeological heritage sites and fund relevant research. UNDERSTRESS is a proposal for funding which does research and provides data to predict damage done to such archaeological site by construction of linear infrastructure. As a preliminary study this BSc thesis is carried out in the framework of UNDERSTRESS. Although research has been done on archaeological artefacts embedded in sand, charred organic seeds have not been investigated thoroughly yet. The sand, which comes from a depot near Dronten in the Netherlands, has been used because multiple archaeological artefacts have been found in that sand layer. As analogue for the charred organic seeds coco pops, the cereal, have been used. The characteristics of the sand as well as of the coco pops have been investigated. A falling height of fifty centimetres has proven to create a reproducible density. To test the damage to the coco pops samples have been triaxial tested with a vacuum pressure applied of 80 kPA. This vacuum pressure create an effective confining pressure of 80 kPA as well. With the falling height and the confining pressure, a sample configuration in which two layers of coco pops are placed, the damage to those coco pops is zero when applied to a strain of five millimetres. The damage is made visible by using 3D visualising software called Avizo. The grain have not been damage during that test and they have not reallocated as well. For another configuration the coco pops did not react the same. The entire sample was filled with coco pops and sand as supporting material and this time the strain was 15 millimetres. Three scans made at three different times during the loading show that the coco pops are not damaged until after the sample has reached its maximum stress. All the damage to the coco pops as well as the reallocation of the coco pops happens between the peak stress and the unloading. At the slice where the radia, Geo-Engineering, Geoscience & Engineering, Civil Engineering and Geosciences

This paper presents the development of a new high-pressure triaxial apparatus specifically prepared for inducing and tracking the degradation of clayey rocks. Total suction—used to induce the hydraulic degradation—is applied with vapor transfer technique by controlling the relative humidity of air in contact with the material. The evolution of the degradation process along different hydro-mechanical stress paths is continuously tracked with bender elements, as well as with air or water permeability measurements on partially saturated or saturated states, respectively. Relevant test results on a low porosity clayey rock (Lilla claystone, Spain) are presented to evaluate the main capabilities of the new equipment. The results bring up the high sensitivity to water of the material, which is evidenced by the important reduction of shear wave velocity induced on first wetting and drying at low confining stress, as well as by the significant increase in the air permeability of the degraded material (around four orders of magnitude larger than the intact material). Test results also showed clear differences in the volume change and shear strength behavior of undisturbed, saturated, and degraded samples, highlighting the relevance of degradation on macroscopic behavioral features., Peer Reviewed, Postprint (published version)

Most soils that concern geotechnical engineering are in the state of partial water saturation. Current practice tries to predict engineering properties of cohesionless soils using data from tests on saturated specimens, regardless of the saturation in the field. Due to complexity of test setups and high technical requirements, unsaturated soil tests are not among the common equipment of soil mechanics laboratory. One of these problems is the existence of suction, which is a function of water content and affects the strength behavior of unsaturated soils. Procedures to keep the water content of the partially saturated specimens constant and homogeneous in conventional soil tests are not well-established. The exception to this is unsaturated test setups, which are costly, complicated and found only in research institutions, hence prohibiting the industry from keeping up with the developments in this field. This study explores simple modifications to conventional methodologies of triaxial and direct shear tests, with the ultimate aim of preventing temporal and spatial variability of specimen water content throughout test duration. For different modifications, specimens of each test are dissected at the end of the test, and water content profiles of the specimens are obtained.

In order to increase the applied efficiency of crushed rock base (CRB) in pavement structure design for Western Australia roads, the material modelling based on the experimental results was investigated, and the disturbed state concept (DSC) was used to predict the resilient modulus of CRB because of its simplicity and strong ability in capturing the elastic and inelastic responses of materials to loads. The actual deformation of DSC, at any loading state, was determined from its assumed relative intact (RI) state. The DSC equation of CRB was constructed by using a set of experimental results of resilient modulus tests, and an idealized material model, namely the linear elastic model, of relative intact (RI) part was considered. Analysis results reveal that the resilient modulus-applied stress relationships back-predicted by using the DSC modelling are consistent with the experimental results, so, the DSC equation is suited for predicting the resilient modulus of CRB specimen. However, the model and the equation coming from the test results are conducted in accordance with the Austroads standard, so further investigation and validation with respect to the field behaviours of pavement structure should be performed.

A modified failure criterion is proposed to determine the strength of transversely isotropic rocks. Mechanical properties of some metamorphic and sedimentary rocks including gneiss, slate, marble, schist, shale, sandstone and limestone, which show transversely isotropic behavior, were taken into consideration. Afterward, introduced triaxial rock strength criterion was modified for transversely isotropic rocks. Through modification process an index was obtained that can be considered as a strength reduction parameter due to rock strength anisotropy. Comparison of the parameter with previous anisotropy indexes in literature showed reasonable results for the studied rock samples. The modified criterion was compared to modified Hoek-Brown and Ramamurthy criteria for different transversely isotropic rocks. It can be concluded that the modified failure criterion proposed in this study can be used for predicting the strength of transversely isotropic rocks.

(1) Försöksutrustningar för bestämning av dränerad skjuvhållfasthet; (2) Allmänt om dränerad hållfasthet och olika försök; (3) Utförda försök

(1) Försöksutrustningar för bestämning av dränerad skjuvhållfasthet; (2) Allmänt om dränerad hållfasthet och olika försök; (3) Utförda försök