Roads and highways in cold regions are negatively affected by settlement of embankments in areas of degraded or degrading permafrost, particularly in areas with mean annual temperatures close to 0°C where permafrost is locally discontinuous. Climate warming and human activities can lead to increases in the temperature of permafrost and to thawing. In regions of discontinuous permafrost, thawing may produce thickening of the active layer, large settlements and non-recoverable shear deformations. These can cause potentially dangerous trafficability issues. The research program involved a test site on Provincial Road PR391, about 18 km northwest of Thompson, Manitoba. The foundation material of PR391 is currently classified as “degraded (thawed) permafrost”. The purpose of this research was to investigate and understand the performance of highway embankments on thawed permafrost. The research involved field instrumentation and data collection, laboratory testing, thermal modelling and frost heave predictions. The results of the field instrumentation and data collection show net heat flow into the ground, as well as development of cyclic seasonal gradients of total head. This is believed to be a significant original contribution to understanding the effects of climate change on highway infrastructure. The results also show that displacements observed at the PR391 embankment are a combination of consolidation and shearing strain of the foundation material. Most studies of embankments concentrate on vertical settlements. This research shows that horizontal movements are also present, a contribution that helps explain the mechanism of lateral spreading. The results of the laboratory testing show that the mechanical and shearing properties of the soil collected from the PR391 embankment are not significantly affected by differences in temperature once water in the soil has actually thawed. The results of the thermal modelling show reasonable trends in simulated ground temperatures compared with the data obtained from the thermistors underneath the embankment. The frost heave prediction of PR391 shows that in situ frost heave characteristics can be estimated by applying the Segregation Potential (SP) frost heave method in field conditions. This provides a valuable field study to the limited number of such studies of Segregation Potential, which are normally done under laboratory conditions.

There is a growing need to better understand the relationship between time, strain rate, and temperature on the load-deformation behaviour of clay soils in engineering applications. These applications may include: infrastructure constructed in northern regions where climate change is a growing concern; disposal of nuclear waste; and, industrial structures, such as furnaces, foundries, and refrigeration plants. Temperature variations may induce changes in internal pressure in the soil, swelling and shrinkage, and affect the mechanical properties of the soil. This thesis presents thermal numerical modeling for two instrumented field sites in northern Manitoba. Thermal conductivity testing on samples from these sites and field data are used to calibrate these thermal numerical models. Various boundary conditions are examined. The capabilities of the models are evaluated to determine if the models adequately simulate and predict changes in temperature in geotechnical structures. A discussion is presented on the strengths and weaknesses in the models and the predictive capabilities of the models. The thesis then shifts into understanding the concepts of thermoplasticity and viscoplasticity and the mathematics relating these concepts. Mathematical models that describe these concepts are examined and compared with traditional soil mechanics approaches. The concepts of thermoplasticity and viscoplasticity are combined in an encompassing elastic thermo-viscoplastic (ETVP) model using a semi-empirical framework. A sensitivity analysis is used to evaluate quantitatively the response of the model. The model is then validated qualitatively against published laboratory data. Applications of the ETVP model are discussed.

Roads and highways in cold regions are negatively affected by settlement of embankments in areas of degraded or degrading permafrost, particularly in areas with mean annual temperatures close to 0°C where permafrost is locally discontinuous. Climate warming and human activities can lead to increases in the temperature of permafrost and to thawing. In regions of discontinuous permafrost, thawing may produce thickening of the active layer, large settlements and non-recoverable shear deformations. These can cause potentially dangerous trafficability issues. The research program involved a test site on Provincial Road PR391, about 18 km northwest of Thompson, Manitoba. The foundation material of PR391 is currently classified as “degraded (thawed) permafrost”. The purpose of this research was to investigate and understand the performance of highway embankments on thawed permafrost. The research involved field instrumentation and data collection, laboratory testing, thermal modelling and frost heave predictions. The results of the field instrumentation and data collection show net heat flow into the ground, as well as development of cyclic seasonal gradients of total head. This is believed to be a significant original contribution to understanding the effects of climate change on highway infrastructure. The results also show that displacements observed at the PR391 embankment are a combination of consolidation and shearing strain of the foundation material. Most studies of embankments concentrate on vertical settlements. This research shows that horizontal movements are also present, a contribution that helps explain the mechanism of lateral spreading. The results of the laboratory testing show that the mechanical and shearing properties of the soil collected from the PR391 embankment are not significantly affected by differences in temperature once water in the soil has actually thawed. The results of the thermal modelling show reasonable trends in simulated ground temperatures compared with the data obtained from the thermistors underneath the embankment. The frost heave prediction of PR391 shows that in situ frost heave characteristics can be estimated by applying the Segregation Potential (SP) frost heave method in field conditions. This provides a valuable field study to the limited number of such studies of Segregation Potential, which are normally done under laboratory conditions.

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

No description available.

As a consequence of the 2010 – 2011 Canterbury earthquake sequence, Christchurch experienced widespread liquefaction, vertical settlement and lateral spreading. These geological processes caused extensive damage to both housing and infrastructure, and increased the need for geotechnical investigation substantially. Cone Penetration Testing (CPT) has become the most common method for liquefaction assessment in Christchurch, and issues have been identified with the soil behaviour type, liquefaction potential and vertical settlement estimates, particularly in the north-western suburbs of Christchurch where soils consist mostly of silts, clayey silts and silty clays. The CPT soil behaviour type often appears to over-estimate the fines content within a soil, while the liquefaction potential and vertical settlement are often calculated higher than those measured after the Canterbury earthquake sequence. To investigate these issues, laboratory work was carried out on three adjacent CPT/borehole pairs from the Groynes Park subdivision in northern Christchurch. Boreholes were logged according to NZGS standards, separated into stratigraphic layers, and laboratory tests were conducted on representative samples. Comparison of these results with the CPT soil behaviour types provided valuable information, where 62% of soils on average were specified by the CPT at the Groynes Park subdivision as finer than what was actually present, 20% of soils on average were specified as coarser than what was actually present, and only 18% of soils on average were correctly classified by the CPT. Hence the CPT soil behaviour type is not accurately describing the stratigraphic profile at the Groynes Park subdivision, and it is understood that this is also the case in much of northwest Christchurch where similar soils are found. The computer software CLiq, by GeoLogismiki, uses assessment parameter constants which are able to be adjusted with each CPT file, in an attempt to make each more accurate. These parameter changes can in some cases substantially alter the results for liquefaction analysis. The sensitivity of the overall assessment method, raising and lowering the water table, lowering the soil behaviour type index, Ic, liquefaction cutoff value, the layer detection option, and the weighting factor option, were analysed by comparison with a set of ‘base settings’. The investigation confirmed that liquefaction analysis results can be very sensitive to the parameters selected, and demonstrated the dependency of the soil behaviour type on the soil behaviour type index, as the tested assessment parameters made very little to no changes to the soil behaviour type plots. The soil behaviour type index, Ic, developed by Robertson and Wride (1998) has been used to define a soil’s behaviour type, which is defined according to a set of numerical boundaries. In addition to this, the liquefaction cutoff point is defined as Ic > 2.6, whereby it is assumed that any soils with an Ic value above this will not liquefy due to clay-like tendencies (Robertson and Wride, 1998). The method has been identified in this thesis as being potentially unsuitable for some areas of Christchurch as it was developed for mostly sandy soils. An alternative methodology involving adjustment of the Robertson and Wride (1998) soil behaviour type boundaries is proposed as follows:  Ic < 1.31 – Gravelly sand to dense sand  1.31 < Ic < 1.90 – Sands: clean sand to silty sand  1.90 < Ic < 2.50 – Sand mixtures: silty sand to sandy silt  2.50 < Ic < 3.20 – Silt mixtures: clayey silt to silty clay  3.20 < Ic < 3.60 – Clays: silty clay to clay  Ic > 3.60 – Organics soils: peats. When the soil behaviour type boundary changes were applied to 15 test sites throughout Christchurch, 67% showed an improved change of soil behaviour type, while the remaining 33% remained unchanged, because they consisted almost entirely of sand. Within these boundary changes, the liquefaction cutoff point was moved from Ic > 2.6 to Ic > 2.5 and altered the liquefaction potential and vertical settlement to more realistic ii values. This confirmed that the overall soil behaviour type boundary changes appear to solve both the soil behaviour type issues and reduce the overestimation of liquefaction potential and vertical settlement. This thesis acts as a starting point towards researching the issues discussed. In particular, future work which would be useful includes investigation of the CLiq assessment parameter adjustments, and those which would be most suitable for use in clay-rich soils such as those in Christchurch. In particular consideration of how the water table can be better assessed when perched layers of water exist, with the limitation that only one elevation can be entered into CLiq. Additionally, a useful investigation would be a comparison of the known liquefaction and settlements from the Canterbury earthquake sequence with the liquefaction and settlement potentials calculated in CLiq for equivalent shaking conditions. This would enable the difference between the two to be accurately defined, and a suitable adjustment applied. Finally, inconsistencies between the Laser-Sizer and Hydrometer should be investigated, as the Laser-Sizer under-estimated the fines content by up to one third of the Hydrometer values.

Tagungsband des Ohde-Kolloquiums 2014. Die Fachtagung fand am 26.03.2014 an der TU Dresden statt.

Das Ohde-Kolloquium 2018 mit der traditionellen Überschrift — Aktuelle Themen in der Geotechnik – wird wieder in Zusammenarbeit mit der Bundesanstalt für Wasserbau an der Technischen Universität Dresden veranstaltet. Damit werden die beiden Wirkungsstätten von Professor Johann Ohde gewürdigt, mit denen er seine Lehr- und Forschungstätigkeit verknüpft hat. Die Beiträge des diesjährigen Kolloquiums können grob in drei Themengruppen unterteilt werden: • Bodenverhalten • Feld- und Modellversuche • Numerik und Anwendungen Die meisten Themen sind eng mit der Komplexität des Bodenverhaltens verbunden. In Abhängigkeit ihres Zustandes und einer aufgebrachten Belastung können Böden verschiedene Zustandsformen – gasförmig, flüssig und fest. Insbesondere der Übergang vom Feststoff zur Flüssigkeit (Bodenverflüssigung, hydraulischer Grundbruch, usw.) ist mit einem hohen Schadenspotenzial für Bauwerke und Menschen verbunden. Modellversuche im Labor und Monitoring im Feld sind für das Verständnis und die rechtzeitige Erkennung der Gefahrenzustände unumgänglich. Inwieweit die jetzigen Prognosen ausgereift sind, zeigen die numerischen Berechnungen für ausgewählte Anwendungen.

Tagungsband des Ohde-Kolloquiums 2014. Die Fachtagung fand am 26.03.2014 an der TU Dresden statt.:Experimentelle Untersuchung der Kapillarität bei Sand unter monotoner und zyklischer Belastung, Marius Milatz Mehrphasen-Modell zur Simulation von Suffosion, Heike Pfletschinger-Pfaff, Jan Kayser, Holger Steeb Experimentelle Ermittlung intergranularer Kräfte unter Nutzung von 2D-DIC, Max Wiebicke, Edward Andò, Denis Caillerie, Gioacchino Viggiani Systeme paralleler Scherbänder - Experimentelle und analytische Untersuchungen, Lars Röchter Rechnerischer Stabilitätsnachweis für verflüssigungsgefährdete Standorte, Nándor Tamáskovics Untersuchung des Einflusses von Gaseinschlüssen unterhalb des Grundwasserspiegels auf Druckausbreitung und Bodenverformungen mittels gekoppelter FE-Berechnungen, Hector Montenegro, Oliver Stelzer Zeitabhängige Setzungen von Sand und FE-Simulationen einer Tagebaukippe, Stefan Vogt, Emanuel Birle, Gero Vinzelberg Über die Berücksichtigung großer Bodendeformationen in numerischen Modellen, Daniel Aubram Die Gefrierkernmethode - Weiterentwicklung des Erkundungsverfahrens zur geohydraulischen Charakterisierung von Sohlsedimenten, Daniel Straßer, Hermann-Josef Lensing, Dominik Richter, Simon Frank, Nico Goldscheider Nutzung von Verfahren der Bildanalyse zur Baugrundbeurteilung, Markus Wacker, Thomas Neumann, Jens Engel, Gunter Gräfe Anwendung von Elektroosmose zur Reduzierung des Herausziehwiderstandes von Spundwänden: Großmaßstäbliche Modellversuche in Ton, Christos Vrettos, Kai Merz Zementfiltration bei der Herstellung von Verpressankern in nichtbindigen Böden, Xenia Stodieck, Thomas Benz Modell- und Elementversuche zur Bodenverflüssigung, Erik Schwiteilo, Ivo Herle Dynamische Probebelastung einer Mikropfahlgründung - Feldversuch und dynamische 3D-FE-Simulation mittels Hypoplastizität, Thomas Meier, Jens Jähnig, Sina Meybodi Numerische und analytische Berechnungen zur Erdbebenbemessung von Böschungen, Hassan AlKayyal

Collapse phenomenon is exhibited by two types of residual soils. The first category of collapsing residual soils is believed to be transported soils that have undergone post-depositional pedogenesis. The second category of collapsing residual soils is highly weathered and leached soils formed by in-situ weathering of parent rock. Residual red soils occur in Bangalore District of Karnataka State. Physical and chemical weathering of the gneissic parent rock formed the residual soils of Bangalore District. The red soils of Bangalore District are generally moderate to very highly porous (porosity range 35-50%). These soils are also unsaturated owing to presence of alternate wet and dry seasons and low ground water table. Moderately to highly porous, unsaturated red soils occur in Pernambuco State of Brazil. These residual soils formed by weathering of gneissic rock significantly collapse on wetting under external pressures. Kaolinite is predominant clay mineral in the red soils of Bangalore and Pernambuco Districts. Similarities exist in the mode of soil formation, clay mineralogy, porosity and degree of saturation (Sr) values of the red soils from Pernambuco State, Brazil, and Bangalore District. Given the collapsible nature of red soils from Pernambuco State, Brazil, the red soils from Bangalore District also deserve to be examined for their potential to collapse in the compacted and undisturbed conditions. The roles of initial dry density, compaction water content, clay content and flooding pressure (the external stress at which a laboratory specimen is inundated is termed as flooding pressure in this thesis) in determining the collapse behaviour of compacted soils are well recognized. However, the influences of above parameters on the collapse behaviour of compacted red soil specimens from Bangalore District are lacking. Such studies are essential as they help to identify the critical compaction parameters (dry density and water content), soil composition, and applied stress level that needs to be controlled by the fill designer in order to minimize wetting-induced collapse. The importance of matric suction in the collapse behaviour of unsaturated soils is well recognized. Yet, the influence of matric suction in the collapse behaviour of compacted soils has only been indirectly examined by varying the compaction water content/degree of saturation of the soil specimens. The climate of Bangalore District is characterized by alternate wet and dry seasons which affects the soil microstructure and the matric suction. Both these parameters have a significant influence on collapse behaviour of unsaturated soils. Cyclic wetting and drying is expected to have a significant bearing on the collapse behaviour of residual soils and is therefore examined. The red soil deposits of Bangalore District are important from foundation engineering view point as they are subjected to structural loading. Owing to the presence of alternate wet and dry seasons and low ground water table, red soil deposits of Bangalore District are more often than not unsaturated. These foundation soils would however be susceptible to increase in moisture content from causes such as infiltration of rainwater, leakage of pipes or watering of lawns and plants. Given the porous and unsaturated nature of undisturbed red soils from Bangalore district, their collapsible nature deserves to be examined for reliable estimation of foundation settlements. To achieve the above objectives, experiments are performed that study: 1.The influence of variations in compaction dry density, initial water content and matric suction, clay content and flooding pressure on the collapse behaviour of a representative red soil sample from Bangalore District. 2.The influence of repeated wetting and drying on the collapse behaviour of compacted red soil specimens. 3.The collapsible nature of undisturbed red soil samples from different locations in Bangalore District. The organization of this thesis is as follows: After the first introductory chapter, a detailed review of literature highlighting the need to study the collapse behaviour of unsaturated red soils of Bangalore District, Karnataka in the compacted and undisturbed states comprises Chapter 2. Chapter 3 presents a detailed experimental programme of the study. Details of representative and undisturbed red soil samples from Bangalore District, Karnataka State, India were used in the study are provided. Determination of collapse potential of compacted and undisturbed soil specimens using conventional oedometer is discussed. Determination of matric suction of compacted and undisturbed specimens by ASTM Filter paper method and pore size distributions by mercury intrusion porosimetry is detailed. Methods to perform cyclic wetting and drying of compacted red soil specimens in modified oedometer assemblies is detailed. These experiments are performed to examine the influence of cyclic wetting and drying on the collapse behaviour of compacted red soil specimens. Chapter 4 examines the collapse behaviour of a compacted red soil from Bangalore District. The influence of variations in compaction dry density, initial water content and matric suction, flooding pressure and clay content on the collapse behaviour of the representative red soil from Bangalore District are examined. Besides measuring the initial matric suction of the compacted red soil specimens, mercury intrusion porosimetry was performed on selected compacted red soil specimens. Experimental results showed that compacted red soils from Bangalore District exhibited tendency to swell and collapse at the experimental range of densities and water contents. Red soil specimens compacted to relative compactions > 90 % at water contents below OMC swelled at flooding pressures lower than 200 kPa. Red soil specimens compacted to relative compactions < 90 % at water contents below OMC significantly collapsed at flooding pressures larger than 200 kPa. Hence maintenance of the design water content during construction of compacted red soil fills is essential to minimize wetting induced volume changes. Experiments showed that the relative abundance of coarse pores (60 to 6 μm, pore radius) were mainly affected on increasing the relative compaction of the specimens from 84 % (dry density = 1.49 Mg/m3) to 100 % (dry density = 1.77 Mg/m3). The relative abundance of the coarse and fine (0.01 to 0.002 μm) pores were both affected on increasing the compaction water content from 10.6 to 26.4 %. These variations in pore size distributions provided better insight into the variations of collapse potential with variations in compaction parameters. ASTM filter paper method showed that for the selected compaction conditions the initial matric suction of the compacted red soil specimens varied between 60 and 10,000 kPa. Further, variations in degree of saturation at a constant relative compaction or variations in relative compaction at a constant degree of soil saturation notably affected the matric suction of the compacted soil specimens. It was also inferred that a clay soil with a higher liquid limit is characterized by a higher matric suction at a given water content. Variations in clay content affected the collapse potentials of soil specimens compacted to dry densities of 1.49 and 1.66 Mg/m3. These specimens exhibited maximum collapse at about 26 % clay content. It is suggested that greater destabilization of inter-particle contacts caused by loss of matric suction on flooding was primarily responsible for the soil specimen containing the critical clay content of 26 % to exhibit maximum collapse potential. Increase in initial dry density, initial water content, clay content of the soil specimen and flooding pressure increased the time-duration of collapse of the compacted soil specimens. The time-duration of collapse was observed to range between 3 and 100 minutes for the tested specimens. Chapter 5 examines the influence of alternate wetting and drying on the collapse behaviour of compacted red soil specimens of Bangalore District. The compacted specimens were subjected to alternate wetting and drying cycles at surcharge pressures of 6.25 and 50 kPa in modified oedometer assemblies. Studies were also performed to examine whether the initial placement conditions have any bearing on the collapse behaviour of red soil specimens subjected to four cycles of wetting and drying. Mercury intrusion porosimetry was performed on a few desiccated red soil specimens. Experimental results showed that cyclic wetting and drying caused the desiccated specimens to exhibit similar or lower swell and collapse potentials than the compacted specimens. Such a behaviour resulted despite the desiccated specimens (specimens subjected to four cycles of wetting and drying are termed as desiccated specimens) possessing similar void ratios but much lower water contents than the compacted specimens. The restraining influence of the desiccation bonds and alteration of soil structure is considered responsible for the reduced swell and collapse tendencies of the desiccated specimens. The desiccation bonds imparted higher apparent preconsolidation pressures to the desiccated specimens. The initial compaction conditions also have a strong bearing on the collapse potentials of the desiccated specimens. Compacted red soil specimens subjected to cyclic wetting and drying under a higher surcharge pressure of 50 kPa exhibited larger swell potentials and lower collapse potentials than specimens desiccated at 6.25 kPa. Besides their lower void ratios, the presence of stronger desiccation bonds also contributed to their lower collapse potentials. The presence of stronger desiccation bonds in specimens desiccated under higher surcharge pressure was indicated by their higher apparent preconsolidation pressures. Chapter 6 examines the collapse behaviour of undisturbed red soil specimens from three locations in Bangalore District at a range of flooding pressures. Studies on the variations in initial water content and effect of remoulding on the collapse behaviour of the undisturbed specimens is supplemented by measuring the initial matric suction and performing mercury intrusion porosimetry experiments. Experimental results showed that based on their collapse potential at 200 kPa, the undisturbed red soils of Bangalore District classified as troublesome to moderately troublesome foundation soils. The bonded structure of the undisturbed red soil specimens imparted them higher apparent preconsolidation pressures and lower swell/collapse potentials than their remoulded counterparts. Variations in in-situ dry density, degree of saturation and relative distribution of pore sizes affected the matric suction and collapse potentials of the undisturbed specimens Chapter 7 summarizes the conclusions of this thesis.