Tesi sul tema "Loess"

A number of studies have been published in the last few decades on Pleistocene palaeo-temperature reconstruction based on isotopic studies on deep sea cores and ice core records from Greenland. Such temporal high-resolution data represents northern hemispheric circulations and has to be reconfirmed through the study of terrestrial archives in order to recognise the character of such fluctuations in different regions. Loess-palaeosol sequences (LPSs) are suitable to interpret them as palaeoenvironmental archives, because loess is a widely distributed terrestrial deposit and is datable using luminescence techniques. The Saxon loess region (SLR) is characterised by a loess cover of ca. 8 m thickness, mainly representing deposits of the last glacial cycle. Over the past 35 years, Saxon loess remains under-researched wherefore a reactivation with the objective of contributing to the European loess research is important. There is a clear need to re-examine Saxon LPSs and close this gap of knowledge, because in recent years much work has been done on important and European-wide known loess sections as well as in adjacent loess areas. In this study, LPSs from Saxony were investigated and a regional palaeoenvironmental reconstruction of the last Glacial/Interglacial cycle was developed. The established stratigraphical scheme has to be advanced by results of optically stimulated luminescence (OSL) dating. The stratigraphical results should be compared with previous work from Saxony and with results from adjacent loess areas, to verify if our results have to be interpreted as singularities or if they are in accordance with known European conceptions. Therefore, 8 sections, mostly never investigated before, were described and correlated with each other to finally generate an independent standard stratigraphy for this area. Carbonate content, pH-value, soil organic matter, total and pedogenic iron, magnetic susceptibility and classical grain size analyses were obtained from every section. Furthermore, rare earth elements concentrations were measured from selected positions in order to prove if there are variations in the deposit composition during the glaciation. The OSL dating results were processed by Kreutzer (2012). As previously noted, the first step towards a regional palaeoenvironmental reconstruction was to establish a standard stratigraphic scheme where all found units are involved. Based on features regarding grain size distribution, the found palaeosols and the magnetic susceptibility Baumgart et al. (2013), 5 units could be defined. Unit V reflects the pre-Weichselian sediments modified by the Eemian soil formation. Unit IV contains deposits from the beginning of the Weichselian glaciation. Typically, this unit starts with the first Weichselian deposit, a bright-greyish Mn- and Fe-precipitates enriched layer which shows an aggregation of charcoal at its top. This layer is covered by a greyish, humus-enriched and reworked relict of a Chernozem-like soil. After a Gelic Gleysol and a reddish-brownish soil sediment, a loess package with an embedded interstadial Cambisol-like soil is preserved. The top of the unit is represented by another brownish soil sediment which forms the lower part of the Gleina complex. Typically, unit IV is characterised by stronger reworked layers and soil sediments but at the Rottewitz section an older loess package is preserved. Unit III represents the reactivation of aeolian sedimentation. The base of this unit is made up of a strong Gelic Gleysol (upper part of the Gleina complex). The deposits of this unit are mostly pedogenically overprinted and show features of at least two Gelic Gleysols. Unit II is dominated by unweathered loess. Its lower part (unit IIb) is built of a more stratified loess facies whereas the upper part (unit IIa) is built of a homogeneous loess facies. They are separated by a strong Gelic Gleysol. Unit I represent the upper part of the loess section, which is modified by the Holocene and Late Pleistocene soil development. Within this succession, a huge hiatus is found between unit III and IV of ca. 35 ka. It is labelled as the Gleina complex according to Lieberoth (1963). Furthermore, we demonstrate how combined analyses of high-resolution grain size distributions and microscopic analysis can be used to discriminate depositional and pedogenetic features of loess-palaeosol profiles from the SLR. Generally, it was observed that an increase of coarse material is linked with an increase of the mineralogical components which refers to slope processes. Rounded shapes of Mn- and Fe-precipitates, mostly found in Early Weichselian humus layers, indicate strong interstadial soil development modified by subsequent redeposition. Further observations suggest that the class of medium sand is dominated by secondary precipitates. The varying amount of very fine sand shows that sequences are cyclically built up of pure loess comparable to the Nussloch section. Studying coarse grain size fractions by microscopic analysis, a differentiation between loessic layers formed by periglacial slope processes and layers overprinted by pedogenetic processes is possible. Furthermore, an increase of fine material and secondary Mn- and Fe-precipitates can be attributed to soil forming processes (clay formation, redoximorphic processes, and illuviation). Additionally, a palaeoenvironmental reconstruction for the Late Pleistocene is proposed. As palaeo-temperature proxies ice wedges, pure loess sedimentation or the platy soil structure due to former ice lensing for cold periods and soil formations or vegetation remnants for warmer periods were used. A reconstruction of wind speed is directly deduced from the very fine sand content. The stability/instability of the landscape surface could be indicated by soil formation (stable) or through an increase of coarse sand (active). The type of soil development for the reconstruction is of major importance. For example, a humus enriched soil indicates warmer and dryer conditions than a Gelic Gleysol. The results of grain size analyses reveal a similar temporal and lithogenic pattern of Weichselian aeolian dynamics of the study area and other records from Europe. Furthermore, grain size results independently confirm the luminescence chronology of the studied sections. Reworked loess-like sediments show varying OSL age estimates; aeolian loess shows a systematic change of OSL ages. Generally, the findings of this study agree with observations from other loess areas. In most areas, a similar hiatus between Middle and Upper Weichselians is documented. Additionally, OSL dating suggests that we found an older loess package with an age between ca. 60 and 70 ka and a younger loess package with an age of ca. 15 and 30 ka. These periods of aeolian deposition are in accordance with MIS 4 and MIS 2 as well as with dust concentrations results derived from lake sediments and from ice cores. A major finding of this study is that we uncover the internal differences of loess-palaeosol sequences regarding their temporal resolution. In periods of loess sedimentation, a temporally high-resolution record is preserved. In contrast, in periods dominated by interstadial soil development or redeposition, a temporal low-resolution record is preserved and a reconstruction of palaeoenvironment is almost impossible
In den vergangenen Jahrzehnten wurden viele Studien über die Rekonstruktion der pleistozänen Temperaturentwicklung veröffentlicht, welche anhand von Isotopenanalysen aus Tiefsee- und Eisbohrkernen des grönländischen Eises abgeleitet werden konnten. In solchen zeitlich hochaufgelösten Daten sind nordhemisphärische Klimaschwankungen repräsentiert und diese sollten durch Untersuchungen terrestrischer Archive validiert und deren regionale Ausprägung in verschiedenen Räumen abgeschätzt werden. Löss-Paläobodensequenzen eignen sich hervorragend als Paläoumweltarchiv, da der Löss ein weit verbreitetes Sediment und mittels Lumineszenzverfahren datierbar ist. Die Sächsische Lössregion ist durch eine ca. 8 m mächtige Lössdecke charakterisiert, welche vornehmlich aus Ablagerungen des letzten glazialen Zyklus besteht. In den vergangenen 35 Jahren wurde die Lössforschung in diesem Raum vernachlässigt, sodass eine Wiederbelebung wichtig ist, um einen Beitrag zur europäischen Lössforschung zu leisten. Da in den letzten Jahren an wichtigen europäischen Lössprofilen, wie auch in angrenzenden Lössregionen, intensiv geforscht wurde besteht der dringende Bedarf, die Forschungen an sächsischen Löss-Paläobodensequenzen wieder aufzunehmen und die entstandene Wissenslücke zu schließen. In dieser Studie werden sächsische Löss-Paläobodensequenzen untersucht und eine regionale Umweltrekonstruktion für den letzten glazialen Zyklus vorgestellt. Die Standardstratigraphie wird dabei durch optisch stimulierte Lumineszenz (OSL)-Alter erweitert. Die Ergebnisse werden mit älteren Arbeiten aus diesem Raum verglichen, um abzuschätzen, ob es sich hierbei um Einzelbefunde handelt oder ob sich die Ergebnisse in schon bekannte europäische Konzepte einordnen lassen. Es werden 8, meist noch nie bearbeitete Profile beschrieben und miteinander korreliert, um schließlich eine unabhängige Standardstratigraphie für diesen Raum zu erarbeiten. Von jedem Profil wurde der Kalkgehalt, der pH-Wert, der Anteil der organischen Substanz, das pedogene und Gesamteisen, die magnetische Suszeptibilität und die Korngrößenverteilung (klassisch) bestimmt. Zudem wurde die Konzentration der Seltene Erden Elemente an ausgewählten Positionen bestimmt, um zu prüfen, ob es Verschiebungen in der mineralogischen Zusammensetzungen über das letzte Glazial hinweg gab. Die OSL-Datierungen wurden dabei von Kreutzer (2012) realisiert. Wie schon erläutert wurde, bestand der erste Arbeitsschritt darin, eine Standardstratigraphie zu erarbeiten, worin alle Befunde integriert werden können. Auf Grundlage der Korngrößenverteilung, der gefundenen Paläoböden und der magnetischen Suszeptibilität Baumgart et al. (2013) konnten 5 Einheiten ausgewiesen werden. Die Einheit V stellt die prä-weichselzeitlichen Sedimente dar, welche von der eemzeitlichen Bodenbildung überprägt wurden. Einheit IV beinhaltet die Sedimente vom Beginn der Weichselkaltzeit. Typischerweise befindet sich an der Basis dieser Einheit eine hellgraue, an Mn- und Fe-Konkretionen angereicherte Schicht, welche eine Häufung von Holzkohlebruchstücken im oberen Bereich zeigt. Diese Schicht ist wiederum von einem Rest einer schwarzerdeähnlichen Bodenbildung überlagert und zeigt eine Anreicherung an organischer Substanz. Über einem Nassboden und einem rotbraunen Bodensediment ist ein Lösspaket, mit einem zwischengelagerten interstadialen braunerdeartigen Boden, erhalten. Der obere Bereich der Einheit IV ist durch ein weiteres rötlichbraunes Bodensediment geprägt, welches dem unteren Teil des Gleinaer Komplexes entspricht. Normalerweise ist die Einheit IV in Sachsen durch stark umgelagerte Schichten charakterisiert, jedoch ist im Profil Rottewitz in dieser Einheit ein älteres Lösspaket erhalten. Die Einheit III repräsentiert eine Reaktivierung der äolischen Sedimentation. Ihre Basis bildet ein kräftiger Nassboden (oberer Teil des Gleinaer Komplex). Die Sedimente dieser Einheit sind meist pedogen überprägt und es können mindestens zwei separate Nassböden ausgewiesen werden. Die Einheit II besteht vornehmlich aus unverwittertem kalkhaltigen Löss. Ihr unterer Abschnitt (Einheit IIb) wird durch eine streifige Löss-Fazies gebildet, wohingegen der obere Teil von einer homogenen Löss-Fazies dominiert wird. Diese sind durch einen kräftigen Nassboden voneinander getrennt. Die Einheit I bildet den oberen Teil des Lössprofiles und ist durch die pedogene Überprägung der spätpleistozänen und holozänen Bodenentwicklung geprägt. In dieser Abfolge ist ein Alterssprung von ca. 35 ka zwischen der Einheit IV und III nachgewiesen. Dieser Hiatus befindet sich im durch Lieberoth (1963) definierten Gleinaer Komplex. Weiterhin konnte gezeigt werden, dass mit Hilfe einer kombinierten Untersuchung aus Korngrößenanalyse und Mikroskopieren es möglich ist, eine durch Bodenbildung bedingte und eine durch Umlagerung hervorgerufenen Überformung von Lösssedimenten voneinander zu unterscheiden. Generell wurde festgestellt, dass ein Anstieg der groben Kornfraktionen oft mit einer Erhöhung der mineralischen Komponente einhergeht und dies auf laterale Umlagerungsprozesse hindeutet. Abgerundete Mn- und Fe-Konkretionen aus humosen frühweichselzeitlichen Schichten lassen eine kräftige interstadiale Bodenentwicklung mit anschließender Umlagerung vermuten. Es wurde zudem festgestellt, dass die Mittelsandfraktion durch sekundäre Fe- und Mn-Konkretionen dominiert wird. Der variierende Feinstsandanteil zeigt, dass die Sequenzen in verschiedenen Zyklen aus unverwittertem Löss aufgebaut wurden, wie es auch aus dem Profil Nussloch beschrieben wird. Bodenbildungsprozesse bedingen demgegenüber ein Anstieg der Feinkomponenten und der Mn- und Fe-Konkretionen in den Sandfraktionen. Weiterhin wird eine Paläoumweltrekonstruktion für das Spätpleistozän vorgeschlagen. Hierbei werden verschiedenste Indikatoren als Paläotemperaturzeiger herangezogen. Für kalte Phasen stehen zum Beispiel Eiskeilpseudomorphosen, Pakete aus unverwittertem Löss oder plattige Strukturen infolge von Schichteisbildung. Für wärmere Phasen sprechen Paläoböden oder Pflanzenreste. Eine Rekonstruktion der Paläowindgeschwindigkeiten wird direkt über die Feinstsandanteile abgeleitet. Die Stabilität einer Landschaftoberfläche wird durch Bodenbildungen (stabil) oder einem Anstieg der groben Sandkomponenten (aktiv) repräsentiert. Den Paläoböden kommt bei einer solchen Rekonstruktion eine Schlüsselstellung zugute. Zum Beispiel signalisiert ein Steppenboden wärmere und trockenere Bedingungen im Vergleich mit einem Nassboden. Die Ergebnisse der Korngrößenuntersuchungen zeigen, dass hinsichtlich ihres Aufbaues und ihrer chronologischen Einordnung die äolisch dominierten Phasen der sächsischen Lössprofile bekannten Mustern aus anderen Archiven in Europa folgen. Zudem zeigt sich, dass die Ergebnisse der Korngrößenverteilung die mittels OSL bestimmten Alter untermauern. Umgelagerte Sedimente zeigen größere Altersschwankungen, wohingegen äolische Sedimente eine kontinuierliche Altersentwicklung haben. Die Ergebnisse dieser Untersuchungen stimmen mit Beobachtungen aus anderen Lössgebieten überein. In den meisten Regionen wird ein ähnlicher Hiatus zwischen der mittleren und oberen Weichselkaltzeit beschrieben. Zudem deuten die OSL-Ergebnisse an, dass in Sachsen ein älteres Lösspaket mit einem Alter von ca. 60 bis 70 ka und ein jüngeres Lösspaket mit einem Alter von ca. 15 bis 30 ka existiert. Die beiden äolischen Phasen korrelieren mit der marinen Isotopenstufe 4 (MIS) beziehungsweise der MIS 2, sowie mit Ergebnissen pleistozäner Staubkonzentration der Atmosphäre, abgeleitet aus Seesedimenten oder Eisbohrkernen. Eine wichtige Erkenntnis dieser Untersuchungen ist, dass wir innerhalb eines Lössprofiles Pakete unterschiedlicher zeitlicher Auflösung identifizieren konnten. Aus Phasen kräftiger Lösssedimentation sind zeitlich hoch aufgelöste Sequenzen erhalten. Demgegenüber ist aus Phasen, dominiert durch Bodenbildungen oder Umlagerungen, ein zeitlich nur sehr schlecht aufgelöstes Archiv erhalten, weshalb anhand dieser Abschnitte eine Paläoumweltrekonstruktion nur bedingt möglich ist

Ce mémoire de thèse est consacré à l'étude expérimentale du comportement hydromécanique d'un lœss naturel non saturé effondrable provenant d'un site proche de la ville de Bapaume (nord de la France) dans une zone où des problèmes de tassement le long de la ligne nord du TGV ont été attribués à l'effondrement du lœss, du fait d'infiltrations d'eau. Un nouvel appareil triaxial permettant de mesurer localement l'ensemble des caractéristiques du loess non saturé (déformation, teneur en eau et succion) a été développé. La courbe de rétention d'eau, déterminée à l'aide d'un tensiomètre de haute capacité et de la méthode du papier filtre a fait l'objet d'une attention particulière : elle présente autour de la teneur naturelle une zone sans hystérésis bordée par deux boucles d'hystérésis des côtés secs et humides. L'analyse de la courbe de rétention et du phénomène d'hystérésis a été approfondie grâce à une étude microstructurale réalisée à l'aide de la porosimétrie au mercure et de la microscopie électronique à balayage. Une structure assez complexe composée d'un arrangement métastable de grains de limon secs (probablement liés par la recristallisation du calcaire) et d'une phase argileuse répartie de façon hétérogène a été mise en évidence. L'étude du comportement hydromécanique a compris une investigation de l'effondrement à partir de faibles valeurs de contraintes proches de la contrainte in-situ, à l'aide d'essais oedométriques à taux de déformation constant avec mesures de succion. Le maximum d'effondrement et une dépendance fonction de la vitesse de chargement ont été identifiés. Une campagne d'essais triaxiaux à différentes teneurs en eau constantes avec mesure de succion a permis de déterminer l'allure de la limite élastique du limon naturel dans un diagramme p/q, ainsi que ses variations avec la teneur en eau et la succion et confirmer l'écrouissage en succion

Soil collapse is amongst one of the most significant ground related hazards. A collapsible soil, in particular loess, typically has an open-structure and collapse occurs when as a consequence of the addition of water and/or load the particles rearrange to form a more dense fabric. Collapse leads to a suite of problems for buildings and infrastructures built on or in collapsing soil. Treatment to mitigate collapse often involves in densification. However, such approaches have been reported not always effective enough to combat the problem. This stems from a lack of understanding of soils’ geochemistry and structure, the result of which is an oversimplification of complex geotechnical and geological interactions. An important example of such limited knowledge is the increasing evidence of restoration of the collapsing structure upon wetting-drying cycles, which is widely ignored in the current compaction practice. This research aims to first identifying collapse micro-mechanisms in fine-grained soils, examining the contribution of a handful of soil constituents in collapsibility, and finally developing a practical tool for ground engineers to evaluate the efficiency of the current compaction practice for systematically classified fine-grained soils, and to take modified/novel earthwork approaches where the current practice fails to fully remove the collapse risk.

Loess has a metastable structure and undergoes structural hydrocollapse when loaded and wetted, leading to subsidence and damage of overlying structures, which presents enormous engineering problems in many countries in the world. This problem is a focus of much research on both the nature of the phenomenon and the means. of overcoming its negative consequences. However, there remains a need for fundamental experimental and theoretical studies aimed at understanding the many uncertainties involved in the hydrocollapse phenomenon. An experimental programme has been conducted to study the fundamental nature of the hydrocollapse phenomenon in loess, and the primary features of the metastable structure controlling it. High quality disc-shaped specimens were prepared from natural undisturbed, very soft and slightly cemented loess soils using two simple devices which were designed and manufactured in the laboratory. Artificial loess materials were prepared by mixing pure silt particles of different geometrical characteristics (crushed sand, ballotini glass balls) with various clay types (kaolinite, bentonite) to produce mixes with different clay/silt ratios. Soil specimens of metastable structure were created from natural and model loess materials using the air-fall technique, which allowed full control over the critical variables. The index properties of the materials were determined experimentally, together with their geometrical characteristics from scanning electron microscope (SEM) studies. The compressibility characteristics and hydrocollapse behaviour were measured via one-dimensional (oedometer) compression tests. Two testing methods were used: the single oedometer test and the double oedometer test. The results indicated that the experimental approach used in this research can be used successfully to investigate the hydrocollapse problem of loess deposits. The small-clay loess model was constructed and examined. The results proved that this model is valid. The collapse behaviour of reconstituted and undisturbed loess specimens prepared from the same material was qualitatively similar, although the reconstituted materials exhibited greater collapsibility, particularly under low normal effective stresses. Specimens prepared from pure silt revealed very little collapse in spite of relatively high initial voids ratios (e ≤ 0.9). The existence of bonding materials, such as clay minerals at the points of particle contact, is thus apparently essential for hydrocollapse to occur. Specimens prepared from pure silt-bentonite mixtures exhibited low hydrocollapse values in comparison with those for pure silt-kaolinite mixtures. It was observed that there is an optimum clay mineral content for maximum hydrocollapse and it depends on the type of clay mineral and the level of applied stress. Higher values of hydrocollapse were obtained with smooth, spherical glass balls as the silt fraction, thus confirming that the geometrical properties of the silt particles also have a significant effect on the hydrocollapse behaviour of loess deposits. The position and distribution (mixing method) of clay particles inside the soil structure were equally found to have a significant effect on the hydrocollapse behaviour. The index properties of Libyan loess were found to be very similar to those of other loess deposits world-wide. The Tripoli loess can be classified as silty loess with high susceptibility to structural hydrocollapse in the same manner as other better known loess deposits in the world.

High resolution dating of loess on the Chinese Loess Plateau (CLP) using Optically Stimulated Luminescence (OSL) has increased the understanding of past monsoon climate but also raised questions regarding dust mass accumulation rate (MAR), the presence of disturbances or gaps in the sediment record, a possible teleconnection between North Atlantic and East Asian monsoon climate, and whether these events are due to climate variability, local settings, or age model uncertainties. This study undertakes a detailed (<20cm sampling resolution) -OSL investigation of the Lingtai section to create an independent age model using linear regression, to reconstruct monsoon climate changes using magnetic susceptibility(MS) and grain size (GS) proxies, as well as to calculate MAR for the site. The data shows that between 44-15 ka climate changes from a period of strong summer monsoon to a strong winter monsoon. GS data show variable trends attributed to changes in dust storm activity and local environmental conditions. MAR data does not correlate with grain size and is different from other loess records on the CLP. Such differences are either due to local variations or age model uncertainties. No clear correlation with Heinrich events or teleconnection with North Atlantic climate is visible in the records over the Last Glacial period, and hiatuses or gaps are not obviously present at this site. It is suggested that using linear regression for continuous age model construction from the luminescence ages comes with uncertainties due to subjective bias when fitting the lines and determining shifts in the data, especially during MAR calculations. Further studies are needed to ascertain optimal methods for creating age models, and to constrain the reasons behind the variability between different sites and loess records on the CLP.
Högupplöst OSL-datering av loessjordar från CLP har ökat förståelsen av dåtida monsunklimat, men har även lyft frågan gällande MAR, närvaron av avbrott eller småskaliga event i jordsektionerna, möjligheten av en relation mellan de Nordatlantiska och Ostasiatiska monsunklimaten, och om dessa förändringar sker till följd av faktisk klimatvariation, lokala förutsättningar, eller osäkerheter i åldersmodellen. Studien genomförde en detaljerad (<20cm) OSL-undersökning av Lingtai-sektionen för att skapa en oberoende åldersmodell, återge monsunklimatförändringarna genom tillämpning av MS och GS proxies, samt beräkna MAR från platsen. Resultaten påvisar att mellan 44-15 ka förändrades klimatet från en period av stark sommar- till en stark vinter-monsun. Kornstorleks-resultaten påvisar stora variationer vilka kan kopplas till en förändring i sandstormsaktivitet samt de lokala förutsättningarna för deposition av sediment. MAR-resultaten överensstämmer inte med kornstorleksdatan och skiljer sig från den övriga empirin, detta kan bero på lokala variationer i regionen eller osäkerheter i åldermodellen. Det finns ingen klar korrelation mellan "Heinrich events" eller en "teleconnection" i sektionen, och avbrott samt störningar i sektionen är inte förekommande. Avsaknaden av korrelation antyder att användningen av regressionslinjer för att skapa kontinuerliga åldermodeller kommer innebära fortsatta osäkerheter i empirin, speciellt gällande beräking av MAR. Ytterligare studier krävs för att bestämma optimala metoder för att framställa åldersmodeller, samt att utröna orsaken till skillnaden mellan resultat från olika platser på plat

Thesis: M. Arch., Massachusetts Institute of Technology, Department of Architecture, 2014.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (page 124).
Ten percent of the earth's land surface area is covered with loess deposits, a type of highly erodible soil consisting of less than 20% clay. Loess soil has topped eroding hills and valleys and supported an earthen construction tradition in loess landform territories. The Loess Plateau in China has been suffering from heavy soil erosion. Soil erosion is caused by the scale of the hill and valley watershed and exacerbated by the scale of earthen dwellings. These dwellings are mostly populated by low-income agricultural households. They obtain soil resources from exposed loess sections and build dwellings on nearby flat land. This approach increases erosion to both the landforms and the dwellings, and worsens the living quality of the local residents. Nevertheless, considering affordability, environmental load, and soil stabilization, local soil and natural fiber are good choices of building material. Can earthen dwellings be designed so as not to increase soil erosion but to reconcile their relationship to the eroding landform? Meanwhile, can vegetated landforms be designed to contribute to the built form? If so, how? In this design thesis, I show that considering the landform and the built form as a whole is the key to resolve the loess soil erosion problem. Vegetation and grading can be designed to extend from the ridge, to the terraced land, and to the gully slopes to control soil erosion. Five new earthen dwelling types can be introduced, according to various degrees of uncontrolled slopes, in order to reduce both exposed soil sections and earthen walls and not exacerbate soil erosion in the future. Settlements can be upgraded as a result of negotiation between the landforms and the built forms. Such a settlement can triple the number of households to help meet the demand for replacing decrepit houses and for hosting younger families. The scaling-in research method from the globe to a single dwelling and the design sequence of landscape, dwelling, and settlement together constitute an innovative approach to addressing a complex problem.
by Bin Li.
M. Arch.

The dispersive and erodible nature of some loess soils on the Port Hills results in a variety of mass movement, surface and sub-surface erosion features. These features produce engineering problems for residential development, and chemical stabilisation techniques have been used to reduce and/or prevent further erosion by rendering the soils non-dispersive and non erodible. Field and laboratory investigations were undertaken to characterise the dispersive and erodible nature of Whaka Terrace subdivision loess, as well as to assess changes in chemistry and mineralogy of the chemically stabilised soils. Field investigation included engineering geological mapping, geophysical surveying, hand auger hole drilling and logging, and sampling. The application of 1%, 2%, and 4% hydrated lime, quicklime, Portland cement, gypsum, and a mixture of hydrated lime and gypsum (on a 1:1 basis) was used to stabilise erodible loess-colluvium in the laboratory. Evaluation tests included permeability, pinhole erodibility, jar slaking, uniaxial swelling, crumb dispersion, unconfined compressive strength, undrained shear strength, and the determination of optimum moisture content, Atterberg limits and grainsize distribution. Soil chemistry was analysed using pH, soluble salts, organic content, cation exchange capacity and XRF, while XRD, SEM and EDAX were used to study soil mineralogy and fabric. Application of 1 and 2% quicklime and hydrated lime produces a non-erodible, non-dispersive and durable material which resists slaking and swelling during saturation, and wetting and drying cycles. Application of Portland cement at higher concentration (2 and 4%) produces similar results to that of hydrated lime and quicklime, while gypsum fails to produce a non-erodible and durable material. Furthermore, although the application of a mixed hydrated lime and gypsum stabiliser produces a non-dispersive and non-erodible material, it fails to produce a durable material and mixed stabiliser soils possess a high potential for swelling and slaking. The unconfined compressive strength and shear strength of all stabilised samples except gypsum increases by 2-3 times relative to the untreated samples. This increase in strength is related to the production of pozzolanic cementing agents (pozzolanic reaction) in the chemically stabilised samples. The presence of cementing agents also changes the strain deformation of treated samples by producing a more brittle material relative to the untreated samples.

This thesis explores the relationship between environmental restoration and social-economic factors. It focuses on the erosion treatment on the Loess Plateau, especially the Grain to Green Project (GGP), the biggest national-range environmental treatment program in China in recent years. GGP produced significant impact on local landform, landuse and livelihood. On one hand, the program effectively controlled torrent by increasing soil aggregation; on the other hand, it lacked long-term perspectives and had underestimated the complexity of the environment and of local residents. The thesis seeks to bridge the gaps between soil treatment policy and the actual effect. Research was conducted on soil erosion across multiple scales and key issues are generated based on typical cases. Findings from the research serve as guidelines for the following design proposition. The design applies hierarchical method, including both top-down and bottom-up interventions. First, a division method for erosion states was developed which can divide the erosion problem within the range of the yellow river into small catchment basins. Second, a typical catchment basin was selected as an example to show proposed strategy in three scales: catchment, slope and patches. The core design idea is to conserve resources and maximize output in sustainable ways. The fragmented land patches are integrated to complete the production model. The study site is planned according to field condition, such as erosion process, slope ratio, lighting, water resource and distance to settlements. Patches were identified using vegetation coverage and appropriate planting strategies were proposed accordingly. In sum, the thesis is a critique of existing GGP. A new solution is proposed that can mitigate the conflict of soil erosion treatment and socio-economic development of local communities.
published_or_final_version
Architecture
Master
Master of Landscape Architecture

The loess deposits of the Port Hills, Canterbury, are subject to erosion by natural processes. Urban development of the Port Hills has encountered difficulties due to loess erosion, and in some instances, contributed to erosion. Lime stabilisation is one remedial method that can be used to reduce erosion problems. This necessitates investigation of the changes to soil properties and strength gains that occur to the loess with the addition of lime. An erodible loess colluvium, from a subdivision with a history of erosion problems, was stabilised with 1%, 2.5%, 5%, 7.5%, and 10% hydrated lime, and cured under various laboratory conditions. Pinhole erodibility, uniaxial swelling strain, Atterberg limits, grainsize analysis, Proctor compaction testing and a slaking test were used to determine the improvements to soil properties with the addition of lime. Unconfined compressive strength was tested to determine strength gains of lime stabilised soil. The addition of 1% lime to the soil produced a non-erodible, non-dispersive material. Slaking and swelling were minimised with the addition of higher percent ages of lime (5%-7.5% respectively). The effective grainsize of the soil was increased on the addition of lime, and plasticity was increased with the addition of up to 5% lime. Optimum moisture content increases, and dry density decreases with increasing amounts of lime. Strength gains of the lime stabilised loess, varied from 3 – 14 times the strength of the untreated soil depending on the curing method. Strength gains were greatest for air dried samples, although the untreated soil cured in the same manner had a higher dry strength than the lime stabilised soil. Strength gains are optimised at and above 7.5% lime with significant strength losses recorded between 2% and 5% lime. Strain deformation is reduced with the addition of lime, and the modulus of deformation is increased significantly indicating that lime stabilised loess acts as a brittle material on deformation. The addition of lime to loess in low percentages (1%), has the effect of producing a non-erodible, non-dispersive material that resists erosion. However, it would appear that to achieve maximum strength of lime stabilised loess, 7.5% lime or more must be added to the soil.

A series of laboratory tests have been conducted with Port Hills loess from the Ahuriri quarry. Tests have been conducted to obtain a theoretical basis for suggestions of good design practice for retaining wall filtration/drainage systems. The study has concentrated on investigation of geotextiles as filtration options, with granular filters being tested for comparison. Two of the tests (stage 1 test and gradient ratio test) are designed to provide comparative information on filter performance with specific soil types. The third test is a series of three laboratory scale retaining wall simulations. Information from these tests provides evidence of potential problems with commonly used retaining wall filtration/drainage systems. In conjunction with laboratory testing, field observations have been carried out to assess the current state of the practice, and identify additional areas of concern. Results from both the gradient ratio and stage 1 tests indicate good performance of a range of needle punched nonwoven geotextiles for filtering the specific soil tested (Ahuriri quarry loess). Scanning Electron Microscope investigation of the soil and geotextile filter structures formed during testing indicate bridging to be the dominant filter network, with one example of a vault network for the needle punched range. Small amounts of clogging observed within the geotextile structure have not resulted in significant reductions in permeability. Gradient ratio values for a selection of the needle punched range support evidence from the stage 1 test that satisfactory filter performance is provided. Gradient ratio values of greater than 3.0 are recorded for two heat bonded nonwoven geotextiles, indicating a concerning level of clogging. Observations of tested heat bonded samples under the SEM show a degree of "blocking" (a specific form of clogging). These observations are supported by lower permeability values in both tests, comparative to the needle punched range, suggesting the needle punched range is better suited to filtering this specific soil type. Indications from the retaining wall simulations suggest a need for impermeable drain channels under drainage pipes to prevent erosion of loess resulting from water flow under the drain pipes. Also indicated by these tests is the presence of salts on the backfill material obtained from a local quarry. Although further investigation is recommended, the potential exists for corrosion of steel reinforcing where adequate water proofing is not placed. The need for adequate surface drainage (particularly during construction) in combination with good retaining wall design is emphasised. As a culmination of the testing and field work, a number of suggestions are put forward as aspects of good design practice for filtration/drainage systems for use in retaining walls on the Port Hills. Selection of an appropriate geotextile for a specific filtration project should ideally follow an in-depth design process, and should not be controlled by budget constraints, as is sometimes the case. Numerical design criteria, based on site specific soil properties and geotextile properties, as well as compatibility tests (such as the gradient ratio test, or the stage 1 test) are available to aid in the design process.

This thesis project has examined the moisture dependency of shear strength in the loess soils of Banks Peninsula. These dominant silt materials are generally regarded as having an angle of internal friction between 25 and 30°, and cohesion of zero, when the soil is saturated. However, soil behaviour in terms of slope stability would appear to support a cohesion value higher than zero as vertical cliffs of loess can be seen to stand indefinitely. It is agreed that loess soils upon saturation do show very low shear strengths, but these soils rarely become saturated due to their low permeability (k<10⁻⁶). To address the quantity of water content dependency of shear strength, five field sites have been sampled for unconsolidated undrained triaxial shear strength to determine c and ø at varying water contents in the total stress state, which most closely simulates observed behaviour. The field sites were: 1) Moncks Spur primary airfall in situ loess; 2) Stonehaven Subdivision loess-colluvium; 3) Worsleys Spur primary airfall in situ loess; 4) Duvauchelle primary airfall in situ loess; 5) Whaka Terrace uncompacted loess fill. Nominated water contents for the shear testing program were 6%, 10%, 14% and "as wet as possible". Samples were prepared in the laboratory by immersing the stainless steel sampling tube containing the soil sample in water for up to 2 weeks to a water content maximum, and then drying them back to the nominated water content. Analysis of results of all five field sites tested at the four nominated water contents showed a new cohesion trend, which has not previously been reported in Banks Peninsula Loess. As water contents increase from 6% cohesion increases to a maximum value and then decreases, whilst for angle of internal friction there is a linear decrease over the entire range of water contents, for example 52° at 6% to 13° at 23% for Stonehaven Subdivision loess colluvium. Maximum values for primary airfall (in situ) Port Hills loess fill and colluvium the cohesion maximum was approximately 210 kPa at 10% water content. Friction angle trends were quite similar for all sites. A secondary aim of this thesis was to examine lime stabilising effects on compacted loess fill. Trials were carried out at the Whaka Terrace field site where excavated loess fill from a test pit was mixed with hydrated lime at 2% by weight of the total soil mass, and then compacted back into the same test pit so that the treated soil could be cured under field conditions. Untreated samples were taken from the base of the test pit and treated soils were extracted from the treated compacted layers at intervals of 1 week, 1 month and 2 months after compaction. Samples were prepared at two different water contents, 15% and as "as wet as possible", so that a shear strength dependence on water could also be established. Results suggest that 15% water content treated samples had 30-40 kPa more cohesion and 5° more angle of internal friction than the "as wet as possible" treated samples. For example after 7 days of field curing cohesion was recorded at 30.7 kPa and 4 kPa for water contents of 16.9% and 19.1% respectively, and angle of internal frictions were 30° and 23.4° for the same respective water contents. Shear strength values increased over time with a rapid rate of increase after the first week of curing, and then a slowing down thereafter. A maximum cohesion of 25 kPa and angle of internal friction was recorded for samples cured in the field for 68 days as compared to untreated loess, which had cohesion of 0 kPa and 11.5° for the angle of internal friction. Both were tested at "as wet as possible" water contents. Future work should entail the determination of effective stress parameters c and ø’ by determining matric suctions (negative pore pressures) to determine if the trend seen in this project is something new or an artefact of the analysis used, and more study centred on loess from the Akaroa Harbour region. In conclusion it has been demonstrated in this thesis that Banks Peninsula Loess shear strength has a dependency on water content in terms of total stress parameters c and by way of using the triaxial test apparatus in the unconsolidated undrained condition.

In this thesis, the mechanism of landslides in loess slope is studied based on a field test in association with laboratory tests and numerical modeling. The field test was carried out in the Heifangtai Plateau in China. Heifangtai belongs to semiarid monsoonal with scarce precipitation. Therefore, agricultural irrigation is the major source of water infiltration for the loess slopes in Heifangtai. The test site was selected at the crest of a steep loess slope with developed cracks, covered by more than 40m loess layer. Ground investigation, including lithological composition, groundwater level, soil sampling and soil permeability, was conducted. A field monitoring program was then performed by installation of inclinometers, piezometers, moisture probes, tensiometers and crackmeters. The field irrigation test with instrument monitoring was conducted at the test site on October 2009, lasting for 12 days. Based on field observation and monitoring results, some typical failures occurred in the field test were analyzed in details, including development of cracks, formation of sinkholes and failures on slope surface. These failures are representative in loess regions and are potential factors of loess landslides. A conceptual model was proposed to reflect soil failures induced by water infiltration along the crack. To characterize the loess behavior to infiltration, a comprehensive triaxial testing program was conducted on trimmed loess specimens sampled in Heifangtai. The fundamental behavior of loess was investigated following different stress paths under both saturated and unsaturated conditions. Based on triaxial tests, the soil parameters including mechanical properties and hydraulic properties were obtained. The finite difference program FLAC3D was adopted in this study, the fluid model of which was extended from saturated flow to saturated/unsaturated flow. A numerical model was built to study the mechanism of soil failures induced by variation of water level in the crack, using a proposed moving boundary algorithm. In the numerical modeling, fluid-mechanical coupled analysis was conducted by solving Biot’s consolidation equation, utilizing soil parameters obtained in the laboratory tests. The proposed conceptual model in the field test was verified in the numerical analysis. Subsequently, different draining rates of water in the crack were simulated to investigate soil failures affected by the dropping of water level in the crack. Based on the numerical analysis, the mechanism of sinkhole formation was discussed. Finally, conclusions and recommendations for future research on loess landslides induced by infiltration were made. It is hoped that the study on the mechanism of loess landslides can provide a useful reference for the future research.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy

Climate change is today one of our highest priority challenges. But to understand the change in climate and to be able to make predictions about the future, knowledge about past climate is of substantial importance. The key archive of past climate change can be studied through loess deposits. This paper examines loess sources in Europe and how deposits can tell us about different origins through different geochemical techniques and methods.    Secondary data of loess deposits and sources over Central-Eastern Europe have been collected and examined in order to test some of the possible major dust source areas for European loess deposits that have been suggested by other scientists.   Different techniques and methods are used to examine loess sediments when trying to identify their origin. Generally, techniques and methods can be divided into geochemical and analytical parameters, which are XRD (X-ray diffraction) and XRF (X-ray fluorescence spectrometry), elemental ratios, SrNd isotopic analyses, zircon U-Pb geochronology, combined bulk and single grain analyses, as well as more statistical approaches.    The results are based on the three mainly studied articles show that it is more likely that loess sources are coming from High Alps and mountain areas, such as the Carpathians, rather than from glaciers, as was previously the main idea.   This paper therefore draws the conclusion that loess material, in most cases, seems to be originating from relatively nearby and local mountain areas and only a small portion appear to have been transported longer distances.

Loess is a well sorted, fine grained, windblown (aeolian) sediment and deposits as a blanket over large areas, reaching from a few centimetres to several hundreds of meters in height and can drape large landscapes in form of mountains. During a more humid and warmer climate, redox conditions are changed in the loess deposits, with greater seasonal moisture creating greater soil formation (pedogenesis), i.e. palaeosol.  The Chinese Loess Plateau is dominated by the East Asian monsoon climate, and consists of an alternating Loess-palaeosol Formation, spanning back to at least the whole Quaternary period and late Pliocene (~2.8 Ma), and overlays a Red Clay Formation ranging into at least Miocene. This deposit covers therefore the onset of the latest Quaternary Ice Age. The Magnetic Susceptibility (MS) is used to investigate the magnetism of a rock which is inferred to be driven by the pedogenetic activity changes, i.e. during a stronger pedogenesis a higher amount of magnetic minerals forms. In turn the MS measurements becomes as a good indicator of the intensity and duration of the East Monsoon climate. In present study, a newly applied technique in palaeoenvironment is used to investigate the reasons for the out-of-phase response by the MS measurements. The study shows that this is due to viscous relaxation. Thus, the ultrafine superparamagnetic mineral magnetite is giving rise to the out-of-phase response and no other mechanisms.
Lössjord är ett välsorterad, finkornigt, vindblåst (eolisk) sediment som avsätts som ett täcke över stora områden, och kan variera från några centimeter till flera hundra meter i höjd och drapera stora landskap i form av berg. Under ett mer fuktigt och varmare klimat förändras de redoxa förhållandena i lössjordarna, då större säsongsfuktighet skapar en större paleosol-bildning, under en så kallad pedogenes. Den Kinesiska Lössjordsplatån domineras av det östasiatiska monsunklimatet och består av en alternerande Lössjord-paleosol Formation, som sträcker sig tillbaka till åtminstone hela kvartära perioden men även sena Pliocen (~ 2,8 Ma), och överlagrar en Rödlera Formation som sträcker sig minst tillbaka till Miocen. Dessa avlagringar täcker därför övergången till början på den kvartära istiden. Den magnetiska susceptibiliteten (MS) används för att undersöka de magnetiska egenskaperna hos avlagringarna som drivs av de pedogenetiska aktiviteterna, dvs under en starkare pedogenes bildas en högre mängd magnetiska mineraler. I sin tur blir därför MS-mätningarna en bra indikator på intensiteten och varaktigheten av östasiatiska monsunklimatet. I denna studie används en nyligen tillämpad teknik inom paleo-miljö för att undersöka orsakerna bakom ur-fas responsen som fås genom MS-mätningar på avlagringarna. Studien visar att detta beror på viskös relaxation. Således är det ultrafina superparamagnetiska mineralet magnetit som ger upphov till ur-fas responsen och inga andra mekanismer.

This study investigates a slope failure complex in loess at Allandale, Lyttelton Harbour. Literature relevant to the slope stability and strength of Banks Peninsula loessial soils is reviewed. Laboratory and in situ strength testing shows that both C and P layer loess in a partially saturated state displays a significant reduction in undrained shear strength with increasing degree of saturation. Strength reduction can be attributed to reduced pore water tension due to capillary suction which results from an increased degree of saturation. The moisture controlled strength component in partially saturated loess can be defined by any two of dry density, moisture content and degree of saturation. When comparing loess C and P layer remoulded strengths with peak strengths, the P layer is significantly more sensitive to remoulding than C layer. Drained direct shear testing of C layer loess produces remoulded and peak strength parameters of c'=O, Ø'=28.4° and c'=6kPa, Ø '=28.4° respectively. Drained direct shear testing of P layer loess produced remoulded and peak shear strength parameters of c'=O, Ø '=28.4° and c'=20kPa, Ø '=28.4° respectively. The slope failure complex investigated has been formed by an earthflow initiated by a tension crack in C layer loess (which acts as an unconfined leaky aquifer). Subsequent retrogressive upslope and lateral migration of the slope failure complex involves "turfmat slides" in S layer loess which also acts as an unconfined leaky aquifer, and more tension crack initiated earth flows in C layer loess. Back analysis suggests both forms of slope movement may have failed by translational sliding at the base of their respective loess layer, with a piezometric level coincident with the ground surface. Mobilisation of the "turfmat slide", requires drained remoulded shear strengths, whereas mobilisation of the earth flow is more likely to involve drained peak shear strengths.

Muitos negócios possuem exposição às variações climáticas e com poucas alternativas para mitigar este tipo de risco. Nos últimos 20 anos o mercado de derivativos climáticos se desenvolveu principalmente em locais como Canadá, EUA e Europa para transferir os riscos relacionados às variações climáticas para investidores com maior capacidade de absorção, tais como seguradoras, resseguradoras e fundos de investimentos. Este trabalho implementou uma metodologia de precificação destes contratos para a variável temperatura média diária no Brasil. Foram utilizados os dados de 265 estações meteorológicas cadastras no site do BDMEP/INMET, utilizando-se observações diárias durante o período 1970-2012. Enquanto a maior parte dos trabalhos de precificação fora desenvolvida para um local específico, neste estudo buscou-se uma solução mais generalizada e que permitisse aos participantes deste novo mercado balizar suas expectativas de preço para qualquer ponto com uma estação meteorológica no país. O principal desafio para esta abordagem foram as falhas nas séries temporais e para isto desenvolveu-se uma metodologia de preenchimento utilizando as informações do projeto NCEP/NCAR. Cada estação foi submetida ao algoritmo de análise e modelagem das séries de temperatura. Considerou-se \"Sucesso\" (36.2% dos casos) as estações cujo processo de modelagem culminou em um resíduo ruído branco, estacionário e homoscedástico. Por \"Fracasso\" (63.8% das estações) entendem-se os casos que violaram pelo menos uma destas condições. Para a incorporação da tendência nos dados utilizou-se a Regressão Polinomial Local (LOESS). Para a estimação da sazonalidade foi empregada análise espectral e utilizada a série de Fourier. Para o tratamento da autocorrelação serial nos resíduos utilizou-se modelos ARFIMA, que contempla um parâmetro para memória longa do processo. A análise espacial dos resultados sugere uma maior taxa de \"Sucesso\" para a precificação de contratos na região Centro-Sul do país e piores para Norte e Nordeste. O método de preenchimento das falhas não deve ser utilizado indiscriminadamente por todo o país, uma vez que a correlação entre as séries do BDMEP/INMET e NCEP/NCAR não é constante, além de apresentar um claro padrão na dispersão espacial. A precificação dos contratos foi feita pelos métodos de \"Burning cost\", \"Modelagem do Índice\" e \"Modelagem da temperatura média diária\". Para este último caso as temperaturas simuladas apresentaram um viés ligeiramente acima dos dados históricos, podendo causar grandes distorções na precificação dos contratos. Deve-se realizar uma correção dos valores simulados antes da precificação dos contratos. A qualidade e consistência dos dados climáticos representam a maior ameaça para a utilização de derivativos climáticos no país, principalmente na região Cento-Oeste, aonde existem poucas estações meteorológicas, e Nordeste, com baixíssima taxa de \"Sucesso\", mesmo com um razoável número de estações.
Many business are exposed to weather variations and managers did not use to have a tool to avoid it. In the last twenty years, weather derivative markets has developed mainly in Canada, USA and Europe, transferring these risks to investors who are willing and able to assume it and receive a financial compensation for that, such as investment funds, insurance and reinsurance companies. This study developed a methodology to price weather contracts with daily average temperature as underlying. It was used 265 public weather stations from BDMEP/ INMET and data was collected from 1970 up to 2012. While the most part of studies in this area have focused in one or few stations, the goal of this study was to develop a more general pricing tool which would allow assessing weather risk and quoting it at any place in Brazil with an available weather station. The main issue was the gaps that occur so frequently in weather time series data and a methodology using interpolated data from NCEP/NCAR was proposed to deal with it. At the bottom of modelling process, weather stations were classified as \"Success\" (36.2%) or \"Failure\" (63.8%) according to the analysis of residuals. To be considered \"Success\", residuals of a time series must be stationary, homoscedastic and white-noise, i.e., free of autocorrelation. If at least one of these was not reached, the modelling process of this weather station was considered \"Failure\". Detrend data was done using Local Polynomial Regression (LOESS). Seasonality was estimated using spectral analysis and Fourier analysis. Autocorrelation of residuals was incorporated into the model using ARFIMA models, which have a parameter to deal with long memory process. Spatial analysis of results suggests a higher \"Success\" rate for contracts priced in the Center south region and worst results were obtained in North and Northeast. Methodology to fill the gaps should not be used in all situations, once correlation is not constant through the country and has a strong spatial pattern (clustering). Pricing was done using \"Burning cost\", \"Index modelling\" and \"Daily modelling of average temperature\". In this former case, simulated temperature has shown a slightly positive bias, which could create huge differences in prices compared with other models. A correction should be done to these values, to use it for pricing purposes. The quality and consistency of weather data is the main issue to develop a weather market in Brazil, mainly in Center-West region, where there is a small number of weather stations and Northeast with the lowest \"Success\" rate, even with a not so small number of weather stations.

Tunnel gully erosion is common in the loess deposits of the South Island of New Zealand. The loess deposits found on the Wither Hills (Marlborough) and Port Hills (Banks Peninsula) are prone to extensive tunnel gully erosion which has caused significant damage in both rural and urban areas. However, the loess deposits found on the Timaru Downs (South Canterbury) and the hills surrounding Akaroa (Banks Peninsula) are significantly less affected. Geotechnical tests including pinhole erosion, uniaxial expansion, crumb test and dispersion % were carried out to determine the erosive and dispersive characteristics of loess samples from locations in the aforementioned areas. From this data, the extent to which geotechnical properties influence the incidence of tunnel gully erosion was determined. Other geotechnical characteristics such as grain size, clay mineralogy, exchangeable sodium content and insitu dry density were also evaluated in order to determine the controlling factors on the erosive and dispersive characteristics of the different loess samples. In general, it was found that laboratory test results did not correlate fully with field erodibility. For instance, the two non tunnel gullied soils exhibited characteristics which suggested that they should be prone to tunnel gully erosion. The lack of correlation between laboratory test data and field erodibility suggests that other factors such as climate, land use and soil profile characteristics are important in determining the occurrence of sub-surface erosion. A comparison was made of the loess stabilising properties of an enzyme based product known as Endurazyme and quicklime (CaO), a commonly used loess stabiliser. Tests were carried out on samples from the Timaru Downs and the Ahuriri quarry on Banks Peninsula. It was found that Endurazyme has a negligible effect on important geotechnical properties such as erodibility, dispersivity, durability, strength and maximum dry density/optimum moisture content.

Tesis (DCI)--FCEFN-UNC, 2008
Plantea la implementación de una nueva metodología alternativa a las existentes que permita obtener en forma simultánea el hidrograma de escurrimiento superficial e infiltración que genere además, curvas de perfiles de la humedad del suelo. Desarrolla un programa (NETRAIN 3.0) para el cálculo de la infiltración a través de datos de campo medidos

When measuring weathering intensity of paleosols there arevarious methods and ratios that can be used. This studyexamines several weathering indicators too see which are bestapplied and most effective on loess and paleosols from Yukon,Canada. This region today is considered sub-arctic, but duringpast time this area and its soils has been characterized byglaciations and interglaciations. These changes are the origin ofthe unweathered Kluane loess and the weathered Slims Soilthat are analyzed in the study. Methods used to determine themost sensitive weathering indicator was; CIA (the ChemicalIndex of Alteration), CPA (the Chemical Proxy of Alteration),oxide ratios ((CaO + Na2O + MgO)/TiO2 and (CaO + Na2O +K2O)/TiO2), and elemental ratios (Rb/Sr, Ba/Sr, Ti/Sr). Theresults from the CIA and oxide ratios show that calcium is thevarying factor, and thereby a good weathering indicator forthese samples. The elemental ratios showed a great variationbetween weathered and unweathered samples, and a cleardecrease strontium is apparent. These ratios would also beuseful indicators, but since Sr is associated with Ca, it isprobably calcium that is the main feature. The methods withoutcalcium as a factor did not give any clear separation betweenKluane loess and Slims Soil. Thereby it is concluded that proxyscontaining Ca are the most useful indicators of weathering inthis area.

Loess is an unique record of the paleoclimate of the Quaternary. Because it is directly deposited from the atmosphere, it can be used as a proxy for wind speed and circulation patterns. It can also be directly dated using luminescence. The site of the loess being investigated for this paper is PrimelTrégastel (Brittany), which lies in north-western France of the shore to the English Channel. The English Channel may be one of the sources for loess of the last glaciation, the Wichselian, and is the reason for choosing Primel-Trégastel to investigate. It is the purpose of this paper to investigate the climate of the time the loess was formed at Primel-Trégastel using grain-size distribution analysis, as well as comparing its properties to other loess sites in north-western Europe. The results show that the loess of Primel-Trégastel is coarse and have a relatively high sand content. That may imply that the loess was deposited during cold and arid conditions by high wind speeds, and at that it may have had a relatively close source. The results also exhibit cycles in the coarseness of the grain-size, indicative of the climate varying between cold and relatively warmer, resulting in relatively higher and lower wind speeds respectively. The loess of Nantois and Pegwell Bay are also relatively coarse, and the loess of Pegwell Bay also have a high sand content. The loess of Nussloch was in comparison more unlike the one of Primel-Trégastel, possibly due to the lack of a local source of sand at Nussloch.

Huge changes in climate occurred at the end of the last Quaternary glaciation. The end of this glaciation corresponds with the end of Pleistocene with its repeated glacial cycles and the start of the current geological epoch, the Holocene interglacial. The climate at this time was characterized by increasing temperatures and an increase in rainfall. This project focuses on understanding and examining these changes in climate using loess deposits from south-western England. Loess is an aeolian sediment and covers around 10 % of the Earth’s land surface and these deposits are excellent archives of past climate. Investigating loess can give understanding of past regional and local wind circulation patterns, atmospheric dustiness as well as weathering conditions. Studying paleoclimate is important since studying and understanding trends in past climate can increase our understanding of how the climate will change in the future. This study examined loess from two sites in south-western England, Porth Cressa and Lowland Point. These are relatively thin deposits; Lowland Point has a thickness of 180 cm and Porth Cressa has a thickness of 97 cm. England lacks the thick loess deposits that can be found in other parts of the world and thus the study of English loess has mostly been neglected. These deposits thus could contain unutilized information about paleoclimate. The elemental composition of the samples was examined using X-Ray Fluorescence (XRF). With the measured elemental composition, it’s possible to use weathering indices to see trends in postdepositional weathering. Low weathering intensities indicate a colder and drier climate, while higher weathering intensities indicate a warmer and more humid climate. The results from the weathering indices were plotted against depth at the two sites to identify changes in weathering and hence climate over time. Compared with the results from previous studies the results from some weathering indices seemed credible. Previous studies have indicated that the Chemical Proxy of Alteration (CPA) is the most appropriate weathering index for loess and the results from this study supports that theory. The results from the CPA show a trend with decreasing weathering intensities followed by a trend with increasing weathering intensities This implies that there was a period with decreasing temperatures/humidity followed by a period with increasing temperature humidity sometime at the end of the last glaciation. The geochemical data also showed support for a previous archaeological theory that there has been human reworking in the upper horizons at Lowland Point.
Slutet av den sista kvartära glaciationen var en tid med stora klimatförändringar. Denna tid sammanfaller med slutet av Pleistocene och dess glaciära cyklar samt starten på den nuvarande geologiska epoken, Holocen. Klimatet vid den här tiden karaktäriserades av ökande temperaturer och ökande nederbörd. Det här projektet fokuserar på att granska och förstå dessa klimatförändringar med hjälp av lössjordar från sydvästra England. Löss bildas av vindburet sediment och täcker ungefär 10 % av jordens landyta, dessa avlagringar är utmärkta arkiv för historiskt klimat. Att undersöka lössjordar kan ge information om historiska regionala och lokala vindcirkulations-mönster, vittringsförhållanden samt mängden damm i atmosfären. Att undersöka paleoklimat är viktigt då förståelse för trender i tidigare klimat kan ge oss förståelse för hur klimatet kommer förändras i framtiden. Den här studien undersökte löss från två platser i sydvästra England, Lowland Point och Porth Cressa. Dessa avlagringar är relativt tunna; Lowland Point har en tjocklek på 180 cm och Porth Cressa har en tjocklek på 97 cm. England har inte de tjocka lössavlagringarna som går att hitta i andra delar av världen och därför har lite forskning utförts på brittiskt löss. Dessa avlagringar kan alltså innehålla oanvänd information om paleoklimat. Provernas grundämnessammansättning undersöktes med X-Ray Fluorescence (XRF). Med den uppmäta grundämnessammansättningen är det möjligt att använda vittringsindex för att se trender i vittring efter deposition. En låg vittringsintensitet indikerar ett kallare och torrare klimat medan en högre vittringsintensitet indikerar ett varmare och fuktigare klimat. Resultaten plottades mot djup för att visuellt identifiera förändringar i klimatet över tid. Vid jämförelse med tidigare studier verkade resultaten från vittringsindexen trovärdiga. Tidigare studier har föreslagit att CPA (Chemical Proxy of Alteration) är det mest lämpliga vittringsindexet för lössjordar och resultaten från denna studie stödjer den teorin. Resultaten från CPA visade på en trend med minskade vittringsintensitet följt av en trend med ökande vittrings intensitet. Detta antyder att det var en period med minskande temperatur/fuktighet följt av en period med ökande temperatur/fuktighet runt slutet av den senaste istiden. De geokemiska resultaten stödde också den tidigare arkeologiska teorin att mänsklig aktivitet har påverkat de övre horisonterna vid Lowland Point.

Le but de ce travail est l'étude de plusieurs gisements loessiques. Cette étude porte sur leurs caractères sédimentologiques à travers plusieurs types de dépôts. Les uns épais et localisés comme à Lédenon, Collias, ou la plaine de Gémenos-Aubagne, les autres plus dispersés comme sur la Costière de Nîmes. Cette étude stratigraphique a permis aussi de montrer que certaines accumulations sablo-limoneuses ne sont pas des loess comme une partie des dépôts de la vallée de la Cèze. Enfin, nous avons cherché les zones de déflation qui aurait pu alimenter la sédimentation loessique et nous avons pris comme exemple les dépressions hydroéoliennes de St-Cécile-les-Vignes et de Ruth au Nord du Vaucluse et la surface pierreuse du Plan de Dieu que l'on peut considérer comme un reg. L'ouvrage comporte trois parties : une première partie sur le cadre géographique de ces recherches, une seconde partie sur les différentes formations de loess et enfin une dernière partie consacrée aux dépressions hydroéoliennes.

Soil organic carbon (SOC) is important both for its influence on agricultural productivity and for its role in the carbon cycle. The distribution of SOC is highly variable at the field scale both horizontally and vertically; a portion of SOC's variability can be attributed to differences in vegetative cover and to slope position. This study characterized and compared SOC concentration to a depth of 2 meters across 6 loess-veneered watersheds in the central United States. Data were collected as part of the Shawnee Hills Loess Catenas project, a collaboration between the U.S. Department of Agriculture (USDA) Natural Resources Conservation Service, USDA Forest Service, Purdue University, University of Kentucky, Southern Illinois University at Carbondale, and Illinois State Geological Survey, among others. The study consists of pairs of sites, one under forest cover and one grass cover, located in southern Illinois, southern Indiana, and western Kentucky. Bulk density and SOC data were calculated from genetic horizon samples taken from soil pits laid out as transects along slopes at each site. SOC concentrations were significantly higher under forest cover. Footslopes and toeslopes had significantly higher SOC densities than summits, shoulders, and backslopes. A three-part exponential decay model was the best fit for the relationship between SOC density and depth from the surface. The comparisons and models may be used to more accurately predict SOC concentration and carbon pool size on similar loess-veneered landscapes in the central United States.

Analyzing climate changes by loess sediment deposits formed after the last glacial maximum gives us information about how the environment was dynamically before humans physically could record climate changes. Sampling and analyzing loess from different places in the world give us a more reliable view of when events and changes in climate took place. Loess is a last step eolian transported, fine grained sediment and can be a good record as a Quaternary climate archive (Muhs 2013; Stevens et al. 2020). Loess-paleosol sequences can be used as a relative record for climate change. The paleosols in the sequence corresponds to soil which can indicate warmer interglacial/interstadial periods when chemical weathering was active at site. Loess in these sequences reflects on cold and dry climate during glacial periods (Buggle et al. 2008; Muhs 2013). By analyzing geochemical composition of bulk-samples from chosen site one can get information about if paleosols or loess deposits are present at certain depths of profile. Also, if a glacial or interglacial period was present then (Buggle et al. 2011; Johansson 2017). In this study X-ray fluorescence Spectroscopy (XRF), will be used to analyze elemental composition of loess. This to see how soluble and mobile elements relate to immobile and non-soluble ones. This can indirectly tell how paleosols and loess are distributed over the site and if shifts attempt by depth. The samples of loess in this study were taken from north-western France at a site called Primel-Tregastel. Soil weathering indexes will be used in this study to calculate weathering intensities for deposit. Na/Al-based indices called CIA, CIW, CPA, PIA, Index B and Sr-based ratios Ba/Sr and Rb/Sr was used (Buggle et al. 2011). The purpose of the study is to see if weathering has been active at site. And if, to reconstruct at which depths and to make a paleoclimatic interpretation of the site. Na/Al-based indices CIA, CIW, CPA, PIA and Index B shows indications of active weathering at site. Sr-based ratios Ba/Sr and Rb/Sr do also show same indications but with more dramatically variations. The content of mobile and immobile elements does also follow the principle that when mobile elements decrease in percentage, immobile elements get enriched in bulk-sample. The trends shown are a long time of cold climate due to low weathering intensities followed by one warmer and more humid period. Increasing weathering intensities, indicating an interglacial/interstadial period happens as a first development. Continuously a decrease happens in weathering intensity which would indicate a start of a colder period. Topmost layer has been improved and re-worked by human activity and will be misleading to use in a geochemical analysis and paleoenvironmental interpretation.
Att analysera klimatförändringar genom lössjordar formade efter senaste glaciala maximumet ger oss information om hur miljön såg ut dynamiskt innan människan hade möjligheten att mäta klimatvariationer. Genom analys och provtagning av lössjordar från olika platser i världen ger oss en mer trovärdig bild över när händelser och förändringar i klimat skedde. Lössjord är ett slutligen vindtransporterad, finkornigt sediment som även fungerar bra som register för Kvartära klimatarkiv (Muhs 2013; Stevens et al. 2020). Loess-paleosol sekvenser kan användas som ett relativt register för klimatförändringar. Paleosolerna i sekvensen motsvarar jord som indikerar varmare interglaciala/interstadiala perioder när kemisk vittring kan ha varit aktiv. Lössavlagringar i sekvensen reflekterar kallare och torrare klimat under glaciala istider (Buggle et al. 2008; Muhs 2013). Genom att analysera geokemiskt innehåll av prover från lokal kan man få fram information om paleosoler eller lössavlagringar finns vid visst djup i profilen. Indirekt även om en glacial eller interglacial period pågick då (Buggle et al. 2011; Johansson 2017). I den här studien används X-ray fluorescens Spektroskopi (XRF) för att analysera geokemiskt innehåll av lössjord. Detta för att se hur lösliga och mobila element är relaterade till icke-mobila och icke-lösliga element. Det kan indirekt peka på hur paleosoler och löss är fördelat över en lokal och visa om skillnader finns vid olika djup. Proverna i denna studie är tagna från nord-västra Frankrike vid en lokal som heter Primel Trégastel. Jord vittrings index kommer att användas i studien för att beräkna vittringsintensiteter för avlagringen. Na/Al-baserade index som heter CIA, CIW, CPA, PIA och Index B och Sr-baserade förhållanden Ba/Sr och Rb/Sr kommer användas (Buggle et al. 2011). Syftet med studien är att se om vittring har skett vid lokalen. Och om vittring påvisas, kunna rekonstruera vid vilka djup och slutligen göra en paleoklimatisk tolkning över lokal. Na/Al-baserade index CIA, CIW, CPA, PIA och Index B visar indikationer av vittring som varit aktiv vid studerad lokal. Sr-baserade förhållanden Ba/Sr och Rb/Sr visar samma indikation men med mer dramatiska variationer. Innehållet av mobila och icke-mobila element följer även principen om att när mobila element minskar i procent så ökar dom icke-mobila elementen. Trenderna som visas är en lång tid av kallt klimat med låg vittringsintensitet som följs av en varmare och fuktigare period med högre vittringsintensitet. Utvecklingen av denna ökande vittringsintensitet indikerar en pågående interglacial/interstadial period. Fortsättningsvis sker en minskning i vittringsintensitet vilket påvisar en början av en kallare period. Det översta lagret i lokalen har bevisats blivit förändrat av mänsklig aktivitet och kan var missvisande i en geokemisk analys och paleoklimatologisk tolkning.

Thesis (Ph. D.)--University of Oregon, 1999.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 202-211). Also available for download from the Internet; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948017.