Progressive deformation of glacial till due to viscoplastic straining and pore pressure variation

The stress regime in a cutting (slope) is complex, with different principle stresses acting in different directions along the potential failure plane. For example, stresses may be primarily in extension near the toe and in compression near the crest of a slope. Cuttings in heavily overconsolidated clays are known to be susceptible to progressive failure which usually starts at the toe of the slope. Softening and the development of rupture surfaces have been observed in the field and are well documented for London Clays. However, this failure mechanism is yet to be established for glacial tills. To better understand the progressive failure mechanism, this paper discusses a series of laboratory tests conducted on reconstituted glacial till samples from Northern Ireland. Initial observations indicate that, a soil with insitu stress states between 80-90% of peak strength may undergo significant viscoplastic straining as a result of the combination of pore-pressure cycling and elevated stress level.

Estimation of the small strain stiffness of glacial till using geophysical methods and barometric loading response

Stiffness values in geotechnical structures can range over many orders of magnitude for relatively small operational strains. The typical strain levels where soil stiffness changes most dramatically is in the range 0.01-0.1%, however soils do not exhibit linear stress-strain behaviour at small strains. Knowledge of the in situ stiffness at small strain is important in geotechnical numerical modelling and design. The stress-strain regime of cut slopes is complex, as we have different principle stress directions at different positions along the potential failure plane. For example, loading may be primarily in extension near the toe of the slope, while compressive loading is predominant at the crest of a slope. Cuttings in heavily overconsolidated clays are known to be susceptible to progressive failure and subsequent strain softening, in which progressive yielding propagates from the toe towards the crest of the slope over time. In order to gain a better understanding of the rate of softening it would be advantageous to measure changes in small strain stiffness in the field.

Strength reduction of till under dynamic pore pressure condition

Cuttings in heavily overconsolidated clays are known to be susceptible to progressive deformation caused by creep and fatigue that usually begins at the toe of the slope. The progressive deformation leads to strength reduction with time at constant stress (or called softening) and could be accelerated by fluctuation of groundwater level associated with more extreme rainfall events predicted through climate change. The purpose of this paper is to assess the mechanism of progressive deformation due to creep and fatigue using element testing on samples of till. The samples were subjected to fully drained loading and the deviator stresses were held constant at various percentages of peak failure stress, while the pore water pressure was kept static or dynamic (fluctuating ±5 kPa) over a period of time. The results have shown that the samples experienced significant deformation even at a higher factor of safety (i.e. the failure deviator stress/deviator stress at which the pore water pressure was fluctuated) under pore water pressure dynamics.

Geografisk och historisk karta öfver Finland till skolornes bruk 1858

1 kartta kahdessa osassa :, vär. ;, 53,3 x 44,1 cm, lehti 59 x 48 cm

Kartor och beskrifningar öfver socknarne i Nylands län / upprättade å general landmäteri kontoret, lithografierade och utgifne till granskning och berigtigande år 1844.

1 kartasto ([35] s., [24] karttalehteä (7 taitettuina)) : 24 karttaa, vär. ; 56 cm

Suomen kulkuneuvojen kartta Karta till Finlands kommunikationer

1 kartta kahdessa osassa :, vär. ;, 43 x 37 cm, 1:2000000

Suomen kulkuneuvojen kartta Karta till Finlands kommunikationer

1 kartta kahdessa osassa :, vär. ;, 44 x 37 cm, 1:2000000

Karta öfver Finlands södra skärgård, från Jussarö till Porkala

Kartan esitystekniikka: maastokartta

Litteracitet i fem högstadieungdomars en-till-en-datorpraktiker

The study focuses on five lower secondary school pupils’ daily use of their one-toone computers, the overall aim being to investigate literacy in this form of computing. Theoretically, the study is rooted in the New Literacy tradition with an ecological perspective, in combination with socio-semiotic theory in a multimodal perspective. New Literacy in the ecological perspective focuses on literacy practices and place/space and on the links between them. Literacy is viewed as socially based, in specific situations and in recurring social practices. Socio-semiotic theory embodying the multimodal perspective is used for the text analysis. The methodology is known as socio-semiotic ethnography. The ethnographic methods encompass just over two years of fieldwork with participating observations of the five participants’ computing activities at home, at school and elsewhere. The participants, one boy and two girls from the Blue (Anemone) School and two girls from the White (Anemone) School, were chosen to reflect a broad spectrum in terms of sociocultural and socioeconomic background. The study shows the existence of a both broad and deep variation in the way digital literacy features in the participants’ one-to-one computing. These variations are associated with experience in relation to the home, the living environment, place, personal qualities and school. The more varied computer usage of the Blue School participants is connected with the interests they developed in their homes and living environments and in the computing practices undertaken in school. Their more varied usage of the computer is reflected in their broader digital literacy repertoires and their greater number and variety of digital literacy abilities. The Blue School participants’ text production is more multifaceted, covers a wider range of subjects and displays a broader palette of semiotic resources. It also combines more text types and the texts are generally longer than those of the White School participants. The Blue School girls have developed a text culture that is close to that of the school. In their case, there is clear linkage between school-initiated and self-initiated computing activities, while other participants do not have the same opportunities to link and integrate self-initiated computing activities into the school context. It also becomes clear that the Blue School girls can relate and adapt their texts to different communicative practices and recipients. In addition, the study shows that the Blue School girls have some degree of scope in their school practice as a result of incorporating into it certain communicative practices that they have developed in nonschool contexts. Quite contrary to the hopes expressed that one-to-one computing would reduce digital inequality, it has increased between these participants. Whether the same or similar results apply in a larger perspective, on a more structural level, is a question that this study cannot answer. It can only draw attention to the need to investigate the matter. The study shows in a variety of ways that the White School participants do not have the same opportunity to develop their digital literacy as the Blue School participants. In an equivalence perspective, schools have a compensational task to perform. It is abundantly clear from the study that investing in one-to-one projects is not enough to combat digital inequality and achieve the digitisation goals established for school education. Alongside their investments in technology, schools need to develop a didactic that legitimises and compensates for the different circumstances of different pupils. The compensational role of schools in this connection is important not only for the present participants but also for the community at large, in that it can help to secure a cohesive, open and democratic society.

Determining rotational direction of rotation structures using prolate shaped grains within till

Micromorphology is used to analyze a wide range of sediments. Many microstructures have, as yet, not been analyzed. Rotation structures are the least understood of microstructures: their origin and development forms the basis of this thesis. Direction of rotational movement helps understand formative deformational and depositional processes. Twenty-eight rotation structures were analyzed through two methods of data extraction: (a) angle of grain rotation measured from Nikon NIS software, and (b) visual analyses of grain orientation, neighbouring grainstacks, lineations, and obstructions. Data indicates antithetic rotation is promoted by lubrication, accounting for 79% of counter-clockwise rotation structures while 21 % had clockwise rotation. Rotation structures are formed due to velocity gradients in sediment. Subglacial sediments are sheared due to overlying ice mass stresses. The grains in the sediment are differentially deformed. Research suggests rotation structures are formed under ductile conditions under low shear, low water content, and grain numbers inducing grain-to-grain interaction.

10 minutes till bedtime.

Todos a bordo. Son diez minutos hasta la hora de acostarse, en este tiempo hay que cepillarse los dientes, ponerse el pijama, leer un cuento, darse un baño. En la cama, papá da un beso a su niño y, dulces sueños.