Soil mechanics. Solutions manual / Механика грунтов. Руководство по решениям

Q1.1 Describe the main depositional environments and transport processes relevant to soils, and explain their influence on soil fabric and structure.
Q1.1 Solution Use material in Section 1.3.1 to describe and explain
• transport processes: water, wind, ice, ice and water
• depositional environment: water might be fast or slow flowing, eg upstream (fast) or downstream (slow), or ebbing floodwater (probably slow). Windborne material might be washed out of the atmosphere by rain. Material can be transported either on the top of, within or below a glacier or icesheet, or by a combination of ice and meltwater (outwash streams – possibly fast flowing) and perhaps deposited into a glacial lake (slow flowing).
• effect of transport mechanism and depositional environment on particle size – soils transported by wind and water are likely to be sorted, with finer particles remaining in suspension and being transported longer distances than coarse particles. Fine particles fall out of suspension where the water velocity is low, eg deltaic and flood plain deposits. Coarse particles on a river bed are left behind as terraces when a river changes course. Sand dunes migrate due to wind action; deposits of windborne dust washed out by rain may be very lightly cemented with a delicate and potentially unstable structure (loess). Material transported purely by ice tends to be less sorted (eg boulder clay typically has a very wide range of particle size). If final transport or deposition is by or through water some sorting will take place - perhaps vertically rather than horizontally, eg mixed material washed off the top of a glacier and deposited into a glacial lake will have a laminated structure as coarse material settles quickly and fine material more slowly, a pattern repeated over many seasons as the deposit accumulates.
• effect on particle shape – materials transported by ice are likely to be more angular, and materials transported by water more rounded. <...>