Data Presentation and Analysis - Investigation to establish if sorting and size (textural maturity) influence the angle of repose of sediment - using beach and desert sand.

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Data Presentation and Analysis

          The main aim of my investigation is to establish if sorting and size (textural maturity) influence the angle of repose of sediment. I use am going to use a beach and a desert sand and I am going to take into account and record the lithologies of the two sediments as lithology can affect the angle of repose in terms of the mineralogy which affects the shape of the grains.  I have made the following hypotheses;

  1. The fine sediment will have the highest angle of repose. This is because the grains are smaller and therefore there are smaller pore spaces between the grains and so there is more contact between the grains and therefore more friction between the grains so a larger shear force is needed to cause the grains to slide.
  2. Poorly sorted sediment will have a higher angle of repose. This is because there are much more contact between the grains because the finer grains can pack in tightly between the coarser grains increasing the contact and friction.
  3. The beach sand will in, in general, have a higher angle of repose as it is more angular and is likely to be poorly sorted whilst the desert sand is likely to be well sorted and have rounded grains.

Methodology;

         This experiment is carried out in a lab environment. This means that there are some risks in carrying out this investigation. For example, if sand is spilt on the table and is blown off into your eye then you could damage your eye. To avoid this carrying the experiment out on paper means that any spilt sand can just be tipped back into the container. There is also a chance that a glass beaker may smash and to avoid any cuts a brush and glass bin should be used to clean up the glass. To avoid heavy objects such as the sieve stacks being knocked over and possibly hurting someone experiments should be set up in the middle of a table and not the edge. Also there will be other people working around you in an enclosed space and so you need to be aware of these people and be careful when carrying things around.

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Results;


Lithologies;

Beach sand;

  • Poorly sorted
  • Angular grains and some rounded grains
  • 50 % coarse quartz grains and 10 % muscovite mica – flaky tabular medium grains.
  • 20 % platy medium shell fragments
  • 20 % black sub rounded mineral

Desert sand;

  • Grains all well rounded and well sorted.
  • Mainly fine-medium grains
  • 95 % quartz grains
  • 5 % plant fragments
  • Grains red coloured – desert varnish

         Figure 1 shows the angles of repose of different sized sediments and the differences ...

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