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Compressibilty and 1D settlement
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- 1How can volumetric change be brought about?Change in normal or mean effective stress due to compression or swelling/expansion.
Change in shear stress due to contraction or dilation.
Time due to consolidation and swelling or creep. - 2What is 1D loading and give examples.Soil element deforms only in direction of applied load. Soil is constrained laterally in other directions.
E.g. Natural deposition and erosion of the soil; foundation of a large plan area building; pre-loading to strengthen soils; landfill sites. - 3Describe the set up of an oedometer test.The sample is thins so side friction is low and drainage can occur quickly (75mm diamter, 20mm thick). Soil is constrained laterally by a steel ring so only vertical deformation can occur under the verical load. Drainage supplied at top and bottom through porous stones. Water bath surrounds the sample so that it remains saturated during the test. No lateral strain.
- 4What is meant by normally consolidated and overconsolidated?A soil that has never experienced a higher effective stress than it is feeling now is called normally consolidated. A soil that have previously been loaded higher is called overconsolidated.
- 5What happens to a soil on first time loading?Particles of soil rearrange and may locally break. New deformation is due to slippage of particles into new positions. More efficient at resisting higher loads. Deformation is plastic. The higher the applied stress, the desner the packing becomes. It is increasingly hard to push particles even closer together.
- 6What happens to a soil on unloading/reloading?Particles of soil do not need to rearrange to take higher stress. So deformation is due to expansion/compression of solid particles themselves and small reversible particle rotations. Deformation is elastic.
- 7What is the overconsolidation ratio?The ratio between the maximum previous effective stress and current applied effective stress.
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- Geotechnical Engineering Fichas sobre Compressibilty and 1D settlement, creado por Billie Santos el 04/03/2017.
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- Billie Santos
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