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The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes.
[4] [5] The percentage of each soil size is measured by weighing the amount retained on each sieve and comparing the weight to the total weight of the sample. The results of a sieve analysis are plotted as a grain size distribution curve, which is then analyzed to determine the soil gradation of the particular soil.
The R-Value test [1] measures the response of a compacted sample of soil or aggregate to a vertically applied pressure under specific conditions. This test is used by Caltrans for pavement design, replacing the California bearing ratio test.
The ability of the first fill layers to be properly compacted will depend on the condition of the natural material being covered. If unsuitable material is left in place and backfilled, it may compress over a long period under the weight of the earth fill, causing settlement cracks in the fill or in any structure supported by the fill. [4]
Less than 5% fines Cu ≥ 6 and 1 ≤ Cc ≤ 3 SW Well-graded sand Cu < 6 and/or Cc < 1 or Cc > 3 SP Poorly graded sand Sands with Fines. More than 12% fines Fines classify as ML or MH SM Silty sand Fines classify as CL or CH SC Clayey sand FINE-GRAINED SOILS. 50% or more passes the no. 200 Sieve Silts and Clays. Liquid limit less than 50 Inorganic
Soil compaction also impacts infiltration capacity. Compaction of soils results in decreased porosity within the soils, which decreases infiltration capacity. [4] Hydrophobic soils can develop after wildfires have happened, which can greatly diminish or completely prevent infiltration from occurring.
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The Proctor compaction test is a laboratory method of experimentally determining the optimal moisture content at which a given soil type will become most dense and achieve its maximum dry density. The test is named in honor of Ralph Roscoe Proctor [ de ] , who in 1933 showed that the dry density of a soil for a given compactive effort depends ...