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Unified Soil Classification System
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<h2 id="symbol-chart">Symbol chart</h2> <table><tbody><tr><th colspan="3">Major divisions</th><th>Group symbol</th><th>Group name</th></tr><tr><td rowspan="8">Coarse grained soilsmore than 50% retained on or above No.200 (0.075 mm) <a href="/facts/Sieve/LJBztC9f">sieve</a></td><td rowspan="4"><a href="/facts/Gravel/IwHG9JfI">gravel</a>> 50% of coarse fraction retained on No.4 (4.75 mm) sieve</td><td rowspan="2">clean gravel <5% smaller than No.200 Sieve</td><th>GW</th><td>well-graded gravel, fine to coarse gravel</td></tr><tr><th>GP</th><td>poorly graded gravel</td></tr><tr><td rowspan="2">gravel with >12% fines</td><th>GM</th><td>silty gravel</td></tr><tr><th>GC</th><td>clayey gravel</td></tr><tr><td rowspan="4"><a href="/facts/Sand/MdTIt0M8">sand</a>≥ 50% of coarse fraction passes No.4 (4.75 mm) sieve</td><td rowspan="2">clean sand</td><th>SW</th><td>well-graded sand, fine to coarse sand</td></tr><tr><th>SP</th><td>poorly graded sand</td></tr><tr><td rowspan="2">sand with >12% fines</td><th>SM</th><td>silty sand</td></tr><tr><th>SC</th><td>clayey sand</td></tr><tr><td rowspan="6">Fine grained soils50% or more passing the No.200 (0.075 mm) sieve</td><td rowspan="3"><a href="/facts/Silt/HAxJkhDP">silt</a> and <a href="/facts/Clay/xnwouEkB">clay</a><a href="/facts/Liquid_limit/vVBMPgoH">liquid limit</a> < 50</td><td rowspan="2"><a href="/facts/Inorganic/TfFfzxSz">inorganic</a></td><th>ML</th><td>silt</td></tr><tr><th>CL</th><td>lean clay</td></tr><tr><td><a href="/facts/Organic_material/t17tVCvk">organic</a></td><th>OL</th><td>organic silt, organic clay</td></tr><tr><td rowspan="3">silt and clayliquid limit ≥ 50</td><td rowspan="2">inorganic</td><th>MH</th><td><a href="/facts/Elasticity_(physics)/wcJoIFg1">elastic</a> silt</td></tr><tr><th>CH</th><td>fat clay</td></tr><tr><td>organic</td><th>OH</th><td>organic clay, organic silt</td></tr><tr><td colspan="3">Highly organic soils</td><th>PT</th><td><a href="/facts/Peat/F0kJcsLt">peat</a></td></tr></tbody></table> <h3>ASTM D-2487</h3> <table><tbody><tr><th rowspan="2" colspan="4">Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests</th><th colspan="2">Soil Classification</th></tr><tr><td>Group Symbol</td><td>Group Name</td></tr><tr><td rowspan="8">COARSE-GRAINED SOILS<p>More than 50% retained on No.200 Sieve</p></td><td rowspan="4">Gravels<p>More than 50% of coarse fraction on No. 4 Sieve</p></td><td rowspan="2">Clean Gravels<p>Less than 5% fines</p></td><td>Cu ≥ 4 and 1 ≤ Cc ≤ 3</td><td>GW</td><td>Well-graded gravel</td></tr><tr><td>Cu < 4 and/or Cc < 1 or Cc > 3</td><td>GP</td><td>Poorly graded gravel</td></tr><tr><td rowspan="2">Gravels with Fines<p>More than 12% fines</p></td><td>Fines classify as ML or MH</td><td>GM</td><td>Silty Gravel</td></tr><tr><td>Fines classify as CL or CH</td><td>GC</td><td>Clayey gravel</td></tr><tr><td rowspan="4">Sands<p>50% or more of coarse fraction passes No.4 sieve</p></td><td rowspan="2">Clean Sands<p>Less than 5% fines</p></td><td>Cu ≥ 6 and 1 ≤ Cc ≤ 3</td><td>SW</td><td>Well-graded sand</td></tr><tr><td>Cu < 6 and/or Cc < 1 or Cc > 3</td><td>SP</td><td>Poorly graded sand</td></tr><tr><td rowspan="2">Sands with Fines<p>More than 12% fines</p></td><td>Fines classify as ML or MH</td><td>SM</td><td>Silty sand</td></tr><tr><td>Fines classify as CL or CH</td><td>SC</td><td>Clayey sand</td></tr><tr><td rowspan="8">FINE-GRAINED SOILS<p>50% or more passes the no. 200 Sieve</p></td><td rowspan="4">Silts and Clays<p>Liquid limit less than 50</p></td><td rowspan="2">Inorganic</td><td><a href="/facts/Plasticity_index/vVBMPgoH">PI</a> > 7 and plots on or above "A" line</td><td>CL</td><td>Lean clay</td></tr><tr><td>PI < 4 and plots below "A" line</td><td>ML</td><td>Silt</td></tr><tr><td rowspan="2">Organic</td><td>Liquid limit—oven dried < 0.75</td><td>OL</td><td>Organic clay</td></tr><tr><td>Liquid limit—not dried</td><td>OL</td><td>Organic silt</td></tr><tr><td rowspan="4">Silts and Clays<p>Liquid limit 50 or more</p></td><td rowspan="2">Inorganic</td><td>PI plots on or above "A" line</td><td>CH</td><td>Fat clay</td></tr><tr><td>PI plots below "A" line</td><td>MH</td><td>Elastic silt</td></tr><tr><td rowspan="2">Organic</td><td>Liquid limit—oven dried < 0.75</td><td>OH</td><td>Organic clay</td></tr><tr><td>Liquid limit - not dried</td><td>OH</td><td>Organic silt</td></tr><tr><td colspan="4">HIGHLY ORGANIC SOILS</td><td>PT</td><td>Peat</td></tr></tbody></table><p><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><h2 id="see-also">See also</h2> <ul><li><a href="/facts/AASHTO_Soil_Classification_System/0ycTLo0q">AASHTO Soil Classification System</a></li> <li><a href="/facts/AASHTO/IlB1BuPQ">AASHTO</a></li> <li><a href="/facts/ASTM_International/xzdCexYJ">ASTM International</a></li> <li><a href="/facts/USDA_soil_taxonomy/HgpyDsEX">USDA Soil Taxonomy</a> (Soil classification for agricultural purposes)</li></ul> <ul><li><a href="http://www.astm.org/Standards/D2487.htm"><i>Classification of Soils for Engineering Purposes: Annual Book of ASTM Standards</i></a>, D 2487-83, vol. 04, American Society for Testing and Materials, 1985, pp. 395–408</li> <li>Evett, Jack and Cheng Liu (2007), <i>Soils and Foundations</i> (7 ed.), Prentice Hall, pp. 9–29, <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0132221382</li></ul> Specific <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Day, Robert W. (2013). Geotechnical engineer's portable handbook : with the 2012 international building code (2nd ed.). New York: McGraw-Hill. ISBN 978-0-07-178971-4. OCLC 837179787. <a href="978-0-07-178971-4" target="_blank">978-0-07-178971-4</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Day, Robert W. (2013). Geotechnical engineer's portable handbook : with the 2012 international building code (2nd ed.). New York: McGraw-Hill. ISBN 978-0-07-178971-4. OCLC 837179787. <a href="978-0-07-178971-4" target="_blank">978-0-07-178971-4</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>D 2487 – 06: Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System) (PDF) (Technical report). ASTM International. 2006. <a href="https://lauwtjunnji.weebly.com/uploads/1/0/1/7/10171621/astm_d-2487_classification_of_soils_for_engineering_purposes_unified_soil_classification_system.pdf" target="_blank">https://lauwtjunnji.weebly.com/uploads/1/0/1/7/10171621/astm_d-2487_classification_of_soils_for_engineering_purposes_unified_soil_classification_system.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>D 2487 – 06: Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System) (PDF) (Technical report). ASTM International. 2006. <a href="https://lauwtjunnji.weebly.com/uploads/1/0/1/7/10171621/astm_d-2487_classification_of_soils_for_engineering_purposes_unified_soil_classification_system.pdf" target="_blank">https://lauwtjunnji.weebly.com/uploads/1/0/1/7/10171621/astm_d-2487_classification_of_soils_for_engineering_purposes_unified_soil_classification_system.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>D 2487 – 06: Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System) (PDF) (Technical report). ASTM International. 2006. <a href="https://lauwtjunnji.weebly.com/uploads/1/0/1/7/10171621/astm_d-2487_classification_of_soils_for_engineering_purposes_unified_soil_classification_system.pdf" target="_blank">https://lauwtjunnji.weebly.com/uploads/1/0/1/7/10171621/astm_d-2487_classification_of_soils_for_engineering_purposes_unified_soil_classification_system.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>ASTM Standard D2487, 2000, "Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)," ASTM International, West Conshohocken, PA, 2000, DOI: 10.1520/D2487-00, www.astm.org. <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> </ol>