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Home My WebLink About20A Geotech Report - Part 2 GEOTECHNICAL TERMINOLOGY R ' I ' ' ROCK , PaEo� , GEOTECHNICAL ENGINEERING "' CR �tiy7Oq�G�O Standard D 2487 �� Classification of Soils for Engineering Purposes �U- (Unified Soil Classification System) Particle Size Identification Boulders.........................over 12" Soil Classification Cobbles...........................3"to 12" Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Group symbol Group Name' Gravels Cu>_4 and c GW Well-graded gravels' Gravels Clean Gravels 1 `5 Cc`5 3 coarse............................3/4"to 3" More than 50% o Cu<4 and/or GP Poorly-graded gravels° fine................................ No.4 to 3/4" COARSE-GRAINED of coarse Less than 5%fines 1>Cc>3 Sand SOILS fraction Fines classify as ML 0 r G coarse............................ No.4 to No. 10 retained on Gravels with Fines or MH GM Silty gravel ' No.4sieve medium......................... No. 10 to No.40 More than 12%fines Fines classify as CL or GC Clayey grave F,G More than 50% Cu>_6 and fine................................ No.40 to No.200 retained on Sands Clean Sands :5 < SW Well-graded sand" Silt.................................. No.200 to 0.005 mm No,200 sieve 50%or more Less than 5%fines Cu<6 and/or SP Poorly-graded raded sand" Clay less than 0.005 mm of coarse 1>Cc>3 Y g y................................. Fines c assl y as ML G," fraction Sand with Fines or MH SM Silty sand passes I Fines classify as CL or F G," Relative Density of No.4sieve More than 12%fines y SC Clayey sand' BPF=Blows Per Foot PI>7 and Plots on or CL K,L,M COhensionless Soils above'A"line Lean clay ver loose............................0 to 4 BPF FINE-GRAINED Silts and Clays inorganic PI<4orplots blow y SOILS Liquid limit "A' line' ML Silt loose loose....................................5 to 10 BPF less than 50 LL,oven dried K L M,N - organlc LL not ne `0J5 0l OrganicclayK,'L,'M,o medium dense......................11 to 30 BPF 50%or more Or anic silt dense...................................31 to 50 BPF PI plots on or above CH K,L,M passes Silts and Clays inorganic Fat clayvery dense............................over 50 BPF PI lots below"A"line MH Elastic siltK,L,M the No.200 sieve Li uid limit K,L,11,P q LL oven dried 075 OH Organic clay Consistent of Cohesive Soils 50 or more organic LL not ne Organic silt K,L,M,n y HIGHLY ORGANIC very soft............................0 to 1 BPF SOILS Primarily organic matter,dark in color,and organic odor PT Peat soft....................................2 to 3 BPF "Based on the material passing the Sin.(75-mm)sieve. rather Soft..........................4 t0 5 BPF e If field sample contained cobbles or boulders,or both,add"with cobbles or boulders,or both'to group name. medium .............................6 to 8 B P F cCu=D6/D,o Cc=(1330i'/o1e X 40 rather stiff,,,,,,,,,,,,,,,,,,,,,,,,,9 to 12 BPF *If soil contains_-15%sand,add"with sand"to group name. e Gravels with 5 to 12%fines require dual symbols: stiff..................................13 to 16 BPF GW-GM well-graded gravel with silt If Atterberg limits plot in hatched area,soil is a CL-ML,silty clay. Very stiff...........................17 t0 3O BPF GW-GC well-graded gravel with clay K If soil contains 15 to 29%plus No.200,add"with saner'or"with gravel,"whichever is predominant. GP-GM poorly graded gravel with silt L If soil contains>30%plus No.200,predominantly sand,add"sand"to group name. hard ..................................over 30 B P F GP-GC poorly graded gravel with clay "If soil contains-30%plus No.200,predominantly gravel,add"gravelly"to group name. F If fines classify,as CL-ML,use dual symbol GC-GM,or SC-SM. N PI a 4 and plots on or above"A"line. Moisture Content(MC) c If fines are organic,add"with organic fines"to group name. o PI c 4 or plots below"A"line. N If soil contains>l5%gravel,add"with graver to group name. PPI plots on or above"A"line. Description Sands with 5 to 12%fines require dual symbols: o p rather dry MC less than 5%,absence SW-SM well-graded sand with silt PI lots below"A"line. �/ SW-SC well-graded sand with clay of moisture,dusty SP-SM poorly graded sand with silt Sp-SC poorly graded sand with clay moist MC below optimum, but no visible water 60 wet MC over optimum,visible For classlficatlonoffine-grained soils ,% free water,typically below and fine-grained fraction of coarse-grained water table soils 5o Equation of"A"-Line saturated Clay soils where MC over Horizontal at PI=4 to LL=25.5. optimum then PI=0.73(LL-20) J,� a _ Equation of"U"-Line •P 40 Verticle at LL=15 to PI=7 then PI=0.9(LL-8) o� USDA Textural Soil Classification Z 30 0° 20 - s° a MH r Olt 10 GL� 70 k� clay 7 4 _--410 ML or OL 0 10 20 30 40 50 so 70 60 90 100 110 silty s nd7 I •'� '� clay LIQUID LIMIT(LL) 40 cta '� cIA•: silty clay '�� Dam Ipam Laboratory Tests Terminology 30 -- o san ay clay:na— e. DID Dry density, pcf OC Organic,content% LL Liquid Limit 2g WD Wet density, pcf P200 Percent passing 200 sieve PL Plastic Limit ndr:"am41 qu Unconfined compressive strength, psf PI Plasticity Index 'D - qp Pocket penetrometer strength,tsf MC Natural moisture content, /o SAnil 'od ill/ 'aU '`Oc two 0 6n 'rp ■percent sand