|
U.S. UEYdNINLNI Ut aGmICULl UNE CAUL [ Ut
<br />KATURAL RESOURCES CONSERVATION SERVICE • • 11/11/98
<br />Emdnote -- ENGINEERING INDEg PROPERTIES
<br />ENGINEERING INDEX PROPERTIES
<br />This report gives estimates of the engineering classificatios and of the range of inder properties for the
<br />major layers of each soil in the acne) tree. Moat soils have layers of cootreating properties uithis the upper
<br />i or 6 feet.
<br />DEPTH to the upper end lamer bousderiea of eec4 Inver is indicated. The range in depth and information on other
<br />properties of each layer are given in the published Smil Survey for each soil series under 'Soil Series and Their
<br />Norphology.'
<br />TEXTURE is given in the atnsderd tens used by the U.S. Departeent of Agriculture. These terms ere defised
<br />according to percestagea of sand, silt, and cloy in the fraction of the soil that is less then 2 millimeters in
<br />diameter. 'Lose,' for example, is soil that is 1 to 21 percent clay, 18 to SO percent silt, end lees then S1
<br />percent send. If the contest of particles coarser than sand is as moth as about IS percent, as appropriate modifier is
<br />added, for eraeple, 'gravelly.' Tertmral terms are defined in the Soil Survey Glossary.
<br />:'tassification of the soils is determined according to the Unified soil classification system and the system
<br />adopted by the American Assmciatios of State Righmey end Trensporteliom Officials.
<br />The UNIFIED system clasaifiea soils accordiag to properties that affect their use as construction material. Soils are
<br />classified according to grain-sire distribmtios of the fraction leas than J inches in diameter and according to
<br />elasticity inder, liquid limit, nod organic matter contest. Sandy and gravelly soils ere identified ae G~, CP, GM, GC,
<br />SR, SP, SM, and SC; silty and clayey soils as NL, CL, OL, MN, CE, and ON; amd highly organic soils as PT. Soils
<br />::hibiting engiseerisg properties of tmo groups can have a dual claasificstion, for eremple, CL-ML.
<br />The AASHTO system clasaifiea sails accordiag to those properties that affect roadmay construction and maintenance.
<br />In this system, the traction of a mineral soil that is less them J inches in diameter is classified is one of ae-en
<br />stoups from A-I through A-1 on the 6esia of grain-slue distribution, liquid lima , and plasticity isder. Soils in
<br />Troup A-I ere coarse grained and tom is content of fisea (silt and clay. At the other ertreme, voila in group A-1
<br />are fine grained. Righly organic sails are classified in group A-8 on the basis of visual isapectios. If laboratory
<br />data ere available, the A-I, A-1, tad A-1 groups ere further classified as A-I-a, A-I-b, A-1-1, A-1-S, A-1-A, A-1-1, A-1-
<br />i, or A-1-A. As as edditionel refinement, the suitability o(e soli as subgrade material cam be indicated by a group
<br />inder number. Group inder number range from 0 for the best subgrade material to 30 mr higher for the poorest.
<br />tact PRAGMENTS larger than J inches in diameter are indicated as a percentage of the to tai soil os a dry-weight
<br />oasis. The percentages are estimates determined mainly by converting volume percentage in the field to meight
<br />percentage.
<br />'ercentage of soil particles passing designated sieves (PERCENTAGE PASSING SIEVE NUMBER--Iis the percentage of the
<br />soil fraction less than J inches in diameter based on an ovendry weight. The sieves, numbers 1, 10. 10, and 100 I.USA
<br />standard Seriesl, have openings of 1.16, 2.00, 0.110, and 0.011 millimeters, respectively. Estimates are based on
<br />aboratory tests of sails sampled in the survey area amd in nearby areas and on estimates made in the field.
<br />IpUIU LIMIT and PLASTICITY INDEX lAtlerberg limitsi indicate the plasticity characteristics of a soil. The
<br />:stimates are based on test data from the survey area or from nearby areas and on field eramination. The estimates
<br />~i drain-sine distribution, liquid limit, and plasticity inder are ¢enerally rounded to the nearest S percent. Thus,
<br />:~ the ranges of gradation and Atterberg limits attend a marginal aeount II or 1 percentage points) across
<br />assi(uation boundaries, the classification in the marginal tone is omitted in this report.
<br />
|