materials and pavement(part 1)

8/13/2019 Materials and Pavement(Part 1)

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CONTENT



Soil Characteristic



Soil Characteristic…cont’d● Causes the disintegration of the rocks into smaller particle sizes by the action of forces ex● e.g● Result of oxidation carbonation and other chemical actions that decompose th



Surface Texture

The texture of a soil can be described in terms of itsappearance, which depends mainly on the shapes andsizes of the soil particles and their distribution in the soilmass.

For example-soils consisting mainly of silts and clays with very smallparticle sizes are nown as fine-textured soils,

-soils consisting mainly of sands and gravel with muchlarger particles are nown as coarse-textured soils.



Basic Engineering Properties Of

Soils



Basic Engineering Properties Of

Soils..cont’d



Atterberg limits



Shrinkage imit !S "!hen a saturated soil is slowly dried, the volume shrin s,but the soil continues to contain moisture.

"ontinuous drying of the soil, however, will lead to amoisture content at which further drying will not result inadditional shrin age.

The volume of the soil will stay constant, and further

drying will be accompanied by air entering the voids.The moisture content at which this occurs is the shrin agelimit, or #$, of the soil.



Plastic limit !P "The plastic limit, or PL, is defined as the water contentthat caused the soil to change from a plastic to a semisolidstate.



i#$id imit ! "The li%uid limit, or $$, is defined as the moisture content at whichthe soil will flow

Plasticity &ndex 'P&(

The range of moisture content over which the soil is in the plasticstate is the difference between the $$ and the P$

P& ) $$ * P$

!here,

$$ li%uid limit

P& plasticity index

P$ plastic limit



i#$id imit ! "..cont’d



AAS%TO Soil Classification S&stem



AAS%TO Soil Classification S&stem&n general, the suitability of a soil deposit for use inhighway construction can be summarized as follows.

1. #oils classified as +-1-a, +-1-b, +- - , +- - , and +-/can be used satisfactorily as subgrade or subbase material ifproperly drained. &n addition, such soils must be properlycompacted and covered with an ade%uate thic ness ofpavement 'base and0or surface cover( for the surface load tobe carried.



. aterials classified as +- -2, +- -3, +- , +- , +-2, +-3-, and +-3-2 will re%uire a layer of subbase material if used

as subgrade. &f these are to be used as emban mentmaterials, special attention must be given to the design ofthe emban ment.

3. !hen soils are properly drained and compacted, theirvalue as subgrade material decreases as the 4& increases. Forexample, a soil with a 4& of zero 'an indication of a goodsubgrade material( will be better as a subgrade material thanone with a 4& of 5 'an indication of a poor subgradematerial(.



#oils are evaluated within each group by using an empirical formula todetermine the group index '4&( of the soils,

given as

4& ) 'F - / (65. 7 5.55 '$$ - 5(8 7 5.51'F - 1 ('P&- 15(!here

4& ) group index

F ) percent of soil particles passing 5.53 mm '9o. 55( sieve in wholenumber based on material passing 3 mm '/ in.( sieve

$$ ) li%uid limit expressed in whole number

P& ) plasticity index expressed in whole number

materials and pavement(part 1)

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