CLASSIFICATION OF SOILSCREATED BY :-

ALAY MEHTA 141080106011SHIVANI PATEL 141080106021KAVIN RAVAL 141080106026KUNTAL SONI 141080106028

byPranam

esh Chakraborty

GEOTECHNICS AND APPLIED GEOLOGY [G.T.A.G.]

Purpose

Purpose

Arrange various types of soils into groups according to their engineering or various other characteristics.

Soil possessing similar characteristics can be placed in the same group.

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CLASSIFICATION OF SOIL 1. Particle Size Classification 2. Textural Classification 3. Highway Research Board (HRB)

Classification 4. Unified Soil Classification System (USCS) 5. Indian Standard Classification System

(ISCS)

PARTICLE SIZE CLASSIFICATION

Soils arranged according to grain sizes.Terms such as gravel, sand, silt and clay are used to indicate grain sizes.These terms are used only as designation of particle sizes.They do not signify naturally occurring soil types.Naturally occurring soil are mixture of particles of different sizes.

Introduction

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IS Classification of Grain Size

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TEXTURAL CLASSIFICATION

Soil classification of composite soils exclusively based on Particle Size Distribution.Most popular is the Triangular Classification of U.S. Public Roads Administration.Classification based on % of sand, silt and clay size.More suitable for describing coarse grained soil.Clay soil properties are less dependent on particle size distribution.

Introduction

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Textural Classification Chart

HIGHWAY RESEARCH BOARD (HRB)CLASSIFICATION

Based on both particle-size composition as well as plasticity characteristics.Mostly used for pavement construction.7 primary groups (A-1, A-2,…., A-7).

A-1 subdivided into 2 subgroups.

A-2 subdivided into 4 subgroups.

Introduction

Used to describe performance of soil when used for pavement construction.Not used to place a soil in a particular group.

It means rating the value of soil as a subgrade material

within its own group.

Higher the value of GI, poorer is the quality of material.

Group Index (GI)

Group Index of a soil depends on:

1. Amount of material passing 75 micron IS sieve.

2. Liquid Limit.

3. Plastic Limit.

GROUP INDEX (GI) DETERMINATION

Classification Group SymbolsMain Soil

Type Prefix Subgroup Suffix Classification Group symbols

Gravel GWell-graded

Poorly-gradedSilty

Clayey

WPMC

GWGPGMGC

Sand SWell-graded

Poorly-gradedSilty

Clayey

WPMC

SWSPSMSC

Silt M LL < 50%LL > 50%

LH

MLMH

Clay C LL < 50%LL > 50%

LH

CLCH

Organic O LL < 50%LL > 50%

LH

OLOH

Peat Pt Pt

Group Symbols and Group NamesGroup Symbol Typical Name

GW Well-graded gravels.

GP Poorly-graded gravels.

GM Silty gravels.GC Clayey gravelsSW Well-graded sands.SP Poorly-graded sands.SM Silty sands.SC Clayey sands.

Group Symbol Typical Name

CL Inorganic clays of low plasticity.

ML Inorganic silts with slight plasticity.

OL Organic soil of low plasticity.

CH Inorganic clays of high plasticity.

MH Inorganic silts with high plasticity.

OH Organic soil of high plasticity.

Pt Peat.

Group Symbols and Group Names

INDIAN STANDARD CLASSIFICATION SYSTEM (ISCS)

IS:1498-1970

IntroductionBased on USCS systemModifications are:

Fine grained soils subdivided into 3 groups (low, intermediate and high plasticity) as against two groups(low and high) in USCS.

wL <35=L, 35<wL <5o=I, wL >50=H

Thus, soil classified into 18 groups as against 15 in USCS. 19

Classification Group SymbolsMain Soil

Type Prefix Subgroup Suffix Classification Group symbols

Gravel GWell-graded

Poorly-gradedSilty

Clayey

WPMC

GWGPGMGC

Sand SWell-graded

Poorly-gradedSilty

Clayey

WPMC

SWSPSMSC

Silt MLL < 35%

35<LL<>50LL > 50%

LIH

MLMIMH

Clay CLL < 35%

35<LL<>50LL > 50%

LIH

CLCICH

Organic OLL < 35%

35<LL<>50LL > 50%

LIH

OLOIOH

Peat Pt Pt 20

Plasticity Chart

High Plasticity use H - wL >50

Intermediate Plasticity use I – 35< wL >50

Low Plasticity use L - wL <35

Below A-line, use M (Silt) or O (Organic)

Above A-line, use C - Clay