important soil

8/9/2019 Important Soil

1/14

Procedure order for classification of soil

GOVERNMENT OF INDIA

MINISTRY OF RAILWAYSRESEARCH DESIGNS AND STANDARDS ORGANISATION

LUCKNOW-226 011

PROCEDURE ORDERFOR

CLASSIFICATION OF FORMATION SOIL

INCLUDING

GUIDELINES FOR TESTING

CIRCULAR NO. GE- P1

GEO-TECHNICAL ENGINEERING DIRECTORATE

MAY-2003


2/14


PROCEDURE ORDER FOR CLASSIFICATION OF FORMATION SOILRef: Correction Slip no: 89 dated 19.09.2003 to IRPWM-para 211(1)(V)

Scope: This procedure order details the methodology to be followed for classification of

soils of existing formations, both embankments and cuttings for the purpose of

maintenance of details in track diagram, as well as create database for up-gradation of

formations, when required. The testing procedure has been included in brief. The

principles of classification and reporting are equally applicable to new constructions

where formation soil classification and blanket depth etc. are to be recorded during

construction itself.

1.0 Definitions:

1.1 Formation: It is a general term referring to the whole of blanket, sub-grade andsubsoil. (Fig. 1)

1.2 Subgrade: It is part of embankment/cutting provided above subsoil by borrowedsoil of suitable quality upto bottom of blanket/ballast.

1.3 Blanket: Blanket is a layer of specified coarse, granular material of designedthickness provided over full width of formation between subgrade and ballast.

1.4 Subsoil: Soil of natural ground below subgrade.

1.5 BIS: Bureau of Indian Standards (formerly known as ISI), BIS lays downstandard terminology, definitions, testing requirement and procedures of various

engineering and other materials in addition to other things.

2.0 The following procedure for classification of formation soil shall be followed.

2.1 Classification: Formation soil will be classified as per BIS Classification

contained in IS -1498 -1970 (enclosed as Annexure-I), duly modified and

simplified for our purpose to the extent that no clay content calculation will be

made based on hydrometer analysis.

2.2 Grouping of soils: Grouping of soils for the purpose of planning of works havingbearing on soil behaviour will be done as per Annexure-II.

2.3 Phasing of work load:

2.3.1 Classification of soils will be done at one location per 2.5 kilometres. The workmay be phased as per para 2.3.2 below.

2.3.2 Asstt. Engineer in open line will have the soil samples collected from the sectionat the rate of one sample per block section, starting with more important routes.

2.3.3 Collection of samples and testing of the same shall be organised at divisional levelby Sr.DEN/Coordination through Divisional, Zonal or any other agency.


3/14


2.3.4 The work of collection of data should be done in a phased manner depending uponthe importance of routes, problem of maintenance and possibility of running of

heavier axle loads. However, it may be preferable to complete the entire work in

four to five years and effort should be made to do the first classification from each

block section within two years of issuance of this circular.

3.0 Collection of samples:

Simple sampling tools normally available with the permanent way inspector may

be used for collection of samples. ( Sampling procedure is enclosed as Annexure-

III).

4.0 Storage of samples:

The samples may be kept in a self-sealing polythene bag alongwith a paper slip

showing location (chainage/kilometre) and other details.

5.0 Transportation:

The samples so collected can be transported to the laboratory by normal means at

the end of the day.

6.0 Testing:

Only two types of test would be performed on the test samples as per the details

enclosed in Annexure-III. Classification of soil will be done as per simplified

procedure based on IS Code 1498 - 1970 as explained in para 2 above.

7.0 Compilation of results:

Results so obtained may be entered in a register which may be seen by the

Sr.DEN (Coordination) every month for monitoring the progress of work and

incorporation of the data generated in the track diagram. (sample proforma

enclosed).

8.0 Monitoring of progress:

Chief Track Engineers of the Railways may monitor the over all progress of thisactivity at least once in a year through track diagrams.

9.0 Assistance:

Assistance to the divisions in establishment of testing facilities may also be

rendered by the GE Organisations of all the Zonal Railways, ensuring that only

qualified staff is posted to carry out work in the laboratory and the same is

equipped well.

10.0 Construction Records:

Dy.CE's in-charge of construction projects shall maintain details of subgrade soil

classification along with the thickness and particle size distribution records of the


4/14


blanket material used for every kilometre of the project and handover the same to

open line counterparts while handing over the section.

-----------------------


5/14


Annexure I

(Page 1 of 5 )

BRIEF DETAILS OF SOIL CLASSIFICATION

(Ref: IS: 1498 - 1970)

Background and Basis of Classification:

The Geotechnical Engineers/Agencies had evolved many soil classification systems, over

the world. The soil classification system developed by Casegrande was subsequently

modified and named as 'Unified Classification system. In 1959, Bureau of Indian

Standards adopted, the Unified classification system as a standard, which was revised in

1970. According to BIS classification system, soils are primarily classified based on

dominant particle sizes and its plasticity characteristics. Soil particles mainly consist of

following four size fractions.

Gravel : 80 4.75 mm Sand : 4.75mm 0.075mm (75 micron) Silt : 75 2 micron Clay : less than 2 micronParticle size distribution of a soil is determined by a combination of sieving and

sedimentation analysis as per procedure detailed in IS: 2720 (Part 4) 1985 and its

plasticity characteristics are determined by Liquid Limit and Plastic Limit as per

procedure detailed in IS:2720 (Part 5) 1985.

Symbols used in Soil Classification:

Symbols and other soil properties used for soil classification are given below. Brief

procedure for Classification of soils has been explained in tabular form and Flow Chart.

Plasticity Chart required for classification of fine grained soils has also been given.

Primary Letter Secondary Letter

G : Gravel W : well-graded

S : Sand P : poorly graded

M : Silt M : with non-plastic fines

C : Clay C : with plastic finesO : Organic soil L : of low plasticity

P: Peat I : of medium plasticity

H : of high plasticity

Other soil parameters required for soil classification:

Cu : Coefficient of Uniformity = D60 / D10 . Cc : Coefficient of Curvature = (D30)2/ (D60 * D10) . D60, D30 & D10 are particle sizes, below which 60,30 and 10 percent soil particles by

weight are finer than these sizes.

Plasticity Index, PI = Liquid Limit (LL) - Plastic Limit ( PL). Coarse-grained soils: Soils having fines ( particles of size less than 75 micron) < 50%. Fine grained soils: Soils having fines more than 50%.


6/14


Annexure I

(Page 2 of 5 )

Brief Procedure for soil classification:

Conduct Sieve analysis and Hydrometer analysis on soil sample and plot particlesize gradation curve and determine Cu and Cc.

Conduct liquid limit and plastic limit test on soil samples as per procedure givenin Annexure III.

Based on above soil parameters, classification should be done as per procedureexplained in the following table/Flow Chart. The classification should be done in

conjunction with the Plasticity Chart given below.


7/14


TABLE EXPLAINING BIS SOIL CLASFICATION SYSTEM

Laboratory criteriaDescription Group

Symbol Fines (%) Grading Well graded gravels, sandy gravels,

with little or no fines GW 0 - 5

Cu > 4

1 < Cc < 3

Poorly graded gravels, sandy gravels,

with little or no fines GP 0 - 5

Not satisfying

GW requirements

Silty gravels, silty sandy gravels

GM > 12

Bel

PI 12

Abo

PI >

Well graded sands, sandy soils, with

little or no fines SW 0 - 5

Cu > 6

1 < Cc < 3

Poorly graded sands/,sandy soils, withlittle or no fines SP 0 - 5

Not satisfyingSW requirements

Silty sands SM > 12 Belo

or P

Coarse

grained

soils:Fine

particles

(size smaller

than 75

micron) less

than 50%

Sands

particles

more than50% of

coarse

fraction (size

above 75

micron) Clayey sands SC > 12 Abo

PI >

Inorganic silts , silty or clayey fine

sands, with slight plasticity

ML Plasticity Index less than 4

Inorganic clays, silty clays, sandy clays

of low plasticity

CL Plasticity Index more than 7

Silts and

clays (Liquid

Limit 50)

Inorganic clays of high plasticity CH Above A- line of Plasticity Chart


8/14


LABORATORY IDENTIFICATION PROCEDURE

HIGHLY ORGANIC SOILS

(Peat)

Fibrous texture, colour, odour, very high

moisture content, particles of vegetable

matter (sticks, leaves etc.)

COARSE GRAINED

50% or less pass 75 micron IS

GRAVEL (G)

Greater percentage of coarse fraction

retained on 4.75 mm IS Sieve

Less than 5% pass

75 micron IS Sieve

Between 5% &

pass 75 micron

Sieve

Borderline, to have

symbol appropriate

ing & plasticity chara

for example, SW

Below A line

or hatched zone

on plasticity chart

SM

Well

graded

SW SP

Poorly

graded

Examine grain

size curve

Less than 5% pass

75 micron IS Sieve*

Between 5% & 12%

pass 75 micron IS

Sieve

Borderline, to have double

symbol appropriate to grad-

ing & plasticity characteristics,

for example, GW-GM

Below A line

or hatched zone

on plasticity chart

Limit plot in

hatched zone on

plasticity chart

GCGM-GCGM

Above A line

and hatched zone

on plasticity chart

Run WL & Wp on

minus 425 micron

IS Sieve fraction

Well

graded

GW GP

Poorly

graded

Examine grain

size curve

More than 12% pass

75 micron IS Sieve

SAND (S)

Greater percentage o

fraction pass 4.75 mm

Run sieve analysis

Make visual examination of soil to determine whet

HIGHLY ORGANIC, COARSE GRAINED OR FINE

In borderline cases determine amount passing 75 micro

WL = Liquid limit Wp = Plastic limit*If fines interfere with free drainage properties use double symbol, such as GW-GM.


9/14


L

Liquid limit less than 35

I

Liquid limit BETWEEN 35-50

Belo

pla

Inorganic

MH

Colour,

WL and

Below A line

or hatched zone

on plasticity

Limit plot in

hatched zone on

plasticity chart

Inorganic

OIMI

Organic

Colour, odour, possibly

WL and Wp on oven dry

soil

Below A line on

plasticity chart

CI

Above A line on

plasticity chart

CLML-CL

Inorganic

OLML

Organic

Colour, odour, possibly

WL and Wp on oven dry

soil

Above A line

and hatched zone

on plasticity chart

Run WL & Wp on minus

425-micron IS Sieve fraction

FINE GRAINEDMore than 50% pass 75 micron IS Sieve

LABORATORY IDENTIFICATION PROCEDURE

(Continued from previous page)


10/14


ANNEXURE II

Broad categorization of soil types

The classified soil types shall be grouped in four broad categories for the purpose of

planning of works (Blanket thickness requirement as indicated in bracket is for new

constructions. Planning for rehabilitation, if any, is to be done in consultation with

RDSO.)

a) Soils type A (not needing blanket): Rocky beds except those, which are very susceptible to weathering e.g.

rocks consisting of shales and other soft rocks, which become muddy after

coming into contact with water.

Well graded Gravel (GW) Well graded Sand (SW) Soils conforming to specifications of blanket material.

b) Soils type B (needing 45cm thick blanket): Poorly graded Gravel (GP) having Uniformity Coefficient more than 2. Poorly grade Sand (SP) having Uniformity Coefficient more than 2. Silty Gravel (GM) Silty Gravel Clayey Gravel (GM GC).

c) Soils type C (needing 60cm thick blanket): Clayey Gravel (GC) Silty Sand (SM) Clayey Sand (SC) Clayey Silty sand (SM-SC)

Note: The thickness of blanket on above type of soils shall be increased to 1m, if

the plasticity index exceeds 7.

d) Soils type D (needing 1m thick blanket): Silt with low plasticity (ML) Silty clay of low plasticity (ML-CL) Clay of low plasticity (CL) Silt of medium plasticity (MI) Clay of medium plasticity (CI) Rocks which are very susceptible to weathering

Soils having fines passing 75 micron sieve between 5 & 12%, i.e. for soils with dual

symbol e.g., GP-GC, SW-SM, etc., thickness of blanket should be provided as per soil of

second symbol (of dual symbol).


11/14


ANNEXURE III

1.0 Sampling:

1.1 Sampling tools:i) Crow bar and pickaxe alongwith khurpi etc.ii) Hand carved sampler , chunk sampling

1.2 Sampling Procedure:

i) Ballast shall be removed up to the bottom of ballast penetration, and/or uptothe top of subgrade i.e., just below the blanket level. (160 cm from CL of track

or 20-30 cm away from the edge of the sleeper)

ii) Disturbed /undisturbed soil sample (min 2.0 kg) shall be collected byexcavation or other means.

iii) The excavation pit shall be at least 100 mm below the bottom of ballast.iv) Collected soil sample shall be kept in a poly bag with seal, so that, fines are

preserved.

v) A slip of location (km/chainage), section, divisions alongwith name of zonalrailway shall be placed in the poly bag.

vi) The excavated pit shall be refilled with local material and be well compacted.2.0 Testing:

2.1 Only two types of tests shall be performed on each sample.

a) Atterberg limit tests (Liquid Limit and plastic limit).

b) Grain size analysis (Mechanical sieving).

2.2 Laboratory equipment and procedure:

2.2.1 Atterberg limit tests: IS: 2720 pt V 1985.

a) Equipment:

i)

Mechanical /LL apparatusii) Grooving tool , Casagrande, ASTMiii) Procelain evaporating dish, 12 to 15cm diaiv) Spatulav) Balance (Physical or electronic)vi) Ovenvii) Wash Bottleviii) Air tight container, IS Sieve 4254 of a 600 mm x 600mm glass sheet,ix) A soil sample weighing about 120 gm


12/14


b) Procedure:

i) Liquid limit:

Air dry the soil sample remove the organic matter like tree roots, pieces ofbark etc.

About 270gm of air dried pulverised soil which is already sieved through 425micron, IS Sieve is taken . Water is added with air dried soil to make a paste and ensure uniform

distribution of moisture through out the soil mass. Clayey soil left to stand for

24 hours.

A standard groove is made in the soil paste by the grooving tool suitable forthe type of soil.

The cup is made to fall freely through a height of 1cm by turning e ram at therate of two revolutions per second.

The no. of drops required to close, the grave by about 12mm in the centralportion is noted.

Determine moisture content of representative slice of soil from the groove andincluding the soil flowed.

With increasing water content, the number of drops required to close thegroove shall not be more than 35 or less than 15.

Determine the moisture content in each case. A graph is plotted on semi log paper, with no. of drops on log scale as abscissa

and moisture content on natural log scale as ordinate.

The water content at 25 drops is read from the graph. It is the liquid limit (LL)for the soil sample. Generally these points lie on a straight line.

ii) Plastic limit:

After doing liquid limit test, the leftover soil paste is worked with a spatula onglass sheet to drive away a part of moisture content to make it plastic enough

to be shaped into a ball.

A small mass of the plastic mass is taken of rolled on a glass sheet by pressureof the palm into a solid thread 3mm dia until it crumbles.

These rolls are collected of put into oven for drying for moisture for each test.The average content is reported as plastic limit.


13/14


2.2.2 Grain Size Analysis Test IS: 2720 Pt IV 1985

a) Equipment:

1. Sieve set of 20, mm 10mm, 4.75mm, 2mm, 405mm 0.212mm and0.075mm with bottom pa

2. Physical Balance to 0.01gm3. Wash Bottle4. Porcelain dishes5. Stop watch6. Electric stirrer7. Rubber pastle8. Distilled water

b) Procedure:

Air dried soil sample free from organic matter like tree roots, pieces ofbark etc and sieved through 4.75mm, IS sieve is taken.

Sample above the size of 4.75 mm is sieved separately though 20mm,and10mm and weights retained are recorded.

Sample passing 4.75 mm is weighed in physical balance and washedthrough 0.075 mm sieve. The left over portion is oven dried and weighed

again. The difference gives the weight of the soil below 0.075 mm size, i.e.

the content of fines.

Method of sieve analysis (dry)1. In this test a set of standard IS sieves having square opening will be

needed.

2. The remaining sample will be sieved through 2.0mm, 0.6mm0.425mm, and 0.212mm, and then the bottom pan.

3. The sample may be sieved through the above sieve set either byhand or by electrically operated sieve shaker.

4. Soil particles retained on various sieves will be weighed.5. These results will be tabulated and cumulative percentage of

weights passed through various sieve sizes will be found out.

3.0 Plotting of data:

3.1 Plotting of sieve analysis data shall be done on a semi-log graph either manually

or on a computer.

3.2 Classification of soil will be done as per the chart given in Annexure II.


14/14


FIG 1: BG track showing nomenclature of track foundation components

NW RAILWAY

JU DIVISION

SOIL CLASSIFICATION

FL-JU SECTION

SNoBlockSection

ChainageBlanketthickness

LL PL PI %Gravel %Sand %Fines Classification

FIG 3: Proforma for keeping records in a register

important soil

Documents