Engineering Classification of Soil

4 .1

DifTerent soils with similar propcrties may be classified into groups and sub-groupsacctlrding to thcir engineering bchavior. Classification systems provide a commonlanguage to concisely cxpress the gcneral characteristics of soils, which arc infinitelyvaricd, without dctailcd descriptions. Currently. two elaboratc classification system.sare commonly used by soi ls engineers. Both systcnts take in to considcrat ion thepart ic le-s ize d is t r ibut ion and At tcrberg l imi ts . Thcy are the Anter ican Associat ionof State Highway and

' l 'ransportation Olflcials (AASHTO) classification systcm and

thc Unified Soil Classification Systern. 'fhc AASHTO classil ication system is uscd

most ly by statc and county h ighway dcpartments. Geotechnical engineers general lvprefcr thc Unificd system.

AAS HTO CI assificatio n System

Thc AASHTO system of soil classification wi,rs developed in 1929 as the Public RoadAdministration Classification System. It has undergonc several revisions, with theprescnt version proposcd by the Con.rmittee on Classil lcation of Materials for Sub-gradcs and GranulerrType Roercls of thc Highway Research Board in 1945 (ASTMdesignat ion D-3282 AASHTO mcrhod M14.5) .

The AASHTO classification in prcsent use is given in Table 4.1. According tothis system. soil is classified into seven major groups: A-l through A-7. Soils classi-f ied undcr groups A-1, A-2. and A-3 are granular materials of which 35% or less ofthe particles pass through the No. 200 sieve. Soils of which more than 35% passthrough the No. 200 sieve are classified under groups A-4, A-5, ,4-6, and A-7. Thesesoils are mostly silt and clay-type materials. The classification system is based on thefollowing crit iera:

l. Groin sizea. GrttveL: fraction passing the 7-5-mm (3-in.) sieve ancl retained on the No. l0

(2-mm) U.S. sieveb. sand: fraction passing the No. 10 (2-mm) U.S. sieve and retained on the

No.200 (0.07-5-mm) U.S. sievec. Sl/r and clay: fraction passing the No. 200 U.S. sieve

83

84 Chapter 4 Engineering Classification of Soil

Table 4.7 Classification of Highway Subgrade Materials

Generalclassif icat ion

Granular materialsl35o/o or less of total sample passing No. 200)

A - 1

Group classif icat ion A-1-a A-1-b A-2-6 A-2-7

Sieve analysis(perccntage passing)

N o . 1 0No.4 i )No.200

Charactcrist ics of frac-t ion passing No. 40

L iqu id t im i tPlastici ty index

Usua l typcs o l ' s ig -nif icant consti tucntmater ia ls

Gencral subgradera t lng

-50 max.30 max.l-5 max.

50 max.2-5 max.

5 1 m i n .l0 max. 3-5 max. 35 max. 3-5 max. 3-5 max

6 max.Stone fragmcnts,gravcl, and sand

'10 max. 4 l m in . 40 max. 41 min .

N P l 0 m a x . l 0 m a x . 1 1 m i n . 1 l m i n .Finc Si l ty or clayey gravcl and sandsand

Excellent to good

General classif icat ionSil t-clay materials

(more than 35o/o ol total sample passing No. 200)

Group classif icat ion A-4 A-5

A-7A-7-5',

A-6 A-7-6r

Sieve analysis (percentagc passing)N o . l 0No. 40No. 2(X)

Characterist ics of fract i t tn passing No. 40L iqu id l im i tP las t ic i t y index

Usual typcs oi signif icant consti tucnt rnatcrials

General subgrade rat ing

36 rnin.

40 nrax.l 0 max .

Si l ty so i ls

36 min

4 1 m i nl 0 m a x

36 rn in .

40 max.l l m i n .

36 min .

4 l m i n .1 1 m i n .

Clayey soi lsFair to poor

"For A-7-5. PI < LL - 30i 'For 4-7-6, PI> LL - 30

2. Plasticityr The term sllry is applied when the fine fractions of the soil have aplasticity index of 10 or less. The term clayey is applied when the fine fractionshave a plasticity index of l1 or more.

3. If cobbles and boultlers (size larger than 75 mm) are encountered, they are ex-cluded from the portion of the soil sample from which classification is made.Howevcr, the percentage of such material is recorded.

To classify a soil according to Table 4.1, one must apply the test data from left

to right. By process of elimination, the flrst group from the left into which the test

data Iit is the correct classification. Figure 4.1 shows a plot of the range of the liq-

4.1 AASHTO Classification Svstem 85

c + t ,

.:

. 9; l oF-

A-1-6

A-7-5

A 2-5A-5

Io 20 3o ot'r,uull',,n,,,t 'o 7o 80 eo lo0

Figure 4. 1 Rangc of l iquid l imir ancl plasricity index for soils in groups A-2, A-4,A-5. 4-6,and A-7

uid l imit and the plasticity index for soirs rhat fall into groups A-2, A-4, A-5, ,4-6,and A-7.

To evaluatc the quality of a soil as a highway subgrade material, one must alsoincorporate a number called thc group index (G1) with the groups and subgroups ofthc soil. This index is written in parentheses aftcr thc group or subgroup clesignaiion.The group index is given by thc equalion

GI: (F2op - 35)[0.2 + 0.005(tL * 40)] + 0.01(.F200 * 15Xp1 _ 10) (4.1)

wherc Fr,,,, : percentage passing through thc No. 200 sieveLL - - l i qu id l im i tP1 : p last ic i ty index

The first term of Eq. (a.1) - that is, (Fr,u, - 35)[0.2 + 0.005(LL - 40)]- is the partialgroup index determined from the l iquid l imit. The second term - that is, 0.01 (F200 -15)(H - 10) - is the partial group index determined from the plasticity in<iex. iol-lowing are some rules for determining the group index:

1. If Eq. (4.1) yields a negarive value for G1, it is taken as 0.2. The group index calculated from Eq. (4.1) is rounded off to the nearest whole

number (for example , GI :3.4 is rounded off to 3; GI :3.5 is rounded off to 4).3. There is no upper l imit for the group index.4. The group index of soils belonging to groups A-1-a, A_1_b, A_2_4,A_2_-5, and

A-3 is alwavs 0.

86 Chapter 4 Engineering Classification of Soil

5. When calculating the group index for soils that belong to groups A-2-6 and iA-2-'7, use the partial group index for P{ or

GI : 0.01(Izoo * 15XP1 * 10) (4.2)

In general, the quality of performance of a soil as a subgrade material is inversely

proportional to the group index.

Example 4.1

The results of the particle-size analysis of a soil are as follows:

Percent passing through the No. 10 sieve : 100Percent passing through the No. 40 sieve : 80Percent passing through the No. 200 sieve : 58

The liquid limit and plasticity index of the minus No. 40 fraction of the soil are 30and 10, respectively. Classify the soil by the AASHTO system.

EolutionUsing Table 4.1, since 58% of the soil is passing through the No. 200 sieve, it fallsunder silt*clay classifications - that is, it falls under group A-4, A-5, A-6, or A-7.Proceeding from left to right, it falls under group A-4.

From Eq. (4.1),

GI : (F2(\0* 35)10.2 + 0.005(LL - 40) l + 0.01(F200 - 15XP/ * 10)

: (sB - 35)[0.2 + 0.005(30 * 40)] + (0.01x58 * 1sx10 * 10)= 3 . 4 5 : 3

So. the soil will be classified as A-4(3). I

Example 4.2

Ninety-five percent of a soil passes through the No. 200 sieve and has a liquid limitof 60 and plasticity index of 40. Classify the soil by the AASHTO system.

SolutionAccording to Table 4.1, this soil falls under group A-7. (Ppceed in a manner sim-ilar to Example 4.1.) Since i

4 0 > 6 0 - 3 0

+ +t l

PI LL

2

4.2 Unified Soil Classification Svstem

lh is is an 4-7-6 soi l . Hence.

Gr : (F21e- 3s)10.2 + 0.005(rr - 40)l + 0.01(.qm - 1sxp1 * 10): (es - 3s)10.2 + 0.00s(60 - 40)l + (0.01xes - 1sX40 * 10)_ A a- + z

So, the classification is A-7-6(42).

Example 4.3

For a soil, given

Sieve No. Percont passing

Liquid limit = 37Plasticity index = 12Classify the soil by the AASHTO system.

SolutionThe percentage passing through the No. 200 sieve is less than 35, so the soil is agranular material. From Table 4.1, we see that it is type A-2-6. From Eq. (4.2),

GI : 0.01(Fzoo - 15)(P1 * 10)

For this soil, Fiee : 34 and PI : l2,so

G1 :0.01(34 * 15)(12 - 10) :0 .38 = 0

Thus, the soil is type A.2.6(0),

Unified Soil Classification System

The original form of the Unified Soil classification System was proposed by Casa-grande in 1942 during World War II for use in airf ield construction undertaken bythe Army Corps of Engineers. In cooperation with the U.S. Bureau of Reclamation.the corps revised this system in 1952. At present, it is widely used by engineers(ASTM designation D-2481).In order to use the classification system, the followingpoints must be kept in mind:

1. The classification is based on material passing a 75 mm (3 in.) sieve.2. Coarse fraction : percent retained above No. 200 sieve : 100 , Fztxi : Rzrxr.

907634

41 0

200

88 Chapter 4 Engineering Classification of Soil

Table 4.2 Unified Classification System (Based on Materials Passing 75 mm (3 in.) Sieve (Based on ASTM-2487)

GroupMaior division symbol Criteria

F2{x} < 50 Gravels GW Fruu < 5; C,,2 4;1 < C- < 3GP F:,r, < 5; Not meeting the GW cri teria of C,, and C.

R* r ' , , . GM F2,,, ' ) 12; PI < 4 or plots below '4-l ine (Fig' 4'2)

Rr,r, - " ' - CC Fr,, , ,> 12' PI > 7 an<J plots on or ubove,4-l ine (Fig' 4.2)

GM-GC F.,, , ,> 12; P1 plots in the hatched area (Fig. 4.2)

GW-GM -5 s Fr,u, < 12; satisf ies C,, and C- cri teria of GW and meets the PI

cri teria for GMGW-GC 5 < Fi,u, < 12; satisf ies C,, and C, cri tcr ia of GW and meets the P1

criteria lbr GCIGP-GM 5 < Fr,r, < 12; does not satisly C,, and C.- cr i ter ia of GW and meets

thc P1 cri teria for GMGP-GC -5 < F:,u, < 12; docs not satisfy C,, and C- cri teria of GW and meets

the P/ cr i ter ia lbr GCI

Sands SW F)'u, < -5; Ci,, > 6; I = C- < 3

SP Fi,u, < -5; Not meeting the SW cri tcr ia of C,, and C.O.

= U., SM 1"., , , ,> 12; PI < 4 rtr plots bclr lw,, l- l ine (Fig. 4.2)Rz,r, SCI F.,, , ,> 12; PI >'7 and plots r.rn or ubove,4-l ine (Fig.4.2)

SM-SC F'r, , , ,> 12; P1 plots in the hatchcd area (Fig.4.2)

SW-SM 5 < F:,u, < 12; satisl ies C,, and Ci- cr i ter ia of SW and rneets the P/

cri tcr ia for SMSW-SC 5 = lr ,r , < 12; satisf ics C,, and C- cri tcr ia of SW and meets thc f '1

cri teria for SCISP-SM -5 < F:,u, < 12; docs not satisty C', , and C.- cr i ter ia of SW and nleets

the P/ cr i tcr i l lor SMSP-SC 5 < F:,r, < 12; dttes not satisfy C,, ancl C" cri ter ia of SW and meets

thc P1 cri teria for SC

Fz,r, = 50 Si l ts and ML PI < 4 or plots below,4-l ine (Fig. 4.2)

Clays CL I ' l > 7 and plots on or above, '1-l inc (Fig. 4.2)

LL < 50 CL-ML P1 plots in the hatched area (Fig. 4.2)L I

OL Z##

< 0.75; P/ plots in the oL area in Fig.4.2

Silts and MH P1 plots bebw A-line (Fig. a.2)Clays CH P1 plots on or ubove,4-l ine (Fig. 4.2)

LL > 50 Llk,u"n d.ie.t)OH

.1;,__* < 0.75; P1 plots in the OH area in Fig.4.2

Highly Pt Peatorganicmatter

Dn, ^ Di,,Notc: C, , - uni formi tycoef f ic ient : ; ' : C - coef l ic ient of gradat ion : -

Dru- - ' - D" ' , ' Dr , ,

LL : liquid limit on minus 40 sieve fractionp7 : plasticity index on minus 40 sieve tiaction

4.2 Unified Soil Classification System gg

3. Fine fraction : percent passing No. 200 sieve : Frs6.4. Gravel fraction : percent retained above No. + sieve : R+.

According to the Unified Soil Classil ication System, the soils are divided into twomajor categories:

l. Coarse-grainetl solls that are gravelly and sandy in nature with less than 50%passing through the No. 200 sieve (that is. Fxn,'-50). The group symbols startwith prefixes of either c or S. G stands for gravel or g.uu"ily soil, and S forsand o r sandy so i l .

2. Fine-grained soils with -50% or more passing through the No. 200 sieve (that is,Fr,u, > 50). The group symbols start with prefixes of M, which stands for inor-ganic silt, c for inorganic clay, and o for clrganic silts and clays. The symbol ptis used for peat, muck, and other highly organic soils.

Othcr symbols usecl for the classification are:

. W-wel l gradedr P- poor ly gradedr | - low p last ic i ty ( l iqu id l imi t less than 50)o l - { - h igh p last ic i ry ( l iqu id I imi t morc than .50)

Table 4.2 gives the dctails of thc soil classiflcation system to determin e the grottpsymbols.

M.rc recently, ASTM dcsignation D-2497 creatcd an elaborate system to as-sign group natnes to soils. These names ilre summarized in Figures 4.3,4.4, and 4.,5.In using these figurcs, it is important to remember that, in a given soil, percentage ofgravel : Ro and percentagc of sand - Rzur R4.

!.E 40.=

E

l0 16 20 30 .10 50 60 70 u0 goLiquid I imit

Figure 4.2 Plasticity chart

Chapter 4 Engineering Classification of Soil

Group Symbol

cw-q:

GP-:

GW-GM=

cw-GC-

GP-GMq

cp-cc -

GM- :

GC-:

cc-GMa

sw_:sp-l

GrouP Name

( l -57o sand+ Wel l -graded gravel

>15% sand + Wel l -graded gravel wi th sand

<157" sand + Poor lv graded gravel

> I 5'ln sand + Poorly graded gravcl with sand

< l5% sand + Wel l -graded sand wi th s i l t

> l -57" sand + Wcl l -graded gravel wi th s i l t and sand

< l57u sand + Wel l -gradcd gravel wi lh c lay (or s i l ty c lay)

> l -57. sancl + Wel l -graded gravel wi th c lay and sand (or s i l ty c lay and sand)

{15.7, sand Poor ly graded gravel wi th s i l t

>15(% sand Poor ly gradcd gravcl wi lh s i l t and sand

{ I 5(% sand + Poor ly gradcd gravel wi th c lay (or s i l ty c lay)

> I 5 ,% sand -> Poo r l y g radec l g rave l w i t h c l ay and sand (o r s i l t y c l ay and sand )

{ 1.5%, s i lnd + Si l ty gravcl

: l5(% sancl + Si l ty gravcl wi th sand

{ l -5%, s i lnd+ Claycy gravcl> l5(2, s i lnc l + Claycy grave I wi lh sand

{157, s i lnd Si l tY c laYeY gravel

=15(X, s i lnd+ Si l ty c layey gravcl wi th sand

< l -5%, gr i ivc l + Wcl l -g,raded sand

= 15'X, gravcl------* Wcll-gradcd sand wilh gravcl

.-- l-5(X, Srirvcl + Poorly gradcd sand=15'2, gravcl _* Poor ly gr i idcd sand wi th gravcl

SW-SM q-+ ' l5 '2, gravcl _* Wcll-graclcd sand with si l t--- ' t5'2, grave I -* Wcll-gracled sand with si l t and gravel

SW-SC-+ l5 " , , u r r rve l - . - - - - * Wc l l -g . r : r t l cd s : rnd w i th c lay 1or s i l t y c l ry )------ - 1-5,2, graucl---* Wcll-gradccl sand with clay and gravcl (or si l ty clay and gravel)

SP-SM --* < 1.5'2, grave l* Poorly gradcd sand with si l t----.- =15'2, gravcl -----* Poorly gradcd sand with si l t and gravcl

SP-SC q-* < l-5(7o grave l+ Poorly graded sand wilh clay (or si l ty clay)=---*

- 1 5,7, gravel ------ Poorly gradcd sancl with clay and gravcl (or silty clay and gravel)

SM -==-* 15"" grrvcl .------* Sill) sanrl--------..* =157, gravcl_* Silty sand with gravel

SC ------------* 15",, lrrvel -----'* ( lrYel santJ------ > l5'lo gravel -+ Claycy sand with gravel

SC-SM q_+ < l .5o/o grovel + Si l ty claycy sand=- =tS% gravcl_-* Si l ty clayey sand with gravel

Figure 4.3 Flowchart group names for gravelly and sandy soil. Source: From "Annual Book

of ASTM Standarcls, 04.08." Copyright O 1999 American Society for Testing and Materials.

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; 1 . t , F o a z ! l a , o z a L j , a Z t ' i , L i L - E

V E i ' r Z Z , ! ' - . 4 Z r r 4 E ; e ; € : r Fj a ^ = C - a t L a r ! Q ^ 6 j= - = ^ ; . ';", = z .;;- : E ;a E Z i i E E 7;v: . . 1 j j . ? , . ' , ' , , , i . ^ 7 t ; .? , i > 'd

; i j j v i s s i : ; ; i : ; ; * Et r \ / + t \ / + t \ / + l \ / € c c

I I \ / I I \ / I I \ / I I \ / E>v v rl V V V |l V -":

- C O r - €

H X X - . r . i - - . P l

2 2 i 2 2 2 . t 2 F ;' 3 2 3 3 3 3 3 " . H 9- = = = - ; 7 7 7 " r

;e S S S S -a f d oq :

3 3 3 3 3 3 e s ? lv ^ v A l v , r i v A H P\ t \ r \ r \ + H E\ t \ t \ t \ t + ?i \ \ t \ t g B

= a ^ . \ t ^ . \ ! -

i : E+ i ' g E E€E ; ; s ; : ; l i : ; a€ l = I i : : a : = r ;t \o \ , '/ \ ./ $ai \ " Y S i5 d 5 8 8

92

4.2 Unified Soil Classification Svstem 93

Example 4.4

figule {.6 gives the grain*size distribution of two soils. The liquid and plastic lim-its of minus No. 40 sieve fraction of the soil are as follows:

^ Don 0.135L " :

D ^ : o ^ o g 5 : l ' 5 9 < 6

$.142

Soil A Soil B

Liquid limitPlastic limit

Determine the group symbols and group names according to the unified soil clas-si{ication System.

No. 200Soi l A s icve

Part ic le d iarreter (mm )

Figure 4.6 Particle-size distribution of two soils

SolutionS o i l AThe grain-size distribution curve indicates that F21,e = g. So this is a coarse-grainedsoil, and

Rzoo : 100 - F2oo : 100 - I : 92

From Figure 4.6, R4 = 0; therefore,

+=9*0 . ,Rron 92 j

!glr", it is a sandy soil (Table 4.2). From Figure 4.6, Dn;,:0.0g5 mm, Dn =0.1,2 m, and D6o = 0.135 mm. Thus,

3022

2620

E m|I

E

P 4( \

\

D3oD6o x Dn

c r =(0.13sx0.08s)

= 1 . 2 5 > 1

94 Chapter 4 Engineering Classification of Soil

With fl, : 30 and PI : 30 - 22 = 8 (which is greater than 7), it plots above theA-line in Figure 4.2. Hence, the group symbol is SP'SC.

In order to determine the group name, we refer to Figure 4.3.

Percentage of gravel - Ra : 0 (which is < 15 % )

So, the group name is poorly graded sand with clay.

So i l BFrom the grain-size distribution curve, F2qo: 61. Hence, this is a fine-grained soil.Given: LL : 26 and PI :26 - 20 = 6.In Figure 4.2,the P/ plots in the hatchedarea. So, from Table 4.2,the group symbol is CL'ML.

For group name, assuming that the soil is inorganic, we go to Figure 4.4 and obtain

Plus No. 200 sieve : Rzoo : 100 * F200 : 100 - 61 :39 (which is greater than 30)

Percentage of gravel * R+ : 0; percentage of sand : Rzoo - Rq: 39

Thus, because the percentage of sand is greater than the percentage of gravel, thesoil is sandy silty clay. r

Example 4.5

t

The grain-size analysis for a soil is given next:Sieve no. % passing

10 6320 2140 l06 0 7

100 5200 3

Given that the soil is nonplastic, classify the soil by using the Unified Soil Classifi-cation System.

Solution

Fzoo : 3

Rroo: 100 - 3 : 97 j

R+ * 100 - Fq* tOO - 94 - 6,

R o : 9 o 0 . ,Rroo 97

Thus, this soil is sandy. The grain-size distribution is shown in Figure 4.7. Ftomthis figure, we obtain

D5,6 = 1.41 mm D3s : 0.96 mm Dto : 0.41 mm

94

4.3 Summary and Comparison between the AASHTO and lJnified Sysfems 95

crrin .lr! tn',' ') o l

Figure 4.7 Grain-size distribution curve

Thus,

c . : 3 : , : # : 3 4 4c . :

D l u * 0 ' 9 6 2 * i { q" D6rx Drc l .4 l x 0 .41

From Table 4.2,we see rhat the group symbol is Sp. For this soil, R4 : 6. Refer_ring to Figure 4.3, we find that the group name is poorly graded sand. r

Summary and Comparison hetweenthe AASHTO and Unified Systems

Both soil classification systems, AASHTO and Unifiecl, are based on the textureand plasticity of soil. Also, both systems divide the soils into two major categories,coarse grained and fine grained, as separated by the No. 200 sieve. Accordingto theAASHTO system, a soil is considered fine grained when more than 3-57o passesthrough the No. 200 sieve. According to the Unified system, a soil is consiclered finegrained when more than 50% passes through the No. 200 sieve. A coarse-grained soilthat has about 35% fine grains wil l behave like a fine-grained material. This is becauseenough fine grains exist to fill the voids between the coarse grains and hold themapart. In this respect, the AASHTO system appears to be more appropriate. In theAASHTo system, the No. 10 sieve is used to separate gravel from sind;in the unified

E

E

d + o

4.3

Chapter 4 Engineering Classification of Soil

system, the No. 4 sieve is used. From the viewpoint of soil-separate size l imits, the

No. 10 sieve is the more accepted upper l imit for sand. This l imit is used in concrete

and highway base-course technology.In the Unified system, the gravelly and sandy soils are clcarly separated; in the

AASHTO system, they arc not. The A-2 group. in particular. contains a large variety

of soils. Symbols l ike GW SM, CH. zrnd others that arc used in the Unified system

arc more descriptive of the soil properties than the A syrnbols used in the AASHTO

system.The classification of organic soils as OL. OH, and Pt is provided in thc Unified

system. Under the AASHTO systcm. there is no place lor organic soils. Peats usu-

allv have a high moisture contcnt, low spccific gravity of soil solids, etnd low unit

weight. Figure 4.8 shows the scanning clectror.r micrographs ol'four peat samplcs col-

lccted in Wisconsin. Somc of the properties of thc pcats are given in Table 4.3.

Liu (1967) cornpared the AASHTO and tJnificd systems. Thc results of his

study arc presented in Tables 4.4 and 4.-5.

t{ lD0LETotl PgAT MUPACA P€AT

FOA$S€ r€&T FOND DU LAC PEAT

@

l00r*

Figure 4.g Scanning electron micrographs for four peat samples (after Dhowian and Edil,

1 980)

ffi

t

4.3 summary and comparison between the AASHT) and LJnified systems 97

Table 4.3 Propcrties of the Pcats Shown in Figurc 4.8

Source of peat

Moisturecontent

t%l

Unit weisht :l""J,il:

kN/m3 tb/ft3 e

Ashcontent

(%l

Midd le tonWaupaca ClountyPortagcFond clu Lac C'ounlv

.5 l04606(X)240

9 . 19 .6().6

to.2

57.96 l . t6 l . l64.9

1 . 1 11 .681 .721 .94

12 .01.s.019.-539.8

Table 4.4 compariso' . l t l rc AASHTO Systcnr with thc LJnif icd Svstcm*

Soil groupin AASHTO

system

Comparable soi l groups in Unif ied system

Most probable Possible Possible but improbable

A - l - i t

A- l - t rA-3A-2-1A-2-5A-2-6A-2-7A-4A-5A-6A-7--5A-7-6

c;w. ( iPSW SP. ( ;M. SMS P( IM. SM( ; M . S Mc;('. s('( ; M . ( ; ( ' , S M . S ( 'M I , , O LO F I . M H . M L . O I ,( ' t_O H . M I I( ' t I . ( ' L

SW SP( i t ,

( i( ' . s( '

( JM. SM

CI - . SM. S ( '

ML , OL . S ( 'M l . . oL . c ' t lMI , , OL. SC'

G M . S M

SW GI,C;W. (iP. SW SPGW. CrP. SW SP(;W GP. SW SPCiW. GP, SW SPGM. CJCS M . G Mci( . ' c iM. sMGM. SM, GC], SC]OH, MH. GC. GM. SM

'"Af tcr L iu (1967)

Table 4.5 Comparison of the LJnificcl Systcnr with thc AASHTO Svstcln,i

Soil groupin Unifiedsystem Most probable Possible Possible but improbable

GWGPGMGCSWSPSMSCMLCLOLMHCHOHPt

A - l - a

A - l - a

A-1-b, A-2-4. A-2-5. A-2-1A-2-6. A-2-7A-1 -bA-3 . A - l - bA-l-b, A-2-4. A-2-5, A-2-1A-2-6, A-2-7A-4. A--5A-6, A-7-6A-4, A--5A-7-5. A-5A-7-6A-7-5, A-5

A - l - bA-2-6A-2-1A - l - a

A - l - a

A-2-6. A-1A-2-4. A-6. A-4. A-7-6,{-6. A-7-5, 4-7-6A-4A-6, A-7--5, 4-7-6

A-7--5

A-2-4. A-2-5, A-2-6. A-2-7A-3. A-2-'t. A-2-5. A-2-6. A-2-'lA-4. A--s. ,4-6, A-7_.s, A_7_6, A_1_aA-4. 4-6, A-7-6. A-7-5A-3. A-2-,1, A-2-5. A-2-6, A-2-7A-2-4. A-2-5, A-2-6, A-2-7A--5. 4-6. A-7--s, 4-7-6, A_1_aA-7--5

A-7-6

A-7-6

*After Liu (1967)

98 Chapter 4 Engineering Classification of Soil

Problems4.1 The sieve analysis of 10 soils and the liquid and plastic limits of the fraction

passing through the No. 40 sieve are given in the following table:

Sieve analysis, o/o linerLiquid Plasticl imit l imitS o i l N o . 1 0 N o . 4 0 N o . 2 0 0

12345676

9i 0

9510010090909,5

1009685

1(X)

799-5805571655.s826092

537862

6t)- )L

865L J

86

366535284025

402010

2126202026t 6N P24l-538

4.2

Classify the soils by the AASHTO classification system and give the group

indices for each.Classify the following soils using the AASHTO classification system, andgive the group indices:

Sieve analysis, o/o linerLiquid Plasticl imit l imitSoi l No. 10 N o . 4 0 N o . 2 0 0

ABCDE

629090

100t3-5

3067767868

6

35-r4

d

4-5

-', z

37

38

NPti

l 2N P

9

4.3 Classify the following soils using the AASHTO classification system, andgive the group indices also:

Percent passing

A B C D ESieve size

N o . 4No . 10No .20No .40No .60No. 100No.2000.01 mm0.002 mm

Liquid limit

Plasticity index

9463211 07

3

98865028181 41 0

10010098938883776560

100 100100 i00100 10099 9495 8290 6686 4542 2647 21

63 55 36

NP NP 25 28 22

t

4.5

References 99

classify soils l-6 given in Problem 4.1 using the Unified classification sys-tcm. Give the group symbols and the group names.classify the soils given in Problem 4.3 using the Unified classification sysrem.Give the group symbols and the group names.classify the following soils using the Unified classification system:

Sieve analysis, /o finerLiquid

Soil No. 4 No. 200 l imitPlasticity

index

d

4

l 22

u0799 lc)5

82

A

BCDE

I (X)9064

313l 8l 3

) l

u()

1 l

3026604 l) ,1

4.7Givc the group symbols and thc group namcs.For an inorganic soi l , the fo l lowing gra in-s ize analys is is g iven:

U.S. Percent

ru4

I 02040u()

200

For this soil. LL : 23 ancl pL : lL). classif 'y the soil .cc.rcling r.a. the AASHTO soi l c lass i f icat ion system;b. thc Uni f ied soi l c lass i f icat ion systcm. Give group namcs and group

symbols.

ReferencesAven lc 'nN Assr lc ' t x l l t lN t ln S ' l ' nTu Hrc ;nwav, rND Tr r ,qNsp( )R|At ' loN Or . r , rc . rnLs (19U2) .

AASHTO Materiuls, I,urt I, Spacifit:utiorts, Washington, D.Ci.AIrar:.nrc'eN Soc'rErv r.on TcslrN<; lNo MR.r.nnlnm (1999). Anrtrut l Book o.f ASTM stun-

danls, Sec.4. Vol. 04.08. West Conshohoken. pa.C,q.sn<;nRNon, A. (194t3). "Classif icat ion and Identi f icat ion o1'Soi ls." Zran.racrrr, ,ns, ASCE,

Vtr l . I 13. 901 930.Dtr<rwr,tN, A. W.. and Eoll- , l - . B. (19S0). "Consoliclat ion Behavior of Pe1ts." Cestachnit.ul

Testi t tg. lournul ASTM, Vol. 3, No. 3. 10-5-114.Ltu. T. K. (1967). "A Rcview of E,nginecring Soil Classifrcation Systems," I l ighway Research

RecordNo. I56 , Nat iona l Academyof Sc ienccs ,Wash ing ton . D.C. , 1_22.