1. 1
Sistemas de Clasificación de Suelos
2021
MSc. Jorge Dueñas
Facultad de Geología Geofísica y Minas
UNSA
www.unsa.edu.pe
Email: jduenasr@unsa.edu.pe
Propósito
Caracterizar el suelo en grupos de similar comportamiento, en
términos de índices, estas características representan una guia
para los ingenieros a fin de determinar las propiedades
geotécnicas del suelo.
Índices simples
GSD, LL, PI
Sistemas de
Clasificación
(Lenguaje
común)
Estimar las
propiedades
geotécnicas
Lograr los
propósitos de
ingeniería
Uso de
experiencia y
buen senso
Comunicación
entre Ingenieros
2. 2
Clasificación
Existen dos sistemas comunmente usados:
• USCS (Unified Soil Classification System).
• AASHTO (American Association of State
Highway and Transportation Officials).
Sistema Unificado de Clasificación del
Suelo (USCS)
Origen del USCS:
Este sistema fue desarrollado por el profesor A. Casagrande
(1948) con el propósito de la construcción del campo de la aviación
durante la Segunda Guerra Mundial. Posteriormente, fue
modificado por el profesor Casagrande, el Bureau of Reclamation
EE.UU., y el Cuerpo de Ingenieros del Ejército para que el sistema
pueda ser aplicable a las presas, fundaciones y otras
construcciones (Holtz y Kovacs, 1981).
Tiene cuatro grandes divisiones:
• Suelos de grano grueso
• Suelos de grano fino
• Suelos orgánicos
• Turba
3. 3
5
Tamaño de Grano
Boulders Cobble
s
Grave
l
Sand Silt and
Clay
Coarse Fine Coarse Fine
Medium
300 mm 75
mm
19
mm
No.4
4.75
mm No.10
2.0 mm
No.40
0.425
mm
No.200
0.075
mm
No hay tamaño de uso
específico del tamaño
de grano – Use los
límites de Atterberg
6
Guia General
Suelos de grano grueso:
Grava Arena
Suelos de grano fino:
Limo Arcilla
NO.200
0.075 mm
•Distribución granulométrica
•Cu
•Cc
•PL, LL
•Carta de plasticidad
50 %
NO. 4
4.75 mm
Ensayo requerido: Tamizado
Límite de Atterberg
LL>50 LL
<50
50%
4. 4
7
Simbología
Simobología Suelos:
G: Grava
S: Arena
M: Limo
C: Arcilla
O: Organico
Pt: Peat
Simbología Límite Liquido
H: Alto LL (LL>50)
L: Bajo LL (LL<50)
Simbología de gradación:
W: Bien gradado
P: Pobremente gradado
Ejemplo: SW, Arena bien gradada
SC, Arena arcillosa
SM, Arena limosa,
MH, Limo elástico )
sands
for
(
6
C
and
3
C
1
)
gravels
for
(
4
C
and
3
C
1
soil
graded
Well
u
c
u
c
8
Carta de Plasticidad
(Holtz and Kovacs, 1981)
LL
PI
H
L
•The A-line generally
separates the more
claylike materials
from silty materials,
and the organics
from the inorganics.
•The U-line indicates
the upper bound for
general soils.
Note: If the measured
limits of soils are on
the left of U-line,
they should be
rechecked.
5. 5
9
Cómo Utilizar la Carta de Plasticidad
Del suelo que se desea clasificar debemos conocer (LL,IP).
Sustituimos en la ecuación de la línea “a”, el limite liquido del suelo.
Ipa = 0.733 (LL-20)
Si Ipa > Ip del suelo enestudio, se encuentra por debajo de la línea“a”, de
lo contrario se encontrará por encima de la linea “a”
Si nos encontramos por debajo de la línea“a”, solo encontramos los
subgrupos ML y MH, comparamos el LL del suelo,
Si LL>50%, Lo clasificaremos como MH.
Si LL<50%, Lo clasificaremos como ML.
Si nos encontramos por encima de la línea“a”, solo encontramos los
subgrupos CL y CH, CL–ML y ML
Si LL>50%,lo clasificaremos como CH.
Si LL < 50% y 4 < Ip < 7, lo clasificaremos como ML-CL
Si LL < 50% y Ip > 7, lo clasificaremos como CL
Si LL < 50% y Ip < 4, lo clasificaremos como ML
10
Material
grueso
Distribución
granulométrica
Material
fino
LL, PI
(Santamarina et al.,
2001)
Highly
Cómo Utilizar la Carta de Plasticidad
6. 6
11
Ejemplo
Pasa el tamiz No.200 30 %
Pasa el tamiz No.4 70 %
LL= 33
PI= 12
PI= 0.73(LL-20), Línea-A
PI=0.73(33-20)=9.49
SC
(15% grava)
Arena arcillosa con
grava
(Santamarina et al., 2001)
Pasa el tamiz No.200 30%
Pasa el tamiz No.4 70%
LL= 33
PI= 12
12
Suelos Orgánicos
• Suelo altamente orgánico – Turba (Simbologia PT)
Muestra compuesta principalmente de material vegetal en
distintas etapas de descomposición y tiene una textura
fibrosa a amorfa, de color marrón oscuro a negro, y un olor
orgánico debe ser designado como un suelo altamente
orgánica y se clasificará como turba, PT.
• Arcilla o Limo orgánico (Simbología OL or OH):
"El límite líquido del suelo (LL) después del secado en horno
es inferior al 75% de su límite líquido antes del secado." Si
la afirmación anterior es cierto, entonces el primer símbolo
es O.
El segundo símbolo se obtiene mediante la localización de
los valores de PI y LL (sin secar en horno) en el gráfico de
la plasticidad.
7. 7
13
Casos Límite (simbología dual)
Para las siguientes tres condiciones, se debe utilizar un símbolo
dual.
Suelos de grano grueso de 5% - 12% de finos.
Cerca de 7% de finos pueden cambiar la conductividad hidráulica del
material de grano grueso (en órdenes de magnitud).
El primer símbolo indica si la fracción gruesa está bien o mal clasificado.
El segundo símbolo indica el contenido de finos. Por ejemplo: SP-SM,
Arena pobremente gradado con limo.
Suelos de grano fino con límites dentro de la zona sombreada. (PI
entre 4 y 7 y LL entre aprox 12 y 25).
Es difícil distinguir la predominancia entre el limoso y el arcilloso.
CL-ML: Arcilla limosa, SC-SM: Limoso, areno arcilloso.
El suelo contiene finos muy similares y fracciones de gruesos.
Posibles símbolos duales GM-ML
14
(Holtz and Kovacs,
1981)
Casos Límite (simbología dual)
8. 8
15
Sistema de Clasificación: American Association of
State Highway and Transportation Officials
(AASHTO)
Orígen del AASHTO: (Para construcción de vias)
El sistema fue desarrollado originalmente por
Hogentogler y Terzaghi en 1929, como el Sistema de
Clasificación de Vías Públicas. Después, se realizaron
varias revisiones. La versión actual AASHTO (1978) se
basa principalmente en la versión de 1945. (Holtz y Kovacs, 1981)
16
Tamaño de Grano
Pedregones Grava Arena Arcilla-Limo
Grueso Fino
75 mm No.4
4.75
mm No.40
0.425 mm
No.200
0.075
mm
No hay tamaño de uso
específico del tamaño
de grano – Use los
límites de Atterberg
9. 9
17
Guia General
8 grandes grupos: A1 ~ A7 (con varios subgrupos) y los suelos orgánicos A8
Las pruebas requeridas son el análisis granulométrico y los límites de
Atterberg.
El índice de grupo, una fórmula empírica, es usado para evaluar más a fondo
los suelos dentro de un grupo (subgrupos).
El propósito original de este sistema de clasificación era para la
construcción de carreteras (evaluación de la subrasante).
A4 ~ A7
A1 ~ A3
Materiales Granulares
35% pasa el tamiz No. 200
Materiales Arcillosos - Limosos
36% pasa el tamiz No. 200
Usando LL y PI se separa los materiales
limosos de los materiales arcillosos
Usando LL y PI se separa los materiales
limosos de los materiales arcillosos (sólo
para el grupo A2)
18
Índice de Grupo
)
10
PI
)(
15
F
(
01
.
0
)
40
LL
(
005
.
0
2
.
0
)
35
F
(
GI
200
200
)
10
PI
)(
15
F
(
01
.
0
GI 200
Para el grupo A-2-6 y A-2-7
El primer término es determinado por el LL
El segundo término es determinado por PI
En general, la calificación para una sub-base de pavimento es inversamente
proporcional al índice de grupo,GI.
Use solo el segundo término
F200: porcentaje que pasa el tamiz No.200
11. 11
21
Referencias
Principales
Das, B.M. (1998). Principles of Geotechnical Engineering, 4th
edition, PWS Publishing Company. (Chapter 3)
Holtz, R.D. and Kovacs, W.D. (1981). An Introduction to
Geotechnical Engineering, Prentice Hall. (Chapter 3)
Otros:
Santamarina, J.C., Klein, K.A., and Fam, M.A. (2001). Soils and
Waves, John Wiley & Sons, LTD.
What are the soil classification systems commonly used in
practice? What are the most common uses of each?
The soil classification systems commonly used in practice are:
1. Unified System (p. 78) => Used primarily for geotechnical and
foundation engineering.
2. AASHTO (p. 78) => Used primarily for selection of highway
construction materials.
3. Indian Standard Soil Classification System (p. 79)=> Used
primarily for general engineering purpose.
2. Soil Classification
2-3. Soil Classification Systems (p. 77-90)
12. 12
2. Soil Classification
2-3. Soil Classification Systems (p. 77-78)
Unified Soil Classification System (source:wikipedia)
The Unified Soil Classification System (or USCS)
is a soil classification system used in engineering and
geology disciplines to describe the texture and grain
size of a soil.
The classification system can be applied to most
unconsolidated materials, and is represented by a
two-letter symbol.
2. Soil Classification
2-3. Soil Classification Systems (p. 77-78)
Unified Soil Classification System (source:wikipedia)
1st and/or 2nd letters
G ---Gravel
S --- Sand
M --- Silt
C --- Clay
O --- Organic
2nd letter
P --- pooly graded
W --- well graded
H --- high plasticity
L --- low plasticity
13. 13
2. Soil Classification
2-3. Soil Classification Systems (p. 77-78)
Unified Soil Classification System (source:wikipedia)
Coarse grained soils more than
50% retained on No. 200 sieve
GW---well graded gravel, fine
to coarse gravel
GP---pooly graded gravel
GM---silty gravel
GC---clayey gravel
SW---well graded sand, fine to
coarse sand
SP---pooly-graded sand
SM---silty sand
SC---clayey sand
Fine and clay liquid limit < 50
ML---silt
CL---clay
OL---organic silt, organic clay
MH--- silt of high plasticity,
elastic silt
CH---clay of high plasticity, fat
clay
OH---organic clay, organic silt
Highly organic soils-> Pt---peat
2. Soil Classification
2-3. Soil Classification Systems (p. 77-78)
Unified Soil Classification System (source:wikipedia)
14. 14
2. Soil Classification
2-3. Soil Classification Systems (p. 78-79)
AASHTO Soil Classification System (source:wikipedia)
Developed by the American Association of State
highway and Transportation Officials, and is used as a
guide for the classification of soils and soil-aggregate
mixtures for highway construction purposes.
The classification system was first developed by
[needs attribution] in 1929, but has been revised
several times since.
2. Soil Classification
2-3. Soil Classification Systems (p. 78-79)
AASHTO Soil Classification System (source:wikipedia)
15. 15
2. Soil Classification
2-3. Soil Classification Systems (p. 79)
AASHTO Soil Classification System (source:wikipedia)
Group Index
2. Soil Classification
2-3. Soil Classification Systems (p. 79-84)
Indian Standard Soil Classification System
Indian Standard Soil Classification System
(source:theconstructor.org)
Indian Standard Classification System (ISC) was adopted by Bureau of Indian
Standards is in many respect similar to the Unified Soil Classification (USC) system.
Soils are divided into three broad divisions:
Coarse grained soils, when 50% or more of the total material by weight is
retained on 75 micro IS sieve.
For fine grained soils, when more than 50% of the total material passes through
75 micron IS sieve.
If the soil is highly organic and contains a large percentage of organic matter
and particles of decomposed vegetation, it is kept in a separate category marked
as peat (Pt).
In all there are 18 groups of soils: 8 groups of coarse grained, 9 groups of fine
grained and one of peat.
16. 16
2. Soil Classification
2-3. Soil Classification Systems (p. 79-84)
Indian Standard Soil Classification System
2. Soil Classification
2-3. Soil Classification Systems (p. 77-78)
Unified Soil Classification System (source:wikipedia)
17. 17
Sieve
No.
Sieve
Opening
(mm)
Weight
Retained on
Sieve (g)
Cumulative
Weight
Retained
% Finer
4 4.75 0
10 2.00 25
20 0.85 50
40 0.43 75
60 0.25 100
100 0.15 200
200 0.075 40
pan 0.00 10
Total 500
Draw the grain size distribution curve for the data shown below.
What is the unified soil classification? Give the group
symbol and group.
% Finer = (Total - Cumulative Weight Retained)/Total
2. Soil Classification
2-1. Grain Size Distribution (p. 26-27, p. 33-34)
2-3. Soil Classification System (p.77-78)
Sieve No. Sieve Opening
(mm)
Weight
Retained on
Sieve (g)
Cumulative Weight
Retained
% Finer
4 4.75 0 0
10 2.00 25
20 0.85 50
40 0.43 75
60 0.25 100
100 0.15 200
200 0.075 40
pan 0.00 10
Total 500
Compute table ->Red numbers ->See Instruction P. 27
% Finer = (Total - Cumulative Weight
Retained)/Total
2. Soil Classification
2-1. Grain Size Distribution (p. 26-27, p. 33-34)
2-3. Soil Classification System (p.77-78)
23. 23
A 20-foot thick reddish-brown layer of
soil is underlain by dense sand. It has a
plastic limit of 30, a plasticity index of
50 and a water content of 60%. What
is the reddish brown soil classified
as? What are the strength
characteristics of this layer?
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
A 20-foot thick reddish-brown layer of soil is
underlain by dense sand. It has a plastic limit
of 30, a plasticity index of 50 and a water
content of 60%. What is the reddish brown
soil classified as? What are the strength
characteristics of this layer?
GIVEN: PL = 30 PI = 50 wc = 60%
Calculate Liquid Limit, LL:
LL = PL + PI , LL = 80
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
24. 24
2. Soil Classification
2-3. Soil Classification Systems (p. 77-78)
Unified Soil Classification System (source:wikipedia)
A 20-foot thick reddish-brown layer of soil is underlain by
dense sand. It has a plastic limit of 30, a plasticity index
of 50 and a water content of 60%. What is the reddish
brown soil classified as? What are the strength
characteristics of this layer?
GIVEN: PL = 30 PI = 50 wc = 60%
STEP 1: Calculate Liquid Limit, LL:
LL = PL + PI , LL = 80
By the United Classification System, using LL = 80 and PI = 50 on
the Plasticity Chart, the reddish brown soil can be classified as CH,
Inorganic clay. Since the water content falls within the plastic
range and relatively close to liquid limit, the soil is suitable to
support low rise structure only.
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
25. 25
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
100 96 90 80 66
The following classification tests were performed on a specimen
recovered from a borehole from a depth of 20 feet. The material is
black with a strong odor. Give the group symbol and group
name.
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
100 96 90 80 66
The following classification tests were performed on a specimen
recovered from a borehole from a depth of 20 feet. The material is
black with a strong odor. Give the group symbol and group
name.
GIVEN: LL = 80, PL =55
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
26. 26
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
100 96 90 80 66
The following classification tests were performed on a specimen
recovered from a borehole from a depth of 20 feet. The material is
black with a strong odor. Give the group symbol and group
name.
GIVEN: LL = 80, PL =55
STEP 1:
Calculate Plasticity Index, PI:
PI = LL − PL= 25
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
2. Soil Classification
2-3. Soil Classification Systems (p. 77-78)
Unified Soil Classification System (source:wikipedia)
27. 27
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
100 96 90 80 66
The following classification tests were performed on a specimen
recovered from a borehole from a depth of 20 feet. The material is
black with a strong odor. Give the group symbol and group
name.
GIVEN: LL = 80, PL =55
STEP 1:
Calculate Plasticity Index, PI:
PI = LL − PL= 25
From the Atterberg Chart, using
LL = 80 and PI = 25 => MH or
OH
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
100 96 90 80 66
The following classification tests were performed on a specimen
recovered from a borehole from a depth of 20 feet. The material is
black with a strong odor. Give the group symbol and group
name.
GIVEN: LL = 80, PL =55
STEP 1:
Calculate Plasticity Index, PI:
PI = LL − PL= 25
From the Atterberg Chart, using LL =
80 and PI = 25 => MH or OH
STEP 2:
95% passing #40 and 90%
passing #200 sieve => fine
grained soils
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
28. 28
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
100 96 90 80 66
The following classification tests were performed on a specimen
recovered from a borehole from a depth of 20 feet. The material is
black with a strong odor. Give the group symbol and group
name.
GIVEN: LL = 80, PL =55
STEP 1:
Calculate Plasticity Index, PI:
PI = LL − PL= 25
From the Atterberg Chart, using LL =
80 and PI = 25 => MH or OH
STEP 2:
95% passing #40 and 90%
passing #200 sieve => fine
grained soils
specimen color => black with
strong smell
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
100 96 90 80 66
The following classification tests were performed on a specimen
recovered from a borehole from a depth of 20 feet. The material is
black with a strong odor. Give the group symbol and group
name.
GIVEN: LL = 80, PL =55
STEP 1:
Calculate Plasticity Index, PI:
PI = LL − PL= 25
From the Atterberg Chart, using LL =
80 and PI = 25 => MH or OH
STEP 2:
95% passing #40 and 90% passing
#200 sieve => fine grained soils
specimen color => black with strong
smell
liquid limit = 88% > 50%
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
29. 29
Sieve Analysis, %
finer
Atterberg Limit
No.1
0
No.4
0
No.20
0
Liquid
Limit
Plastic
limit
98 80 66 38 29
What is the unified soil classification of the soil described
below?
GIVEN: LL = 38, PL =29
STEP 1:
Calculate Plasticity Index, PI:
PI = LL − PL= 9
From the Atterberg Chart, using LL = 38
and PI = 9 => ML or OL
STEP 2:
80% passing #40 and 55%
passing #200 sieve => fine
grained soils
liquid limit = 38% <50%
Soil group symbol is ML or OL ;
Depending on odor and color, if
no odor, then the soil is inorganic
silt (ML), if the soil has an odor
and a dark color, then the soil is
organic silt or organic silty clay
(OL)
2. Soil Classification
2-2. Consistency of Soils - Atterberg Limits (p. 34-42)
2-3. Soil Classification System (p.77-78)
5
8
Sistemas de Clasificación
Sistema de Clasificación Unificada (USCS)
AASHTO (American Association of State
Highway and Transportation Officials
System)