engineering properties of soil.pdf

8/9/2019 Engineering Properties of soil.pdf

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Engineering Properties of soil

Assoc. Prof. Tirawat Boonyatee


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Soil and engineering construction

2


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As supporting material

3

Bearing capacity (Strength) Settlement (Deformation)


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As sustained material

4

Lateral pressures Lateral pressures & Settlement


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As transported material

5

Weight, Volume / Compaction Stability of borehole wall


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As contaminated material

6

Permeability Permeability


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Basic soil’s properties

7

/

Physical PropertiesEngineering Properties

Chemical Properties


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8

/


Chemical Properties


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9

VoidSolid

Soil as a group of particles


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Weight - Volume Relationships

10

Solid

Liquid

Gas Va

Vw

Vs

V

Vv

Ws

Ww

W

Volume of soil = V solid + V void = V solid + V air + V water = V s + V a + V w

Weight of soil = W solid + W liquid = W solid + W water

= W s + W w


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Volume relationships

→ Void ratio, Porosity, Degree of Saturation

Void ratio e =

Porosity n =

Degree of Saturation S = =

Solid

Liquid

Gas Va

Vw

Vs

V

Vv

Ws

Ww

W

v

s

V

V

vV

V

w

v

V

V 100%w

v

V

V


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Relationship between Void ratio and Porosity

e =

n =

11

v

v v

v s v

V V V nV

V V V V n

V

11

v

v v s

v s v

s

V

V V eV

V V V V eV


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13

Weight relationships→ Water content, Unit weight

Water content w =

Unit weight g =

Dry unit weight g d =

Solid

Liquid

Gas Va

Vw

Vs

V

Vv

Ws

Ww

W

w

s

W

W

(1 ) s v sW W W W w

V V V

sW

V g = g d (1+w)

g = r g

หนวยน หนัก

ควมหนแนน


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ควมถวงจเพะ (Specific gravity)

14

o

Unit weight of a given material

Unit weight of water (at 4 c) sG

G s of soil particle usually falls within

a range of 2.6 – 2.9

Mineral

Specific gravity

Quartz 2.65

Kaolinite 2.60

Illite 2.80

Montmorillonite

2.65 –

2.80

Halloysite 2.00 – 2.55

Potassium feldspar 2.57

Sodium feldspar 2.62 – 2.76

Hornblende

3.00 – 3.47

Limonite 3.60 – 4.00

Olivine 3.27 – 3.70

Soil G s

Gravel 2.65 – 2.68

Sand 2.65 – 2.68

Silty sand 2.67 – 2.70

Silt

2.65 –

2.68

Clay (inorganic) 2.68 – 2.70

Clay (organic) 2.62 – 2.66

Soils with mica orFe

2.75 – 3.00


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15

Apparent and Absolute G s

Apparent specific gravity

Volume of air included

Absolute specific gravity Volume of air excluded

Solid

Water

Air


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16


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17


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Relative density (Dr)

Indicate the in-situ denseness or looseness ofgranular soil

Dr =

Dr = relative density

e = in-situ void ratio of the soil

emax = void ratio in the loosest state

emin = void ratio in the densest state

18

max

max min

e e

e e


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19

D r and densities

by relation e =

D r =

1 s w

d

G g

g

( ) ( )

( ) ( ) ( ) ( )

1 1

1 1

s w s w

d min d d min d

s w s w

d min d max d min d max

G G

G G

g g

g g g g

g g

g g g g

( ) ( )

( )( )

d min d maxd r

d min d d max

Dg g g

g g g


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ASTM D-2049 : for gd(min) of granular soils

Mold volume = 0.1 ft3

(2,830 cm3)

Drop height = 1 inch

Mold

V m

= 0.1 ft3

Sand

1"

0.5"

20

s

d(min)m

W

=V g


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ASTM D-2049 : for gd(max) of granular soils

Mold volume = 0.1 ft3

(2,830 cm3)

Drop height = 1 inch

Vibrated table 2 lb/in2 surcharge at top of mold

vibrate frequency = 3600 rpm

vibrate amplitude = 0.025 in

vibrate time = 8 min

Mold

V m

= 0.1 ft3

Sand

1"

0.5"

21

sd(max)

m

W =

V g


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Qualitative Description of granular soil

The problem indetermining of Dr is due to

the difficulty to obtain the

undisturbed sample from

the field.

Granular soil

=>Cohesionless

Practically, Dr is

determined from

the N value of SPT (standard

penetration test)

the vertical effective stress

Gibbs and Holtz ‘s chart

Dr Designation

0~15 Very loose

15~50 Loose

50~70 Medium

70~85 Dense

85~100 Very dense

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23

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Chemical Properties


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Soil Particle Size Definitions

24

Gravel

Sand

Silt

Clay

4.75 mm

75 m

5 m

โ

10 mm

100

m

10 m

1 mm

1 m

โ(Earth's crust)

(Rocks)

(Soils)

(Gravels)

ท(Sands)

ท(Silts)

(Clays)

(Granular Soils)

(Cohesive Soils)


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Soil Particle Size Definitions

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Name Size (mm) cobbles, boulders, rock fragment > 60

gravel: 4.75 - 60

sand: 0.075 – 4.75 silt: 0.005 - 0.075

Limit of unaided vision.

clay < 0.005

Limit of optical microscope resolution.


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Structure of coarse grained soil

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Angular Loosed state

Densed state

HoneycombRound

Subangular

Subround


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Structure of fine grained soil

27

PacketFlocculatedDispersed

ตกตะกอนในน จด ตกตะกอนในน ทะเล


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28

Particle size analysis of soils

Determination of the size range of particles present in a soil Expressed as a percentage of total weight of dried soil

Composed of

Sieve analysis for large grain (>75m)

Hydrometer analysis for fine grain (< 75 m)


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Sieve analysis

Shaking the soil sample through a set of sieves that have

progressively smaller openings

Each successive lower sieve is approximately half of theopening of upper sieve

29

O i ( )Si O i ( )Si


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Sieve no. and Opening

Sieve no 4=> 4 divisions in 1”

Opening ~ ¼ “

Sieve no 200

=> 200 divisions in 1”

Opening ~ 1/200 “

0.053270

0.075200

0.090170

0.106140

0.125120

0.150100

0.18080

0.21270

0.25060

0.35550

0.42540

0.50035

0.60030

0.71025

0.85020

1.0018

1.1816

1.4014

1.7012

2.0010

2.368

2.807

3.356

4.005

4.754

Opening (mm)Sieve no

0.053270

0.075200

0.090170

0.106140

0.125120

0.150100

0.18080

0.21270

0.25060

0.35550

0.42540

0.50035

0.60030

0.71025

0.85020

1.0018

1.1816

1.4014

1.7012

2.0010

2.368

2.807

3.356

4.005

4.754

Opening (mm)Sieve no

30


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31

Example

Percentage finer than size D2

4 3100%

1 2 3 4

weight below D2total weight

mp m m

mp m m m m

Size D1

Size D2

Size D3

Size D4

Pan

m1

m2

m3

m4

mp

mass retained on sieve SIEVES


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Example

32


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Hydrometer analysis

Analysis based on Stoke’s Law

Sediment velocity is proportional to diameter

The larger, the faster

As time lapse, concentration along depth varies

Indirect measure for percent finer of soil particles

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34 Hydrometer


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Schematic diagram of hydrometer test

35


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36 Grading curves


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37

Fuller packing

0.5

xat x

max

D% finer 100 D


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38 Important indexes

10

60

u

D

D C

D D

D C

6010

2

30c

B i il’ i


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39

/


Chemical Properties

ท

C i f l


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40 Consistency of clays

Behavior of clays depends on amount of water

Addition of water reduce cohesion flow

Brittle solid Plastic Liquid

Plasticity: Property of a material that can be deformed rapidly withoutrupture, without elastic rebound, and without volume change

Cause of Plasticity: double-layer water

ff f d bl l l


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4

1

Effect of double-layer water to clay

A b ’ li i


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42

Atterberg’s limits

Water contents when the soils change their behavior

Atterberg’s limits

Shrinkage limit (SL) : No further volume change when moisture decreases

Plastic limit (PL) : Lower limit of that soils will exhibit plastic behavior

Liquid limit (LL) : Soils are about to flow when the moisture increases

Plasticity index = LL - PL

Li id li i (LL)


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43

Liquid limit (LL)


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44

Li id li it diti


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Liquid limit condition

Groove width 2 mm Water content, required to close a distance of 0.5

in along the bottom of groove after 25 blows

One blow generates shear stress of ~ 0.01 t/m2

At liquid limit, Shear strength of clay ~ 0.25 t/m2

45

Fl


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46

Flow curve

Flow index

Fl i d


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47

Flow index

1

1

1 10 10 100

log

, or,

F

F

w w I N

N

I w w w w

tan

If [20,30]

; tan 0.121

25n

N

N LL w

Pl ti li it (PL)


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Plastic limit (PL)

Roll into 1/8” thread

Moist content at which soil crumbles

48

Sh i k li it


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Shrinkage limit

49

Shrinkage limit :Moisture content at which the volume of soil stop to change

C l l ti f Sh i k li it


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50

Calculation for Shrinkage limit

iSL w w

1 2

2

2

x 100 (%)

x 100 (%)

i

i f w

m mw m

V V w

m

r

PI d LI


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51

PI and LI

The amount of water that a soil can absorb during plastic state

The amount of water in natural state, normalize by PI

PI LL PL

w PL w PL LI

LL PL PI

PL LL

PI

LI = 0

LI = 1

Important of PI


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52

Important of PI

Indicate the strength of clay minerals in a soil The higher w it can hold, the stronger the plasticity it can exhibit

PI Type of clay

0

Nonplastic

1 - 5 Slightly plastic

5 - 10 Low plasticity

10 - 20 Medium plasticity

20 - 40 High plasticity

40++ Very high plasticity

53Meaning of Liquidity index


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53 Meaning of Liquidity index

Soils with LI > 1, when remolded will transformed toliquid phrase

Soil deposits that are heavily overconsolidated mayhave a LI < 0

Implicitly indicate the stress history of soil LI = 1 : Normally consolidated clay

LI = 0 : Over consolidated clay


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54


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Activity (A)

Index that shows the influence of particle < 2 to the

plasticity index of soil

%

percent finer at 2

slope of PI -

engineering properties of soil.pdf

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