Cimentaciones

SOIL MECHANICS
•NATURE.
•SOLIDS, AIR, AND WATER PHASES
•AGENTS GENERATORS OF SOILS
•RESIDUAL AND TRANSPORTED SOILS

Professor: Alfredo Zepeda Garrido
January 21, 2010

February 2, 2010

Microstructure
in
Clays

Professor: Alfredo Zepeda Garrido
January 21, 2010

Typical Kaolinite

Element

Weight%

Atomic%

OK

14.83

26.83

Na K

0.75

0.94

Mg K2.25

2.68

Al K

2.75

2.95

Si K

46.61

48.04

KK

2.31

1.71

Ca K

5.01

3.62

Fe K

25.50

13.22

Totals

100.00

Spectrum processing:
Peaks possibly omitted: 2.149, 8.036, 8.475, 8.900, 9.706, 11.501, 13.367 keV
Processing option: All elements analyzed (Normalised)
Number of iterations = 2. Jurica Clay, Queretaro city. Mexico. Alicia Del Real LJU100-2 sitio 1 espectro2

Element

Weight%

Atomic%

OK

18.71

31.06

Na K

0.68

0.79

Mg K

1.75

1.92

Al K

10.36

10.20

Si K

46.95

44.40

KK

2.59

1.76

Ca K

4.57

3.03

Fe K

14.38

6.84

Totals

100.00

Spectrum processing :
Peaks possibly omitted : 2.149, 8.036, 8.515, 8.905, 9.706, 11.486, 13.350 keV
Processing option :All elements analyzed (Normalised)
Number of iterations = 3. Jurica Clay, Queretaro city. Mexico. Alicia Del Real L.
Sample: JU100 2 espectro4. Site of Interest 2 Type: Default. JU100-2 sitio 2

Electronic microscopy of sweep, natural soil
of Queretaro (López-Lara, 2001).

Three-phase system: soil grains (particles),
water and gas (air).

σn
τ

∆σn

Real soils have both structures,i.e. have a
macrostructure consisting of large particles and
large pores and a microstructure composed
glomeruli with very small pores.

WATER IN THE SOIL

Soil grain
Adsorbed water
Gas (Air)
Capillary
water
Saturated soil

Volume

TRADITIONAL THREE
PHASES DIAGRAM FOR
UNSATURATED SOIL

Weigth

Vm

air

Vw

water

Ww

soil
solids

Ws

Vv

Vs

Volume

WmWeigth
Va

Vm

Wa≈0

Va

air

Wa≈0

Vc

Wc
Vw
Vs

Contractil skin
water

Ww

soil
solids

Ws

Wm

FOUR PHASES DIAGRAM
FOR UNSATURATED SOIL,
ACCORDING TO FREDLUND.

Clay particles

agua capilar
Capillary water

agua
Adsorbed
adsorbida
water

Electrical forces of adsorption
that are developed on the
surface of the mineral particles
attract watermolecules and
ions. These forces decrease
as the water molecules and
ions are further away from the
surface of the grain.

Water in unsaturated soil, with the capillarity and the
adsorption effect, both produce the matric suction.

Picture of a vertisol in Bulgaria. There is carbonate concretions.

Electronic microscopy of sweep

Slickensides, the glossy surface seen in the picture,are an obligatory requirement for vertisols (USDA).

Soil Mechanics.
Soil mechanics is the application of the laws of mechanics and
hydraulics to engineering problems that deal with sediments and
other solid particles produced by mechanical breakdown or chemical
decomposition of rocks and other non-consolidated accumulations of
solids particles, produced by mechanical breakdown or chemicaldecomposition of rocks, regardless of whether or not they have
content of organic matter (Karl Terzaghi).
Agents generators of soils
The Earth´s crust is mainly attacked by air and water. Soil is formed from
the weathering of rocks and minerals. The surface rocks break down into
smaller pieces through a process of weathering
All attack mechanisms may include into two groups:
•Mechanicaldisintegration (mechanical weathering) and
•Chemical decomposition (chemical weathering).

Mechanical weathering : Refers to the weathering of the rocks by physical
agents such as periodic changes of temperature, the freezing of water in
the joints and cracks in the rocks, effects of organisms, plants and other
action.
Because of these phenomena rocks generate sands, in extreme cases can...