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UNIVERSIDAD DEL MAGDALENA
Programa de ingeniería Civil
Curso: Geotecnia II
Tema: Tipos de cimentaciones
Docente: Luis Ángel Avilés
Periodo: 2022-II
Outline
1. Shallow foundations.
2. Deep foundations
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1. Shallow foundations - definition
The definition of a “shallow foundation” varies
from author to author but generally is thought
of as a foundation that bears at a depth less
than about two times the foundation width.
1. Shallow foundations- criteria
Shallow foundation generally is when the ratio is D/B ≤ 2.5 or
when the depth is less than 4 m.
a) Isolated foundations
• Square
• Rectangular
• Circular
b) Continuous foundations
c) Combined foundations
• Rectangular
• Trapezoidal
d) Ring foundations
e) Mat foundations
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1. Isolated spread footing
1. Isolated spread footing
• Designed to distribute the concentrated loads delivered by a single
column.
• Simple geometrical shapes.
• Minimize settlement by reducing the applied bearing stress.
• Can be designed uniform or variable using pedestals in order to control
stresses in the soil.
• Are used in low compressible soils.
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1. Isolated spread footing - diaphragms
1. Continuous strip spread footings
Continuous or strip footings
generally have a minimum
length to width ratio of at least
5 (i.e., length > 5 x width).
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1. Continuous strip spread footings
• Elements with length much larger tan width. (Approx.
Length > 5*width)
• Used for linear loads (load-bearing wall) or columns in line
with a given spacing that the required areas to isolated
foundations will be almost together.
• It seeks to integrate the foundation for various structural
supports into a single foundation due to:
Potential overlap of load bearing areas.
To control differential settlements.
Increase structural rigidity.
Bridge effect in weak areas in the soil.
Construction and economical conveniences.
1. Continuous strip spread footings
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1. Combination footings
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1. Combination footings
Is used when…
• when isolated spread footings become so closely spaced that a
combination footing is simpler to form and construct .
• Exist eccentricity of loads with respect to centroid of the
support area.
• High differential settlements occurs in isolated foundations
between structural supports.
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1. Combination footings
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1. Ring footing
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1. Mat foundations
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1. Mat foundations
Are appropriated to control differential settlements in different
load situations, structural configuration, and load-bearing
conditions. Are used when:
• High different in loads between columns and adjacent
load-bearing walls.
• In situations when using isolated or continuous
foundations, overlaps occurs or when more tan 50% of the
construction area is occupied by the foundations.
• Excessive compressibility, low capacity, heterogeneity and
uncertainty of the soil.
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1. Mat foundations
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1. Compensated foundations
Consist in removing by excavation a weight of soil
equivalent to a fraction or the total of the
construction weight and support to a convenient
depth using a mat o continuous foundation.
When
• Weight of the structure = weight of the
excavate soil, building floating, there will be no
stress changes below the structure, will be few
settlements, at least that the soil be a semi-
fluid deposit.
• Weight of the excavated soil < weight of the
structure, partially compensated.
• Weight of the excavated soil > weight of the
structure, overcompensated.
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1. Compensated foundations
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1. Compensated foundations
According with Golder(1975):
Type I → The soil is not a problem by shear failure, but the settlements
(specially differentials) can be big. Compensated foundations can reduce
settlements.
Type II → shear failure, soil strength is very low. Compensated foundation
can reduce shear stress to tolerable values. Depth can be enough to
control settlements.
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1. Shallow foundations – when to use?
Square foundations
- Under isolated columns
- Equals moment are produced
- Easy design and constructive process
Rectangular foundations
- When there is not enough space to construct square foundations
- Eccentricity problems, higher moments in the long side
- For limiting columns
- For columns with section elongated.
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1. Shallow foundations - when to use?
Ring foundations
- Foundations for silo or specials structures like transmission towers –
circular tanks, etc.
Trapezoidal foundations
- High different between two columns
- Limiting Columns
- Eccentricity cases
Foundations with pedestals
- Columns with high load in order to reduce punching shear failure
- Recude the quantity of concrete
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1. Shallow foundations - when to use?
Tie beam
- Reduce eccentricity
- When the big distance between foundations
- Used for columns in limiting foundations
- Give uniformity to the pressure
- Reduce differential settlements
- Tie the structure to carry horizontal and seismic loads
- No should be supported directly in the soil. Can be tie to pedestals or
between the base of the foundations.
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Outline
1. Shallow foundations.
2. Deep foundations
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2. Deep foundations
Cuando (profundidad/base)>4 ó profundidad de desplante mayor de 4 mts.
• Pilotes
- Pilares excavados → Cilindro hueco se funde en el terreno, se excava de nuevo
y se vuelve a fundir otro anillo. Si se produce ensanchamiento de la base, en
forma de tronco (pata de elefante), para reducir presiones de contacto sobre el
manto portante.
- Pilas → Igual al anterior pero la columna de concreto queda aislada en el
interior de un pozo permanentemente revestido.
- Cajones (Caissons) → caja estructural que se hunde o funde en el sitio,
excavando el suelo por debajo y extrayéndolo, hasta descender a la profundidad
requerida.
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2. Deep foundations
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2. Deep foundations Cimentación Profunda
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2. Deep foundations Cimentación Profunda
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2. Deep foundations Cimentación Profunda
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2. Deep foundations Cimentación Profunda
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2. Deep foundations Cimentación Profunda
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2. Deep foundations Cimentación Profunda
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2. Deep foundations Cimentación Profunda
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2. Deep foundations Cimentación Profunda
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