Shallow foundation full information

Salahaddin university-Erbil
College of engineering
Civil engineering department
Foundations
(shallow foundations)
By
Nazik Falah
Esra Mohamed
Eman Dler
Supervisor
Zina M. Mudheher
Ali Rizgar
April, 2019

2
Summary
In this report, we will answer some questions concerning the
foundations because the foundations are the main part of the building
where the project cannot be started without them. These questions
include: "What is the foundation? and what types and what types of
shallow institutions? What is the difference between this and the other
type?" In the beginning, we will explain what the basics are and how to
design them at lower cost and greater resistance. We will discuss the
points needed for the engineer or designer to follow, and the foundation
is the element of the structure that corresponds to the ground, and the
loads of the structure on the ground, institutions either shallow or deep
in general an essential part of the building, so we will answer these
questions. We discuss what is the damage of this kind, so the basic soil
and task role in the implementation of the foundations should know the
soil types and how to deal with them.

3
TABLE OF CONTENTS
SUMMARY 2
1.0 INTRODUCTION TO FOUNDATIONS 4
2.0 SHALLOW FOUNDATIONS 5
2.1 CLASSIFIED BY SHAPE 6
2.2 FORMATION FORMS 7
2.3 PROTECTION OF FOUNDATIONS 8
2.4 STRENGTHENING FOUNDATIONS 8
2.5 ADVANTAGES OF USING SHALLOW FOUNDATION 8
2.6 DISADVANTAGES OF USING SHALLOW FOUNDATION 8
3.0 DIFFERENT TYPES OF SHALLOW FOUNDATIONS 9
1. 3.1 SLAB-ON-GRADE FOUNDATION 9
2. 3.2 STRIP FOOTING 10
3. 3.3 SPREAD OR ISOLATED FOOTING OR INDIVIDUAL FOOTING 11
4. 3.4 COMBINED FOOTING 12
5. 3.5 STRAP OR CANTILEVER FOOTING 12
6. 3.6 MAT OR RAFT FOUNDATIONS 13
4.0 SHALLOW FOUNDATION DESIGN 14
1. 4.1 TO PERFORM SATISFACTORILY 14
2. 4.2 DESIGN CONSIDERATIONS 14
3. 4.3 FOR THE SHALLOW TYPE 15
5.0 ADVANTAGES & DISADVANTAGES OF SHALLOW FOUNDATION 15
1. 5.1 ADVANTAGES OF SHALLOW FOUNDATION 15
2. 5.2 DISADVANTAGES OF SHALLOW FOUNDATION 15

4
6.0 CONDITIONS TO BE CONSIDERED WHEN DESIGNING AND IMPLEMENTING
FOUNDATIONS 16
1. 6.1 THE DESIGN OR PERFORMING ENGINEER SHALL OBSERVE THE
FOLLOWING 18
2. 6.2 SHALLOW FOUNDATION VS DEEP FOUNDATION 20
7.0 CONCLUSION 22
8.0 REFERENCE 22
List of Figures
2.0 Shallow Foundations ………………………………………(7)
3.1 Concrete Slab…………………………………………….(11)
3.2 Strip footing………………………………………………(12)
3.3 Spread or Isolated Footing or Individual Footing…….(13)
3.4 Combined Footing…………………………………………(14)
3.5 Strap or Cantilever Footing……………………………….(15)
3.6 Mat or Raft Foundations………………………………….(16)
1.0 Introduction to Foundations
A foundation is a lower portion of building structure that transfers its
gravity loads to the earth. Foundations are generally broken into two

5
categories: shallow foundations and deep foundations. To make a
foundation, we normally dig a trench in the ground, digging deeper and
deeper until we come to subsoil, which is more solid than the topsoil
that is used to grow plants and crops. When the trench is deep enough,
we fill it with any strong, hard material we can find. When the concrete
dries, the steel acts like the bones in our body to tie the foundation
together. We call this reinforced concrete. Once the foundation has
been packed down tightly, or dried hard, we can begin to build the
building superstructure. This has been a brief insight about foundation
and its type’s. "A building generally consists of (superstructure –
substructure and foundation system) , the superstructure generally
refers to the part of the building that is above the ground level ,the
substructure refers to basements and the foundation system refers to
the structure that lies below the substructure"1
.
2.0 Shallow Foundations2
Shallow foundation is a type of construction foundation that transfers
construction loads to the ground near the surface so that its depth does
not exceed 10 meters. If the soil conditions directly under the structure
are strong enough and able to support the desired load, then the
shallow spread foot can be used to transport the load. On the other
hand, if the soil conditions are weak, then piles are used to transfer the
loads to a soil that is deeper and more suitable. Soil should be studied
to detect the nature and deposition of its layers and thickness. In order
to determine the soil which provides the four conditions (durability,
1
This introduction on the foundations we have obtained through an interview with two students of
the second stage they are (Yara and Ala) (3/4/2019).
2
https://ar.wikipedia.org/wiki/%D8%A3%D8%B3%D8%A7%D8%B3_(%D8%A8%D9%86%D8%A7%D8%A1)
27/2/2019

6
balance, stability, To know the nature of the soil there is no one way but
the most appropriate methods are at the site of the establishments to
take samples from which analyzes are carried out in the laboratory and
then classified and maintained and the results are placed in the report
of the study of soils.
The sounding is done in a different way: sounding with manual drills,
sounding with hydraulic drill, sounding with precision and sounding with
rotary drilling for the hard soil. Soil data are then available and
properties are verified by soil detection by cone drill and cone.
The length of the sounding is usually 3 times greater than the base
dimension (the insole) and not less than 3 meters from the regular
foundations. The wedges are to be lowered to the required depth. The
sounding is usually 15 meters between each probe and another 30
meters between the earth dams and the tunnels. Properties: Soil
resistance to pressure; Soil cohesion; Friction angle; Soil resistance
was calculated by dividing the load on the surface. In the large
establishments, we define other properties such as the Nafadiyya
coefficient, the compressive pressure, and the characteristics of the
deformation and its effects on soil stability, balance and stability.
Fig. 2.0(Shallow foundation
2.1 Classified by shape
• A single (isolated) foundation that is often a surface foundation made
of stone and concrete and is a foundation with only one column.

7
• The common foundation holds two or more columns.
• Continuous foundation holds a wall.
• Concrete foundations are poured into the reinforced concrete at the
same site and are pre-fabricated and subsequently deposited. Most of
the time, the concrete is poured with a thickness of 4-5 cm before
laying the foundation. Cement in concrete is estimated at 150 kg per
meter. 250 kg per m3 at least for single foundations with unarmed
concrete.
• 350 kg per meter of armed conflict.
• 300 kg per cubic meter of single foundations of concrete buried
underwater.
• The mat is one of the surface foundations, often bearing columns and
walls, are reinforced concrete and resort to their use is an economic
solution, first of the descent into deep depths and this when the
resistance of the soil is weak and in which the distribution of payloads
regular distribution and this to identify the local degeneration leading to
cracking walls and pour Clean concrete with at least 5 cm of regular
concrete 150 kg / m.
2.2 Formation forms
There is a relationship between the level of establishment and the right
class, which is the class that meets the four conditions is durability,
stability, stability, balance, and this relationship determines the form of
founding, which is divided into three sections:
• Direct foundation on good soil
• The establishment level is higher than the groundwater level.
• Indirect foundation on the soil
• In this case the foundations are very deep and are often in the
offshore establishment such as: wave breakers, beach docks and
the substrate are above surface soil.
• Establishment on the soil is invalid
• There are special forms in the poles and pillars, which are
sometimes serrated sides are large forms that resist loads.

8
2.3 Protection of foundations3
Groundwater is one of the biggest problems of the foundations. This is
when it contains chemical substances that affect the concrete steel and
its flow by drifting the soil from under the foundation. Therefore, we use
special concrete to resist the effects.
Solution The base can be protected with metal sheeting or pavement of
rock around the foundation. The drainage system shall be constructed
in the case of deep foundations and sealants shall be put in place.
2.4 Strengthening foundations
The foundations need to be strengthened when deep drilling is done.
Often the foundations are substituted or strengthened. This process is
very complex and requires great precision and experience.
The foundations are mounted on temporary foundations and the
foundations are applied and linked to structures structures, but little is
used to solve this solution.
2.5 Advantages of using shallow foundation
• Cost (affordable)
• Construction Procedure (simple)
• Materials (mostly concrete)
• Labor (does not need expertise
Disadvantages of using shallow foundation2.6
Settlement Irregular ground surface (slope, retaining wall) Foundation
subjected to pull out, torsion, moment
3
wikipedia.org/wiki/%D8%A3%D8%B3%D8%A7%D8%B3_(%D8%A8%D9%86%D8%A7%D8%A1).https://ar
27/2/2019

9
3.0 Different Types of Shallow Foundations
The different types of shallow foundation are:
1. Slab on grade
2. Strip footing
3. Spread or isolated footing
4. Combined footing
5. Strap or cantilever footing
6. Mat or raft foundation
3.1 Slab-on-grade foundation
Slab-on-grade or floating slab foundations are a structural engineering
practice whereby the concrete slab that is to serve as the foundation for
the structure is formed from a mold set into the ground. The concrete is
then placed into the mold, leaving no space between the ground and
the structure. This type of construction is most often seen in warmer
climates, where ground freezing and thawing is less of a concern and
where there is no need for heat ducting underneath the floor. The
advantages of the slab technique are that it is cheap and sturdy, and is
considered less vulnerable to termite infestation because there are no
hollow spaces or wood channels leading from the ground to the
structure. The disadvantages are the lack of access from below for
utility lines, the potential for large heat losses where ground
temperatures fall significantly below the interior temperature .Slab-on-
grade foundations are commonly used in areas with expansive
clay soil. While elevated structural slabs actually perform better on
expansive clays.

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fig. 3.1 (Slab-on-grade foundation)
Elevated structural slabs are generally only found on custom homes or
homes with basements .Copper piping, commonly used to carry natural
gas and water, reacts with concrete over a long period, slowly
degrading until the pipe fails. This can lead to what is commonly
referred to as slab leaks. These occur when pipes begin to leak from
within the slab. Signs of a slab leak range from unexplained dampened
carpet spots, to drops in water pressure and wet discoloration on
exterior foundation walls.[1]
Copper pipes must be lagged (that
is, insulated) or run through a conduit or plumbed into the building
above the slab.
3.2 Strip Footing
A strip footing is provided for a load-bearing wall. A strip footing is also
provided for a row of columns which are so closely spaced that their
spread footings overlap or nearly touch each other. In such a case, it is
more economical to provide a strip footing than to provide a number of
spread footings in one line. A strip footing is also known as continuous
footing.

11
fig. 3.2 (Strip Footing)
3.3 Spread or Isolated Footing or Individual Footing
A spread footing also called as isolated footing, pad footing and individual footing is
provided to support an individual column. A spread footing is circular, square or
rectangular slab of uniform thickness. Sometimes, it is stepped or hunched to
spread the load over a large area.
fig. 3.3 (Spread footing)

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3.4 Combined Footing
A combined footing supports two columns. It is used when the two columns are so
close to each other that their individual footings would overlap. A combined footing
is also provided when the property line is so close to one column that a spread
footing would be eccentrically loaded when kept entirely within the property line. By
combining it with that of an interior column, the load is evenly distributed. A
combined footing may be rectangular or trapezoidal in plan.
fig. 3.4 (Combined Footing)
3.5 Strap or Cantilever Footing
A strap (or cantilever) footing consists of two isolated footings connected with a
structural strap or a lever. The strap connects the two footings such that they
behave as one unit. The strap is designed as a rigid beam. The individual footings
are so designed that their combined line of action passes through the resultant of
the total load. a strap footing is more economical than a combined footing when the
allow able soil pressure is relatively high and the distance between the columns is
large.

13
fig. 3.5 (strap footing)
3.6 Mat or Raft Foundations
A mat or raft foundation is a large slab supporting a number of columns and walls
under the entire structure or a large part of the structure. A mat is required when
the allowable soil pressure is low or where the columns and walls are so close that
individual footings would overlap or nearly touch each other.
Mat foundations are useful in reducing the differential settlements on non-
homogeneous soils or where there is a large variation in the loads on individual
columns.

14
fig. 3.6 (mat foundations)
4.0 SHALLOW FOUNDATION DESIGN4
4.1 To perform satisfactorily
• The foundation has to be safe against overall shear failure in the soil that
supports it. (bearing capacity)
• The foundation cannot undergo excessive displacement → settlement.
4.2 Design considerations
• Foundations must be designed both structurally and geotechnically.
• Able to safely carry compression , tension and shear loads , and possible
moments.
• Structurally efficient.
• Geotechnically efficient.
3
Mehta, Walter scarborough, DianeBuilding Construction, Principles, Materials, and Systems, Mandan
armpriest,2009 update (28/2/2019)

15
• Take tolerance of structure to movement into account.
4.3 For the shallow type
" Soil layer is suitable for supporting a structure at a relatively shallow depth ".
All loads that may act on foundations should be studied and determined.
Site investigation should be carried out.
Depth of foundation must be determined.
Foundations must be analyzed with respect to two failure types:
Settlement failure
Bearing capacity failure
5
dvantages of shallow foundation5.0 Advantages & Disa
5.1 Advantages of shallow foundation
Foundation with shallow depths are beneficial for some aspects. Some advantages
of shallow foundation is listed below.
1.Shallow foundation is convenient for foundation having depth is equal or less than
the foundation width
2. It is used if bearing capacity of soil is high at shallow depth.
3. For compressive soils, it helps to reduce settlement.
4. No piling is required. So it reduces a great cost.
5.2 Disadvantages of shallow foundation
This foundation can not be used everywhere. The major disadvantage of shallow
foundation are given below:
1. If weight of structure is high and load of the structure is distributed unequally.
5
disadvantages-advantages-foundation-http://civilengineersforum.com/shallow/
(3-3-2019)

16
2. The bearing capacity of top surface soil is less.
3. If sub-soil water level is high and it is uneconomical to pump out the water from
the hole or canal.
4. If there is a chance of scouring as the structure is near sea or river shallow
foundation cannot be used
6.0 Conditions to be considered when designing and
6
implementing foundations
First, the foundation soil should be homogenous, unchanged, and fishy as
possible, while considering the possible movements of the soil after incorporation.
Second: the safety of the data bearing the soil after the confirmation of its type,
taking into account the safety factor necessary for the design to be sufficient
ground area for the distribution of loads on the soil and face all possibilities, taking
into account the depth and dimensions of the basis with the possibility of change of
forces affecting the basis.
Third: The distribution of pressure and loads of the building regularly on the basis,
regardless of the kind to avoid the irregular landing that causes cracks and cracks,
taking into account the possibility of lack of capacity to withstand the soil.
Fourth: taking into account the stability of the surface of the base mattress with the
outcome of loads and also take into account the applicability of the outcome of the
pressure with the axis of the foundation, as possible, but in the case of the walls
adjacent to the neighbors, replaced by strengthening and linking them with armed
ties and the work of heel base.
6
-%D8%A7%D8%B9https://engineer.tn/%D8%A7%D9%86%D9%88
%D8%A7%D9%84%D8%A7%D8%B3%D8%A7%D8%B3%D8%A7%D8%AA-
%D9%88%D9%83%D9%8A%D9%81%D9%8A%D8%A9-
%D8%A7%D8%B3%D8%AA%D9%84%D8%A7%D9%85%D9%87%D8%A7/(13/3/2019)

17
Fifth: Take into consideration the design of the base mixtures of materials suitable
for the forces of influence and the conditions of the site of movement and moisture
and others.
Sixth: To make necessary insulation precautions against humidity and vibration,
site conditions and the possibility of passing connections or facilities during the
foundations or the existence of old foundations on the site.
Seventh: The distribution of the building loads on the columns regularly and the
placement of columns or walls and therefore bases on the distances proportional to
the loads on which homogeneous.
Eighth: Take into account the following:
i. Calculation of permanent loads alone is called dead loads.
ii. Calculation of live loads alone is known as additional load.
iii. Calculation of mobile loads alone, such as cars and cranes.
iv. Calculate the self loads of the columns themselves and the base and is
estimated at about 10% , 5% of the loads.
v. The water and dust pressure of the retaining walls is estimated, taking into
account the soil density, height and angle of erosion.
vi. Estimated friction forces between dust and wall objects.
vii. The weight of the soil above the feet of the foundations and the heel in the
calculation of pressure from top to bottom and may neglect the safety of the
account.

18
6.1 The design or performing engineer shall observe the following7
1. If a soft layer is found at a distance from the base level, the additional pressure
on the layer must not increase its safe loading capacity.
2. If the base is close to a natural tendency in the soil, the soil must be protected
from loss of its ability to resist shear by making sand walls or working the
foundation more deeply than the sliding surface.
3. The safety factor in estimating the safe efforts of soft clay lands is increased
because the vertical foundation load causes slow soft side movements with a drop
in the building.
4. If clay or clay soil is compacted to interfere with its granules under the building or
due to vibrations, the soil size decreases and causes the soil to fall. This is treated
with soil blood by vibrating vibrations or by poking the piles around it or by
immersing the soil in water in case of dehydration.
5. Water moves in the ground to the sources of heat, which loses the soil a large
part of the water and harden and increase in drought until it shrinks and falls.
6. The building is dropped if the ground water is withdrawn or decreased around it
with hardening of the soil and the drop increases as the clouds are quick and
therefore the water withdrawals should be organized in a way and at a slow rate.
7 - Excavation near the building and the construction of new buildings adjacent
because of the reduction of the ability to withstand the soil and therefore must
provide adequate stents.
8. Evaporation on and around the foundation, especially in sandy soil, causes the
collapse of the foundation, especially if the water movement is rapid.
9. Leaking water to dry clay or dry clay soil may cause soil fall or stretch with failure
to resist shear effort.
10. Do not leave the foundation ground in mud or clay soil exposed for a long time
so as not to change the natural properties of the soil.
11. The foundations shall be used with aluminum cement instead of Portland if the
soil contains harmful or degradable chemicals.
7-https://engineer.tn/%D8%A7%D9%86%D9%88%D8%A7%D8%B9
%D9%88%D9%83%D9%8A%D9%81%D9%8A%D8%A9-
%D8%A7%D8%B3%D8%AA%D9%84%D8%A7%D9%85%D9%87%D8%A7/ (14/3/2019)

19
12. The main water pipes passing through the site shall be higher than the
foundation level so as not to cause the possibility of any pipe being blown into the
soil by the force of the flow of water.
13. Vertical force on the foundations shall be calculated as follows if the axle of the
load is:
Dead load + live load + self-weight of the foundation - the weight of the soil joking
14. There should be no disparities in the soil effort under the different base rules of
more than 25% of the maximum permissible effort.
15. In the case of pressure of soil or water on the retaining walls or in the case of
horizontal forces of the neighboring facilities, the maximum effort arising from the
vertical outcome of the forces acting on the base should not exceed the permissible
load effort for the soil. The horizontal result should not exceed the friction force
Between the bottom of the foundation and the contact soil, plus a part of the
negative pressure of the soil above the foundations.
16. In the case of large variations in pressure under parts of a building, the
foundations of large loads are separated from the rest of the building as well as the
vibration-prone penalty.
17. In the case of the use of complete bedding foundations, ie, the butterflies and
the assumption of uniformity of the distribution of soil pressure efforts under the
lash, reduced efforts should be used for the base material:
• Depth of foundation level.
• Display the basis.
• Soil density.
• The value of the inner friction angle of the soil.
• The strength of cohesion.

20
6.2 Shallow Foundation vs Deep Foundation8
Shallow foundation VS Deep foundation
Shallow foundation and deep foundation have many variations. Sources of major
differences between deep and shallow surfaces are definition, depth of foundation,
cost, feasibility, load transfer mechanism, advantages, defects, species, etc.
The following table presents the main differences between the shallow and deep
foundation:
8
-difference-ngineering/180e-engineering/foundation-https://civiltoday.com/geotechnical
between-shallow-and-deep-foundation (29/3/2019)
Shallow Foundation Deep Foundation
1 Definition Foundation which is
placed near the surface
the earth or transfersof
the loads at a shallow
depth is called shallow
foundation.
Foundation which is placed
at a greater depth or
transfers the loads to deep
strata is called deep
foundation.
2 The depth of
foundation
The depth of shallow
foundation is generally
about 3 meters or the
depth of foundation is
less than the footing
with.
Greater than shallow
foundation.
3 Cost Shallow foundation is
cheaper.
Deep foundations are
generally more expensive
than shallow foundation.
4 Feasibility Shallow foundations are
easier to construct.
The construction process of
a deep foundation is more
complex.
5 Mechanism of
load transfer
Shallow foundations
transfer loads mostly by
end bearing.
Deep foundations rely both
inon end bearing and sk
friction, with few exceptions

21
like end bearing pile.
6 Advantages Construction materials
are available, less labor
is needed, construction
procedure is simple at
an affordable cost etc.
Foundation can be provided
at a greater depth, Provides
lateral support and resists
uplift, effective when
foundation at a shallow depth
is not possible, can carry
huge load etc.
7 Disadvantages Possibility of a
settlement, usually
applicable for
lightweight structure,
weak against lateral
loads etc.
nsive, needsMore expe
skilled labors, complex
construction procedure, can
consuming and-be time
some types of deep
foundations are not very
flexible etc.
8 Types Isolated foundation, strip
foundation, mat
foundation, combined
foundation etc.
foundation, pilePier
foundation, caissons etc.

22
7.0 Conclusion
We conclude from this report that the use of the shallow foundation provides a
lower cost and has many types fit almost all types of soil. The most problem facing
shallow foundation is groundwater and we can solve this problem by adding
concrete slabs.
8.0 Reference
1- https://ar.wikipedia.org/wiki/%D8%A3%D8%B3%D8%A7%D8%B3_(%D8%A8%D9%
86%D8%A7%D8%A1)
2- Building Construction, Principles, Materials, and Systems, Mandan Mehta, Walter
scarborough, Diane armpriest,2009 update.
3- http://civilengineersforum.com/shallow-foundation-advantages-disadvantages/
4- https://engineer.tn/%D8%A7%D9%86%D9%88%D8%A7%D8%B9-
%D9%88%D9%83%D9%8A%D9%81%D9%8A%D8%A9-
%D8%A7%D8%B3%D8%AA%D9%84%D8%A7%D9%85%D9%87%D8%A7/
5- https://civiltoday.com/geotechnical-engineering/foundation-engineering/180-
difference-between-shallow-and-deep-foundation

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