This document discusses geotechnical aspects related to building foundations. It covers topics like geotechnical surveys, investigation objectives and stages. It describes different field and laboratory tests done during investigation. The document discusses classification of foundations, design procedures, planning considerations like footing depth and effects of groundwater. It also covers shallow foundations like isolated, combined, spread and raft footings and deep foundations like pile and pier foundations.

1. BUILDING CONSTRUCTION
TECHNOLOGY AND SERVICES
UNIT-1

2. UNIT I
1. GEO-TECHNICAL SURVEY TO DEFINE STRATA FOR BUILDING FOUNDATIONS.
2. GEO-TECHNICAL ASPECTS OF FOUNDATIONS.
3. PLANNING AND DESIGN CONSIDERATIONS OF: FOUNDATION SYSTEMS
FABRICATION AND ERECTION OF STEEL STRUCTURE.

3. GEO-TECHNICAL SURVEY
• Geotechnical investigations are carried out to obtain necessary data related
to engineering properties of soil for proposed structures’ foundations and
the repair of distress earthworks for other types of structures caused by
subsurface conditions.
• The geotechnical investigation includes surface and subsurface exploration
of a site. Subsurface exploration usually requires soil sampling and
laboratory tests.
• In contrast, surface exploration can include geologic mapping, geophysical
methods, and photogrammetry.

4. GEOTECHNICAL INVESTIGATION OBJECTIVES:
• The primary objective of the geotechnical investigation is to find out the
nature of the soil and rock deposit.
• As per the foundation requirement, the depth and thickness of various soil
types and rock strata can be obtained after geotechnical investigation.
• It helps to identify the location of the Ground Water Table(GWT).
• After geotechnical investigation, in-situ soil properties can be obtained by
performing different Subsurface exploration and field tests (SPT, DCPT,
SCPT, Vane Shear Tests, PMT etc.)
• The collection of soil and rock samples for determining engineering
properties in the laboratory is under geotechnical investigation.
• Based on the available data after geotechnical investigation, the foundation
type and depth can be decided.
• Geotechnical engineering assessment of foundations regarding their load-
bearing capacity and settlement aspects shall be possible.

5. GEOTECHNICAL INVESTIGATION STAGES:
1. RECONNAISSANCE STAGE:
• Soil and groundwater conditions.
• Topography, drainage pattern, vegetation.
• Condition of existing structures.
• Suitability of site for the proposed project.
• Types of soil and rock formations from geology.
• Presence of natural resources.
• Stream pattern, if any.
• Seismic activity in the area.

6. GEOTECHNICAL INVESTIGATION STAGES:
2. PLANNING OF GEOTECHNICAL INVESTIGATION:
• Location of geotechnical investigations.
• Numbers of geotechnical investigations (i.e.) Boreholes
• Depth of investigation.
3. GUIDELINES FOR LOCATION, NOS AND DEPTH OF BOREHOLE:
• IS: 1892-1979 – Code of practice for subsurface investigation for
foundations.
• IRC: 78-2014 – Standard specifications and code of practice for road
bridges, section-Vii: Foundations and substructures (revised edition) –
Appendix-2 under clause no-704.3.
• Specification for road and bridge works, fifth revision, 2013 of MORTH by
IRC -section 2400 (surface and subsurface investigation), section 2100
(open foundation), section 1100 (pile foundation) and section 1200 (well
foundation).

7. GEOTECHNICAL INVESTIGATION TESTS:
FIELD INVESTIGATION:
• Vertical loading tests.
• Deep penetration tests – Standard penetration test and Cone penetration
tests.
• Vane shear tests.
• Measurement of density of the soil.
• Pressure meter test.
LABORATORY INVESTIGATION:
o Physical tests:
• Liquid and plastic limits.
• Grain size analysis.
• Specific gravity.
• Natural moisture content.
• Unit weight.
• Consolidation test ( including pre-consolidation pressure).
• Shear strength: Unconfined compression.
• Triaxial compression.
• Direct shear permeability test.

8. GEOTECHNICAL INVESTIGATION TESTS:
o Chemical tests:
• Soluble salt content: Chlorides and sulphates.
• Calcium carbonate content (if warranted).
• Organic matter content (if warranted).
o Groundwater:
• Chemical analysis, including pH determination.
• Bacteriological analysis ( if necessary ).
o Rock drilling:
• Visual examination.
• Petrographic analysis.
• Unit weight.
• Compressive strength.
• Water absorption.
• Shear strength.

9. GEOTECHNICAL INVESTIGATION REPORT:
• The geotechnical investigation report contains the area’s geological history
and geographical background.
• The total scope of work and a plot plan showing the locations of all tests
should be recorded in the report.
• A brief description of the procedure adopted for field and laboratory tests
should be recorded.
• Detailed bore-log/drill-log in the approved format should be maintained.
• Laboratory test results in approved tabular and graphical form with the
summary should be attached.
• True cross-sections/profiles of all boreholes and trial pits should be
present.
• All geotechnical engineering parameters should be as follows.
i. Recommendations on geological and lithological information of the area
should be mentioned in the report.
ii. The details of the landslide, if any, should be recorded.
iii. The report contains the recommendation for the foundation system of
structures, and recommendations for ground treatment/improvement,
foundation and embankment/subgrade treatment in case of weak sub-soil,
expansive clay, liquefaction and artesian condition etc.

10. GEO TECHNICAL ASPECTS OF FOUNDATION
• Foundations are essential to transfer the loads coming from the
superstructures such as buildings, bridges, dams, highways, walls, tunnels,
towers and for that matter every engineering structure. Generally that part
of the structure above the foundation and extending above the ground level
is referred to as the superstructure. The foundations in turn are supported
by soil medium below. Thus, soil is also the foundation for the structure and
bears the entire load coming from above. Hence, the structural foundation
and the soil together are also referred to as the substructure.

11. • Building Support - It is the foundation that bears the load of the entire
structure and keeps it even. It should be able to bear live load as well as dead
load to avoid cracking or buckling. In case if the foundation malfunctions or
fails at any point, the building might become unstable or even collapse.
Building foundations is not just pouring concrete but also fitting it properly
into soil as if it were sewn into soil. It should be compacted as required to
ensure load bearing.
• Protection from Calamities - Before constructing the foundation, it is
necessary to study about the weather of the region and its ground condition.
The foundation is made strong enough to withstand the effects of any natural
calamities such as earthquakes, cyclones, etc. The foundation's strength is
always designed according to the extreme natural calamity that has already
occurred in the respective area.
• Protects from settlement - One of the primary reasons for the construction
of foundation is to protect the building from settlement as it starts to
minutely sink over time. The shape and structure of the foundation is
designed according to the soil condition prevalent in the area to resist
settlements in excess of permissible limits.

12. General Guidelines for Design
Following broad guidelines may be useful for foundation design and
construction, depending on site.
1. Footings should be constructed at an adequate depth below ground level to
avoid passive failure of the adjacent soil by heaving.
2. The footing depth should be preferably below the zone of seasonal volume
changes due to freezing, thawing, frost action, ground water and so on.
3. Adequate precautions have to be taken to cater for expansive soils causing
swelling pressure (upward pressure on the footing).
4. The stability of the footing has to be ensured against overturning, sliding,
uplift (floatation), tension at the contact surface (base of the footing), excessive
settlement and bearing capacity of soil.
5. The foundation needs to be protected against corrosion and other harmful
materials that may be present in the soil at site.
6. The design should have enough flexibility to take care of modifications of the
superstructure at a later stage or unanticipated site conditions.

13. DESIGN PROCEDURES FOR A BUILDING FOUNDATION (STEP BY STEP)
1. Decide the Location of Columns & Foundation and Type of Loads Acting on
Them.(e.x Deal load, Live load or Wind load)
On the building plan, the position of columns and loadbearing walls should be
marked, and any other induced loadings and bending moments. The loads
should be classified into dead, imposed and wind loadings, giving the
appropriate partial safety factors for these loads.
2. Estimate Allowable Bearing Pressure of Soil Using Ground Investigation
Report.
From a study of the site ground investigation (if available), the strength of the
soil at various depths or strata below foundation level should be studied, to
determine the safe bearing capacity at various levels. These values – or
presumed bearing values (from any standards or codes) in the absence of a site
investigation – are used to estimate the allowable bearing pressure.

14. 3. Decide Depth of Foundation
The invert level (underside) of the foundation is determined by either the
minimum depth below ground level unaffected by temperature, moisture content
variation or erosion – this can be as low as 450 mm in granular soils but,
depending on the site and ground conditions, can exceed 1 m – or by the depth of
basement, boiler house, service ducts or similar.
4. Calculate Foundation Area
The foundation area required is determined from the characteristic (working)
loads and estimated allowable pressure. This determines the preliminary design of
the types or combination of types of foundation. The selection is usually based on
economics, speed and buildability of construction.
5. Determine Variation in Vertical Stresses
The variation of vertical stress w.r.t depth is determined, to check for possible
over-stressing of any underlying weak strata.
6. Calculate Settlement
Settlement calculations should be carried out to check that the total and
differential settlements are acceptable. If these are unacceptable then a revised
allowable bearing pressure should be determined, and the foundation design
amended to increase its area, or the foundations should be taken down to a
deeper and stronger stratum.

15. 7. Cost Control
Before finalizing the choice of foundation type, the preliminary costing of
alternative superstructure designs should be made, to determine the economics
of increasing superstructure costs in order to reduce foundation costs.
8. Consider Time
Alternative safe designs should be checked for economy, speed and simplicity of
construction. Speed and economy can conflict in foundation construction – an
initial low-cost solution may increase the construction period. Time is often of the
essence for a client needing early return on capital investment. A fast-track
programm for superstructure construction can be negated by slow foundation
construction.
9. Variation in Ground Condition
The design office should be prepared to amend the design, if excavation shows
variation in ground conditions from those predicted from the site soil survey and
investigation.

16. Classification of Foundation
Different types of foundations need to be built according to the building
structure and existing soil conditions. Foundations can specifically be divided
into two main types -
1) Shallow Foundation –
This type of foundation can be built for
a maximum depth of 1-1.5m.
2) Deep Foundation - Deep foundations
are built for depths greater than 3m upto
65m generally.

17. Shallow Foundation are of five types :
1. Isolated Footing - This is the most commonly used foundation type that is
used for single columns. The shape of an isolated footing can be square or
rectangular and is used when the load of the structure is transferred through
columns. Square footings are used for vertical loads and rectangular footings
are used in case of eccentric loading. Pad footing, Stepped Footing and Sloped
footing are 3 types of isolated footing. Step footings are used in case of heavy
load from superstructure.

18. 2) Combined Footing - When two or more columns
are close enough to cause overlapping of isolated
footings, these are replaced by combined footing. It is
also used when the bearing capacity of the soil is less
than required or if the column is near property/sewer
lines.
3) Spread Footing - It is also known as Strip footing or
Wall footing. These types of footings are used for
individual columns or walls. The base width of these
footings are wider than the typical footings . Wider the
base, greater the spread of load and better the
stability of the structure. The bearing capacity of the
soil must be enough to support the excess load of the
footing. These are also used for bridge piers when the
bearing soil is less than 3m from the ground surface.

19. 4) Raft Footing - Also known as Mat Footing these are
built across the entire area of the building to resist
structural heavy loads from columns and walls. It is
built to prevent unequal settlement from individual
footings. Thus it is designed as a raft or mat for all load
bearing elements of the structure. It is used in soils
with low bearing capacity such as expansive soils.
5) Strap footing -
Strap footing is the type of footing constructed to
connect the eccentrically loaded footing to interior
column footing. Further, these types of footings can be
identified as a combined footing as it connects two or
more columns. Strap footing is more common in
building construction as we have to construct the
building up to the boundary wall. We can not place
our foundation in someone else land. Therefore, the
column has to be placed at the edge of the footing. It
creates load eccentricity.

20. 2) Pier Foundation - These foundations are mainly used
when foundations are to be built below water bodies
and bridge constructions. Caissons are huge hollow
watertight retaining structures used in construction of
dams or as piers for bridges. These are easily
transported by floating in water and sunk into water or
ground upto the desired depth. They are then filled with
concrete to form a foundation.
Deep Foundation are of two types :
1)Pile Foundation - Pile foundations are used to transfer
load from the base of footings to the hard rock strata
situated quite deep from the ground level. These are like
thin columns made of concrete, timber or steel, driven or
cast into the ground. This is used when the bearing
capacity of the soil is not enough to bear the load of the
building and transfer it to the hard rock strata. The primary
purpose of pile foundation is to resist loads by using
friction piles that cause skin friction and end bearing piles.

21. Following factors need to be considered in design and planning of foundations:
1. Footing depth and spacing
footings should be carried below the topsoil or organic materials, peat and muck
and unconsolidated material such as abandoned garbage dumps
2. Displaced soil effects
Soil is always displaced by installing a foundation. In the case of spread footings
the displacement is the volume of the footing pad and the negligible amount
from the column resting on the footing. In cases where a basement is involved,
the basement floor slab usually rests directly on top of the footing pad. In other
cases, a hole is excavated for the footing, the footing and column are installed,
and the remainder of the hole is backfilled to the ground surface
3. Net versus gross soil pressure: design soil pressures
When the soil engineer gives an allowable bearing pressure to the structural
designer, as is often the practice
Is it a net pressure, i.e., pressure in excess of the existing overburden pressure
that can be safely carried at the foundation depth?
Is it a gross pressure, i.e., the total pressure that can be carried at the foundation
depth, including the existing overburden pressure?
PLANNING AND DESIGN CONSIDERATION OF FOUNDATION SYSTEMS:

22. 4. Erosion problems for structures adjacent to flowing water
Bridge piers, abutments, bases for retaining walls, and footings for other
structures adjacent to or located in flowing water must be located at a depth
such that erosion or scour does not undercut the soil and cause a failure.
5. Corrosion protection
In polluted ground areas such as old sanitary landfills, shorelines near sewer
outfall lines from older industrial plants, or backwater areas where water stands
over dead vegetation, there can be corrosion problems with metal foundation
members as well as with concrete. Concrete is normally resistant to corrosion;
however, if sulfates are present, it may be necessary to use sulfate-resistant
concrete.
6. Water table fluctuation
A lowered water table increases the effective pressure and may cause
additional settlements. A raised water table may create problems for the owner
from the following:
Floating the structure (making it unstable or tilting it)
Reducing the effective pressure (causing excessive settlements)
Creating a wet basement if the basement walls are not watertight

23. 7. Foundations in sand and silt deposits
Foundations on sand and silt will require consideration of the following:
Bearing capacity.
Densification of loose deposits to control settlement.
Placing the footing at a sufficient depth that the soil beneath the footing is
confined. If silt or sand is not confined, it will roll out from the footing perimeter
with a loss of density and bearing capacity. Wind and water may erode sand or
silt from beneath a footing that is too near the ground surface.
Uncontaminated glacial silt deposits can have a large capillary rise because of
the small particle sizes. Sometimes these deposits can be stabilized by
excavation to a depth of 0.6 to 1 m, followed by placement of a geotextile water
barrier. The silt is then backfilled and compacted to provide a suitable
foundation. An overlying water barrier or other drainage
may also be necessary since downward-percolating water will be trapped by the
lower geotextile
8. Foundations on loess and other collapsible soils
Collapsible soils are generally wind-blown (aeolian) deposits of silts, dune sands,
and volcanic ash. Typically they are loose but stable, with contact points well-
cemented with a water-soluble bonding agent, so that certain conditions of load +
wetting produce a collapse of the soil structure with a resulting large settlement

24. • All the members in the steel structure should have adequate strength, stiffness and
toughness to ensure proper functioning during service life.
• Reserved strength must be available to cater for:
a) Occasional overloads - underestimated loads
b) Variability of strength of materials from those specified.
c) Variation in strength due to workmanship, construction practices.
1. Adaptations to site:
If the structure is a building, for instance, the designer must create a plan that has suitable
arrangement for rooms, corridors, stairways, windows, elevators, emergency exits etc and all
this plan should be adapted to site so that it is feasible, accepted aesthetically and at a
reasonable cost. This is called functional planning.
PLANNING AND DESIGN CONSIDERATION OF FABRICATION AND ERECTION OF
STEEL STRUCTURE
2. Structural scheme:
structural scheme is dependent on functional
planning. Structural scheme includes the
location of columns in the buildings, it is to be
worked out with the functional plan and
sufficient space must be anticipated between
finished ceiling and finished floor for location of
columns.

25. 3. Structural analysis:
Once loads are defined and design is laid out, structural analysis must be performed to
determine internal forces that will be produced in various members of the framework.
Assumptions must be made and it should be ensured that structure in reality also behaves as
it is supposed to (and as it was assumed to behave).
4. Proportionality of members:
Members must be proportioned with factor of safety in mind.
5. Factor of safety:
The development of design specifications to provide suitable values of the margin of
safety, reliability and probability of failure must take into consideration the following
factors.
Variability of the material with respect to strength and other physical properties
• Uncertainty in the expected loads
• Precision with which internal forces are calculated
• Possibility of corrosion
• Extent of damage, loss of life
• Operational importance
• Quality of workmanship

26. • The process of steel fabrication involves grinding, welding, cutting, bending, drilling,
punching, burning or melting and other general crafting methods using various high-quality
tools and CNC equipment. The entire steel fabrication process is systematic and requires
utmost planning, precision, and knowledge. Steel fabricators are well aware of all the
crucial steps and measures that need to be taken care of in the fabrication process.
Structural steel is usually fabricated to create structures like beams, trusses, hollow
sections, angles and plates.
• These steel members must be accurately fabricated before assembling them together. All
component parts of these members are fitted-up temporarily with rivets, bolts, or small
amounts of welds. Various fastening methods are employed to deliver different types of
finishes. Finishing is generally performed by milling, sawing or other suitable methods.
• It’s important to understand how structural steel structures are designed before assembling
them together.
• Construction Needs:
First and foremost, it’s crucial to know the type of structure you want to construct. Commercial
structures have a distinct designing process. Similarly, residential structures are totally
dissimilar from industrial structures. Hence, all the structures demand different types of
construction processes. Moreover, any and every type of construction process requires unique
structures varying in sizes, dimensions, and designs. Each structure has to be specifically
designed and fabricated before constructing and assembling them together. For any joint to be
site welded, the members will have to be held securely in position such that the setup for
welding is accurate and rigid.

27. Erection Techniques:
Mobile Elevating Work Platforms (MEWPs) and cranes are predominantly used in the erection
of steel structures for buildings and bridges. However, there various other techniques that are
sometimes used for constructing steel bridges. Cranes are usually divided into two broad
categories, mobile and non-mobile cranes. Truck mounted, crawler and all-terrain cranes are
included in the first category, while tower cranes are included in the second category.
The MEWPs can be used both on the ground or on the partly erected steel structure, in order
to erect lighter steel elements. These MEWPs are used to access the steelwork during erection
to bolt up the pieces lifted by the crane. Important measures need to be taken before using
the MEWPs such as first checking if the steel structure can support the weight of the MEWP
and then determining whether they should be used on the ground or on the erected
structures.
Erection of steel structure

28. Steel Erection:
There are four primary tasks that need to be considered before the steel erection process.
– It is extremely important to establish the foundations and confirm if they are suitable and
safe for erection to commence.
– With the help of cranes or sometimes by jacking, lifting and placing components into
position is essential. Additionally, to secure the components in place, bolted connections are
made but they may not be fully tightened. Similarly, bracings may not be fully secured.
– Aligning the structure is essential, principally by checking that column bases are lined and
leveled and columns are plumb. To allow column plumb to be adjusted, packing in beam-to-
column connections may need to be changed.
– Last but the least, bolting-up is required, which means completing all the bolted
connections to secure and impart rigidity.

29. THANK YOU.