1. 2. Foundations and basements
Building Technology (EG 626 CE)

2. Foundation Definition of foundation
It is the lowest part of structure. It provides base for super structure. It transmits loads to soil below. It is a part that is below the ground level.
Function of foundation
To transmit all superimposed loads (wind, vibration, dead and live loads).
To withstand against all kinds of settlements (against failure of underlying soil).
To give stability to structure by resisting in firm base.
To prevent lateral movement of supporting materials.
Characteristics
Wide enough section to distribute weight over larger base area within safe bearing capacity.
Evenly loaded condition that prevents unequal settlement.
Deep enough preventing overturning and increasing stability.
Foundation

3. Foundation Types of foundation
Shallow foundation
Deep foundation
The depth of the foundation is less than or equal to its width.
It is placed immediately below the lowest part of the superstructure.
It is relatively deep and need special precautions
The purpose of deep foundation is to attain bearing stratum deep inside the ground in case of weak soil.
Foundation

4. Shallow foundation Spread footing Strip footing Raft foundation
Independent footing
Combined footing
Continuous footing
Strip footing
Wall footing
Inverted arch footing
Eccentrically loaded footing
Offset and Strap (cantilever) footing
Raft foundation
Slab (solid)-up to 30 cm
Slab and beam- slab > 30 cm
Cellular- slab >90 cm
Grillage foundation
Timber grillage
Steel grillage

5. Shallow Foundation
Spread footing
Independent
Continuous
Combined

6. Shallow Foundation Strip footing t wall Inverted arch Eccentric
2t + 2J t
wall
Inverted arch
Eccentric

7. Shallow Foundation
Slab Raft
Slab & beam
Cellular
Raft Foundation

8. Shallow Foundation
Steel grillage
Timber grillage
Grillage Foundation

9. Deep Foundation Pile foundation Well foundation (caissons) Piles
Pile is the pillar like structure driven deep in to the ground to strengthen strength of soil below, It acts as support to the spread footing, It is used individually or in cluster through out wall.
Uses of piles
in very poor soil condition,
in waterlogged soil (high water table),
in filling areas,
in areas with heavy loads,
in compressible soil,
in the areas where the mat or grillage foundations are not possible.
as the anchor in docks,

10. Deep Foundation Types of piles According to the uses; Bearing piles
Friction piles
Sheet piles
Anchor piles
Batter piles
Compaction piles
Fender piles
Sheet
Batter
Decking
Fender
Anchor
Bearing
Deep Foundation

11. Deep Foundation Types of Piles According to material use;
Steel piles (H-beam, Box piles, pipe piles, screw piles and disc piles)
Cement concrete piles
Cast-in-situ piles
Cased: Raymond, Mcarthor, Monotube, BSP base driven, Swage etc.
Uncased: Simplex, Franki, Vibro, Vibro-expanded, Pedestral, Pressure etc.
Pre-cast piles
Pre-stressed piles
Timber piles
Composite piles
Sand piles
Deep Foundation

12. Deep Foundation Methods of pile driving Selection of types of pile
Drop hammer
Stem hammer
Water jet
Boring
Selection of types of pile
Nature of structure
Loading in structure
Ground water table
Length of pile required
Availability of material and equipments
Factors causing deterioration of piles
Cost of piles

13. Deep Foundation
Well foundation
Well foundation is the water tight box structure of wood/ RCC/steel and mostly used in the foundation of the bridges.
Purpose: to develop an enclosure below for plumb and provide access shaft to reach a deep tunnel transmitting the loads to hard bearing strata.
Types of well foundations (Caissons)
Box caissons
Well foundation or open caissons- single, double or cylindrical
Pneumatic caissons

14. Soil and soil exploration
Soil and its properties
Soil is uncemented geological deposits
It is the basis of foundation
Property of soil decides the type of foundation
Types of soil: Cohesive and Cohesion less
Sub-soil exploration
Very important phase in construction and determines the characteristics of underlying soil.
Soil investigation is must before undertaking construction works.
Acquires general picture of geology of area.
Objectives of soil exploration:
To determine the value of safe bearing capacity of soil.
To select economic types of foundation.
To determine the depth of proposed foundation.
To predict likely settlement and make allowance for that in design.
To know underground water level and its problem

15. Method of soil exploration
Inspection
Naked eye observation
Test pits
Helps to know type of soil at small depth, pit size: 1.5*1.5 m² and depth 1.5m.
Probing
Hollow tube of mm is driven to ground at about 30 cm at a time.
Boring
Auger
Deep: percussion and rotating boring.
Wash: case tube is driven along with this a wash jet is inserted, this washes the soil below and bring it to the surface.
Test piles
Wood/steel piles are driven under hammer blows.
Geo-physical methods
Electrical method
Electric current is passed through cathode and anode in soil and the flow of current through cathode to anode is the measure of soil below.
Seismic methods
Vibrations are caused by artificial explosions and the movement of these vibration waves measures the soil characteristics.

16. Bearing capacity of soil
It is the ability of soil to support the load coming over it.
It is the strength of soil to resist minimum load coming to its unit area causing no failure.
Maximum bearing capacity of soil = W/ A
Safe bearing capacity = W/(A*f)
where,
W is Total load including self weight
A is area of sole plate and
f is factor of safety

17. Methods of improving bearing capacity of soil
Mechanical stabilization
Mixing different graded soil
Change of grading of soil
Mixing different graded soil
Use of roller
Cement stabilization
Mixing soil, cement and water
Lime stabilization
Mixing soil, lime and water
Bituminous stabilization
Mixing of bitumen with soil
Chemical stabilization
Calcium chloride, Sodium chloride, Polymers, Chrome Lignin, Sodium silicate
Thermal stabilization
Heating, Freezing
Electrical stabilization
Grouting under pressure
Geo-textile and fabric stabilization
Sheet piling
Sub-soil drainage
Methods of improving bearing capacity of soil

18. Suitability of different types of foundation
Basis of foundation design
Total loads of building
Nature and bearing capacity of sub-soil.
A good foundation is judged by;
Firm location
Stability of structure
Free from settlements

19. Foundation in black cotton soil
Good for agriculture and bad for structure.
High shrinkage value due to change in moisture content.
Volume varies as 20-30% of original volume.
Develops very wide and deep cracks due to excessive shrinkage
Very weak in saturation.
Problematic for foundation.

20. Foundation in black cotton soil
Precautions for foundations in black cotton soil
Foundation depth be enough below from cracks to hard strata.
Measures to be applied to avoid water reaching to bottom of foundation.
Prevent foundation from direct contact with black cotton soil.
If thickness of black cotton soil is high, foundation is to be laid on piles.
Raft foundation is the choice in this condition.
Tie-beam in plinth is important.

21. Settlement of foundation
Causes of foundation settlement
Consolidation of soil particles
Reduction of moisture content
Heaving of soil due to pressure
General earth movement
Effects of unequal settlements
Stresses in structure
Distortion of structure fabrics
Failure of structure
Prevention of undue unequal settlements
Proper foundation design
Proper soil investigation

22. Causes of foundation failure
Unequal settlement of sub-soil
Unequal load distribution
Horizontal movement of soil adjoining structure
Lateral pressure tending overturn
Shrinkage due to withdrawal of moisture from soil
Atmospheric action
Lateral escape of soil below foundation
Nearby building construction
Trees etc.

23. Underpinning of foundations of existing building
Definition
It is a process of improving and strengthening existing foundation
It facilitates to support structure and assist in transferring loads to better soil strata
Necessity
Occurrence of excessive settlement
Increasing load bearing capacity of foundation
Change of functional use
Addition in loading pattern
Permitting to lower adjacent ground below existing foundation
Construction of new basement nearby

24. Operation to be carried out before underpinning
Survey of structure
Marking of Settlement if any
Noticing neighbors (adjacent building)
Setting indicators to identify probable cracks while underpinning
Carrying out corrective measures for cracks etc.
Investigate sub-soil

25. Underpinning Sequences of operation Precautions
Suitable holes driven through the wall and a needle beam is inserted & supported on the jack
Excavation is started below foundation and footing of the foundation is reached
The offset of the foundation is cutoff and removed & excavation is reached to the defined depth
New foundation is laid in the desired depth up to the underside of the existing foundation
This process is repeated in stages
Final layer of pinning work just underside of existing foundation should be done with the mortar from rapid hardening cement
Precautions
Excavation in one time done for less than one fourth of length, for weak soil it is done for less than one fifth to one seventh of length, normally length of one bay is taken as 1.5 m
To be carried out slowly in stages and not at a time

26. Methods of underpinning
Pit method
Ordinary
Cantilever
Pile method
Improving of foundation by grouting and chemical consolidation

27. Methods of underpinning
Perforated pipe
wall GL
consolidation
pile
Pile cap
Hard strata
Needle beam
Jack
Existing foundation
New foundation
weight

28. Basement is a space, a storey or a floor immediately below the adjacent ground level.
Retaining wall is essential component of basement.
Basement

29. Function of retaining wall
Basement
Retaining wall
Structural wall that resists lateral thrust of earth mass, pressure of sub-soil water & support vertical loads.
Function of retaining wall
Strength, stability and Durability
Resistance to overturn and horizontal slide
Resistance to overstress in the materials of construction
Resistance to overstress in the soil on which the wall rest

30. Forces acting on the retaining walls
Active earth pressure
Lateral pressure that tends to move or overturn the wall at all times
This is the result of earth wedge retained and any hydrostatic pressure of ground water
Passive earth pressure
The reactionary pressure that builds up to resist any forward movement of the wall, because any forward movement will compress the soil in front and reaction to counteract this movement builds up.
Angle of repose
The natural slope taken up by any soil and given in terms of the angle to the horizontal base line
Varies from 450 to 00 angle for wet clay, but for most soils, this angle of repose is 300.
Wedge of soil
The mass of soil resting on the upper plane of the angle of repose
Surcharge
The additional mass of soil above the top surface of wall
Frictional force

31. Forces acting on the retaining walls
Ground pressure
Mass of wall
surcharge
Active earth pressure
Angle of repose
Friction at interface
Weep hole

32. Factors affecting strength, stability and durability of retaining wall
Effect of ground water
The sub-soil ground water reduces soil shear strength.
Reduces bearing of the base and the soil
Subsoil drainage is the solution for this.
Effect of inadequate passive earth resistance
The passive earth resistance at the front of the wall resists sliding
Insufficient passive pressure is not able to resist sliding
Provision of ribs under the head and toe increased passive pressure

33. Types of retaining walls
Gravity or mass retaining wall
Cantilever or L-Shaped Retaining wall (max H=6 m)
Base entirely in front of stem
Base partly in front and partly behind the stem
Base wholly behind the stem
Counterfort retaining wall (max H=8 m )

34. Types of Retaining wall
Gravity or Mass Retaining Wall
Cantilever Retaining wall

35. Design principle of retaining wall
Overturning does not occur
Sliding does not occur
The soil beneath the wall is not overloaded
The materials in the wall are not overstressed
Factors to be considered during design
Nature and type of soil
Height of water table
Sub-soil water movements
Types of wall
Materials used in the wall