PRESENTATION ON MAT FOUNDATIONDETAILS OF CONSTRUCTION

Submitted By:-Group-04, 2nd Year, 2nd Semester, Section-C, Department Of Civil

EngineeringAHSANULLAH UNIVERSITY OF SCIENCE &

TECHNOLOGY

Contributed By:-Md. Ashif Rayhan Shuvo (12.02.03.041) (Compiler)Nadia Akter Munni (13.01.03.126)Md. Rokanuzzaman (13.01.03.135)Musarrat Mubasshira Atiya (13.01.03.138)Md. Muntasir Salehin (C) (13.01.03.147)Abdullah Al Kafi (13.01.03.159)Mustafidul Hoque (13.01.03.166)Tony Islam (13.01.03.168)Ashiqur Rahman Prottoy (13.01.03.172)

CONTENTSDefinition of Mat or Raft foundationWhen Mat foundation should be providedTypes of Mat foundationPlan & Sectional viewVisited SitesConstruction Flow ChartConstructing a Mat foundationAdvantages & DisadvantagesConclusion

Mat FoundationA continuous, thick, concrete slab foundation heavily reinforced with steel supporting an entire structure.It is a type of shallow foundation (depth ≤ width).All the columns are connected to an large RCC slab and the slab is directly contact with the soil.All vertical structural loadings from columns and walls are supported on the common foundation.Generally used in heavy industrial plant, official and commercial buildings and sometimes in residential buildings.

Sketch Of a Mat Foundation

When Mat foundation should be providedIf foundation area covers 50-60% of the total plot area.

If the individual columns or footings would be undesirably close together or try to overlap.

It is required where soils have low bearing capacity and have to support heavy structural loads.

Structures on marshy land, soft clay and land that are made up of sanitary land fill or other materials (like debris, unconsolidated soil and solid waste etc.) where differential settlement is suspected.

Types Of Mat Foundation

Flat Plate Mat Flat Plate Thickened Under

Column

Two-way Beam & Slab

Plate with pedestals

Piled Raft Rigid Frame Mat

Sectional Design Of A Mat Foundation

Plan View

Main Beam

Seco

ndar

y Be

am Column

Sectional View

BFS & CC Layer

RCC Slab

Main Beam

Column

Visited Sites

Credence, Road-7/A, Dhanmondi, Dhaka

Biswas Builders Limited, Road-9/A, Dhanmondi, Dhaka

Construction Flow Chart

1 • Soil Test

2• Shoring• Water

Proofing

3• Partial

Excavation (Depending upon depth)

4• Strutting• Bracing

5• Full Area

Excavation

6• Soil

Compaction

7• BFS Layer• CC Layer

8• Reinforceme

nt Placing

9• Casting of

RCC• Compaction

10 • Curing

11• Removal of

Shuttering• Further

Curing

12• Retaining

Wall• Shear Wall

Soil Test

Bearing capacity of soilSoil classificationVoid ratioCompressibility characteristics of the soilPresence & amount of garbage in soilGround water levelMoisture contentDepth of Mat

Shoring

Creates a continuous wall along the boundary.Supports the load of the surrounding structures during construction.Prevents the surrounding soil from breaking during construction.Prevents the collapsing of the existing structure.Protects the existing structure from vibration.Remains in the ground and serves as a retaining structure.Can be of three types: Concrete pile shore, Steel sheet shore, Log shore.

Figures of Log Shoring

Steel Sheet Shore Concrete Pile Shore

A temporary wall is provided very next to the shoring so that deposited water can’t enter into the construction site.A cement mortar layer is provided over shoring to prevent moisture.

Water Proofing

Earthwork ExcavationPartial & Full Excavation

is required before further construction.

Soil CompactionAfter full excavation, soil

compaction is needed to obtain a uniform surface for the placement of BFS and other layers.

Bracing & Strutting

A horizontal support system for the boundary shores during excavation and foundation.

Its requirement depends on the depth of foundation.

Generally made of steel sheet.

Also known as horizontal shores.

Braces are the orthogonal members in the system.Strut is the inclined member joining two perpendicular braces.King posts are the vertical compression members supporting the brace & strut system.

Brick Layer Over Compacted Soil

Cement Concrete Layer Over BFS Layer

Reinforcement Placing

Placement of a batch of horizontal bar;

Placement of another batch of bar to complete the bottom mesh;

Placement of Column bars;

Placement of vertical rod (chair) over bottom mesh to hold the upper mesh;

Upper mesh placement.

Bottom Mesh Retaining Wall Bar Placement

(Along with bottom mesh placing)

& Column Placement

Chair Placement Upper Mesh Placement

Chair

Bottom Mesh

Upper Mesh

CC Block

Sectional View Of Mat Mesh Joint Between Column Footing & Mat Mesh

Upper Mesh

Bottom Mesh

Joint Between Reinforcement of Column

& Mat Mesh

Tie

Chair

Inclined Bar to hold the

Column straight

Finished Reinforcement Placement

Other FactorsReinforcement Selection 60~72.5 Graded 12mm~25mm

Rod Cutter

Rod Bending

Chair

Reinforcement Joint(with heavy steel wire)

Tie Bar

CC Block(to maintain Clear Cover)

Shuttering

Timber Shuttering Steel Plate Shuttering

Brick Wall used as a Shuttering of Column

Footing(remains as a part of

foundation)

CastingSide basis castingLayer basis casting

Casting in Mat Mesh Casting in Footing

Compaction

Casting & Compaction both are done simultaneously.Compaction is generally done by vibrator machine.

Vibrator

Machine

Leveling

After casting & compaction, leveling is a must to get the same thickness all over the

mat slab.

Leveling with Patta

Curing

Spraying or Fogging PondingSaturated Wet Coverings (By

Hessian or Gunny Bags)

Retaining Wall & Shear Wall

Reinforcement Placing Shuttering CastingRetaining wall is provided in basement to prevent lateral load of the surrounding soil.Shear wall is a wall that is designed to resist shear & the lateral force (wind, earthquake).

AdvantagesThe foundation and floor slab is combined, which saves time and materials.Loads are spread over the whole area of the structure.It can cope with mixed or poor ground condition.It requires little excavation.It reduces differential settlement.

DisadvantagesLarge thickness, expensive.Shore protection is needed.Susceptible to edge erosion.Weak when supporting point loads, specific treatment required.

Advantages & Disadvantages

Conclusion

This presentation is based on the observations on Mat foundation in various sites & meeting with concerned engineers & workers.

The purpose of this presentation was to gather some practical experience on Mat foundation.

During the making of this presentation, we also practically experienced other major & minor parts of a construction.

Thank You All !!