Df03 Dwall Caisson

8/12/2019 Df03 Dwall Caisson

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Lecture #3

D-wall, Caisson & Well foundation


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Types of deep foundations

Deepfoundations

Pile

Soildisplacement

Soilreplacement

Other

Diaphragmwall

Caisson &well

foundation

Wellfoundation

Caissonfondation


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Deep foundation > Diaphragm wall (Slurry

wall)

Diaphragm wall (D-wall):

A wall is created under the

ground level

Construction sequences: Soil excavation

Temporary support of

trench (panel) is provided

by bentonite slurry

Placement of

reinforcement

Concreteing

Fields of application:

Retaining structure of

(deep) excavations

Side wall of undergroundlevels of buildings

Deep foundation

(deep groundwater barrier)


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Deep foundation > Diaphragm wall >

Excavation

Guide wall is built in

advance

Trench excavation

(under bentonite

slurry) Removal of previous

end stop


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Conreteing

Inserting end stop

placement of

reinforcement

Concreteing (under

bentonite slurry, usingtremie pipe)

Excavation of

subsequent panel


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Deep foundation > Diaphragm wall > Cable hung

clam


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Deep foundation > Diaphragm wall > Hydraulic grab


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Excavation

> Hydrofraise (for hard soils or

rock)

Rotary drum cutters excavate the soil

(or rock).The cuttings (and slurry) are removed

through reverse circulation pumps.

The cuttings are removed from the

slurry in a desanding plant.

Fresh (clean) slurry is added at the top

of the trench.


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Excavation

> Hydrofraise


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Deep foundation > Diaphragm wall

> Bentonite slurry

Bentonite slurry:

Mixture of water and

bentonite (very fine

particles, mostlymontmorillonite)

Density: 1.03-1.12

g/cm3

Role:

Protection against

groundwater inflow

Trench wall support

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> Reinforcment


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> Advantages - limitations

Advantages:

flexible geometry

high bearing capacity

small settlements

horizontal + verticalbearing capacity

can be constructedunder groundwater

minimal dynamic effect

multiple function(retaining structureduring construction +foundation + side wall

Limitations:

Very stiff rock

Very soft soils (trenchstability problem; e.g.

soft clay, organicmaterial, liquefiablesand)

Cavities

Old building remains

Utilities


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Deepfoundations

Pile

Soildisplacement

Soilreplacement

Other

Diaphragmwall

Caisson &well

foundation

Wellfoundation

Caissonfondation


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Deep foundation > Well foundation

WELL FOUNDATION

Stiff soil layer

Well

foundation

Soft

soil

layer

GWL


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WELL FOUNDATION

Well foundations

Superstructure

Footingbeam


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> construction sequences

Superstructure

Well foundation

Prefabrication Sinking and

excavation

Bottom

slab (plug)

Conreteing


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Deep foundation > Well foundation types

CUTTING EDGE TYPES

Cylindrical

Geometry of enlarged base

Cylindrical with

enlarged base

Conical Conical with

enlarged base

Reinforced

concrete

With outer steel edge

Skin friction reduction


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Deep foundation > Well foundation >

Advantages

Advantages:

large diameter

similar to piles, but shorter

if large bearing capacity soil (rock) is between 3-7 m,it can be very effective

if loads are not too large, but the upper 3-7 m of the

soil is not appropriate, can be applied effectively


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Deepfoundations

Pile

Soildisplacement

Soilreplacement

Other

Diaphragmwall

Caisson &well

foundation

Wellfoundation

Caissonfondation


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Deep foundation > Caisson foundation
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Deep foundation

> Caisson foundation


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Documents

Df03 Dwall Caisson