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FOUNDATION ENGINEERINGFOUNDATION ENGINEERING

,,

Budapest3 November 2011


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Foundation Engineering

1. Excavations

,

excavation.

Determinants of the value of the excavation:

Geometry of the building;

Transportation requirments;

Dewatering requirments

Determinants of the t e of the retainin structures:

Size of the site;

Type of the soil;

Groundwater;

me;

Neighbour structures;

Size of the building;

Available facilities technolo .


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sloped (soil, torkret concrete);

1.1. Types of retainings

braced (wood, reinforced concrete, steel, plastic);

sheet piling (wood, steel, reinforced concrete);

diaphragma walls;

ore p e wa s;

freezing or chemical methods;


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2. Sloped open cut method

building

stairs

If c=0, b

Most simple way to make excavation, but it needs bigfree lace and it re uires rather bi volume earthworks.

ditch

Under 6 m it requires slope stability calculations.

Excavated soil deponation must be out of slipsurface.

Under groundwater only in cohesive soils or dewatering is alsoneccesary.Dewatering of rainfalls is required.

Dynamic effects reduces slopestability.


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If the vertical eartwall is stable to excavation level.

3. 1. Braced with standing walls

Procedure:1.Excavate the soil to foundation level.2.Install walls into the excavation. (not continous)3.Install wales.4.Install struts.


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If the excavation is deeper than>

3. 2. Braced excavation with repressing

Procedure:1. Excavate the soil to first stage (mo).2. Install walls, wales and struts temporary.3. Excavate the soil to the next stage.4. Relase struts and push walls down and install wales and struts.5. Repeat 3 and 4 till the designed depth.


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3. 3. Braced excavation with lateral walls

The stable earthwall is very small,

in case of non-cohesive soils.

Procedure. o,

2. Install the walls, wales and struts temporary.3. Excavate the soil to the next stage.4. Rebuild wales and struts.5. Repeat procedure 3 and 4 till the designed depth.


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3. 4. Table braced system


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3. 5. Braced system


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3. 5. Braced system

Chang-Yu Ou:Deep excavation


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3. 6. Design braced excavation

compressed or bended.

Input:

Depth of excavation (H)

Space between wales (t);

Space between struts (y).

Output:

Thickness of walls (v);

Cross-section of wales ( ba );

Cross-section of struts (A).


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4. Soldier pile method

Mostly 6 m deeper or 3-4 m wider excavations.


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4. Soldier pile method



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4. Design soldier pile method

Design:

- Cross-section of Soldier pile

- Depth of embedment

Loads Moment Shear

- Thickness of lagging

- Parameters of anchors

(if it is necessary)


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Sturctural types of sheet-pile walls:

5. Sheet-pile walls

- em e e

- anchored in one level, without embeding- anchored and embeded- struted (braced)

- Death of embeding

- Mmaxcross-section of sheet

- Load of anchorsparameteres of anchors


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5. Sheet-pile walls



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5.1. Design sheet-pile walls

Embeded Anchored in one level,

without embeding


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Anchored and embeded


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Struted (braced)


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5.2. Types of sheet-pile walls

Strate sheets

Half wave sheets

Total wave sheets


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6. Diaphragma walls



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6. Diaphragma walls


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7. Freezing and injection


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7. Freezing and injection

Gravely soils under groundwater and waterproof layer ismissing or in very deep.

Advantages:- Absolute waterproof- Other retaining structures are not neccesary- In any kind of soil (except injection clay)

Disadvanteges:- Difficult technical facilities- Expensive- Long time defrost in case of freezing


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8. Shotcrete method

Excavation Nailing

ExcavationReinforcement, shotcreteApplication field:

Temporary or permanent retaining structure

Retaininig wall

Stabilization of slopes

Repair retaining structures


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Thickness of shotcrete (12-25 cm),

8. Shotcrete method

Reinforcment:

oNetting,oReinforcing steel (1-2 layers),oHajbeton (steel, PE),

oSteel tube,oSteel bar,

oSteel nail, Instalation of nails:

oHit,oScrewed-injected,oJetedoScrewed


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Application field:

8. Shotcrete method

Cohesive soils,Gravely soils,

Can not used:

Soft cohesive soilsOrganic soils, turf,Loose gravely soilsFilling (rocks, ash)

Advanteges

CheapSim le facilitiesVariable formElastic structure

Disadvanteges:

. .Can not install in case of groundwater

flowingDemages of public utilities


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Procedure of designig:

8. Design shotcrete excavation

. e v s

2. Geometry of excavation3. Stability analysis

Sloping

bearingcapacity


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8. Design shotcrete excavation

Compound

failure

Deep failure

Outpulling

Nail breakage

Shotcrete

breakage


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8. Shotcrete method


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Order of nailing

8. Shotcrete qualification

Outpull test

Measure movmentsInclinometer Install points

ShortcreteThicknessStrenght


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Inclination of the wall: 1:8-1:10

8. Geometry of Shotcrete excavation

Tpus L/H

DL/S

d

2/SScrewed-injected nailsin gravely soils

0,5-0,8

0,5-0,6 (4-8)10-4

Hit nail in gravely soil 0,5--

(13-0,6

, ,19)10-

Mantle rock, marl0,5-1

0,15-0,2

(1-2,5)10-4

L: length of nails, H: depth of excavation, D: dimeter of, ,


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Thank You

for your attention!

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