Underground Works

Substructure

Earth Retaining Diaphragm wall

Failure of retaining wall systems

Underground works

TYPES OF EARTH RETAINING SYSTEMS FOR EXCAVATIONS

� Natural Slope � Gravity Walls � Reinforced Soil with Geo-synthesis � Braced Walls or (mostly) strut support � Soldier pile and lagging walls with

anchor or strut support � Sheet piling or sheet pile walls with

anchor or strut support � Pile walls (contiguous, secant) with

anchor or strut support

TYPES OF EARTH RETAINING SYSTEMS FOR EXCAVATIONS

� Diaphragm walls or slurry trench walls with anchor or strut support

� Prefabricated diaphragm walls with anchor or strut support

� Reinforced Concrete (Cast-in-situ or prefabricated) retaining walls (Excavation in stages) mostly anchor support

� Drop shaft sinking and caissons

� Jet-grout walls (or deep soil mixing) + Anchors or Struts

� Soil nail walls

� Top-down excavation and support method

Wall Selection Criteria :

1.Size of excavation

2.Ground condition

3.Groundwater level

4.Settlement of adjacent ground

5.Displacement criteria

6.Others (Availability, Speed of Work etc.)

1.Natural Slope

2.Gravity Walls

3.Geo-synthesis Geotextile/Geogrids

4.BRACED WALLS + ANCHOR/STRUT SUPPORT

� Excavation step by step

� Steel frames with timbering or shotcrete

(sometimes timber frames)

� Usually strut support

� Soils with some cohesion

and without water table are

suitable

� Often limited to small dimension shafts and

trenches with and without

penetration below base

(mostly without)

Strut

Steel and/or

timber panels

BRACED WALLS + STRUT SUPPORT

Soldier pile

and lagging walls

Soldier PilesWale Struts

PLAN VIEW

Soldier pileWales Struts

SECTION

5.SOLDIER PILE AND LAGGING WALLS (Example: BERLIN WALLS)

Strut

WaleH Soldier Pile

Lagging

5cm*15cm or

5cm*20cm 2 to 4 mLagging

INSIDE VIEW

SOLDIER PILE AND LAGGING WALLS (use tieback)

6.SHEET PILE WALLS (SHEETPILING)

Grout

Steel sheet piles

R.C. sheet piles

Sheet Piles

Plan view Elevation

PLAN

Struts

Wale

Sheet

PileSECTION

RakerWales

Another possibility for support

in large excavations

ground

anchors

Retaining wall system Plan

Proper Interlock

Transportation

Pre-loading

Bad shoring

Becareful

Weak ? Checking?

For what?

Heavy equip.

7.PILE WALLS

Tangent pile

Piles

Anchors

Breasting

Beam Anchor Plate &

Anchor Head

Top beam

anchor plate

and head

Breasting Beam

Breasting

Beam

Top

Beam

shotcrete in some cases

Failure of piles wall system

Tangent & secant pile

Breasting

Beam

OR

Casing

Problemgrouted in water

bearing soils

Breasting

Beam

D S

Secondary

Piles

(Reinforced

Con.)

Primary Piles

(Unreinforced)

8.DIAPHRAGM WALLS (Slurry Trench Walls)

Water-stop

(Recent

Design)

Stop-end

Pipe (Old)

Primary

Second

ary

P P PS S

20 -30 cm

1 -2 m

Excavation

& OTHERS

Barratte piles/D-wall

D-Wall: Guide Wall

CRAB

Crab

D-wall diagram

D-wall of Subway Station

Steel cage

Steel cage installation

Water stop

Water stop

9.Prefabricated Diaphragm Walls

Struts

Prefabricated panel

Bentonite-cement

grout

10.Reinforced Concrete(Cast in-situ or prefabricated) Retaining Walls

Type of Caissons

Open Caissons Pneumatic Caissons Box Caisson

(floating)

11. Jet Grout walls or other soil methods like deep soil mixing

double wall if

necessary

cantilever

double wall of vertical

columns (for circular

12. Soıl

Naıl Walls

Soil Nail (Anchor)

grout

PVC (or

similar) seath

drill hole

centralizer

anchor body

(grouted)

grout

anchor

plate

anchor head

tendon

A

A

B

B

A-A B-B

if packer

centralizer

Soil nail machine

Test performance

Sonic Integrity Test

Inclinometer

Monitoring

Drilling Monitoring

Soft clay+Water…….

Below the Manhole

Good : Sheet pile and Wale contact

Steel box piles

Coffer Dam

Top/Down construction

�What benefits?

�Is it suitable for Bangkok?

�Example buildings used this system.

Above and below

Down progress

Connection/Joint