Failures and maintenance of foudations structures

Diversion of tower – craks in sill wall, head, cornice,

Castle Zleby

settlement of outside

part - pier – flushing

of foundation soil

Castle Valdštejn

settlement of

middle part –

flushing or

terrain

roughness

settlement of

right marginal

part –

flushing

settlement of

middle part –

flushing

flushing of

footing

bottom –

shear craks in

head and sill

of wall

Building in vacant space –

failure of an existing building

tensile and shear cracks

Settlement of part of structure

during building pipe tunnel settlement of the left part of building

due to the movement of soil below

foundation

cracks in the facade of buildings caused by defects in the subsoil

undermine of the gable wall

during foundation of

neighboring house

Romance structure – foundation masonry was realist as hand placed rockfill or stone masonry with clay binder, width 1,5 m till 2,5 m and

depth about 1,2 m Gothic structure – foundation was built from hand placed rockfill, wood grid placing on piles, masonry well, as waterproofing was used clay

(50 – 70 mm)

Renaissance and folowing period was used foundation from stone masonry with

lime mortar. For high depth was built masonry piers with masonry vaulting strip

From half of 19–th century was foudation realist from freestone, brick

masonry and concrete

From 20-th years of 20-th century was using for design foundation

structure method permissible stress of foundation soil

Pit foundation

Pier foundation

Historical development (evolutional)

Base strip:

a) stone quarry, h > 0.5 m

b) Concrete, h > 0.3 m

c) on compacted gravel bed (thick of

layers 0.15-0.2 m)

d) two-stage foot of plain concrete

e) Reinforced concrete foot

f) Base strip – wood grid, piles, stones

Non –

loadbearing

capacity

layer

Non –

loadbearing

capacity

layer

Historical foundation – difficult conditions

level of underground water

level of underground water

level of underground

water wooden

pile

wooden

grid

wooden

grid

wooden „grid“

wooden

pile

wooden

pile

logitudinal

beam

transversal

beam

Load bearing capacity soil Soil without load bearing capacity

Load bearing capacity soil

clay

direction of move

rock

moisture

rock

clay

sand

water level

Increased levels of water

Load bearing capacity soil

Less load bearing capacity soil

rock

Permeable

soil

Accumu

lation of

water

rubble

character of

deformation

deformation

deformation

clay

rock

road

water rain

original terrrain

compressibility

stlačitelnost

unsuitable soil

unsuitable soil

character of deformation

Typical cracks – dymanic load Typical cracks – load by nearby

blast

a) Desintegration of front face by oblique tension cracking (move in footing subsoil by oblique impermeable bed of

clay), b) subsidence of right marginal part (incorect drainage), c) subsidance of middle part (curvature shape of footing

bottom by transportation - traffic), d) subsidence of right marginal pier (built a new structure near-by the original

structure)

Meansure during design structure:

•Raft-foundation, pile foundation, mini

pile (root pile) foundation

•Underpinning foudations „original“

structure by mini pile (root pile)

•Using JET Grouting

•Choice of load-bearing system –

foundation

Building in vacant space

Cantilever span

Extension of foundation strip

parallel normal

extension´s

strip

extension

of strip

Original

structure

new

structure declination of structure

failures

of

structures

area of summation

of stresses

compressible subsoil

declination of new structure declination of

new structure

non-consolidated

cohesive subsoil

(clay)

area of

consolidated

subsoil

response of

original

structure

Cause of failures:

„small“ depth of foundation

(longtime compress of footing

subsoil, slushy of footing bottom,

freezing of footing bottom

Maintenance:

Deeping of footing bottom

backfill

clay soil

sand (S) or

gravel (G)

rock

level of underground water

Deepening of foundation with desitegrated foundation structure

Deepening of foundation

original level

deepening

excavation

new deepening foundation –

brick (concreting) in parts

concrete base

reinforce

by net

New deepening

foundation

base concrete reinforce

with net

hydraulic

press

deeped level

Upper

structure

1. phase 2. phase

concrete base

3. phase

concrete +reinfor.

Geological profile

(Geological cross-section)

chess-board process

dep

th

soil

original

found.

masonry structure

Steel beams - steel grid bolt

failure strip foundation

Static protection during deepening and extension of foundation –

during of all action of foundation

brace

brace

brace

brace

brace

struts

new part – brick,

concreting

• deepening of foundation by mini pile (root pile)

backfill

clay soil

rock

level of

underground

water

dep

th Cause of failures:

„small“ depth of foundation

(longtime compress of footing

subsoil, slushy of footing bottom,

freezing of footing bottom

Maintenance:

Deeping of footing bottom - mini

pile (root) pile

Secure of gable wall by mini pile – tension pile

soil

foundation of new internal structure to micropiles (mini pile)

microp

ile

1. level of old piles, 2. footbridge, 3. crown weir, 4.

bottom of the weir, 5. sand-gravel, 6. gravel, 7. slate

Geological profile

(Geological cross-section)

diaphragm wall

sheet pile wall

Working area Steel tie

anchor

Sand-gravel

muddy alluvium

loamy

slate

Secure of wall of excavation by mini pile

• Scheme implementation of jet grouting

backfill made land

clay soil

rock

level of

undergroun

d water

Cause of failures:

„small“ depth of foundation

(longtime compress of footing

subsoil, slushy of footing bottom,

freezing of footing bottom

Maintenance:

Deeping of footing bottom – JET

grouting

1. rotation boring

2. finish of boring

3. jetting of mixture

4. extracting of boring rod

Pile from mixture of cement and

soil

dep

th

soil

jetting

of

mixture

jetting of

mixture

cement mixture

cement

mixture

Geological profile

(Geological cross-section)

Buttons of excavation and support of

existing foundation by JET

GROUTING

Lower surface of

wall after demolition

silt sand

Cement grouting

clay

Chemical grouting

JET grouting

Grout hole

gravel

grain dimension in

Using of diffrent type of grouting

rati

o o

f w

eig

ht

Grout hole

Cause of failures:

Increased loads

Maintenance:

Extension of foundation

• examples of extension of foundations

sand or gravel

rock

level of

underground

water

backfill

Shear claw of

original

structure

additing

concrete

part

reinforce

steel

reinforce

steel

additing concrete part reinforce steel of

claw

ring reinforce

dep

th

soil

hole reinf

orce

ment

reinforce steel

of claw

Reinforcement

of new

foundation

Maitenance of

column

Ring reinforcement

Geological profile

(Geological cross-section)

concrete

• join adaptation of extension of foundation

clean

hacked

surface

Join with claw

Join with reinforce steel bar

Join with hacked surface

Join with reinforce net

loop

vertical

loop

claw

Reinfor

cement

net

Loop with hooks

Double loop

Nu

mb

er o

f cl

aw

Cause of failures: leaching of soil particles (fines)

Maintenance: Deeping of foundation structure

–JET grouting, mini pile (root

pile) grouitng of soil

• examples of grouting of soil

clay soil

rock

level of

undergroun

d water

sand or

gravel

made land, backfill

clay soil

rock

level of

underground

water

Cause of failures: leaching of soil particles (fines)

Maintenance: Deeping of foundation structure,

grouitng of soil

dep

th

soil

injecting the soil under the existing foundation

dep

th

soil

made land, backfill

Geological profile

(Geological cross-section)

Underpinning by bored piles Changes of foundation soil (footing subsoil)

Méně používané metody sanace základů staveb

Other using methods

Concreting

Steel beam

Original

foundation

bea

ring

soil

Non b

eari

ng

soil

New reinforced concret

strip foundation Wall

column

pier

Gravel-sand

compaction layer

Non

bearing soil

reinforced concrete

bored piles

original

foundation

Excavation – length

0,9 – 1,2 m

• podchycení stěny na nové základy

underpinning of loadbear wall by new founadtion

•oplášťování základových pasů

facing of foundation strip

concrete block

cement

mortar

steel beam

new foundation

strip

Original

foundation

var. for desintegration or little of bearing

capacity of wall structure

Desintegrated

part

additing

concrete

part;

hacked

surface

claw in original

structure resin

Desintegrated masonry and concrete of foundation must be mechanical removed

additing

concrete part

steel

pad

gap anticorrosive

protection

steel pad

Steel wedges

• spřažení základů deskou a skořepinou

connection of foundation by RC vaults or RC slab

Connection of foundation by reinforce concrete

vaults

Connection of foundation strip by

grid slab

Connection of foundation by

concrete slab

reinforcement in

anchor pocket

reinforce

concrete slab

reinforce

concrete slab ban

k

concrete concrete

•Dodatečné provádění zedních kleštin (sepnutí zdiva)

Additing wall tie (anchor)

crack

forces in tie

point of rotation

crack

forces in tie

settlement

point of rotation

weight of piers

Historical development of Charles Bridge

Foundation of bridge piers (documentation of 1900)

Staré Město Malá Strana

1432

1496

1784

1890

bridge partsdamagedduring thefloods

a...založení na kesonechb...kesonové věncec...původní založení

ab

c

a

b

•Schema založení mostních pilířů Karlova mostu

•Schem of foudation of bridge piers of Charles bridge

•Foundation of new bridge piers of Charles bridge after flood in 1892

•Zabezpečení základů mostních pilířů „kesonovou obezdívkou“

•Safety of foundations of bridge piers by „caisson facing“

1. sand and gravel, 2. coarse gravel,

3. intermediate layers, 4. slate

1st floor level floor

level of foundation base

Cathedral in Mexico City consolidated and unconsolidated soil

bottom of the lake, Pyramid

Stabilization of the settlement of the cathedral by the "extraction" of soil (shaft with radially arranged holes and

pipes)

Failures

insufficient load-bearing capacity in footing bottom (absence or wrong geological surveying of footing subsoil)

different type of footing subsoil (main different geotechnical property – bearing capacity, compressibility, water

infiltrations, consolidation, …)

changes of geotechnical, hydrological (changes of level of underground water, near-by terrain, new biulding

structures in neighbourhood)

improving the load carrying capacity of existing structural foundation to handle increased loads

changes of climatic conditions (exposing foundation, changing to near-by terrain, excavation, drying-out and frost

penetration of footing bottom),

bad (wrong) design of foundation structures (insufficiency dimenzion, design without dilatation, different depth of

foundation),

desintegration of materials (agents of deterioration: vegetation)

analyse of interaction between subsoil and structure

undermining

shaking

1. Extension of foundation

Higher resistance

Limited setting no sutaible (especially in less compressible soil)

Level of footing bottom

Shearing force – ensure interaction

2. Deeping and underpinning

Non bearing soil is replaced by better (less sompressible), reduce settlement

Foundation in freezing depth

Adaptation

Strat from the most loaded part

3. Underpinning

Load from alod founadtion is transfered to new foundation

(bored piles, jet grouting, mini (micro) piles)

4. Strengthening of disintegrated foudation

http://kps.fsv.cvut.cz/index.php?lmut=cz&part=vyuka&sub=pdre

Main important cause of failures

• insufficient load-bearing capacity in footing bottom (absence or wrong geological surveying of footing

subsoil)

• different type of footing subsoil (main different geotechnical property – bearing capacity, compressibility,

water infiltrations, consolidation, …)

• changes of geotechnical, hydrological (changes of level of underground water, near-by terrain, new biulding

structures in neighbourhood)

• improving the load carrying capacity of existing structural foundation to handle increased loads

• changes of climatic conditions (exposing foundation, changing to near-by terrain, excavation, drying-out and

frost penetration of footing bottom)

• bad (wrong) design of foundation structures (insufficiency dimenzion, design without dilatation, different

depth of foundation)

• desintegration of materials (agents of deterioration: vegetation)

• analyse of interaction between subsoil and structure

• undermining

• shaking

Rehabilitation (rebuilding) and maintenance of foudations

structures

Before design rehabilitation (renovation) and maintenance of foudations structures is necessary:

- Verification state of foundation structure

- Analysis cause of failures

- Check up (verify) geotechnical conditions

- Determinate real load of foundation

- Determinate real calculation model of load bearing system of structure (include foundation)

Possible rehabilitation (rebuilding) and maintenance:

- rehabilitation (rebuilding) foundation structure,

- modification of property of footing subsoil,

- rehabilitation (rebuilding) „top“ part of structure,

- combination of list (describe) possibility

Rehabilitation (rebuilding) of foundation:

- Increace of load bearing capacity of founadation

- Reduce settlement or different settlement

- Eliminate of failures

- Protection of foundation structure before temperature, changes of level of underground water,

- Protection of foundation structure before effects of near-by structures,

- Protection of foundation structure before desintegration of structure and materials.

Subsidence of right

marginal part

Subsidence of both

marginal parts

Subsidence of middle

State of stress of load bearing capacity wall

pressure trajectory

main pressure

tension trajectory

main tension (direction of

larger subsidence, lower

stiffness of support , etc. )

larger subsidence

(settlement)

Foudation of outside stair

Right

solution

Wrong

solution

Foudation of non bearing

wall on foudation strip

unrammed gravel fill

foundation

beam

fixed joint between outside

stair and foundation of

structure

•Zabezpečovací opatření při provádění sanace základů

•Securing of structure during maitenance of foundation

Load transfer on assitent

foundation

brace tie

Underpinning walls and

piers Reinforce

concrete

beam

Steel

beam

Supporting bearing wall

assitent foundation

Securing of middle piers during

maitenance of foundation

•Securing of bearing structure during deppening of

lower floor

•Horizontal waler of near houses by crossbeam

Start from

the most

loaded part

•Postup sanace skeletové konstrukce

Maintenance of frame structure

settlement of midle

column

tie tie

supporting of middle beam by help

(additing) beam

Coupling of column by diaphragm

craks in

beam

partly hanging out of middle column

red

uct

ion

of

load

on

mid

dle

fo

ot