3.3. Evaluation of Building Foundation Damage
Basic Terminology:
Damage: Destruction, deformation, inclination and settlement of a building
foundation caused by an earthquake.
Damage grade: Degree of danger of destruction, deformation, inclination andsettlement of a building foundation caused due to earthquake.
Retrofit: Secure a necessary aseismic capability reinforcing the aseismic capabilityof existing building foundations which decreases due to an earthquake, andassume an existing building to be reusable.
Safety: Building foundation conditions which ensure the safety of human life even ata possible severe earthquake.
Purpose: Methodology for evaluating safety of building foundations after earthquake ortsunami
Important Points:
Timing:Timing
Immediate

Evaluation Methodology· First announcement ofbuilding damage

Within few days

· Quick inspection ofbuilding

Within few
weeks· Damage survey in a
typical area
· Confirmation of building
foundation· Damage Classification

After severalmonths

Example· Reports of eye witness &Feelings by local habitants· Broadcast· Evaluation into 3 ranks,
inspected, limited entry and noentry· Judge the cause of settlementand inclination on building· Seismic capacity assessment· Judge the retrofit method anddesign

Grade:
GradeMinimum
Necessary
BetterMethodology
Reports of eye witness &Feelings by local habitants
Instant evaluation

BestEvaluation of safety ofbuilding foundation

198

Measures
Information to habitants
Advice to habitants about
Restoration
Advice to habitants about
Retrofitting3.3.1. Damage investigation flow chart
The flow of building-foundation damage investigation is presented in Figure
3.3.1-1. Within two or three days after an earthquake, a quick inspection of the buildings isdone to decide on the degree of danger from aftershocks and on whether it is necessary torestrict the use of the buildings (Step 1). An inspection sheet used at the time is presented inExample 1.
To judge whether the inclination or settlement of buildings is due to theirfoundations (Step 2), inspectors enter buildings that had been judged to need detailed
investigation. This is done several weeks after the earthquake. This inspection refers torecords in the quick inspection sheet for the ground in a broad area (Example 1 in Section 3.1)
and to records in the sheet for the ground in each building site (Example 2 in Section 3.1).
Several weeks after the earthquake, experts start the detailed investigation on thedamage to the foundations and the ground for the buildings that have suffered the damage
judged attributable to the former (Steps 3 and 4 in Section 3.1). The investigation refers todamage grade classification sheet for the ground in a broad area (Example 3 in Section 3.1)
and such a sheet for the ground in each building site (Example 4 in Section 3.1). From theresult of this investigation, the damage grade classification of each foundation is determined,
and judgment is made on whether it is in need of repair and reinforcement. When the repair
and reinforcement of the foundation are required, their methods are studied to select the mostappropriate ones.

199

2～3Days
afterEarthquake

START
Earthquake

Quick Inspection of Buildinges
Information of Damage Situation
Newspapers, TV and others
Judgment of theQuick Inspection
Step 1

Inclination or Settlement of Builing

Is it a building where
the damage of thebase is assumed?
Yes

Sevral Weeks ofafter Earthquake

Spread Foundation
PileFoundation ?
Confirmation ofInclination orSettlement ofFoundationYes
Pile Foundation
Step 2

Sevral Months ofafter Earthquake

Investigation for Damage Grade Classification of Building
Foundation by Expert

Step 3,4

Needed Retrofit
DemolishJudgment of the Damege
Grade Classification

Repair, Retrofit orStrengthen ofFoundation

Step 5

Not Needed Retrofit
Investigation for Damage Grade Classification of Building Foundatio
Judgment of the Damege Grade Classification

Fig. 3.3.1-1 Damage Investigation Flow of Building Foundation
200

Damage Investigation Flow of Building Foundation Step
Step 1
Accompanies the quick inspection in the building, and the outline of damages (subsidence,inclination, and situation of limb ground etc.) of the building foundation is investigated.
Step 2
It is investigated to judge the cause of subsidence and inclination in the building.
Step 3
Investigation for the damage grade classification of building foundation by the expert
In Case, there are a settlement and an inclination in the building foundation.
Or the damage of the building foundation is assumed from a surrounding damage situation.
Refer to the example of investigation seat and investigation method for the investigation
item.
Step 4The damage grade classification of the building foundation is executed based on theinvestigation result of the building foundation.
Step 5
Removal of building or a repair and a retrofit in the building foundation are judged basedon the damage grade classification of the building foundation.
When the building foundation is repaired, the repair method is selected.

201

Sheet 1/3

Example 1[1]

Table 3.3.1 Site Investigation Sheet for Building Foundation
Sheet No.
Time&Date
Recoder

Outline of Building
Building Name
Architectural year
AdressType
Stracture Form
Building Use
Building Size
Number of StoriesPlane
Foundation Type

□SRC, □RC, □S, □Others□Wall type, □Rigid Frame□House, □Shoop, □Office□School, □Warehouse, □Others
F, Ground Stories
F
Upper Stories(m) x (m), □Square, □Rectangle, □Others□Pile Foundation, □Spread Foundation

Outline of Building Damage
Settlement
max. (mm), Situation of Settlement :Inclination
max. (mm), Situation of Inclination :Horizontal Movement max. (mm), Situation of Movement :Column□No Damage, □Damage, Damage Level
Inside Wall
□No Damage, □Damage, Damage Level
Outside Wall
□No Damage, □Damage, Damage Level
Other Structures□No Damage, □Damage, Damage Parts

Presence of Materials□Boling Log or Soil Profile□Foundation Plan or Piling Plan
□Topographic Map□Design Documents□Quick Inspection Sheet202

Sheet 2/3

Example 1 (Cont.)

Outline of Buildind Foundation
Pile Foundation
PileType
Pile Diameter
Pile Length
Total Pile Number
Spread Foundation
Foundation Type
Depth of Footing□RC, □PC, □AC, □PHC
□Steel, □Cast in place, □Others((mm)(m))□Raft(Mat) Foundation, □Continuous Footing□Independent Footing(m)Outline of Buildind Foundation Damage
Pile Foundation
Damage Part
Damage Patern
Damage Level
Total Number ofDamage Pile
Total Number ofInvestigation Pile
Damage situation ofDeep Position□Pile Head, □Other Part of Pile□Bending Failure, □Shear Failure, □Axial Failure□Ⅴ, □Ⅳ, □Ⅲ, □Ⅱ, □Ⅰ

Result of Pile Integrity Test, Borehole Camera or Others

Damage situation

Attached Photo

Footing Foundation
Damage Level
Damage situation□Ⅴ, □Ⅳ, □Ⅲ, □Ⅱ, □Ⅰ
Attached Photo

Foooting Beam
Damage Level
Damage situation□Ⅴ, □Ⅳ, □Ⅲ, □Ⅱ, □Ⅰ
Attached Photo203

Sheet 3/3

Example 1 (Cont.)

Outline of Ground Condition□Plain, □Slope, □Plateau□Lowland, □Reclaimed Ground, □Others
Thickness of Alluvial □Sandy Soil Layer (m)(m)□Cohesive Soil Layer
deposit
Load Bearing Layer Depth (m), Soil TypeAttached
Boling Log or Soil Profile
Topography

Outline of Site Damage
GroundDamage situation□Settlement, □Crack, □Sand boil or Sedimentation□Movement, □Slope failure, □Retaining Wall, □Attached Photo

Outline of Eathquake Damage of Circumstances
Seismic Intensity
Damage ofBuilding

Ground□Collapse, □Inclination, □Settlement□Movement, □Others
Distance and Other information□Settlement, □Crack, □Sand boil or Sedimentation□Movement, □Slope failure, □Others
Distance and Other information

Retaining Wall

□Collapse, □Inclination, □Settlement□Movement, □Others
Distance and Other information2043.3.2. Investigation method
Table 3.3.2-1 shows a list of detailed investigation methods used to judge thedamage grade classifications of pile foundations. Cited as investigation methods are a) pile
integrity test, b) borehole camera, c) inclinometer, d) acoustic emissions, and e) visualobservation, each of which is outlined below.

Table 3.3.2-1 Outline of Damage Investigation Method of Foundation
Investigation method
MethodOutlineConfirmation Item
Integrity Test
The pile head is lightly stricken The length of pile, the pile ・Pile lengthwith the hammer.
shape, and the crack point, ・Section shape・Crack
The acceleration response ofetc. is presumed based onpile head is measured.
the elasticity wave motion ・Damage part
Borehole Camera The concrete of pile is observed th
The crack of pile midair part ・Crackwith a small video camera of
the waterproof type.
Inclinometer

The inclinometer of theinsertion type is inserted in thepaling.
The inclination angle of pile iscontinuously measured frompile head.
Acoustic Emission The elasticity wave in thesupersonic wave generated
from the concrete of damaged
pile is measured.
Watchingobservationand the pile borehole isspecified.

・Damage partThe crack and the cutting
part of pile are presumed
from discontinuity in theinclination angle of pile.

・Situation to which
pile is wind・Cutting part・Damage partThe damage part of pile ispresumed from thehistogram of Acoustic
Emission source.

・Cutting part・Damage partThe ground in surroundings of The damage situation of the ・Crackthe building foundation is dug. building foundation can be ・Damage part・Settlement
The damage situation of theobserved directly.
・Inclination situationbuilding foundation is observed
directly.

205

1) Pile Integrity Test
Purpose:Pile integrity test can be used by the following three purposes.
i) Quality management of new establishment pilesii) Shape investigation of existing pilesiii) Damage investigation of existing piles
Here, pile integrity test is used to investigate damage of the existing piles after anearthquake.
Outline of Pile Integrity Test:
Pile integrity test investigates thehealth of regret by using a low warp.
A sonic test in pile integrity test is
an examination method of measuring theresponse of the regret with the acceleration
meter etc. by generating the low strain by hitting
the paling head lightly with the hand hammer asshown in Figure 3.3.2-1.

Acc. meter

Pile

Fig.3.3.2-1 Outline of Pile Integrity Test

PHC Pile(Normal)
Nomalized vel.

20000
10000
0-10000-20000

Pile Top-30000

Pile Tip-40000-4-20246810121416
Length (m)PHC Pile（Bending Crack）
10000
Normalized vel.

5000
0-5000-10000

Crack

Pile Tip

Pile Top-15000-20000-4-20246810121416
Length (m)Fig.3.3.2-2 Output of Pile Integrity Test (PHC Pile in Japan)

206

Nomalized vel.

PHCPile (Normal)
20000
10000
0-10000-20000-30000-40000

T1-1
T1-2
T1-3
T1-4-4-20246810121416
Length (m)Normalized velocity

Belled PHC Pile (Normal)
10000
5000
0-5000-10000-15000-20000-25000-30000

T2-1
T2-2
T2-3
T2-4-4-202

468101214
Length (m)16

PHCPile （Bending Crack No.1）
Normalized velocity

10000
T3-1
T3-2
T3-3
T3-4

5000
0-5000-10000-15000-20000-25000-4-202468101214Length (m)Fig.3.3.2-3 Example of PHC Pile Integrity Test Results

2071612345678910Pile Type
Cast-in-place pile
Design Length 18m
4m-2400mm
Pile Diameter casing pipe
gaide casing pipe
7m-2200mm
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown. The reflection with the casing can beconfirmed to 3.5m and 6.5m.
Pile Type
Cast-in-place pile
Design Length 12m
Pile Diameter 1200mm
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown.
Pile Type
Cast-in-place pile(Belled Type)
Design Length 19.4m
Pile Diameter 2500m (belled diameter 2800mm)
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown.
Pile Type
Cast-in-place pile(Belled Type)
Design Length 20.9m
Pile Diameter 2100m (Belled diameter 3200mm)
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown.
Pile Type
Cast-in-place pile
Design Length 17.5m
Pile Diameter 2000mm
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown.
Pile Type
Cast-in-place pile
Design Length 27m
Pile Diameter 800mm
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown.
Pile Type
Cast-in-place pile(Belled Type)
Design Length 24m
Pile Diameter 1900m (Belled diameter 2600mm)
Measurement The reflection of belled part is indistinct though theResult
reflection of the paling point is plain. It is judged that
this is thought the one by the ground condition.
Pile Type
Cast-in-place pile(Belled Type)
Design Length 15.45m
Pile Diameter 1500m (Belled diameter 2600mm)
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown.
Pile Type
Cast-in-place pile
Design Length 19.33m
Pile Diameter 1100mm
Measurement The measurement wave has received the influence by
Resultcut-off of pile head. It is preferable to the Integrity
Tests again after re-cementation of pile head.
Pile TypeCast-in-place pile
Design Length 24m
Pile Diameter 1500mm
Measurement It is judged that there is no damage in the pile because
Resultthere is no downward shape of waves by which damageis shown.

‑5‑20

50

2

10

415

68

1020

1225

1430

16

18

‑50

510

15

20

25

‑50

510

15

20

25

‑50

510

15

20

25

‑50

5‑5‑200

400

15

20

52

‑5‑510

10

6

5

10

101030

15

8525

1220

1420

25

1615

15

35

1820

25

25

30

Fig. 3.3.2-4 Example of Cast-in-place Pile Integrity Test Results (Not damaged) [4]2081 Pile Type
Cast-in-place pile
Design Length 17.5m
Pile Diameter 2000mm
Measurement A downward shape of waves of about 4m shows the
Resultreduction-of-area. Because the reflection of the pile
point can be confirmed, it is judged that it is partialdamage.
Cast-in-place pile(Belled Type)
2 Pile Type
Design Length 24m
Pile Diameter 1700m (Belled diameter 2600mm)
Measurement A downward shape of waves of about 2.5m shows the
Resultreduction-of-area. Because the reflection of the pile
point can be confirmed, it is judged that it is partialdamage.
Cast-in-place pile(Belled Type)
3 Pile Type
Design Length 24m
Pile Diameter 2200m (Belled diameter 3600mm)
Measurement The cross sectional area of pile of about 2.5m
Resultdecreases. The repetition shape of waves at deeper
position than 2.5m is a reflection of the damage part.
The reflection of the point of pile can be confirmed.
Because the reflection at 2.5m is large, it is thoughtthat the level of damage of pile is large.

‑5051015202530‑10‑5051015202530354045‑10‑5051015202530354045‑10‑5051015202530354045

Cast-in-place pile
4 Pile Type
Design Length 29.95m
Pile Diameter
Measurement
Result1500mm
The shape of waves by which partial damage is shown
can be confirmed to about 27m. The reflection of pile
point is about 30m. It is thought that there is a decreasein a partial pile section in about 27m.

Cast-in-place pile
5 Pile Type
Design Length 18.2m
Pile Diameter 2100mm
Measurement A downward reflection by which the reduction-of-area
Resultis shown can be confirmed to 6m and about 9m. It isthought that it is a decrease in a partial pile section
because it can confirm the reflection of pile point.

‑50510152025Fig. 3.3.2-5 Example of Cast-in-place Pile Integrity Test Results (Damaged) [4]209302) Borehole camera
Purpose: to ascertain the conditions of damage to the pile
Outline of the borehole camera:
Places damaged by cracks in a pile are observed through images obtained by a video
camera or CCD camera inserted into the hollow section of the pile or a borehole made in its
concrete.

Underwater video camera housing
Video camera
fixed type
Spare lightingCable

Lighting controller
Cable

DVD Recorder
Camera controller

Fig.3.3.2-6 Fixed Type Borehole Camera[2]

Cable
Pile
Display

Lighting

Rotarycamera
lensController

Fig.3.3.2-7 Rotary Type Borehole Camera[2]2103) Inclinometer
Purpose: to measure the horizontal displacement of the pile
Outline of the inclinometer:
The horizontal displacement of a pile is determined by successively measuring its
inclination with an inclinometer inserted into its hollow section.

Measuring instrument
Fixing partMoving part
SlideInsert inclinometer
into boreholeFig. 3.3.2-8 Insert Type Inclinometer[2]2114) Acoustic emissions
Purpose: to ascertain the damage conditions at places that cannot be visually observed
Outline of acoustic emissions:Defects such as cracking in the concrete are detected using elastic waves (ultrasonic waves,electromagnetic waves, etc.) that propagate through structures.

AE sensor ch.1

L：difference between AE sensor
V：velocity of AE wave in propagation bar
dt：propagation time lag between AE sensors

AE sensor ch.2

Damaged pile

Wave propagation bar

Fig. 3.3.2-9 Measuring Image of Acoustic Emission[3]5) Visual observation
Purpose: to visually inspect the conditions of damage to foundation members such as
pile-head sections, footing beams, footing slabs, and underground walls
Outline of visual observation:
Foundation members are directly observed when they are observable from the inside of abuilding. Piles and footing beams are observed by excavating the ground around them.

Reference[1] Damage Grade Classification Manual of Building Foundation and Some Examples ofRepair Techniques, Kenchiku Kenkyu Shiryo, BRI, August 1997. (in Japanese)[2] Committee Report on Soundness Judgement Technology of Earth Structure and212

Foundation, Japanese Geotechnical Society, March 1999. (in Japanese)[3] Committee on Building Foundation Technology against Liquefaction and Lateral
Spreading: Study on Liquefaction and Lateral Spreading in the 1995 Hyogoken-Nanbu
Earthquake, Building Research Report No.138, BRI, November 2000. (in Japanese)[4] Ministry of Land, Infrastructure and Transport, General Technology Development
Project, “Technology Development on Quality Management System for Construction
Works”, Volume of Building Construction, March 2001. (in Japanese)213