investigation of soil liquefaction and geotechnical properties in

Investigation of soil liquefaction and geotechnical properties in Kathmandu

Japan-Nepal Urgent Collaborative research/survey program (J-RAPID)

Final Workshop June 21-22 ,Kathmandu Nepal

Mitsu Okamura, Ehime University (Project Leader) Netra Prakash Bhandary, Ehime University. Narayan Prasad Marasini, Ehime University. Ikuo Towhata, Kanto Gakuin University.

Surya Narayan Shrestha, NSET (Nepal side leader) Indra P. Acharya, Tribhuvan University . Sujan Raj Adhikari, NSET Dinesh Pathak, Tribhuvan University

Abstract of the project • The peak accelerations of the 2015 Nepal earthquake observed at a few locations in

Kathmandu valley were approximately 180gals. Although this acceleration was much smaller than that expected (i.e. 300 gal), extensive soil liquefaction was observe at several locations in the vicinity of major rivers in Kathmandu city. This strongly indicate that soils in the city are quite prone to liquefaction and liquefaction assessment is of great importance to prepare for stronger earthquakes in the future.

• Because of the uniqueness of soils in Kathmandu, which are rich in Mica, liquefaction assessment methods established based on the experiences in Japan and the US have to be verified. In order to refine or reestablish liquefaction assessment methods, identification of field evidences of liquefaction including sand volcanos and lateral spreading are necessarily and the 2015 April earthquake provided us a valuable opportunity to do this. Our research team will conduct field survey, in-situ tests as well as laboratory test described below and establish a liquefaction assessment method which is suitable for Kathmandu.

• Extensive field survey to identify locations of soil liquefaction all over the valley and summarize in a map.

• In-situ tests at several liquefied sites including boring, standard penetration tests, undisturbed soil sampling and PS logging. Based on test results we will be able to prepare relationship between N value or S wave velocity and threshold acceleration which separates liquefied and non-liquefied sites.

• Laboratory tests on samples including physical test, cyclic triaxial test to measure liquefaction strength and X-ray deflection test. It is expected from these tests that liquefaction strength characteristics of Kathmandu soils, which may exhibit strong influences of Mica contents, are revealed.

• Extensive microtremor measurements will be conducted all over the valley which is expected to reveal local amplification characteristics.

Background • Peak accelerations of the 2015 Earthquake in Kathmandu was around

160gal (Dixit et al., 2015; Goda et al. 2015) • Observed Peak acceleration is less than that expected (i.e.<300gal) • Even in small acceleration, extensive soil liquefaction was observed at

several locations in Kathmandu city. • This strongly indicate that soils in the city are quite prone to liquefaction

and liquefaction assessment is of great importance to prepare for stronger earthquakes in the future.

Acc

eler

atio

n (c

m/s

/s)

40 60 80 100 120-300-200-1000100200300

Time (sec)

Max. acc. at the central area of KTM, Kanti path= 150-182 gal

• Kathmandu soil is unique and heterogeneously distributed. • Kathmandu soil are rich in Mica, liquefaction assessment methods

established based on the experiences in Japan and the US have to be verified.

• In order to refine or reestablish liquefaction assessment methods, identification of field evidences of liquefaction including sand volcanos and lateral spreading are necessary.

• and the 2015 April earthquake provided us a valuable opportunity to do this.

Background

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50

Diffr

action c

ounts

（cps）

Angle，2θ （°）

X-ray diffractometryQuartz

CalciteMica

feldspar

MicaMica(B)

Mica(W)

MicaQuartzfeldspar

X-ray diffractometric

Objectives To conduct extensive field survey, in-situ tests as well as laboratory tests described below and establish a liquefaction assessment method which is suitable for Kathmandu; • Extensive field survey to identify locations of soil liquefaction

all over the valley and summarize in a map. • In-situ tests at several liquefied sites including boring, SPT,

undisturbed soil sampling and PS logging to prepare the relationship between N value or S wave velocity and threshold acceleration which separates liquefied and non-liquefied sites.

• Laboratory tests on samples including physical test, cyclic triaxial test to measure liquefaction and reveal the liquefaction strength characteristics of Kathmandu soils, which may exhibit strong influences of Mica contents.

• Microtremor measurements to reveal the local amplification characteristics of Kathmandu valley.

: Liquefied by 2015 earthquake


Ramkot

Manamaiju

Guheswori

Syuchatar

Bungmati

NEC

Mulpani

Jharuwarashi

Hattiban

Imadol

Tundikhel

Nayabazar

Kamalvinayak

Identification of liquefaction An extensive field survey was conducted all over the valley and 11 liquefied locations were identified.

Observed liquefaction

Approx.. 150m Silty sand

At Jharuwarashi

Observed liquefaction Cont….

Approx.. 150m Silty sand

0.01 0.05 0.1 0.5 1 5 100

20

40

60

80

100

Grain size (mm)

Perc

ent f

iner

by

wei

ght

Jharuwarashi area (L1) Bungamati are (L2)

At Bungmati

At Nepal Engineering College (NEC) area

Observed liquefaction Cont….

At manamaiju area

Liquefaction of central KTM in 1934

Liquefaction in Tundhikhen and Nayabazar area by the 1934 earthquake (after Rana, 1935)

Nayabazar Tundikhel


: Do not liquefied by 2015 earthquake

Ramkot

ManamaijuNEC

Imadol

Manahara

• Manamaiju

• Imadol

• NEC

• Ramkot

• Manahara

In-situ tests Standard Penetration test (SPT)

Undisturbed soil sampling

PS-logging

Rotary wash boring Energy loss others

SPT

Problem on weight drop

SPT-N value based Liq. Assess. at 5 sites

dvo

vo

vo

av rg

aCSR

=

= '

max' 65.0

σσ

στ

Manamaiju

LegendBlack clay

Filled material

Sand

Silty sand

Silty clay

Sandy gravel

Silt

0

5

10

15

0 100 20SPT N Value

Manahara

0 100 20SPT N Value

Ramkot

0 100 20SPT N Value

0 100 20SPT N Value

NEC

0 100 20SPT N Value

Imadol

dv

v rg

L ** 'max

=

σσα

10 20 30 40

0.25

0.5

0Normalazied N value,�(N1)60cs

Cyc

lic st

ress

ratio

or r

esis

tanc

e,C

SR o

r CR

R

Seed et al. (1983)(M =7.5, Number of cycle=15)

Liquefied site Manamaiju, NEC, Imadol, Ramkot

Not Liquefied site (Manahara)

Ramkot (FC=35%)

Gorkha Earthquake 7.8 (Number of Cycle 5-6)

Liquefaction

No-Liquefaction

10 20 30 40

0.2

0.4

0.6

0.8

0Normalized N value,�(Na)

Cyc

lic st

ress

ratio

or r

esis

tanc

e ra

tio C

SR o

r CR

R

RL (Japan Road Association)(Converted to An-isotropic Condition)

Liquefaction

No-Liquefaction

Liquefied site (Manamaiju, NEC, Imadol & Ramkot)

Not-Liquefied site (Manahara)

Simplified Method

JRA method

Both the curve under estimate the Liquefaction Potential for Kathmandu soil

PS- logging

Time (msec)

Typical PS-Logging data Manamaiju Site

100 200 300

0.1

0.2

0.3

0.4

0.5

0.6

0Normalized shear wave velocity, Vs1 (m/s)

Cyc

lic st

ress

ratio

or r

esis

tanc

e ra

tioC

SR o

r CR

R

CRR (Mw=7.5)

Liquefacion

NoLiquefaction

Andrus and Stokoe (2000) Not-liquefied (JICA Study,2002)

Liquefied (Manamaiju, Imadol, NEC & Ramkot)

Not-liquefied (Manahara)

S-wave (Vs) based Liq. Assessment d

v

v rg

aCSR max

'65.0

σσ

=

25.0

1 '100

=

v

VsVsσ

This curve Over estimate the Liquefaction Potential in Kathmandu soil

00

0 100 200 300100

200

300

Vs1

(m/s

)

N1

ManamaijuRamkotNECImadol

Holocene clean sand(Andrus et al, 2004)

'70170

1v

NNσ+

=

Laboratory Experiment

0.0001 0.001 0.01 0.1 1 10 100

20

40

60

80

100

Perc

enta

ge fi

ner (

%)

Particle grain size (mm)

Manamaiju at 12mNEC at 7mManahara at 5mImadol at 2mRamkot at 5m

Tests Conditions

Cyclic triaxial setup

Triaxial specimen

Manamaiju (Dr=80%)

Typical undrained cyclic triaxial test results

0 5 10 15 20-0.2

-0.1

0

0.1

0.2

Cyc

lic st

ress

ratio

(σ

d/2σ'

c)

0 5 10 15 20-10

-5

0

5

10

Axi

al st

rain

ε a

(%)

Axi

al st

rain

ε a

(%)

0 5 10 15 200

0.5

1

Pore

pre

ssur

e ra

tio

(u/σ

' c)

Number of Cycless-N

DA=5%

0 20 40 60 80 100 12-40

-20

0

20

40

Dev

iato

r stre

ss

σ d(k

Pa)

Mean Effective Principle Stress -P'(kPa)

-10 -5 0 5 10-40

-20

0

20

40

Axial strain,εa(%)D

evia

tor s

tress

σ d

(kPa

)

0.04 0.06 0.08 0.1-2

-1

0

1

2

Shea

r stre

ss(τ=σ

d/2)

Shear strain -γ (%)

G0

1 10 100 1000

0.25

0.5

Number of Cycles -N

Cyc

lic st

ress

ratio

(CSR

)

Effective stress, σ'c = 100kPa

Relative Density, Dr=45%Relative Density, Dr=60%Relative Density, Dr=80%Relative Density, Dr=110%

Liquefaction strength curve

1 10 100 1000

0.1

0.2

Number of Cycles -N


Relative Density, Dr = 45%Relative Density, Dr = 60%Relative Density, Dr =80%Relative Density, Dr =100%

1 10 100 1000

0.1

0.2

Number of Cycles -N

Cyc

lic st

ress

ratio

(CSR

)


Relative Density, DR =45%Relative Density, DR =60%

Manamaiju NEC

Imadol

40 60 80 100 120

0.2

0.4

0.6

0.8

Relative Density, Dr (%)

Cyc

lic re

sist

ance

ratio

(CR

R(σ

d/(2σ

' c)

Tatsuoka et al. (1986) Toyoura sandManamaijuNEC

wet- tampedσ'c=100kPa

Deformation test results

0.00001 0.0001 0.001 0.010

0.4

0.8

1.2[×105]

Shear strain (γ)

Shea

r Mod

ulus

, G (k

Pa)

Kathmandu soil (Manamaiju)Toyoura sand (Kokusho ,1980)

Relative Density, Dr= 60%Confining pressure, σ'

c= 100 kPa

Ottawa sand (A.Gunzman A.,1989)

0.00001 0.0001 0.001 0.010

0.4

0.8

1.2

Shear strain (γ)Nor

mal

ized

shea

r mod

ulus

G/G

0

Confining pressure, σ'c = 100 kPa

Ottawa sand (A-Gunzman A., 1989)

Toyoura sand(Kokusho, 1980)

Kathamndu sand

ManamaijuKathmandu sand

NEC ImadolMore Elastic

4-5 times

• Kathmandu soil is soft & more compressible

• More elastic than Toyoura and Ottawa sand

• Stiffness is 4-5 times less than Toyoura and Ottawa sand

• Deformation characteristic is similar with the Toyoura sand

20 sVG ρ=

Shear wave velocity calculate by using this relation;

100 200 300

0.1

0.2

0.3

0.4

0.5

0.6

0Normalized shear wave velocity, Vs1 (m/s)

Cyc

lic st

ress

ratio

or r

esis

tanc

e ra

tio(C

SR/C

RR

)

CRR (Mw=7.5)

Liquefacion

NoLiquefaction

Andrus and Stokoe (2000)

Not-liquefied (JICA Study,2002)

Cyclic Triaxial test

Field data

NECImadol

Manamaiju

Liquefied (Manahara, Imadol, NEC & Ramkot)

Not-liquefied (Manahara)Proposed boundary curve for kathmandu soil

10 20 30 4

0.25

0.5

0Normalazied N value,�(N1)60cs

Cyc

lic st

ress

ratio

or r

esis

tanc

e,C

SR o

r CR

R

Seed et al. (1983)(M =7.5, Number of cycle=15)

Liquefied site Manamaiju, NEC, Imadol, Ramkot

Not Liquefied site (Manahara)

Gorkha Earthquake 7.8 (Number of Cycle 5-6)

Proposed boundary curve for Kathmandu soil

10 20 30 40

0.2

0.4

0.6

0.8

0Normalized N value,�(Na)

Cyc

lic st

ress

ratio

or r

esis

tanc

e ra

tio C

SR o

r CR

R

RL (Japan Road Association)(Converted to An-isotropic Condition)

Liquefaction

No-Liquefaction

Liquefied site (Manamaiju, NEC, Imadol & Ramkot)

Not-Liquefied site (Manahara)

Purposed Boundary curve for Kathamndu soil

Proposed boundary curve for Kathmandu soil • Field in-situ & laboratory test results are

combined and proposed the new boundary curve based on S-wave velocity

• For the time being until & unless the SPT test procedure improve, new boundary curve based on SPT N-value are proposed to assess the liquefaction in Kathmandu valley

Conclusions Extensive field survey was conducted and identified 11 liquefied locations

during the April 25 Earthquake.

X-ray diffraction analyses were conducted on sands erupted at liquefaction sites and found that quartz, feldspar, mica and calcite are the dominant minerals. The relative amount of minerals in the sands determined by the integrated intensity ratio were quartz 60-–80%, feldspar 10–20%, mica 10–20% and calcite 5–10%

SPT, PS logging and continuous soil sampling were conducted at 5 sites in which 4 are liquefied and 1 did not liquefied during April 25, earthquake.

Undisturbed samples were obtained and carried out the laboratory tests including undrained cyclic triaxail tests to measure the liquefaction strength and found very susceptible for liquefaction.

The detail investigations on in-situ field tests and laboratory experiments carried out in the cyclic triaxil suggested that the existing method either based on SPT-N value or S-wave velocity do not fully valid for Kathmandu soil.

Finally, new boundary curve to separate the liquefaction and non-liquefaction locations based on the relationship between N-value or S-wave velocity and threshold acceleration are proposed. The proposed curve based on N-value are for time being until and unless the field test procedure improve and maintain the standards.

Thank you !!

JST, J-Rapid Kickoff Meeting @Kathmandu, 28 October 2015

JST J-Rapid Final Workshop, 2016.6.21.22, Kathmandu

Ambient Vibration Survey on Ground and Tall Buildings of Kathmandu Valley

Japan side Nepal sideMitsu Okamura Surya Narayan ShresthaNetra P. Bhandary Sujan Raj AdhikariNarayan Marasini Indra Prasad AcharyaIkuo Towhata Dinesh Pathak

Netra Prakash BhandaryEhime University



Building Damage Pattern



Other Low Natural Frequency Structures



One cycle

Ground vibration

Structural vibration characteristics

Natural Period and Vibrational Resonance

Time

Amplitude



Tall building

Short building

Medium-height building

Rotating handle

Small-scale Shake Table Demo (Resonance Effect)

Long period shaking

Short period shaking

Medium period shaking



Mini shake-table video demonstration

(Refer to the video file if time allows!)



Research FrameworkThis study is composed of two parts:Part I: Liquefaction Study

Part II: Ambient Vibration Study

Field Investigation(Site identification, SPT-N value, S-wave

velocity, Sand sampling) Laboratory Testing

(Physical tests, Cyclic triaxial test, X-Ray diffraction test)

Field Measurement(Predominant natural frequency of

ground and tall buildings)Comparative Analysis(with previous data and 2015

Gorkha Earthquake motion data)

Liquefaction Resistance of Kathmandu Soil

Ground-Building resonance characteristics

Natural Frequency-based earthquake intensity and PGA maps

Hazard Predication

PGA prediction for scenario earthquakes and more reliable/accurate liquefaction map for KTM valley

Future Work



Total: 175 points~ 1

1 km.

~ 18 km.



Microtremor (vibration) sources

Tidal currents

Industrial machines

Vehicles

RailwayStrong winds

Shock waves

Measu-rementPoints

Volcano

In Kathmandu:• Vehicle movement• Winds• Industrial machines• etc.

(From Tokyo Soil Research)


JST J-Rapid Final Workshop, 2016.6.21.22, Kathmandu11

SensorTransducer

Computer for data recordingThree components (EW, NS andUP) of ground motion (velocity)measured at single station

-0.004

-0.002

0

0.002

0.004

0.00 20.48 40.96 61.44 81.92 102.40 122.88 143.36 163.84 184.32 204.80 225.28 245.76 266.24 286.72 307.20

Time (T) Sec

Vel. (c

m/s)

16 7

89 10 11 12 13 14 152 543

Noise-0.004

-0.002

0

0.002

0.004

0.00 20.48 40.96 61.44 81.92 102.40 122.88 143.36 163.84 184.32 204.80 225.28 245.76 266.24 286.72 307.20

Time (T) Sec

Vel. (c

m/s)

16 7

89 10 11 12 13 14 152 543

Noise

-0.004

-0.002

0

0.002

0.004

0.00 20.48 40.96 61.44 81.92 102.40 122.88 143.36 163.84 184.32 204.80 225.28 245.76 266.24 286.72 307.20

Time (T) Sec

Vel. (c

m/s)

16 7 8 9 10 11 12 13 14 152 543

Noise

-0.004

-0.002

0

0.002

0.004

0.00 20.48 40.96 61.44 81.92 102.40 122.88 143.36 163.84 184.32 204.80 225.28 245.76 266.24 286.72 307.20

Time (T) Sec

Vel. (c

m/s)

16 7 8 9 10 11 12 13 14 152 543

NoiseNorth- South (NS) component data

East- West (EW) component data

Vertical (UP) component data



MT Instrument

V T (sec)

T (sec)V

Horizontal (R or T) component

Vertical component

Incident wavefield

SedimentBedrock

Three components (EW, NS and UP) of ground motion (velocity)

measured at single station (Time domain)

Analysis process of microtremor data

Fourier amplitude spectra (Af)Horizontal component Vertical component

Fast Fourier Transform

Fourier amplitude versus frequency (Frequency domain)

Frequency correspondences to maximum value of H/V ratio gives the predominant frequency of the

site

Transfer Function or H/V Spectral Ratio

Amax

A(f) HorizontalA(f) VerticalH/V =



Fourier Analysis

tPeriod Function

Fourier Analysis

Frequency analysis

Frequency (Hz.)

Amplit

ude Spe

ctra

-0.004

-0.002

0

0.002

0.004

0.00 20.48 40.96 61.44 81.92 102.40 122.88 143.36 163.84 184.32 204.80 225.28 245.76 266.24 286.72 307.20

Time (T) Sec

Vel. (c

m/s)

16 7 8 9 10 11 12 13 14 152 543

Noise

P 8

0.1

1

10

0.1 1 10Frequency (Hz.)Frequency (Hz.)

H/V spe

ctral ra

tio



P 163

0.1

1

10

100

0.1 1 10

P 8

0.1

1

10

0.1 1 10

P 133

0.1

1

10

100

0.1 1 10 100

P 100

0.1

1

10

0.1 1 10Frequency

H/V sp

ectral

ratio

Frequency

H/V sp

ectral

ratio

Frequency

H/V sp

ectral

ratio

Frequency

H/V sp

ectral

ratio

Analysis and result (F – Predominant frequency of the sites)

F = 3.0 Ｈｚ

F = 8.9 Ｈｚ

F = 0.73 ＨｚF = 0.95 Ｈｚ



0.1

1

10

100

0.1 1 10

Period range D 1.01 s to 1.30 s

Period, s

H/V sp

ectral

ratio

0.1

1

10

100

0.1 1 10

Period range B 0.60 s to 0.80 s

Period, s

H/V sp

ectral

ratio

0.1

1

10

100

0.1 1 10

Period range C 0.80 s to 1.01 s

Period, s

H/V sp

ectral

ratio

0.1

1

10

100

0.1 1 10

Period range E 1.30 s to 2.05 s

Period, sH/V

spect

ral ra

tio

H/V spectral ratio of 5 zones

Predominant period range

Description of zone

A 0.11 s to 0.60 sB 0.60 s to 0.80 sC 0.80 s to 1.01 sD 1.01 s to 1.30 sE 1.30 s to 2.05 s

0.1

1

10

100

0.1 1 10

Period range A 0.11 s to 0.60 s

Period, s

H/V sp

ectral

ratio

Study area is divided into five different range of predominant period using natural break techniquewhich regroups similar values together and represents the distribution properly



Ground Predominant Frequency of the Survey Area

Kathmandu valley center is a low frequency area



Ground Predominant Period Map of the Survey Area

Period in the study area varies from 0.1-2.05 s Period in central part varies from 1-2 s, which covers about 30% of the urban area of the valley



Predominant period contours for the Kathmandu Valley

Higher period range in the eastern and western part of the valley is separated by the long low period line extended from north-west to south-east in the valley



The circle indicates the average value whereas the length of the line suggests deviation from the average

Average standard deviation = 7.44

050

100150200250300350400

0 20 40 60 80 100 120 140 160 180 200Microtremor observation points

Thick

ness (m

)

Microtremor observation points

Thick

ness (m

)

Comparison between depths calculated using Birgöen et al. (2009) and Özalaybey et al. (2011) relationships

Proposed frequency depth relationship for Kathmandu Valley D=146.01fr-1.2079



Predominant Frequency-based Sediment Depth Distribution of the Survey Area (D=146.01fr-1.2079 )



Contour lineMajor road

River and water bodies

Basement Contour map for the Kathmandu Basin based on the proposed relation, D=146.01fr-1.2079

AB

A number of depressions are seen which are connected/separated by the buried ridges



0

200300400

100

W S

NE

Top

Base

I

II0

200300400

100

Thickness (m)

3D view of Basement opography of the Kathmandu Basin

Large deep depression in the center part of the valley represents the main ancient lake of the valley

Longest buried ridge which separated the central large depression from the eastern shallow depression is extended from northwest to southeast



What We Did in This Particular WorkPart II-1: Ground-Tall Building Resonance EffectPart II-2: Estimation of Peak Ground Acceleration in

the Core Kathmandu Valley

Why? Equation-derived value of natural period for a building structure is too

theoretical and does not exactly match with the real measured value. Ground and structural vibrations must resonate for shaking, thereby leading

to damage Still today, we do not know in numerical value what part of Kathmandu was

shaken how severely because we do not have a good network of devices to measure the intensity.



Predominant Period:T = 0.1n

(n: No. of story)e.g., n = 10 storyT = 1 s

Microtremor (Ambient Vibration) Survey Plan on Buildings

Sensor locations

Building structure

Roof floor

Middle floor

Ground

General Relation

Does it hold true for Kathmandu buildings?

What exactly happened to the tall buildings during the Gorkha Earthquake?



KMC College Duwakot

UGC Sano Thimi (Only ground)

DMG Lainchsaur (Only ground)

CDG TU Kritipur (Only ground)

Municipality Kirtipur (Only ground)

NASA Building Gairigaun

Pashupati vision Gaushala

Sunrise apartment Dhobighat

Sunrise apartment Nakhkhu

suncity apartment Gothatar

cityscape apartment Hattiban

Cityview apartment Bakhundol

Downtown apartment Dhapakhel

Bagmati apartment Shankhamul

Gunacolony Gwarko

Kohinoor Hill Housing Sanepa Height

Metro apartment Kuleshwor

Ambe apartment Chabahil

Grand apartment Dhumbarahi

Super builders Sukerdhara

Grande apartment Tokha

Park view horizon Dhapasi

silver luxury apartment Kalikathan

Kings way (Only ground)

Pulchowk engineer college (Only ground)

signature1 Teku

Swoyambnath Temple (Only Ground)

New baneshwor building

Rio apartment Jwagal

Balkumari building

Ekantakuna building

Kumaripati building

LP apartment

Vibor apartment

Imperial apartment

LLP apartment

Mercury sterling Sanepa

Status enclave

The residency apartment Sanepa

Gunacolony Sinamangal

Sunrise city homes Bijulibazar

Kalash apartment Tahachal

Retreat apartment Bijeshwori

Sigunature apartment ⅡTeku

Oriental colony ⅠKuleshwor

Oriental colony ⅡKuleshwor

Sunrise homes Balkumari

Cresha plaza Newroad

Maroitt hotel Thamel

TCH 3 Panipokhari

Kathmandu residensy Baghdole

Tall Building Locations in Kathmandu Valley



Tall Buildings in Kathmandu Valley

Number of story, n

Pre-do

mina

nt Na

tural P

eriod

, T (s

)

T = f (n)



Intensity Map Interpretation

KirtipurMunicipalOffice

IoEPulchowk UGC

Predominant Period, T (s)PG

A, a pg

(gal)

apg = f (T)

DMGAmerican Center

Tribhuvan University



Ambient Vibration Survey 44 building sites 51 ground sites



Survey Glimpses



Analysis Method Separate the data into segments.（2048 data for 1 segment） Remove the noise. Convert the data from time-domain to frequency-domain by

Fourier analysis Find the spectral ratio (H/H for building, H/V for ground)

-0.01

-0.005

0

0.005

0.01

0 20.48 40.96 61.44 81.92 102.4 122.88 143.36 163.84

velocity (cm

/s)

Noise

Fourier transform

Smoothing by Parzen window bandwidth 0.5 Hz



Evaluation of Natural Frequency

ω : Natural frequency of groundω₀ : Natural frequency of building

0123456789

10

0 1 2 3 4

Dynam

ic magn

ifier

Frequency ratio

h=0.05h=0.1h=0.2ωg/ωb

Most of building are amplified by frequency of ground.

h (damping ratio) = 0.05



Wave Forms (Takai et al. 2016)

KATN

PKT

PPT

NTH

MTV

U The only waveform of KTP is different from others.

The seismic motion was overlapped and amplified in basin.



Earthquake Motion Characteristics

The seismic wave reflects and overlap by surrounding hard rock.

The seismic waves is getting the slow velocity and big amplitude from hard rock to sediment.

The long period shaking would occur in Kathmandu valley.



Predominant Period of Earthquake

The predominant frequencyf = 3.33f = 1.43f = 0.66f = 0.33f = 0.20Plot the dynamic magnifier at these values

Multiple periods as observed in velocity response spectra (Takai et al. 2016)



f=3.33 (T = 0.3 s)

f=0.33 (T = 3 s)

f=0.66 (T = 1.5 s)

f=0.20 (T = 5 s)

Fg/Fb



f=1.43 (T = 0.7 s)

The amplitude is not high when T = 3~5 (s) (Long period)

Dynamic magnifiers are greater than 1 for most of the buildings at all case of T except for T = 0.3 (s)



Damage extentPark View Horizon, Basundhara Cityscape Club House, Hattiban TCH Phase II, Thaiba

Oriental Apartment Phase II, Kuleshwor Cityscape Block B, Hattiban Southern Height Apartment, Thaiba

Prestige Apartment, Chandol Dhumbarahi Apartment, Dhumbarahi

Central Park Apartment, Bishal Nagar TCH Tower, Lazimpat

Grande Apartment, Dhumbarahi Bhat Bhateni Apartment, Bhat Bhateni

Grande Towers, Tokha Indreni Apartment, Bhat Bhateni

LP Apartment, Lazimpat Egrace Apartment, Naxal

KL Apartment, Sano Gaucharan

Binayak Apartment, Baluwatar

Sun Rise Apartment, Nakhkhu

Imperial Apartment, Sanepa

City View Apartment, Bakhudol

Mercury Sterling Apartment, Thado Dhunga

Sun Rise Apartment, Dhobighat

Kalash Apartment, Tahachal

Metro Apartment, Kuleshwor

Oriental Apartment Phase I, Kuleshwor

TCH Tower Phase IV, Sitapaila

TCH Tower Phase III, Pani Pokhari

Retreat Apartment, Bijeshwori

Sun City Apartment, Gothatar

Ambe Residence, Chabahil

Downtown Apartment, Dhapakhel

Silver City Apartment, Kalikasthan

Signature Apartment I, Teku

Signature Apartment II, Teku

Civil Apartment II, Dhapakhel

Guna Colony, Sina Mangal

LLP Apartment, Pani Pokhari

Vibor Apartment, Kamal Pokhari

Westar Apartment, Balkumari

DUDBC categorized the damage extent.Red：dangerous to useYellow：available after

repaired Green：safe to livePark view horizon has been damaged seriously.



Damage extentPark View Horizon, Basundhara Cityscape Club House, Hattiban TCH Phase II, Thaiba

Oriental Apartment Phase II, Kuleshwor Cityscape Block B, Hattiban Southern Height Apartment, Thaiba

Prestige Apartment, Chandol Dhumbarahi Apartment, Dhumbarahi

Central Park Apartment, Bishal Nagar TCH Tower, Lazimpat

Grande Apartment, Dhumbarahi Bhat Bhateni Apartment, Bhat Bhateni

Grande Towers, Tokha Indreni Apartment, Bhat Bhateni

LP Apartment, Lazimpat Egrace Apartment, Naxal

KL Apartment, Sano Gaucharan

Binayak Apartment, Baluwatar

Sun Rise Apartment, Nakhkhu

Imperial Apartment, Sanepa

City View Apartment, Bakhudol

Mercury Sterling Apartment, Thado Dhunga

Sun Rise Apartment, Dhobighat

Kalash Apartment, Tahachal

Metro Apartment, Kuleshwor

Oriental Apartment Phase I, Kuleshwor

TCH Tower Phase IV, Sitapaila

TCH Tower Phase III, Pani Pokhari

Retreat Apartment, Bijeshwori

Sun City Apartment, Gothatar

Ambe Residence, Chabahil

Downtown Apartment, Dhapakhel

Silver City Apartment, Kalikasthan

Signature Apartment I, Teku

Signature Apartment II, Teku

Civil Apartment II, Dhapakhel

Guna Colony, Sina Mangal

LLP Apartment, Pani Pokhari

Vibor Apartment, Kamal Pokhari

Westar Apartment, Balkumari

DUDBC categorized the damage extent.Red：dangerous to useYellow：available after

repaired Green：safe to livePark view horizon has been damaged seriously.

Park view horizon



T1: Natural period of vibration of the first mode of the structure (s)D’: Overall length of the building at the base in the direction under consideration (m)

What Nepal Building Code says (Period of Buildings)



Simplified Dominant Period for Buildings Comparing the predominant period, height and width of the

buildings with previously proposed relation/s

Predominant period is influenced by the height and width. The shapes, structures and materials effects on predominant period



Major Assumption (Concept)

Greater depth(i.e. low frequency or high period)

Shallower depth(i.e. high frequency or low period)

Basement Rock Line

Ground surfaceLow Peak Ground Acceleration (PGA)

High Peak Ground Acceleration (PGA)

Sediment Deposit



Estimating Peak Ground Acceleration (2015 Gorkha Earthquake)Accelerometer Stations and MT Survey Points



F = 0.73 Hz

PTN

F = 0.75 Hz

KATNP

F = 0.83 Hz

THM

F = 0.88 Hz

DMG

F = 1.37 Hz

TVU

F = 2.15 Hz

KTP

H/V Spectral Ratio for Accelerogram Stations



S.No Station latitude longitude EW (m/s2) NS (m/s2) UD (m/s2) PGA (gal) Intensity (MMI) IJMA Frequeny (Hz) N. Period (s)1 KATNP 27.71 85.32 1.55 1.542 1.549 155 6.357 5.321 0.75 1.332 KTP 27.68 85.27 2.548 1.536 1.14 254.8 7.147 5.752 2.15 0.473 TVU 27.68 85.29 2.288 1.647 1.383 228.8 6.976 5.659 1.37 0.734 PTN 27.68 85.32 1.281 1.507 1.339 150.7 6.312 5.296 0.73 1.375 THM 27.68 85.38 1.505 1.338 1.837 150.5 6.31 5.65 0.83 1.206 DMG 27.72 85.32 1.268 1.771 2.055 177.1 6.568 4.934 0.88 1.14

(Data source: DMG, USGS, and Takai et al.)

Interpreting PGA on the basis of Natural Period(2015 Gorkha Earthquake)

Preliminary Relationship

apg = 102.8*ln(T) + 183.35



Predominant Natural Frequency (Ground) Distribution



Predominant Period (Ground) Distribution



Estimated Peak Ground Acceleration (2015 Gorkha Earthquake)



Paudyal et al. (2012) reveal that the central Kathmandu Valley is a long period ground composed of thick sediment deposit. This is in agreement with previous research work. During the 2015 Gorkha Earthquake, most tall buildings in the Kathmandu Valley were heavily shaken, which is supposed to be due to long-periodground shaking (i.e., 3-5 s). The ground shaking was long period in the central part while shorter in the peripheral part where the basement rock is close to surface. Post-earthquake evaluation of pre-dominant period of ground and buildings at tall building locations in the Kathmandu Valley reveals that most buildings might have been shaken during 0.5 – 1.5 s dominant period of the ground motion. A very rough relationship of peak ground acceleration (PGA) with the ground natural period was established: PGA (gal) = -102.8ln(T(s)) + 183.35 A very preliminary PGA map has been proposed (using the above relationship) for the core Kathmandu Valley during the 2015 GorkhaEarthquake.

Concluding Remarks



The damage depends on the duration of resonance Possible change in predominant periods of the buildings after earthquake Preliminary micortremor measurement data might be erroneous, and they need precise check

Limitations:

Further Research Plan Precise estimation and verification of peak ground acceleration (PGA) through the use of massive aftershock data (possibly at all six accelerogramstations). Relational analysis for epicentral distance (main shock as well as aftershocks) and peak ground acceleration in the Kathmandu Valley. And finally, interpretation of liquefaction-susceptible areas (locations) on the basis of precisely estimated peak ground acceleration map.

Thank you very much!

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