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Building design: Buildings that are not

designed for earthquake loads suffer

more

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no significant structural damage occurred, even glass is intact

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The solid building tilted as a rigid body and the raft

foundation rises above the ground.

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Nepal Bihar 1934

Narrow escape of Tinsukia Mail Hanginging railway track

Burma-India earthquake 1988

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Sand blow in mud flats used for salt production southwest of Kandla Port, Gujarat

Sand Boil: Ground water rushing to the surface due to liquefaction

JAPAN GREAT EQ 2011

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Wide open cracks showing prominent

displacement affecting the Malya-Bhuj

road near Surajbadi. This is an example

of 'lateral spread' consequent to

earthquake induced liquefaction of the

underlying marshy tract of Gulf of

Kutch

Lateral spreading due to

liquefaction leading to

submergence of part of rail-road

embankment in the Gulf of Kutch

near Naolakhi Port.

EFFECTIVE DAMAGE DUE TO LIQUEFACTION Cont…

2011 JAPAN EQ

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2011 JAPAN EQ

Predicting Liquefaction Resistance

Design of new structures

Retrofitting of existing structures

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Liquefied soil has residual strength

and exhibits complexStress-strain behavior

3.16 LIQUEFACTIONLiquefaction is a state (primarily) in saturated

cohesionless soil wherein the effective shear

strength is reduced to negligible value for all

engineering purpose due to pore pressure caused

by vibrations during an earthquake when they

approach the total confining pressure. In this

condition the soil tends to behave like a fluid

mass.

IS:1893-Part-I

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Liquefaction Susceptibility of Gravels.

(WSDOT Geotechnical Design Manual)

*No specific guidance regarding susceptibility of gravels

to liquefaction is currently available.

*The primary reason why gravels may not liquefy is that

their high permeability frequently precludes the

development of undrained conditions during and after

earthquake loading.

*When bounded by lower permeability layers,

however, gravels should be considered susceptible to

liquefaction and their liquefaction potential evaluated.

*A gravel that contains sufficient sand/silt to reduce its

permeability to a level near that of the sand, even if not

bounded by lower permeability layers, should also be

considered susceptible to liquefaction

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6.3.5.2, Page 14 of IS:1893-Part-I

In soil deposits consisting of submerged loose sands

and soils falling under classification SP with standard

penetration N-values less than 15 in seismic Zones

III, IV, V and less than 10 in seismic Zone II, the

vibration caused by earthquake may cause liquefaction

or excessive total and differential settlements.

• Such sites should preferably be avoided while locating

new settlements or important projects.

• Otherwise, this aspect of the problem needs to be

investigated and appropriate methods of compaction

or stabilization adopted to achieve suitable N-values

as indicated in Note 3 under Table 1. (next slide)

• Alternatively, deep pile foundation may be provided

and taken to depths well into the layer which is not

likely to liquefy.

Note 3.Desirable minimum field values of N are as follows—

Note 4 The above values of N (corrected values) are at the

founding level and the allowable bearing pressure shall be

determined in accordance with IS 6403 or IS 1888.

For values of depths between 5 m and 10 m, linear interpolation is recommended

Note 3 under Table 1

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4. Marine clays and other sensitive clays are

also known to liquefy due to collapse of soil

structure and will need special treatment

according to site condition.

NOTE — Specialist literature may be referred for

determining liquefaction potential of a site.

If soils of smaller N-values are met, compaction may

be adopted to achieve these values or deep pile

foundations going to stronger strata should be used.

2011 JAPAN EQ

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•The piles should be designed for

lateral loads neglecting lateral

resistance of soil layers liable to

liquefy.

IS:1893-Part-I

2011 JAPAN EQ

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COLLAPSE OF PILED STRUCTURES IN EARTHQUAKES

Million Dollar Bridge after 1964Alaska earthquake

Showa Bridge after 1964

Niigata earthquake

Building in Kobe after

1995 earthquake

1964

19951999 2001

Bridge in Taiwan after 1999

Chi-Chi earthquake Kandla port building after

2001 Bhuj earthquake

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Suitably intense earthquake shakes

Loose, saturated sand

Grain structure tends to consolidate to more compact

packing

Process being very rapid

No pore water pressure dissipation

Effective stress becomes zero

Deposit liquefies

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Liquefaction

Most importantInterestingComplexControversial

Soil deformations caused by

Monotonic

TransientRepeated disturbances

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Liquefaction Susceptibility

Historical CriteriaGeologic Criteria

Compositional CriteriaState Criteria

(stress and density)

Liquefaction Zones are areas meeting one

or more of the following:

1. Areas where liquefaction has occurred during

historical earthquakes.

2 . Areas of un-compacted or poorly compacted fills

containing liquefaction-susceptible materials that

are saturated, nearly saturated, or may be expected

to become saturated.

3. Areas where sufficient existing geotechnical data

and analyses indicate that the soils are potentially

susceptible to liquefaction.

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4. For areas where geotechnical data are lacking zones are delineated using one or more of the following criteria:

• a) Areas containing soil of late Holocene age (less than 1,000 years old, current river channels and their historical flood plains, marshes, and estuaries) where the groundwater is less than 40 feet (12.2 m) deep and the anticipated earthquake peak ground acceleration (PGA) having a 10% probability of being exceeded in 50 years is greater than 0.1g.

• b) Areas containing soils of Holocene age (less than 11,000 years old) where the groundwater is less than 30 feet (9.2 m) below the surface and the PGA (10% in 50 years) is greater than 0.2g.

• c) Areas containing soils of latest Pleistocene age (11,000 to 15,000 years before present) where the groundwater is less than 20 feet (6.1 m) below the surface and the PGA (10% in 50 years) is greater than 0.3g.

Quantitative evaluation of

liquefaction hazard potential is not required:

• If the estimated maximum-past-, current-, andfuture-ground-water-levels are determined to bedeeper than 15m below the existing ground surfaceor proposed finished grade liquefaction assessmentsare not required.

• For shallow foundations , liquefaction evaluationmay be omitted when the saturated sandy soilsare found at depths greater than 15 m. (Eurocode8)

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EARTHQUAKE SAFE CONSTRUCTION OF MASONRY BUILDINGS:

Simplified Guideline for All New Buildings in the

Seismic Zone V ( & IV)

of India by P r e p a r e d b y : Professor Anand S. Arya and Jnananjan Panda,

for National Disaster Management Division, Prepared under the GoI – UNDP

Disaster Risk Management Programme

• In sandy soils with high water table within

8m (5m for zone III) depth below ground

level, which may get liquefied during

earthquake of MSK intensity VIII to IX,

(MSK intensity VIII, for zone IV, MSK

intensity VII, for zone III) pile foundation

need to be used in consultation with the

Structural/ Geotechnical Engineer.

Quantitative evaluation of

liquefaction hazard potential is not required:

• If the corrected standard penetration blow count, (N1)60, is greater than or equal to 30 in all samples of clean sands with a sufficient number of tests, liquefaction assessments are not required.

• If cone penetration test soundings are made, the corrected cone penetration test tip resistance, qc1N, should be greater than or equal to 160 in all soundings in sand materials.

• depth-corrected normalized cone penetration

resistance values qc1N > 175, or stress-corrected shear

wave velocity VS1 > 230 m/sec (755 ft/sec) are

considered of sufficient density to pose little risk of

liquefying.

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Seed et al, 1985, state

• that soil layers with a normalized SPT blow

count [(N1)60] less than 22 have been known

to liquefy.

• Marcuson et al, 1990, suggest an SPT value

of [(N1)60] less than 30 as the threshold to

use for suspecting liquefaction potential.

Liquefaction has also been shown to occur

if the normalized CPT cone resistance (qc)

is less than 157 tsf (15 Mpa) (Shibata and

Taparaska, 1988).

• EURO CODE 8 –part5

• (8) The liquefaction hazard may be neglected when α⋅S < 0,15 and at least one of the following conditions is fulfilled:

• - the sands have a clay content greater than 20% with plasticity index PI > 10;

• - the sands have a silt content greater than 35% and, at the same time, the SPT blow count value normalised for overburden effects and for the (N1)60

> 20;

• - the sands are clean, with the SPT blow count value normalised for overburden effects and for the energy ratio (N1)60 > 30.

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Evaluation of Liquefaction

Susceptibility

Cyclic Stress

Approach

CyclicStrain

Approach

Other approaches :

Energy Dissipation,

Probabilistic approach etc.

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Cyclic Stress Approach

Earthquake Loading Cyclic Shear stresses

Liquefaction resistance Cyclic shear stresses

Loading > Resistance Liquefaction occurs

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Cyclic Stresses Induced

Cyclic resistance Available

• Laboratory Testing

• Field Testing

Characterization of Earthquake Loading

amax =PEAK GROUND ACCELERATION

Stresses Induced in the Soil

g = Acceleration due to gravity; = Unit weight of soil

maxmax .ag

h

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h

max=(h/g)amax

h

Maximum Shear Stress at a Depth for a Rigid Soil Column

amax

maxmaxmax .. ag

hrr ddact

rd = Stress reduction factor

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dav rag

hmax65.0

Seed and Idriss (1971) formulated the following equation for

calculation of CSR:

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Evaluation of Liquefaction Resistance

Laboratory Tests Dynamic/Cyclic Triaxial Tests Cyclic Simple Shear Tests

Field Tests SPT CPT Shear Wave Velocity BPT

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Field Testing

Depositional and environmental history is

preserved

SPT

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This equation is valid for (N1)60 less than 30 and may be used in

spreadsheets.

Thomas F. Blake (Fugro-West, Inc., Ventura, Calif., written

commun.) approximated the simplified base curve plotted on

Figure 2 by the following equation 4:

where CRR7.5 is the cyclic resistance ratio for magnitude 7.5

earthquakes; x = (N1)60; a = 0.048; b = -0.1248; c = -0.004721;

d = 0.009578; e = 0.0006136; f = -0.0003285; g = -1.673E-05; and

h = 3.714E-06.

This equation 4 is valid for (N1)60 less than 30 and may be used in

spreadsheets.

Robertson and Wride (this report) indicate that Equation 4 is not

applicable for (N1)60 less than three.

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where Nm is the measured standard penetration resistance,

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Pa=100kPa

The advantages of using the SPT to evaluate the liquefaction potential are as

follows:

Groundwater table: A boring must be excavated in order to perform

the standard penetration test. The location of the groundwater table can be

measured in the borehole, which can then be used to monitor the ground

water level over time.

Soil Type: In clean sand, the SPT sampler may not be able to retain a

soil sample. But for most other types of soil, the SPT sampler will be able to

retrieve a soil sample. The soil sample retrieved in the SPT sampler can be

used to visually classify the soil and to estimate the percent fines in the soil.

Relationship between N value and liquefaction potential: In general,

the factors that increase the liquefaction resistance of a soil will also increase

the N from the SPT. There have been plenty of case histories dealing with N

values and liquefaction dating back from the time of Nigata earthquake.

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FS= (CRR7.5/CSR). MSF. Kσ . Kα

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Revised Seed magnitude scaling factor is

Atmospheric pressure Pa = 100 kPa =1 atm

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Zone of liquefaction in the field

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EUROCODE 8 PART5

If the field correlation approach is used, a soil shall be

considered susceptible to liquefaction under level ground

conditions whenever the earthquake-induced shear

prEN 1998-5:2003 (E)18 stress exceeds a certain fraction λ

of the critical stress known to have caused liquefaction in

previous earthquakes.

NOTE The value ascribed to λ for use in a Country may be

found in its National Annex.

The recommended value is λ = 0.8, which implies a safety

factor of 1.25.

As a final comment on the assessment of liquefaction

hazards, it is important to note that soils composed of

sands, silts, and gravels are most susceptible to

liquefaction while clay soils generally are not

susceptible to this phenomenon.

The curves in Figure 4 are valid for soils composed

primarily of sand.

The curves should be used with caution for soils with

substantial amounts of gravel. Verified corrections for

gravel content have not been developed; a geotechnical

engineer, experienced in liquefaction hazard

evaluation, should be consulted when gravelly soils are

encountered.

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