SPT Based Soil Liquefaction Susceptibility Assessment: A Review

Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 3, Pages: 295-299

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

SPT Based Soil Liquefaction Susceptibility

Assessment: A Review

Sarah Tahsin Noor*, Sherajul Islam, Shaikh Mohammad Shamim Reza

University of Asia Pacific, Dhaka Bangladesh

Received: 23/01/2019

Accepted: 11/06/2019

Published: 30/09/2019

Abstract

Development projects in the low land areas are frequently carried out in Bangladesh after filled lands. Bangladesh lies in the

seismic active zone. Therefore, during the earthquake, severe shaking or liquefaction of the ground may be experienced in these

areas due to the presence of thick loose sand bed. When the loose sand is saturated and under moderate to high shear stresses,

such as beneath a foundation or sloping ground, large shear deformations or even flow failure may take place due to the loss of

shear strength accompanied by the softening. This paper presents the results of a study carried out to examine the variation of

different variable parameters in the cyclic stress-based method while evaluating the liquefaction potential. The risk of

liquefaction in Bangladesh and the issues that are needed to be addressed in evaluation in liquefaction evaluation are also

discussed. The output of the study will enable the practicing engineer to assess liquefaction susceptibility of the construction site

from the borehole data.

Keywords: liquefaction, SPT, cyclic stress ratio, cyclic resistance ratio

ground level) can be eliminated by planning an adequate

Introduction

number of basement floors. However, the basement walls

needs to be designed with special consideration to the

additional lateral pressures, thrusts and also to any changes

in the effective lateral confinements, that may result from

liquefaction in the lands adjacent to the site under

consideration.

This paper presents the results of a study carried out to

examine the variation of different variable parameters used

in the cyclic stress based method, while evaluating the

liquefaction potential. The risk of liquefaction in

Bangladesh and the issues that are needed to be addressed

in evaluation in liquefaction evaluation are also discussed.

All equations are given in the literature section [2, 3, 4, 5,

Soil profiles, in seismic active zone, demands

assessment of liquefaction susceptibility, in terms of

liquefaction potential (alternately factor of safety against

liquefaction), prior to the design of foundation for the

proposed structure. This evaluation is important in

choosing the type of foundation and in also its design with

protection against liquefaction during any earthquake

expected at that location during the life of the structure.

During liquefaction, different foundation types suffers from

different problems. If soil layer(s) at depth can liquefy

during future seismic event, shallow foundation is not

considered for supporting structures there, as it can sink

into the liquefied soil and cause tilting the structure. In case

of pile foundation, liquefaction causes two different

problems. Most importantly, pile suffers from reduction in

its capacity due to the development of negative skin friction

on the pile surface, where positive skin friction was

previously mobilized. Further, liquefied soil can pose

lateral force on the pile [1]. Thus, the drag load due to

negative skin friction needs to be considered during design

of pile in liquefaction susceptible soil. Instead, by choosing

raft foundation, sometimes liquefaction susceptible soil

layers (if at shallow depths within top 15 m below the

, 7].

Evaluation of Liquefaction Susceptibility

Liquefaction susceptibility of a soil profile can be

evaluated by different methods based on the energy, the

cyclic stress and the cyclic strain. The energy-based

approach is theoretically based on the principle that the

dissipated energy reflects both cyclic stress and strain

amplitudes, while the theory of the cyclic strain based

method is based on the fact that there might exist a

threshold volumetric strain below, which densification does

not occur. The time history of the cyclic shear strain is

estimated from the ground response analysis.

Corresponding author: Sherajul Islam, University of Asia

Pacific, Dhaka, Bangladesh. E-mail:

sherajulbd@gmail.com.

In cyclic stress based method, both the earthquake

induced loading (CSR) and the liquefaction resistance

(CRR) of soil are expressed in terms of cyclic shear stress,

Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 3, Pages: 295-299

and these two variables are compared in evaluating factor

of safety (FS) against liquefaction or liquefaction potential.

In general, soil liquefaction is expected to occur at the

location, where the stress due to earthquake loading

exceeds the resistance of the soil to liquefaction. The

equation of determining FS, basically defined by the ratio

of CRR to CSR, undergoes subsequent refinements over

past 30 years [6]. equation 1 gives the present form of FS

calculation against liquefaction:

Resistance Ratio (CRR) can also be determined by equation

3, given by Rauch [7]:



N ₁₆₀

CRR









 7.5



34 



N ₁₆₀

135

[10 .



N ₁₆₀ 45 ]

200

…

………………. (3)

Boulanger and Idriss [3] derived equation 4 for

determining CRR value for cohesionless soil with any fines

content:

FS = (CRR_M₌₇_.₅/CSR) . MSF. K . K_α

(1)

Where, CSR= calculated cyclic stress ratio generated

by the earthquake shaking; CRR = cyclic resistance ratio

for magnitude 7.5 earthquakes; MSF = magnitude scaling

factor; Kσ = correction factor for effective overburden

pressure; and Kα = correction factor sloping ground.











N ₁₆₀_c_s





N ₁₆₀_c_s







N ₁₆₀_c_s







N ₁₆₀_c_s



CRR

 exp

 





 





 





 2.8

 7.5





4 .1

126

23 .6

25 .4





















…

…………….. (4)

MSF and Kσ are to adjust CSR generated by any

earthquake magnitude to a benchmark earthquake of

moment magnitude (Mw) of 7.5 and to an equivalent σ'v of



 N ₁^60

N ₁₆₀_c_sN ₁₆₀  

01kPa, respectively.

where, Δ(N₁)₆₀is the correction for fines content in percent

.1 Cyclic Stress Ratio (CSR)

(FC) in the soil and is expressed by equation 5:

In literature, the intensity and duration of earthquake

shaking, and the density and effective overburden pressure

of the soil are considered the major influencing factors of

liquefaction phenomena, as saturated and loose

cohesionless soil liquefies due to earthquake tremor. CSR

can be estimated in two ways: the simplified procedure as

proposed by Seed and Idriss [8], and a detailed ground

response analysis.

The simplified procedure (given by equation 2) is often

used to calculate CSR generated by the earthquake shaking

in practice [4, 9, 10]:











15 .7







(5)





N ₁₆₀ exp 1 .63 

 





FC  0 .01

 FC  0 .01 

Standard penetration resistance (N₁)₆₀value is used in

this study after other corrections on the field measured

value for overburden pressure, energy ratio, borehole

diameter, rod length and the presence liner, according to

equation 6:

(

N₁)₆₀= N . C . C . C . C . C

(6)

= measured standard penetration resistance; C =

 _a_v_g

a _a_v_g

 _

 _

CSR =

 0.65 



 r_d

(2)

where, N





factor to normalize Nm to common reference effective



overburden pressure (approximately 100 kPa); C =

correction for hammer energy ratio; C = correction factor

where, τ_a_v= average equivalent uniform cyclic shear stress

caused by the earthquake and is assumed to be 0.65 of the

for borehole diameter; C = correction for rod length and

C = correction for samplers with or without liners.

maximum induced stress; a_m_a_x

peak horizontal

acceleration at ground surface generated by the earthquake;

g = the acceleration of gravity; σ_v= total vertical

^o^v^e^r^b^u^r^d^eⁿ^s^t^r^e^s^s^e^s^;^σ^ʹv = effective vertical overburden

^s^t^r^e^s^s^e^s^;^rd = Stress reduction coefficient. The simplified

procedure was verified with the case history data up to a

depth of 15 m below the ground level.

3 Variables in Determining FS against

Liquefaction

3.1 Peak ground acceleration (a

_m_a_x)

Ground movement is resulted from dispersion of

earthquake energy in waves from its hypocenter. Peak

ground acceleration (PGA) records the maximum rate of

change of speed of these movements in absence of excess

pore water pressure of liquefaction generated by the

earthquake. PGA is generally considered the best

determinate of damage in severe earthquakes. During

earthquake, ground acceleration is measured in three

directions: vertically for up-down shaking, and two

perpendicular horizontal directions. In the cases where

recorded motion were available, the larger of the two

horizontal peak components of acceleration was considered

as the a_m_a_xvalue of in the original derivation of CSR [6].

This provides a larger estimate of a_m_a_xbut considered

conservative and allowable. In the cases where recorded

.2 Cyclic Resistance Ratio (CRR)

In literature, cyclic resistance ratio for moment

magnitude of 7.5 (CRR =7.5) is formulated as a function

^o^f⁽^N1⁾ for clean sand and also for sand with different

fines content (non-plastic). While deriving the relationship

of CRR =7.5 with consideration for fines content, the SPT

blow count of silty sands is converted to equivalent clean

sand SPT blow count. Different relationships between

(

CRR =7.5) and (N ) are available in the literature [5, 7,

M 1 60

9]. The graphical representation of this relationship, given

by [9], is widely used for calculating CRRM=7.5. Cyclic

Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 3, Pages: 295-299

values are not available, peak accelerations are

recommended for estimation from attenuation relationship.

This method of determining the value of a_m_a_xis based on

the geometric mean of the two orthogonal peak horizontal

accelerations. As peak vertical accelerations are much

^s^m^a^l^l^e^r^t^h^aⁿ^amax, this component of acceleration is ignored

in the calculation of CSR. PGA of 0.5g is considered as

very high level of ground shaking, as only well-designed

buildings will survive after such an acceleration (even for a

short period of time).

Different complex variable factors, including the length

of fault, magnitude, the depth of the quake, the distance

from the epicenter, the duration of the earthquake cycle and

geology of the ground, are involved in the magnitude of

^g^r^o^uⁿ^d^a^c^c^e^l^e^r^a^tⁱ^oⁿ⁽ⁱⁿ^t^e^r^m^s^o^f^amax) resulting from a

^gⁱ^v^eⁿ^e^a^r^t^h^q^u^a^k^e^e^v^eⁿ^t^.^T^h^u^s^,^t^h^e^v^a^l^u^e^o^f^amax, during

moderate to large earthquakes, can vary significantly within

the sites those are a few kilometers apart, depending on the

geologic features and ground type of the shaked zone. An

earthquake of moderate magnitude can have the significant

^p^o^t^eⁿ^tⁱ^a^l^f^o^r^g^eⁿ^e^r^a^tⁱⁿ^g^amax larger than that of larger

magnitudes. Moreover, shallow focused earthquakes

generate stronger acceleration than deep quakes.

Furthermore, earthquakes of similar magnitude can

^g^eⁿ^e^r^a^t^e^dⁱ^f^f^e^r^eⁿ^t^amax due to variations in ground type.

functional dependence on an index of the soil properties, in

addition to the earthquake magnitude. According to their

specifications, MSF should not exceed 2.2 in the

calculation of FS against liquefaction.

4 Factor of Safety

.1 Conclusions

The soil at depth of the measured SPT blow-count

(employed in determining CRR) is predicted to liquefy

when FS ≤ l, and is predicted as non-liquefiable when FS >

l. The soil could be considered more resistant to

liquefaction if calculated factor of safety is greater [14].

However, soil that has a factor of safety slightly greater

than 1.0 may still liquefy during an earthquake, as FS

against liquefaction depends on the magnitude of amax. For

example, if a lower layer liquefies, then the upward flow of

water could induce liquefaction of the layer that has a

factor of safety slightly greater than 1. In this study, factor

of safety is evaluated for three different magnitudes of a_m_a_x

(0.1g, 0.2g and 0.3g), three different N-values (15, 25 and

30), and three fines content (less than 5%, 15% and 35%)

up to a depth of 23 m below the ground level. The results

are summarized in Table.

Table: FS against liquefaction for different a_m_a_xand SPT N

values

^.²^S^t^r^e^s^s^r^e^d^u^c^tⁱ^oⁿ^c^o^e^f^fⁱ^cⁱ^eⁿ^t⁽^rd⁾

Factor of Safety

(

N )

^amax

Stress reduction coefficient (r ) accounts for flexibility

1 60cs

FC=35%

FC=15%

FC<5%

of the soil profile as a function of depth. At a depth, r_d

varies within a range, depending on the variability at field

sites. The range of r_dvariation increases with depth, as

.1g

2 – 2.5

1.75 – 3.2 1.3 – 1.8

0.2g

1 – 1.25

0.9 – 1.6

0.66 – 0.89

2.5 – 2.9

1.2 – 1.5

3.1 – 4.2

1.6 - 2

1.1 – 1.4

.3g

.1g

≈4

1.6 - 2

noted from the r versus depth curves by Seed and Idriss

3.1 – 4.5

1.6 - 2

[8]. These curves provide the maximum and minimum

0.2g

values of r considering different soil profiles.

.3g

.1g

1.3 – 1.6

1 – 1.4

4.4 – 5.9

2.2 – 2.9

1.5 – 1.9

In literature, several linear and polynomial equations

[11, 12] were suggested for estimating the r_dvalues at

0.2g

.3g

different depths. For routine practice and noncritical

projects, the equations by Liao and Whitman [12] are

recommended for obtaining average values of r . These

It can be noted that FS is highly dependent on the

^m^a^gⁿⁱ^t^u^d^e^o^f^amax^.^D^u^rⁱⁿ^g^aⁿ^e^a^r^t^h^q^u^a^k^e^c^a^u^sⁱⁿ^g^amax of

equations [Liao] yield almost the same average value for r_d.

Minimum, maximum and average values of r_dare very

close (such as 0.95, 0.98 and 0.97, respectively for a depth

of 4 m) at shallow depths, while these values vary widely

.1g, none of (N )

may not liquefy. The same profile

1 60cs

^wⁱ^l^l^lⁱ^q^u^e^f^y^b^y^aⁿ^e^a^r^t^h^q^u^a^k^e^c^a^u^sⁱⁿ^g^amax of 0.3g.

(such as 0.62, 0.92 and 0.75, respectively for a depth of 15

m).

5 Liquefaction Risk in Bangladesh

Two devastating earthquakes that took place in

April and October of 2015, caused severe damage

and great loss of lives in Nepal, and in Pakistan and

Afganistan, respectively. The former earthquake

event of M 7.9 jolted Bangladesh several times

through northern India, and left a trail of damage in

Bangladesh with several buildings developing cracks

or tilts across the country, including capital Dhaka.

According to the historical records, Bangladesh was

affected by earthquakes since ancient times, as the

country is surrounded by five active tectonic blocks.

These recent earthquakes are due to strain energy

accumulation that have been taking place over the

years. Within the last 150 years, Bangladesh was

.3 Magnitude scaling factor (MSF)

MSF was first introduced by Seed and Idriss [13] to

scale CRR value on the plot of CRR₍_M₌₇_.₅₎versus (N ) . In

literature, several equations, as a function of earthquake

moment magnitude (M ), are available [6]. When M <7.5,

MSF is greater than 1, and when M < 7.5, MSF is less than

Idriss [13] and the revised equation by (reported in Youd et

al. [6]). On the other hand, for a given M_wof 5.5, other

equations give MSFs equal 3 or even greater than 4. It has

been noted that Seed and Idriss [13] gives the lowest values

of MSF for the M_wbelow 7.5, while the revised equation

by Youd et al. [6] gives the smallest MSF for M_wgreater

than 7.5. Later, Boulanger and Idriss [2] formulated an

equation of maximum MSF in terms of (N₁)₆₀for including

1 60

. For M of 5.5, MSF is found 1.43 and 2.2 from Seed and

Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 3, Pages: 295-299

jolted by some damaging tremors: the Mandalay

earthquake of 1858 affecting Chittagong division; the

Srimangal earthquake of 1918 affecting Sylhet; the

Bihar-Nepal earthquake of 1934 felt from Dinajpur

and Rangpur; the Assam earthquake in 1950 felt

Ethical issue

Authors are aware of, and comply with, best practice in

publication ethics specifically with regard to authorship

(avoidance of guest authorship), dual submission,

manipulation of figures, competing interests and

compliance with policies on research ethics. Authors

adhere to publication requirements that submitted work is

original and has not been published elsewhere in any

language.

throughout

Bangladesh.

Instead,

earthquake,

considered as the most destructive type of natural

disasters, are not receiving sufficient attention in

Bangladesh. New developments that are carried out

on uncontrolled filling up of wetlands, are highly

vulnerable to earthquake triggering liquefaction. This

paper has identified some issues that need to be

considered by the concerned authority:

Competing interests

The authors declare that there is no conflict of interest

that would prejudice the impartiality of this scientific work.

a) Bangladesh should have more seismic

observatory stations where earthquake moment

magnitude and ground accelerations would be

recorded. Seismic records are important to

obtain the a_m_a_xvalue while evaluation

liquefaction potential. The value of a_m_a_xis

found to vary widely from 0.11g to 0.51g due to

an earthquake tremor of M7.3 – M7.6.

b) In the evaluation of FS against liquefaction,

magnitude scaling factor (MSF) should be

considered equal 1. MSF has not yet been

studied for the soil types usually used for filling

up the wetlands. MSF is known to be affected

by several factors, including the earthquake

source characteristics, distance from the site to

the source, soil profile characteristics and depth

of the soil profile.

Authors’ contribution

All authors of this study have a complete contribution

for data collection, data analyses and manuscript writing.

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Conclusion

Liquefaction susceptibility may only be reduced by

modifying the properties of the soil, as arrangements of

recording the magnitudes of amax and Mw can be recorded

but an earthquake event is absolutely inevitable. The

seismic records will aid in evaluation of FS with regional

data and allow to design a soil stabilization technique (by

using additives) for minimizing the probability of

liquefaction. The soil condition of (N1)60cs equal 15 is

quite critical and unsafe during amax greater than 0.2g. On

the other hand, the soil condition of (N1)60cs equal 25 may

be improved from liquefaction point of view by increasing

percent fines during filling. However, the condition of

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(

N1)60cs equal 30 is found quite stable even under amax of

.3g.

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for Predicting Surface Displacement Due to

Acknowledgment

Authors are very grateful to all the instructors,

employees and other stuffs of The University of Asia

Pacific for their cordial help and support.

Liquefaction-Induced

Lateral

Spreading

Earthquakes,Ph.D.dissertation, Chapter 7,Faculty of the

Virginia Polytechnic Institute and State University,VA.

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Sherajul Islam received his Master of

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Science in Civil Engineering from

Stamford University Bangladesh;

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Dhaka; in 2012. He has more then 6

years working experience on Water

Supply,

impact

Sanitation,

assessment

environmental

and Waste

[

10]

Management sectors. His research

interests are in geotecnical engineering,

environmetal polution control (air and

noise), solid waste management,

recycling of waste for sustainable

development etc.

[

11]

12]

Shaikh Mohammad Shamim Reza

received his Master of Engineering in

Civil Engineering at University of Asia

Pacific, Dhaka; in 2018 Also received

his Bachelor of Science in Civil

Engineering from Stamford University

Bangladesh , Dhaka; in 2012. Currently

he is doing Master of Business

Administration at Army Isntitute of

Business Administration, Savar under

Bangladesh University of Professionals,

[

13]

14]

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and soil liquefaction during earthquakes, Earthquake

Engineering Research Institute, Oakland, CA, 134

pages.

Ishihara, K. (1993). Liquefaction and flow failure

during earthquakes, Geotechnique, 43 (3), 351-415.

Dhaka. He has more then

6 years

working experience on Water Supply,

Sanitation and Waste Management

sectors. His research interests are in

hazardous/medical waste management,

municipal waste management, recycling

of waste for sustainable development

etc.

Author Profile

Dr. Sarah Tahsin Noor completed her

PhD. in Civil Engineering from

Concordia University, Montreal, Canada

in 2011. She completed her Masters in

Civil Engineering from Concordia

University in 2005. She received the

prestigious Alexander Graham Bell

NSERC Canada Graduate Scholarship in

her PhD program. She was also awarded

with the Doctoral Research Scholarship

from Quebec Government and four

scholarships from Concordia University.

Earlier, she completed her bachelor in

Civil Engineering from BUET, Dhaka in

002. Her present research topic

includes pile foundation, unsaturated

soil mechanics, problematic soils

(including sensitive clay and collapsible

soil), numerical modeling, etc. Sarah is a

member of Golden Key International

Honor Society.