SHANSEP

SHANSEP
((Stress History and Normalized Soil Engineering 
y
g
g
Properties) 

Ladd and Foott (1974)
(
)

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Present Design Practice
Present Design Practice
• Phi = 0 method to evaluate the stability of 
y
saturated clay foundation
• Phi = 0 method is considered the most critical 
conditions of no drainage With drainage the
conditions of no drainage. With drainage the 

foundation becomes stronger.
• For very stiff overconsolidated clays 
drainage reduces foundation strength
drainage reduces foundation strength

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Phi = 0 Method of Analysis
Phi = 0 Method of Analysis
• No drainage during loading  undrained 
shear strength constants irrespective of the 
g
p
applied stress
• Limit equilibrium method of analysis 
Limit equilibrium method of analysis  phi = 
phi =
0, c = su
• su is a function of water content
• su is determined by FV, U, or UU

is determined by FV U or UU

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Factors Affecting 
Undrained Shear Strength
• Sample Disturbance  reduced effective 
g
stress   20 – 50% strength reduction
• Strength and Stress‐Strain Anisotropy
– Inherent Anisotropy: differences of soil structure, 
I h
tA i t
diff
f il t t
e.g., varved clays (alternate layer of silt and clay)
– Stress induced Anisotropy: rotation of principal 
stresses during shear

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• Reduction of undrained shear strength
• Increased shear strain
Increased shear strain at failure
at failure

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Factors Affecting 
Undrained Shear Strength
• Strain‐Rate Effect: one log cycle decrease in 
i
ff
l
l d
i
strain rate  10 ± 5% decrease in su
– Due to plasticity and creep susceptibility

– Undrained creep during shear 
p
g
increased pore 
p
water pressure  decreased effective stress 
decreased shear strength
– Slower strain rate  more creep  lower 
strength
– UU strain rate 60%/hr  1.2 – 1.3 x strength at 
strain rate 0.5%/hr
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Normalized Behavior
Normalized Behavior

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Normalized Behavior
Normalized Behavior

• Minor variation in testing procedures
• Heterogeneity in soil deposits, e.g., water content variation
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Normalized Soil Parameter (NSP) 
Concept

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NSP: Laboratory Testing Technique
NSP: Laboratory Testing Technique

Undisturbed sample
Undisturbed sample

OCR 1
OCR = 1
Overconsolidated with
Known OCR

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NSP: Laboratory Testing Technique
NSP: Laboratory Testing Technique
• Consolidated by 1.5x, 2x, and 4x 
ld db
d
vm 
measure su/vc  constant for normalized 
behavior, if not constant NSP method is not 
applicable
• To obtain su/vc  vs OCR
– Use minimum 
Use minimum vc  as the laboratory 
as the laboratory vm
– Perform tests at OCR 2 ± 0.5, 4 ± 1, 6 ± 2  

• Must
Must know insitu

know insitu stresses and 
stresses and vm, high 
high
quality of consolidation test
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SHANSEP Method of Design
SHANSEP –
Method of Design
1. Subdivide the soil profile into component 
bdi id h
il
fil i
deposits based on boring logs, FV data, visual 
classification, etc.
2. Obtain good undisturbed samples 
g
p
determine insitu stresses and 
preconsolidation pressures 

p
p
check whether 
NSP concept is applicable
3 Decide the type of test and the range of 
3.
Decide the type of test and the range of
required OCR
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SHANSEP Method of Design
SHANSEP –
Method of Design
4. Reconsolidate the sample to the virgin 
p
reduce the stress to 
compression curve 
give the required OCR  perform the shear 
tests  obtain the required NSP from these 
tests 

obtain the required NSP from these
tests
5. Apply the NSP values to the soil profile (Step 
l h
l
h
l
fl (
1 and 2) to get the distribution of strength

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