Applications of Vane Shear Test in Geotechnical soil investigations

2. Strength of different materials
Steel Concrete Soil
Tensile strength Compressive strength Shear strength

3. Embankment
Strip footing
Shear failure of soils
Soils generally fail in shear
At failure, shear stress along the failure surface
(mobilized shear resistance) reaches the shear strength.
Failure surface
Mobilized shear
resistance

4. Retaining
wall
Shear failure of soils
At failure, shear stress along the failure surface
(mobilized shear resistance) reaches the shear strength.
Soils generally fail in shear
Failure
surface
Mobilized
shear
resistance
Retaining
wall

5. Other laboratory tests include,
torsional ring shear test, plane
strain triaxial test, laboratory vane
shear test, laboratory fall cone test
Determination of shear strength parameters of
soils (c, φ or c’, φ’)
Laboratory tests on
specimens taken from
representative undisturbed
samples
Field tests
Most common laboratory tests
to determine the shear strength
parameters are,
1.Direct shear test
2.Triaxial shear test
3.Vane shear test
4.Compression test
1. Vane shear test
2. Torvane
3. Pocket penetrometer
4. Fall cone
5. Pressuremeter
6. Static cone penetrometer
7. Standard penetration test

6. Vane Shear Test

7. What does Vane Shear Test measure?
o Shear strength
A term used to describe the maximum strength of soil at which
point significant plastic deformation or yielding occurs due to an
applied shear stress.
o Undrained shear strength
Refers to a shear condition where water does not enter or leave the
cohesive soil during the shearing process.
o Remolded undrained shear strength
Is the peak undrained shearing resistance measured during the
initial rotation of the vane.
o Peak undrained shear strength
Is the shear strength after significant failure and remolding of the
initial soil structure.
o Sensitivity
Is the effect of remolding on the consistency of cohesive soil.

8. PLAN VIEW
Vane shear test
This is one of the most versatile and widely used devices used for
investigating undrained shear strength (Cu) and sensitivity of soft clays
Bore hole
(diameter = DB)
h > 3DB)
Vane
D
H
Applied
Torque, T
Vane T
Rupture
surface
Disturbed
soil
Rate of rotation : 60
– 120
per minute
Test can be conducted at 0.5 m
vertical intervals

9. Vane shear test
Since the test is very fast,
Unconsolidated Undrained
(UU) can be expected
T = Ms + Me + Me = Ms + 2Me
Me – Assuming a uniform
distribution of shear strength
∫=
2
0
).2(
d
ue rCrdrM π
2
0
32
0
2
3
22
d
u
d
ue
r
CdrrCM 





== ∫ ππ
1283
2 33
dCdC
M uu
e
ππ
=





=
d/2d/2
Cu
Cu
Cu
h

10. Surface area of the cylinder = 2πrh = πdh

11. Vane shear test
Since the test is very fast,
Unconsolidated Undrained
(UU) can be expected
Ms – Shaft shear resistance along
the circumference
22
2
hd
C
d
dhCM uus ππ ==
2
122
32
×+=
dChd
CT u
u
π
π






+=
62
32
dhd
CT uπ






+
=
62
32
dhd
T
Cu
π
T = Ms + Me + Me = Ms + 2Me
Cu
Cu
h

12. Vane shear test
Since the test is very fast,
Unconsolidated Undrained
(UU) can be expected
T = Ms + Me + Me = Ms + 2Me
Me – Assuming a triangular
distribution of shear strength
d/2d/2
Cu






+
=
82
32
dhd
T
Cu
π
Cu
Cu
h

13. Vane shear test
Since the test is very fast,
Unconsolidated Undrained
(UU) can be expected
T = Ms + Me + Me = Ms + 2Me
Me – Assuming a parabolic
distribution of shear strength






+
=
20
3
2
32
dhd
T
Cu
π
d/2d/2
CuCu
Cu
h

14. 





+
=
42
32
dhd
T
Cu
βπ
Generally, We have to use this
formula for accounting
By inserting value according to
the shear shape.
u
C
β

15. Vane shear test
Since the test is very fast,
Unconsolidated Undrained
(UU) can be expected
After the initial test, vane can be rapidly
rotated through several revolutions
until the clay become remoulded
τpeak
τultimate
τ
Shear displacement
StengthUltimate
StengthPeak
ySensitivit =
Cu
Cu
h

16. Some important facts on vane shear test
 Insertion of vane into soft clays and silts disrupts the natural soil
structure around the vane causing reduction of shear strength
 The above reduction is partially regained after some time
 Cu as determined by vane shear test may be a function of the rate
of angular rotation of the vane

17. Correction for the strength parameters obtained
from vane shear test
Bjerrum (1974) has shown that as the plasticity of soils
increases, Cu obtained by vane shear tests may give
unsafe results for foundation design. Therefore, he
proposed the following correction.
Cu(design) = λCu(vane shear)
Where, λ = correction factor = 1.7 – 0.54 log (PI)
PI = Plasticity Index
Overconsolidation Ratio:

18. 2006 –– 2007 Pre-Treatment
Phase
South Fraser Perimeter Road
Geotechnical Investigation
Data Report
South Delta (Volue 2)
Date: November 27, 2007
File #: 03-1411-095B/4600/4630
Version: FINAL
Geotechnical Investigation Report done by using
Vane Shear Test

20. FIELD VANE TESTING RESULTS
Small vane – 11.0cm x 5.0cm – Constant = 0.20
Medium vane – 13.0cm x 6.5cm – Constant = 0.1
Large vane – 17.2cm x 8.0cm – Constant = 0.05

21. = 7.75
Small vane – 11.0cm x 5.0cm Max. Torque (T) =
22 N.m PI=60 dry=17.30 KN/m3Ɣ
Cu(design) = λCu(vane shear) = 0.74 * 24 = 17.67
kPa
OCR
kPa

22. FIELD VANE TESTING RESULTS

23. FIELD VANE TESTING RESULTS

24. FIELD VANE TESTING RESULTS

25. FIELD VANE TESTING RESULTS

26. FIELD VANE TESTING RESULTS

27. FIELD VANE TESTING RESULTS

28. FIELD VANE TESTING RESULTS

29. FIELD VANE TESTING RESULTS

30. FIELD VANE TESTING RESULTS

31. FIELD VANE TESTING RESULTS

32. FIELD VANE TESTING RESULTS

33. FIELD VANE TESTING RESULTS

34. According to FHWA Geosynthetic Design and Construction
Guidelines
(Berg, et. al., 1998)
Section No. 5.6
“subgrade undrained shear strength must be not less than about 90
kPa (CBR < 3). “

35. From the results of vane shear test, we summarized the following
notes:
-The major type of soil is Medium and soft (except in two results -
Stiff) .
-All Cu values (except AH06-308B) is less than 90 Kpa, which mean
that subgrade should be treated and improved.
-The project is 40 km Highway located close to the riverbank.
Summarized notes:

36. - Using Geotextile Placement as solution for separating the weak
subgrade away from the sub-base, base course and other
pavement layers and keep it away from ground water.
Recommendations:

37. - Refill the sub-base course by forming embankment with good
compaction according to specifications with high quality materials
the subgrade materials with other high quality materials or adding
aggregate , additive to improve the quality of subgrade materials.
Recommendations:

38. - Spreading Geogrid reinforcement sheets on the top surface of the
sub-grade and in the base course (if necessary).
Recommendations:

39. - Protect the sloped sides of embankment with replacing of Geogrid
reinforcement sheets specially at the side of sea and pouring
concrete slabs or placing precast concrete tiles on the outer slope.
Recommendations: