Unconsolidated Undrained Test related to Geo-technical Engineering.

1. Welcome To
Our
Presentation
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2. Presentation Topic:
unconsolidated undrained Test
Group N0: 02
Name & Id:
Md. Shahedul Islam Siddikh-14306071
Md. Mozzkkirul Islam-15106029
Saiful Islam Bappy- 15106140
Mst. Mousumy Akter- 15106144
Saiful Islam Sajjad-15106156
 S.M. Ferose Iqbal - 15206005
2

3. Types of Triaxial Tests
Is the drainage valve open?
yes no
Consolidated
sample
Unconsolidated
sample
Under all-around cell pressure c
Step 1
Is the drainage valve open?
yes no
Drained
loading
Undrained
loading
Shearing (loading)
Step 2
CD test
CU test
UU test

4. What is UU test??
• UU (unconsolidated undrained) test is type of
triaxial test. In this test:
1.The confining pressure is not zero.
2.We need to test at least three samples at
different confining pressure to obtain the
Mohr-Coulobm failure circles.
3.This is also a quick test, as it is undrained.
4.The test can be performed in any type of soil.

5. Definitions, Objectives and
Applications
Objective
• To determine the shear strength of the soil by
Unconsolidated Undrained test.
Equipment
• Triaxial Machine
• Specimen preparation equipment
• Sample extruder
• Balance
• oven
• Right-circular cylindrical specimen of cohesive soil;

6. Equipment set up

7. Significance and Applications
• A quick test to obtain the shear strength parameters of
both fine and coarse grained soils.
• The test is not applicable when the rate of construction
is slow allowing consolidation of soil.
• Hence the test is representative of soils in construction
sites where the rate of construction is very fast and the
pore waters do not have enough time to dissipate.
• Total stress parameters are obtained as portion of load
applied is also received by the water.
• Quick results. Economical testing. The designs using UU
parameters are mostly conservative.

8. Test Procedure
1. Remolded specimens are prepared in the laboratory
2. If testing undisturbed specimens retrieved from the
ground by various sampling techniques, trim the samples
into regular triaxial specimen dimensions (2.8” x 5.6”)
3. There will be a significant variation in strength of
undisturbed and remolded samples
4. Measure the diameter and length of the specimen to be
tested
5. If curing the sample (treated soils), wrap the samples in a
geotextile and then a zip bag. Place the sample in a
humidity room maintained at a relative humidity of 90%.

9. Test Procedure
6. Prior to testing, avoid any moisture loss in the sample, place
on a triaxial base (acrylic). The ends of the sample are assumed
to be frictionless.
7. The triaxial cell is placed above the sample and
required confinement is applied simulating the effect of
surrounding soil at that depth
8.The rate of strain is maintained at 1.2700 mm/min as
per ASTM specifications.
9.The data acquisition system collects real time data and
the test is stopped when there is a drop observed in
the strain versus load plot.

10. Equation of Ā
• Skempton’s pore water pressure parameter Ā was defined in
• Eq: Ā = Δud / Δσd at failure, the parameter Ā can be written as
• Ā = Āf = (Δud)f / (Δσd)f
• The general range of Āf values in most clay soils is as follows:
• Normally consolidated clays: 0.5 to 1
• Overconsolidated clays: -0.5 to 0
Major principal stress at failure (total): σ3 + (Δσd)f = σ1
Major principal stress at failure (effective) : σ1 - (Δσu)f = σ'1
Minor principal stress at failure (total): σ3
Minor principal stress at failure (effective): σ3 - (Δσu)f = σ'3
In these equations, (Δσu)f = pore water pressure at failure. The preceding derivations
show that
σ1 - σ3 = σ'1 - σ'3

11. Mohr’s circles

12. Test-1

13. Test-2

14. Test-3

16. Conclusion:
• The tests were completed on progressively
denser soil samples.
• The undrained shear strength for a dry
compacted soil specimen may range to over 50
psi.
• The first two tests had values of 45.9 psi ad
42.35psi. While the third value is 55.39 psi,
due partial saturation of the sample, the results
may not be valid.

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