What Is the Penetration Test?

1. 1. The Standard Penetration Test.
   2. The Cone Penetration Test.

What is the SPT Test?

• SPT full name is Standard Penetration Test. The meaning of SPT test is to determine the penetration resistance of the soil.
• The standard penetration test is coming under the category of penetrometer tests.
• An empirical penetration correlation is derived between the soil properties and the penetration resistance.
• This test (IS: 2131-1981) is performed in a clean hole 55 to 150mm (millimeter) in dia
• A casing or drilling mud can be used to support the sides of the hole. A thick-wall split-tube sampler, 50.8 mm OD and 35 mm ID, is driven into the undisturbed soil into the bottom of the hole under the blows of a 63.5 kg drive weight with 75 cm free fall.
• The minimum open length of the sample should be 60 cm.

Procedure for Standard Penetration Test:

• Test procedure: The SPT test procedure involves the split tube sampler, commonly known as split spoon sampler resting on the bottom of the borehole is allowed to sink under its own weight.
• It is then seated 15 cm with the blows of the hammer falling through a height of 75 cm. Then, the split spoon sampler is further driven by 30 cm or 50 blows.
• The number of blows required to affect each 15 cm penetration is recorded.
• The first 15 cm of the drive is considered to be seat drive.
• The total blows necessary for the second and third 15 cm of penetration is termed as the penetration resistance N.
• In case the split spoon sampler is driven less than 45 cm (total), then the penetration resistance will be for the last 30 cm of penetration.
• The whole sampler may sometimes sink under its own weight when very soft subsoil stratum is encountered.
• Under these conditions, it might not be necessary to give any blow for a sampler, and SPT value should be indicated as zero.
• Corrections to Be Observed N Values.
• Overburden Pressure Correction by Other Workers.
• Correlation of N with Soil Properties.

#1. Corrections to Be Observed N Values-

• Correction for Overburden.
• Correction for Dilatancy/submergence.

#1a. Correction for Overburden-

#1b. Correction for Dilatancy/submergence-

#2. Overburden Pressure Correction by Other Workers-

• N 0 = Corrected Value for Overburden Effect
• N = Actual Value
• σ = Effective Overburden Pressure (Not Exceed 282 kN/sq.mm)

• Cn = Normalizing Factor
  • = 0.77 log10 (2000/σ)--------------------------------------- (3)
• σ = Effective overburden pressure (kN/Sq.m) at the test level.

• Here again at σ = 100 kN/Sq.m, Cn = 1
• σ = 50 kN/Sq.m, Cn = 1.141
• σ = 400 kN/Sq.m, Cn = 0.5

Correlation of N with Soil Properties:

• Ø = 25 + 0.15 Id , with fine greater than 5%
• Ø = 30 + 0.15 Id, with fine less than 5%

Efficiency of Standard Penetration Testing:

• Hammer Efficiency.
• Length of Drill Rod.
• Sampler.
• Borehole Diameter.

Advantages and Disadvantages of Standard Penetration Test

Advantages of Standard Penetration Test

1. This very simple and economical.
2. This test provides a representative sample 0for visual review.
3. Actual soil behavior is accessed through the Standard Penetration Test values.
4. The method will help to penetrate dense fills and layers.
5. The test may be applied for a variety of soil conditions.

Disadvantages of Standard Penetration Test

1. The results will vary because of any operator or mechanical variability or drilling disturbances.
2. Teat very costly also time-consuming.
3. The test results from the Standard Penetration Test can't be reproduced.

What Is Meant by Standard Penetration Test?

How Is Standard Penetration Test Calculated?

What Is SPT Drilling?

Standard Penetration Test

What Is SPT N Value in Soil Test?

What Is SPT Boring?

Standard Penetration Test N Value

Standard Penetration Test Procedure

What Is N Value of Standard Penetration Test?

Standard Penetration Test of Soil

How Do You Interpret SPT and Value?

What Is N Value in Soil Testing?

Standard Penetration Test Equipment

What Is SPT Machine?

How SPT Is Done?

Why SPT Test Is Done?

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