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1. Standard Penetration Test (SPT)
• Soil Investigation Test
• Presented by: Rupam Kumar
• Department of Civil Engineering

2. Introduction
• • Standard Penetration Test (SPT) is an in-situ
test.
• • It is widely used to determine soil
properties.
• • Mainly conducted in boreholes during site
investigation.

3. Objective of SPT
• The main objectives are:
• • To determine soil bearing capacity
• • To find relative density of sand
• • To evaluate soil strength parameters
• • To obtain N-value for foundation design

4. Apparatus Required
• • Split spoon sampler
• • Borehole drilling setup
• • Standard hammer (65 kg)
• • Drop height: 750 mm
• • Drill rods
• • Measuring scale

5. Test Procedure
• 1. Borehole is drilled up to required depth.
• 2. Split spoon sampler is placed at the bottom.
• 3. Hammer of 65 kg is dropped from 750 mm
height.
• 4. Sampler is driven into soil for 450 mm.

6. N-Value Calculation
• • First 150 mm penetration is ignored (seating
drive).
• • Number of blows for next 300 mm is
recorded.
• • This recorded number is called SPT N-value.
• N = N₂ + N₃

7. Interpretation of N-Value
• N-Value Range → Soil Type
• • 0 – 4 : Very loose
• • 4 – 10 : Loose
• • 10 – 30: Medium dense
• • 30 – 50: Dense
• • >50 : Very dense

8. Applications of SPT
• • Foundation design
• • Soil classification
• • Estimation of settlement
• • Liquefaction analysis
• • Site investigation reports

9. Advantages
• • Simple and economical test
• • Suitable for sandy soils
• • Provides quick soil strength estimation
• • Widely accepted standard method

10. Limitations
• • Not reliable in soft clay
• • Results depend on equipment and operator
• • Disturbed soil sample obtained
• • Correction factors required

11. Conclusion
• • SPT is one of the most common field tests in
geotechnical engineering.
• • N-value helps in determining soil strength
and foundation safety.

12. Thank You
• Thank You
• Any Questions?