The test consists of driving a standard 50-mm outside diameter
thickwalled sampler into soil at the bottom of a borehole, using
repeated blows of a 63.5 kg hammer falling through 760 mm. The
SPT N value is the number of blows required to achieve a
penetration of 300 mm, after an initial seating drive of 150 mm.
|
The requirements to conduct SPT are: |
|
1. Standard Split Spoon Sampler |
|
2. Drop Hammer weighing 63.5kg |
|
3. Guiding rod |
|
4. Drilling Rig. |
|
5. Driving head (anvil). |
|
Precautions taken for Standard Penetration Test |
|
1. Split spoon sampler must be in good condition. |
|
2. The cutting shoe must be free from wear and tear |
|
3. The height of fall must be 750mm. Any change from this will affect the ‘N’ value. |
|
4. The drill rods used must be in standard condition. Bent drill rods are not used. |
|
5. Before conducting the test, the bottom of the borehole must be cleaned. |
