Question

In the Standard Penetration Test, the split spoon sampler is penetrated into soil stratum by giving blows from a drop weight whose weight (in kg) and free fall (in cm) are respectively
1. 65 and 75
2. 75 and 65
3. 65 and 30
4. 30 and 65

Answer 1

Correct Answer - Option 1 : 65 and 75

Explanation:

Standard Penetration test: Standard penetration test can be used to determine:

(i) Relative density of sand

(ii) Angle of internal friction

(iii) Unconfined compressive strength of clays

(iv) Ultimate bearing capacity based on shear criteria

(v) Load carrying capacity of the pile

Procedure:

(i) This test is conduct at a regular interval of 2-5 m or at the change of stratum

(ii) To conduct this test, a borehole of 55-150 mm is made and a split spoon sampler is used which has tubular shape with 35 mm inner dia, 50.5 mm outer dia, and 650 mm length.

(iii) The sampler is driven in the soil by a standard hammer of weight 65 kg and height of free fall 75 cm.

(iv) The number of blows required for penetration of 300 mm is designated as the standard penetration value.

(v) The test is conducted in three stages having 150 mm penetration each. The number of blows for the first 150 mm penetration is ignored and the number of blows in the last 300 mm penetration is noted and called the observed SPT number.