Standard Penetration Test

Standard Penetration Test

Standard Penetration Test (S.P.T) (IS 2131)

  • It is used to determine the Relative density of undisturbed sand and silt, consistency of clay.
  • Split spoon samples are used for this test.
  • The sample is first driven by light blows of the hammer to a seating penetration of 15cm than the sample is driven under full blows of 65kg with free fall of 75cm hammer to additional penetration of 30cm.
  • The number of blows required for 30cm penetration is known as SPT N value known as “Standard Penetration Resistance”. But „N‟ can‟t be more than 50.
  • The average value of N is calculated from the depth of footing to 2times of the width of footing.
  • For the average value of N, any value greater than 50% of the average value is discarded
  • The N value if underestimated at shallow depth and overestimated at large depth.

Dilatancy Correction or Submerge Correction ⟹ Only applicable to very fine sand or silty sand, below the water level when, the reason is, as the soil is fine during driving the resistance due to excess pore pressure increases, as excess pore pressure is unable to dissipate immediately. (-ve pore pressure in saturated fine sand) this correction is always applied after the overburden correction.

Standard Penetration Test

Standard Penetration Test

Previous articlePlate load Test
मैं रावन, लंका का राजा, मैं वह रावण हूं जिसने अपने सीस रूपी पुष्प चढ़ा चढ़ा कर उमापति महादेव की पूजा की है। जब मेरा हाथ खड़क की ओर जाता है तो आसमान में लोकपाल भय से कांपते हैं। जिन भुजाओं ने स्वयं कैलाश को उठा दिया था उस भुजाओं के फड़कने मात्र से देवता गांधार और नक्षत्र भी भय से सांस लोग लेते हैं।


Please enter your comment!
Please enter your name here