Plastic Limits-Consistency Atterberg Limits | Properties of Soil | Soil Mechanics

  Consistency Atterberg Limits  

  • Liquid Limit (WL)
  • Plastic Limit (Wp)
  • Shrinkage Limit (Ws)

  Plastic Limits(Wp)  

  • It is defined as the minimum water content at which soil is in the plastic stage of consistency or behaves like a plastic material.
  • At the plastic limit, soil passes a plastic state of consistency to a semi-solid state of consistency & visa-versa.

plastic limit of different soil, Plastic Limits(Wp)

NOTE: -Plasticity in the property of soil which allows it to be deformed rapidly, without elastic rebound, without volume change, without rupture.

  • This plasticity of fine-grained soil is due to the presence charge over the surface of particles & bipolar nature of water.
  • Fine-grained does not become plastic when a nonpolarizing liquid like kerosene, Naphthalene is added to it.



  Plastic Limit Determination  

  • From a determination point of view, the plastic limit is defined as the minimum water content at which soil just begins to crumble or crack when rolled in a thread of 3 mm diameter.
  • 15 Gm air dried sample soil passing through 425μ sieve is mixed with a sufficient amount of water so as make it plastic.
  • A ball is formed with about 8 gm of this plastic soil & is rolled between fingers & a glass plate into a thread of 3 mm diameter.
  • The soil is remolded again into a ball & rolled again into the thread of 3 mm diameter up to an extent it begins to crumble.
  • The crumble thread is tested for its water content & termed as Plastic Limit (Wp).
  • An average of three tests is considered as the final result.

SubjectSoil Mechanics
UnitSoil Formation & Properties of Soil
TopicPlastic Limits- Consistency Atterberg Limits
Next TopicShrinkage Limits- Consistency Atterberg Limits
Previous TopicLiquid Limits- Consistency Atterberg Limits


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