To determine the shrinkage limit of a cohesive soil sample.

Object: To determine the shrinkage limit of a cohesive soil sample.

Standard:

AASHTOT90-86

ASTMD427-82

BS1377:part 4

Apparatus:

• Shrinkage dish
  
• Moisture containers
  
• Spatula
  
• Evaporating dish
  
• Electronic balance sensitive to 0.01gm
  
• Thermostatically controlled oven
  
• No. 40 sieve
  
• Distilled water
  
• Graduated cylinder
  
• Mercury (Hg)
  

Theory:

• Soil mass shrinks as moisture is gradually lost from the soil. A stage will come at which more loss of moisture will result in no further volume change. The water content at which the volumetric change of soil mass stops, is called shrinkage limit.
  
• The shrinkage limit (w_s) of a soil sample is calculated by using following formula:
  

Where,

𝑆ℎ𝑟𝑖𝑛𝑘𝑎𝑔𝑒 𝐿𝑖𝑚𝑖𝑡(𝑤𝑠) = 𝑤 − [

𝑣 − 𝑣𝑓

𝑤𝑠

𝛾𝑤 ∗ 100]

W_o = water content

W_s = weight of dry soil (gm) V_o = volume of wet soil (cm³) V_f = volume of dry soil (cm³)

Procedure:

1. Take about 200g of cohesive soil sample and pass it through No:40 sieve, mix it thoroughly with distilled water in the evaporation dish so that uniform soil paste is formed. The water in the soil paste should be somewhat above the liquid limit.
   
2. Clean the mould thoroughly and apply a thin film of silicone grease or petroleum jelly to its inner faces to prevent the soil adhering to the mould. Note the weight of empty shrinkage dish.
   
3. Find the volume of empty shrinkage dish. This is the initial volume or the volume of wet soil which is to be placed in this dish.
   
4. Fill the shrinkage dish with soil paste in three layers. In each layer the shrinkage dish should be tapped gently on the firm base until all the voids and air bubbles are removed. Level off the surface with spatula. Note the weight of shrinkage dish filled with wet soil.
   
5. Place the shrinkage dish in the oven for 24 hours at 105C for drying and shrinkage of soil mass.
   
6. After 24 hours, take out the shrinkage dish from the oven and note the weight of shrinkage dish filled with dry soil.
   
7. Take out the shrunk soil mass (dry soil cake) from the shrinkage dish and determine the volume of this dry soil cake.
   
8. The dry soil mass is put into the glass cup filled with mercury and submerge it with the help of three prongs glass plate, to squeeze off the excess mercury. The volume of over flowed mercury is equal to the volume of dry soil cake. This is the final volume or the volume of dry soil.
   
9. Find the shrinkage limit of the soil sample with the help of above mentioned formula.
   

Observations and calculations:

Determination of water content (w_o):

1. Weight of empty shrinkage dish(w₁) = gm
   
2. Weight of shrinkage dish + wet soil(w₂) = gm
   
3. Weight of shrinkage dish + dry soil(w₃) = gm
   
4. Weight of water(w_w=w₂-w₃) = gm
   
5. Weight of dry soil(w_s=w3-w1) = gm
   
6. Water content (w=(w_w/w_s)*100 = %
   

Determination of volumes:

1. Volume of wet Soil or Initial volume (v) = cm³
   
2. Volume of dry soil or final volume (v_f) = cm³
   

Determination of shrinkage limit:

𝑆ℎ𝑟𝑖𝑛𝑘𝑎𝑔𝑒 𝐿𝑖𝑚𝑖𝑡(𝑤𝑠) = 𝑤 − [ 𝑣 − 𝑣𝑓 𝑤𝑠 𝛾𝑤 ∗ 100] =

Comments: