Flow index, Toughness index; Relative consistency; Liquid index, sesitivity, Unconfined compressive strength;Activity of clay,void ratio

Flow index:

# Flow index is slope of semi log plot of no of blows corresponding to the water content is called flow index.

# It provides to measure the shear strength of soil.
# lower flow index better shear strength.
Flow index = (w1-w2)/log (N1/N2)
Denoted by I sufx (f).

Toughness index :

Which one soil is more tougher is represented by this index.

• Toughness index (It) = PI/FI

Where,
PI = Plastic index ( also Ip)
FI = flow index ( also If)

Relative consistency

It is difficult to state fine grained soil which exist in the nature. By this taste we can state fine grained soil. It is denoted by Cr, given by:
   Cr= (Wl- Wnat)/Ip
Where,
Wl = liquid limit (also ll)
Wnat= water content

Case 1: if Wl = Wnat then, Cr = 0.

Case 2 : if Wl > Wnat, then Cr = -ve, means to tell that it is slurry in remolded, viscous.

Case 3 : if wl <Wnat then Cr = +ve, means to tell that is cannot remould.

Case 4: if Cr =1, can be remould.

Liquid index :

Liquid index is denoted by Li, sometimes Il also. It detemines the % of liquid in the soil. Represented by,
  Il = (Wnat-Wp)/Ip

Case 1 : if Wnat = Wp, then liqid limit = 100%, that means if the soil is remoulded it behaves as a liquid ie; shear strength is equal to zero.

Case 2: If Wnat = Wp then it Il = 0, it says that there is no liquid content and is hard, cannot remolded.

Note : Il = 0.75 to 0.5 - very soft and soft consistency.

Il = 0.5 to 0.25 - medium soft consistency.

# Unconfined compressive strength

Actually its nothing than the compressive strengh is equal to load/ Area.

#sesitivity

Sensitivity = unconfined comp. Strength (undisturbed)/ unconfined comp. Strength  (Remolded)

1-4        : normal
4-8        : sensitivity
8-15      : Extra sensitivity
>15        : quick

#Thixotropy

It is the property of material which say that due to remoulding the strength is loss is regained in short period .

#Activity of clay

      A= Ip/%fine than 2micron

If A= <0.75 = inactive
    A= 0.75 - 1.25 = normal
    A= >1.25 - Active

        : by vivek shah

Void rato:

Unit weight of soil: