BASIC DEFINITIONS AND RELATIONS

• Fully saturated  soil  (solids + water )
• Dry state  soil  ( solids + air )
• Partially saturated  soil  (solids + water + air ) 

①    Void ratio (e) = vol of voids / vol of solids

• void ratio of fine-grained soil(size<75μm) is more than that of  coarse-grained soil (size>75μm)

       Although the coarse-grained soil has more void space, the no. of voids is lesser than that of fine-grained.

                              e_max = 0.91 

②    Porosity (n%) = vol of voids / total volume

                              n =  e / (1+e)

                        

                              e = n / (1-n)

③    Degree of saturation (S_r) = ( vol of water / vol of voids ) x 100

④    Air content (a_c) = (vol of air / vol of voids) x 100

 

⑤    %  air voids (n_a) = (vol of ait / total volume ) x 100

                              n_a   =  n . a_c 

⑥    Water content (w %) = ( weight of water / weight of solids ) x 100

Important values and relations :

Unit weight of water -

• 1 g/cc
• 1 ton/m³
• 9.81 Kn/m³

 _{Bulk unit weight or partially saturated unit weight (} γ ₎ 

• γ = ( G + S.e )γ_w   /  (1 + e) 

S = 1 for saturated unit weight and S = 0 for dry unit weight.

Dry unit weight     

•  γ_d   =  γ _{/ ( 1 + w )}

Submerged unit weight     

• γ_sub  =  ( G - 1 ) γ_w  /  (1 + e)

                                    

• γ_sub  =  γ_sat – γ_w

Overall relationship

• γ_{s  >} γ_sat  > γ  _>  γ_d > γ_sub