The soil in a polder consists of a clay layer of 5m thickness, with aporosity of 50%, on top of a deep layer of stiff sand. The water level in the clay islowered by 1.5 m. Experience indicates that then the porosity of the clay is reducedto 40%. What is the subsidence of the soil?

subsidence  of the soil = 0.85 meter

Explanation:

given data  

clay layer thickness T =  5 m

porosity = 50%

water level = 1.5 m

porosity reduced = 40%

solution

first we get here initial void ratio that is express as

void ratio e =   ................1

here n is porosity

e1  =  

e1 = 1

and  

when water level rise 1.5 m than void ratio e will be

e2  =

e2  = 0.66

and now subsidence will be

subsidence = T ×  

subsidence = 5 ×

subsidence  of the soil = 0.85 meter