Importance of stratification to civil engineering

Stratification helps the civil engineer to:
a- properly understand the nature of the ground and know what is underlying this ground, whether solid rocks or soil
b- develop an understanding of the permeability of the composite soil 
c- develop an understanding of the mechanical properties of the ground such as its strength
d- ensure that the site is properly structured and suitable for the targeted project

Amath expression is a collection of one or more terms, which are separated by the signs ( + , - , x , / ).example :   8+b8+b  or  a−3a−3in algebra, an equation is a mathematical statement with two expressions where, each expression is separated by an equal (=) sign. variables can be present on both the sides of the equality (=) sign and we use letters to denote such variables.example 1:   x=4+2x=4+2  , [here, we can observe that the variable is present only on one side of the equation].example 2:   2x+3=x+42x+3=x+4  , [here, we can observe that the variables are present on both side of the equation].