Solution:

Given data:

Wet soil weight = 126 kg
Density = 2.1 g/cc
Water content = 15%
Specific gravity = 2.7

To find:

Dry density of silty soil.

Formulae:

Bulk density = Wet soil weight / Total volume
Dry density = (1 - Water content) * Bulk density

Approach:

Total volume of soil can be computed as follows:

Total volume = Wet soil weight / Density

Bulk density can be calculated as follows:

Bulk density = Wet soil weight / Total volume

Dry density can be calculated as follows:

Dry density = (1 - Water content) * Bulk density

Substitute the given values in the above formulae to get the dry density of the silty soil.

Calculation:

Total volume = Wet soil weight / Density
Total volume = 126000 / 2.1
Total volume = 60000 cc

Bulk density = Wet soil weight / Total volume
Bulk density = 126000 / 60000
Bulk density = 2.1 g/cc

Dry density = (1 - Water content) * Bulk density
Dry density = (1 - 0.15) * 2.1
Dry density = 1.785 g/cc

Therefore, the dry density of silty soil is 1.785 g/cc.

Explanation:

The bulk density of soil is the ratio of the mass of soil to the total volume occupied by it. It includes both solid and void space. Dry density is the density of soil without any moisture content. It is the ratio of the mass of the solid particles to the total volume of soil.

The given problem can be solved using the above formulae. The total volume of soil is computed by dividing the wet soil weight by the density of soil. The bulk density is calculated by dividing the wet soil weight by the total volume of soil. The dry density is calculated by multiplying the bulk density with the (1 - water content) of soil.

In this problem, the wet soil weight is given as 126 kg. The density of soil is 2.1 g/cc. The water content of soil is 15%. The specific gravity of soil is 2.7. The total volume of soil is calculated by dividing the wet soil weight by the density of soil. The bulk density of soil is calculated by dividing the wet soil weight by the total volume of soil. The dry density of soil is calculated by multiplying the bulk density with the (1 - water content) of soil.

Final answer:

The dry density of silty soil is 1.785 g/cc.