PE Civil Engineering Exam Prep

Answer: B - The porosity of a 950 g dry soil sample, with an undisturbed volume of 900 cm³ and a particle density of 2.65 g/cm³, is 60%. The porosity of a soil is the ratio of the volume of soil pores to the total soil volume, and the soil porosity values range from 0 to 1.

Solution: Use the following equation to determine porosity, n:

n = 1 - (bulk density / particle density)

= 1 - (D_b / D_p)

Given D_p = 2.65

Therefore, n = 1 - [(mass of dry soil / volume of solids and pore spaces) / 2.65]

= 1 - [(950 g / 900 cm³) / (2.65 g/cm³ x 100)]

Porosity = n = 60%