FE Civil Engineering Exam Prep #1

What is the porosity of a dry soil sample that weighs 950 grams (g) and has an undisturbed volume of 900 cubic centimeters (cm3)? Assume a particle density of 2.65 g/cm3.

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 - Db / Dp Given Dp = 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 n = 60%

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