De La Salle University - Dasmariñas

CS 101

SOIL COMPOSITION 1. CE Board May 2017 The ratio between the volume of the water and the volume of the voids in a soil mass is referred to as: Ans. degree of saturation 2. CE Board May 2017 The ratio between the volume of voids and the total volume of the soil mass is referred to as: Ans. porosity 3. CE Board May 2017 A soil sample has a specific gravity of 2.5 for its solid grains. It has a void ratio of 0.40 and a degree of saturation of 40%. Evaluate the unit weight of the soil, in kN/m3. Ans. 18.6 kN/m3 4. CE Board Nov. 2015 If the dry unit weight of a soil is 12 kN/m3, what is the unit weight of soil if water is added causing a water content of 15%? Ans. 13.8 kN/m3 5. CE Board Nov. 2015 A sample of soil has void ratio of 0.40. Evaluate the porosity of the soil. Ans. 28.6% 6. CE Board May 2016 A soil sample has a water content of 20% and moist unit weight of 18 kN/m3. The specific gravity of the solid is 2.65. Obtain the void ratio of the soil. Ans. 0.733 7. Problem For a given soil, the following are known. Gs = 2.74, moist unit weight = 20.6 kN/m3, and moisture content is 16.6%. ➀ Determine the porosity. ➁ Determine the degree of saturation. ➂ Determine the weight of water in kN to be added per cubic meter of soil for a 100% degree of saturation Ans. 0.34, 87.5%, 0.44 Kn 8. Problem For a given soil sample it has a sp.gr. of 2.74, moisture content of 16.6% and a moist unit weight of 20.6 kN/m3. ➀ Compute the porosity of the soil sample. ➁ Compute the bouyant unit weight of the soil sample. ➂ Compute the weight of water in kn to be added per cu.m. of soil for 90% degree of saturation. Ans. 0.34, 11.23 kN/m3, 0.10 kN/m3 9. Problem The unit weight of soil is 15.10 kN/m3. The moisture content of this soil is 17% when the degree of saturation is 60%. Determine the following: ➀ Void ratio ➁ Sp.gr. of soil ➂ Saturated unit weight Ans. 0.59, 2.08, 16.47 kN/m3 10. Problem A sand with Gs = 2.66 and void ratio e = 0.60 is completely dry. It then becomes wetted by a rising groundwater table. Compute the unit weight in kN/m3 under the following conditions: ➀ When the sand is completely dry. ➁ When the sand is 40% saturated. ➂ When the sand is completely saturated. Ans. 16.31 kN/m3, 17.78 kN/m3, 19.99 kN/m3 11. Problem A saturated soil has a moisture content of 38% and a specific gravity of 2.73. ➀ Compute the void ratio. ➁ Compute the porosity. ➂ Compute the moist unit weight in kN/m3 of this soil. Ans. 1.04, 0.51, 18.12 kN/m3 12. CE Board Nov. 2016 A soil sample has a dry unit weight of 15 kN/m3 and a void ratio of 0.50. ➀ Evaluate the specific gravity of the solid soil. ➁ Obtain the unit weight of the sample in kN/m3 when fully saturated. ➂ What is the hydraulic gradient at quicksand condition? Ans. 2.29, 18.25 kN/m3, 0.86 13. CE Board Nov. 2017 Given that the field unit weight of a soil sample is 1800 kg per cubic meter and the unit weight of the soil particles is 2000 kg per cubic meter and the moisture content of the soil is 12 percent. ➀ Evaluate the void ratio. ➁ Evaluate its dry unit.in kN/m3 ➂ Evaluate the degree of saturation, in percent. Ans. 0.244, 15.77 kN/m3, 98.36% 14. CE Board Nov. 2016 A soil sample has a unit weight of 21.1 kN/m3 at a moisture content of 9.8%. When completely saturated, the unit weight becomes 22.58 kN/m3. Evaluate the void ratio of the soil. Ans. 0.52 15. Problem For a given sandy soil, emax = 0.75, emin = 0.46 and Gs = 2.68. If the relative density of the soil Dr = 78% and its water content is 9%, determine the following: ➀ In situ void ratio ➁ Moist unit weight of compaction in kN/m3 ➂ Dry unit weight in kN/m3 Ans. 0.524, 18.8 kN/m3, 17.25 kN/m3 16. Problem A loose, uncompacted sa