Quiz Set 1 Name: _______________________________________________________________________________ 1. Soil sample A has 1 cm3 of water, 1 cm3 of air and 1 cm3 of sand. What is the void ratio of this soil? It is then kept in a bucket filled with water so that the soil becomes fully saturated. What will the new void ratio be? (Answer in fraction/decimals. Assume total volume of the soil remains constant) Void Ratio = Volume of Voids / Volume of Solids Volume of voids = Volume of air + Volume of water e = 1+1 / 1 = 2 For the second case, water will occupy the air voids. The total volume of voids will still be the same. Thus, the answer will not change. 2. A soil sample is kept in a jar. The jar is accidentally dropped and is jarred several times before it comes to a stop. Will the void ratio: a. Remain the same b. Increase c. Decrease Give an explanation to support your answer. The void ratio will decrease. Jarring of the soil sample will result in the particles re-arranging themselves to a denser state. 3. What is the use of the collar in the mold? The collar is used so that we can completely fill the mold with soil. Any excess soil can then be removed with a straight edge. Additionally, in the case of a dense sample, vibration will result in the compaction of the soil. The collar is then necessary to ensure that the mold remains filled completely at all times. Quiz Set 1 4. A field density test was performed to obtain the dry unit weight of a soil. Knowing that the soil dry unit weight is 17 kN/m3 and the specific gravity is 2.65, determine the void ratio of the soil in the field using: e= Gsg w gd -1 where e = void ratio; Gs= specific gravity of soil; w= unit weight of water; d = dry unit weight of soil. e = (2.65 9.81/17) – 1 = 0.53 5. A relative density of 100% corresponds to _____emin________ (emin or emax), in which case the soil is in its __most dense__ state. 6. From a site investigation recently performed, the following field and laboratory data was obtained: Soil type: Sand (below water table) Specific gravity = 2.65 Average in-situ dry unit weight (dry unit weight of the soil in the field): 15.0 kN/m3 emin=0.48 emax=0.75 Given the information above, do you think the ground is suitable for construction? Would you recommend ground improvement before proceeding with construction? (Unit weight of water = 9.81 kN/m3) e= Gsg w gd - 1 = 2.65 (9.81/15) – 1 = 0.73 DR = (emax – e) / (emax - emin) = (0.75 – 0.73) / (0.75 – 0.48) = 7.4% The soil has a low relative density, indicating it is at a loose state. The soil is unfit for construction and ground improvement should be carried out. Quiz Set 1 7. Can you determine maximum or minimum density of a clayey soil following the methods described in this experiment? Explain your answer. No. Clay doesn’t compact on vibration. Neither is it possible to “pour” a clay through a funnel due to its plastic nature. 8. If from the experiment, you obtain a DR value of greater than 100%, what could be the possible reason for it (except for human error)? Explain. Significant crushing of sand particles can cause the DR values to exceed 100%. 9. While performing the experiment for emax using the funnel method, what precautions must one take? 1. The funnel should be kept about 0.5 inch above the height of the soil in the mold. 2. One must be careful not to bump/jar the mold. This can result in compaction of the sand particles.
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