This set of Pavement Design Question Bank focuses on “Problems in Stabilization – 2”.
1. Which of the below is not a type of liquid soil stabilizer?
a) Cation exchange
b) Polymer treatment
c) Anion exchange
d) Enzyme treatment
Explanation: Difficulties are faced while stabilizing highly expansive soils like the black cotton soil. So, modern liquid soil stabilizers are being used. They can be of three types – polymer treatment, enzyme treatment and cation exchange.
2. Which of the below is not designed as a semi-rigid pavement?
d) Pozzolanic concrete
Explanation: There are no specific methods to design the thickness of the stabilizing mixes. So, the mixes like soil-cement, soil-lime and pozzolanic concrete can be designed as a semi-rigid pavement. Bitumen is not designed as a semi-rigid pavement.
3. Drainage is an important parameter to be considered while stabilizing sandy soil.
Explanation: Sandy soils have granular texture and are non-cohesive in nature. If flooding or water seepage occurs, then it would result in the erosion of the sandy soil. So, an appropriate method of stabilization that would take care of drainage must be used.
4. The thickness requirements of semi-rigid pavements must be ______ granular base course.
a) Less than
b) Equal to
c) More than
d) Half of
Explanation: Semi-rigid pavements are considered to be in between flexible and rigid pavement types. It uses a base course of lean cement, soil-cement, etc. So, the design thickness must be less than that of the granular base course.
5. Which of the below is not a problem associated with black cotton soil?
a) Excessive volume changes
b) Round particles
c) Difficult to pulverize
d) Considerable shrinkage
Explanation: Round particles are found in granular sandy soils, not in clayey soils. So, the round particle shape doesn’t affect the black cotton soil. Clayey soils have high volume changes, shrinkage, swelling pressure and are difficult to pulverize.
6. What can be added to black cotton soil to improve its properties?
Explanation: Lime and cement can be added to improve the properties of the highly expansive soil. Usually the addition of lime improves most properties of black cotton soils. Cement requirement is high and becomes costly, hence lime is preferred.
7. It is possible to carry out soil stabilization when the ground is frozen.
Explanation: Soil stabilization is possible in cold weather but it is not done when the ground is frozen. It is important to make sure that the water table is not frozen while stabilizing soil in cold weather. Frozen ground does not permit the proper mixing of the soil and the suitable additive like resin.
8. In which course can additives be added with lime stabilized black cotton soil?
Explanation: Subgrade is treated with a small amount of lime. Then the sub0base is treated with 4-6% of lime and compacted well. The base course is prepared by adding the additives like 3-5% Portland cement or brick aggregates, surkhi, fly ash. Surface course is bituminous premix type.
9. Which of the below cannot be considered as the best additives to be used in the complex stabilization process?
a) Cement + lime
b) Cement + bitumen emulsion
c) Cut-back + lime
d) Cement + naphtha soap
Explanation: Complex stabilization is a method of stabilization that is done using more than one stabilizer. Usual and the best combinations that are considered include cement + calcium chloride + lime, cement + bitumen emulsion, cut-back + lime and cement + naphtha soap.
10. Why is the method of electro-osmosis generally used?
a) Anionic exchange
b) Drain cohesive soils
c) Drain sandy soils
d) Cationic exchange
Explanation: Electric stabilization of soil is done using the method of electro-osmosis. The process is done for draining soils having high moisture content like the cohesive soils. It is an expensive method and is used when no other method is possible.
Sanfoundry Global Education & Learning Series – Pavement Design.
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