Test 7 - Soil Compaction Fundamentals

Question 1 ప్రశ్న 1

Which statement correctly distinguishes soil compaction from soil consolidation?

A Both processes necessarily involve only the expulsion of water from fully saturated soil. B Compaction is mechanical densification primarily through particle rearrangement and reduction of air voids, whereas consolidation involves time-dependent volume reduction associated with dissipation of excess pore-water pressure. C Compaction occurs exclusively under sustained static foundation loads, whereas consolidation occurs only under vibrating rollers. D Compaction necessarily increases void ratio, whereas consolidation necessarily increases porosity.

Question 2 ప్రశ్న 2

Which description correctly defines optimum moisture content (OMC) and maximum dry density (MDD) in a laboratory compaction test?

A OMC is the water content at complete saturation, and MDD is the bulk density at zero water content. B OMC is the water content producing minimum dry density, and MDD is the maximum bulk water content. C OMC and MDD are fixed properties of every soil regardless of the compaction procedure. D OMC is the water content corresponding to the peak dry density obtained under a specified compactive effort, and MDD is that peak dry density.

Question 3 ప్రశ్న 3

A compacted soil has bulk unit weight 19.8 kN/m³ and gravimetric water content 10%. What is its dry unit weight?

A 18.0 kN/m³. B 17.8 kN/m³. C 19.8 kN/m³. D 21.8 kN/m³.

Question 4 ప్రశ్న 4

During a laboratory compaction test, a mould of volume 1000 cm³ contains 1.92 kg of moist compacted soil. The gravimetric water content is 12.5%. What is the dry density of the specimen?

A 1.920 Mg/m³. B 1.800 Mg/m³. C 1.707 Mg/m³. D 2.160 Mg/m³.

Question 5 ప్రశ్న 5

A soil is tested at water contents of 8%, 10%, 12%, 14% and 16%, producing dry densities of 1.68, 1.78, 1.84, 1.81 and 1.74 Mg/m³, respectively. Which water content and dry density correspond to the highest measured trial point?

A 10% and 1.78 Mg/m³. B 12% and 1.84 Mg/m³. C 14% and 1.81 Mg/m³. D 16% and 1.74 Mg/m³.

Question 6 ప్రశ్న 6

The laboratory maximum dry density of an embankment soil is 1.85 Mg/m³, and the measured field dry density is 1.76 Mg/m³. What is the relative compaction, expressed as a percentage?

A 95.1%. B 90.9%. C 105.1%. D 85.0%.

Question 7 ప్రశ్న 7

An earthwork specification requires a minimum field dry unit weight equal to 95% of the laboratory MDD. If the laboratory MDD is 18.5 kN/m³, what is the minimum acceptable field dry unit weight, rounded to two decimal places?

A 18.50 kN/m³. B 19.48 kN/m³. C 16.65 kN/m³. D 17.58 kN/m³.

Question 8 ప్రశ్న 8

For the same soil subjected to progressively higher laboratory compactive effort, which change in its moisture-density relationship is generally expected?

A Maximum dry density decreases and optimum moisture content increases in every case. B Maximum dry density and optimum moisture content always remain identical. C Maximum dry density generally increases while optimum moisture content generally decreases. D Maximum dry density becomes independent of soil type and grain-size distribution.

Question 9 ప్రశ్న 9

For the 1000 cm³ mould procedure, which combination is specified for the Indian Standard light compaction test under IS 2720 (Part 7)?

A 4.9 kg rammer, 450 mm drop, five layers and 25 blows per layer. B 2.6 kg rammer, 310 mm drop, three layers and 25 blows per layer. C 2.6 kg rammer, 450 mm drop, five layers and 55 blows per layer. D 4.9 kg rammer, 310 mm drop, three layers and 10 blows per layer.

Question 10 ప్రశ్న 10

Which laboratory arrangement corresponds to the 1000 cm³ mould procedure for heavy compaction under IS 2720 (Part 8)?

A 4.9 kg rammer, 450 mm drop, five layers and 25 blows per layer. B 2.6 kg rammer, 310 mm drop, three layers and 25 blows per layer. C 4.9 kg rammer, 310 mm drop, three layers and 25 blows per layer. D 2.6 kg rammer, 450 mm drop, five layers and 25 blows per layer.

Question 11 ప్రశ్న 11

Two laboratory compaction procedures use the same 1000 cm³ mould and 25 blows per layer. The light procedure uses a 2.6 kg rammer dropped 0.310 m through three layers, while the heavy procedure uses a 4.9 kg rammer dropped 0.450 m through five layers. Approximately what is the ratio of heavy to light compactive energy per unit volume?

A 1.23. B 3.20. C 5.65. D 4.56.

Question 12 ప్రశ్న 12

Which statement about the zero-air-void (ZAV) line in a dry-density versus water-content diagram is correct?

A It represents the dry density at which the soil has zero water content. B It represents the dry density of a soil having zero solid particles. C It represents the theoretical dry density at 100% saturation for each water content, given by gamma_d = G_s gamma_w/(1 + wG_s). D It represents the locus of minimum dry density for all possible compactive efforts.

Question 13 ప్రశ్న 13

A soil has specific gravity of solids 2.70 and gravimetric water content 20%. Taking gamma_w = 10 kN/m³, what is the theoretical zero-air-void dry unit weight?

A 15.00 kN/m³. B 17.53 kN/m³. C 20.00 kN/m³. D 27.00 kN/m³.

Question 14 ప్రశ్న 14

For a soil with G_s = 2.65, water content 20% and gamma_w = 10 kN/m³, the calculated zero-air-void dry unit weight is approximately 17.32 kN/m³. A laboratory result reports a dry unit weight of 18.00 kN/m³ at the same water content. Which interpretation is correct?

A The reported combination is physically inconsistent under the given phase relationships and should be checked for testing or calculation errors. B The specimen is correctly compacted to exactly 100% saturation. C The reported dry unit weight is acceptable because dry density has no theoretical saturation limit. D The specimen must have a negative void ratio, which is a normal condition for heavily compacted clay.

Question 15 ప్రశ్న 15

A compacted soil has dry unit weight 18.0 kN/m³, specific gravity of solids 2.70, water content 15% and gamma_w = 10 kN/m³. What is its degree of saturation?

A 54%. B 65%. C 90%. D 81%.

Question 16 ప్రశ్న 16

A compacted soil has void ratio 0.60 and degree of saturation 75%. What percentage of its total volume consists of air voids?

A 25.00%. B 37.50%. C 9.38%. D 75.00%.

Question 17 ప్రశ్న 17

A field-compacted soil has dry unit weight 18.0 kN/m³ and bulk unit weight 20.7 kN/m³. What is its gravimetric water content?

A 13%. B 15%. C 18%. D 20%.

Question 18 ప్రశ్న 18

A field soil has true bulk unit weight 20.7 kN/m³ and actual water content 15%. An operator mistakenly uses water content 10% to calculate dry unit weight. Which statement correctly describes the resulting reporting error?

A The dry unit weight is overestimated as approximately 18.82 kN/m³ instead of the correct 18.00 kN/m³. B The dry unit weight is underestimated as 17.00 kN/m³ instead of 18.00 kN/m³. C Both water-content values produce the same dry unit weight because bulk unit weight is fixed. D The reported dry unit weight becomes 22.77 kN/m³ because moisture must be multiplied rather than divided.

Question 19 ప్రశ్న 19

Which combination of field compaction equipment and soil type is generally appropriate?

A Sheepsfoot rollers are always most effective for completely clean coarse gravel, while vibration is unsuitable for granular material. B Vibratory rollers are used only for highly plastic clay because vibration cannot rearrange sand grains. C All soils are compacted most effectively with identical equipment, regardless of gradation or plasticity. D Vibratory rollers or plates are generally effective for granular soils, while sheepsfoot or tamping-foot rollers provide kneading action suited to many cohesive soils.

Question 20 ప్రశ్న 20

For soils compacted using comparable laboratory effort, which general trend is most defensible when comparing well-graded granular soils with highly plastic fine-grained soils?

A Highly plastic soils always achieve the greatest dry density at zero water content. B Well-graded granular soils invariably have a higher optimum water content than every clay. C Well-graded granular soils often achieve relatively high dry densities, while highly plastic fine-grained soils commonly exhibit higher optimum moisture contents and lower maximum dry densities. D Maximum dry density depends only on specific gravity of solids and is independent of gradation and plasticity.

Question 21 ప్రశ్న 21

For the same remoulded clay compacted to similar dry density at water contents on opposite sides of optimum, which soil-structure comparison is generally appropriate?

A Dry-of-optimum compaction necessarily produces a fully dispersed structure, while wet-of-optimum compaction produces only perfectly aligned sand grains. B Dry-of-optimum compaction commonly produces a more flocculated particle arrangement, whereas wet-of-optimum compaction commonly produces a more dispersed or oriented arrangement. C Both states must have identical particle fabric because their dry densities are equal. D The particle fabric depends exclusively on specific gravity and cannot be influenced by compaction water content.

Question 22 ప్రశ్న 22

Which statement correctly distinguishes relative compaction from relative density in soil engineering?

A Relative compaction and relative density are identical ratios using field bulk density divided by water density. B Relative density always equals the percentage of laboratory maximum dry density achieved in the field. C Relative compaction is calculated using the liquid limit and plastic limit, while relative density is calculated using the shrinkage index. D Relative compaction compares field dry density with laboratory MDD, whereas relative density describes the compactness of granular soils using their limiting loose and dense void-ratio states.

Question 23 ప్రశ్న 23

A borrow soil contains 2500 kg of dry solids at an initial gravimetric water content of 8%. The target water content for compaction is 12%. Assuming no losses and unchanged dry-solids mass, how much water must be added?

A 100 kg. B 80 kg. C 200 kg. D 300 kg.

Question 24 ప్రశ్న 24

A soil batch contains 4000 kg of dry solids and initially has gravimetric water content 18%. Before compaction, its water content must be reduced to 14%. Assuming the dry-solids mass remains unchanged, how much water must be removed?

A 40 kg. B 120 kg. C 160 kg. D 720 kg.

Question 25 ప్రశ్న 25

A field-compacted clay layer has bulk unit weight 20.0 kN/m³ and measured water content 16%. Its laboratory MDD is 18.5 kN/m³ at OMC 12%, and the project requires at least 95% relative compaction. Which assessment and corrective action are most appropriate?

A The layer passes because its bulk unit weight exceeds the laboratory maximum dry unit weight. B The layer passes because its water content is greater than optimum. C The layer achieves approximately 108% relative compaction and requires no further investigation. D The field dry unit weight is approximately 17.24 kN/m³, giving about 93.2% relative compaction; the wet layer should be suitably dried or conditioned and recompacted, followed by retesting.

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