Test 8 - Compaction Tests and Field Control

Question 1 ప్రశ్న 1

Which mapping of Indian Standards to soil compaction and in-place density tests is correct?

A IS 2720 (Part 7) - heavy compaction; (Part 8) - light compaction; (Part 28) - core cutter; (Part 29) - sand replacement. B IS 2720 (Part 7) - light compaction; (Part 8) - heavy compaction; (Part 28) - sand replacement; (Part 29) - core cutter. C IS 2720 (Part 7) - sand replacement; (Part 8) - core cutter; (Part 28) - heavy compaction; (Part 29) - light compaction. D IS 2720 (Part 7) - light compaction; (Part 8) - core cutter; (Part 28) - heavy compaction; (Part 29) - sand replacement.

Question 2 ప్రశ్న 2

A project requires at least 95% of the heavy-compaction laboratory MDD. Light and heavy laboratory MDDs for the same soil are 1.80 and 1.95 Mg/m³, respectively, and the field dry density is 1.86 Mg/m³. Which conclusion is correct?

A The field fails because relative compaction against heavy MDD is 90.0%. B The field passes because relative compaction against the light MDD is 103.3%, which is the contractual reference. C The field passes because relative compaction against heavy MDD is approximately 95.4%. D The field fails because field dry density must always equal the heavy-compaction MDD.

Question 3 ప్రశ్న 3

For a 1000 cm³ mould, a light-compaction test uses a 2.6 kg rammer falling 0.310 m, 25 blows per layer and three layers. Taking g = 9.81 m/s², what is the approximate compactive energy per unit volume?

A 593 kJ/m³. B 2704 kJ/m³. C 198 kJ/m³. D 59.3 kJ/m³.

Question 4 ప్రశ్న 4

For a 1000 cm³ mould, a heavy-compaction test uses a 4.9 kg rammer falling 0.450 m, 25 blows per layer and five layers. Taking g = 9.81 m/s², what is the approximate compactive energy per unit volume?

A 1082 kJ/m³. B 593 kJ/m³. C 5408 kJ/m³. D 2704 kJ/m³.

Question 5 ప్రశ్న 5

An engineer compares laboratory MDD and OMC values obtained by light and heavy compaction for the same soil. Which interpretation is technically appropriate?

A The larger numerical MDD should be treated as a universal reference irrespective of the project specification. B OMC and MDD are independent of the applied laboratory compactive effort. C Each OMC-MDD pair belongs to its specified compactive effort, and the reference test for acceptance must match the project specification. D The light-compaction OMC must be used with the heavy-compaction MDD in every field test.

Question 6 ప్రశ్న 6

A laboratory compaction mould has volume 1000 cm³ and weighs 3.05 kg empty. The mould plus compacted moist soil weighs 4.85 kg, and the measured water content is 12.5%. What is the dry density?

A 1.80 Mg/m³. B 1.60 Mg/m³. C 2.03 Mg/m³. D 1.44 Mg/m³.

Question 7 ప్రశ్న 7

Which laboratory procedure most reliably establishes OMC and MDD from a conventional compaction curve?

A Compact one specimen at an assumed OMC and report its dry density as MDD. B Test several water contents on both sides of the peak, calculate dry density at each point, and determine the peak of a smooth moisture-density curve. C Measure only bulk density at one water content because the water content does not affect dry density. D Select the water content of the heaviest moist specimen without accounting for mould volume.

Question 8 ప్రశ్న 8

Two field locations both have water contents within the project tolerance about OMC, but one has field dry density below the specified minimum. What is the correct quality-control decision?

A Accept both locations because water content alone establishes satisfactory compaction. B Accept the deficient location if its bulk density exceeds the laboratory dry density. C Ignore the dry-density result because water content is measured only in the laboratory. D Reject or rework the deficient location according to the specification because moisture compliance does not replace the dry-density requirement.

Question 9 ప్రశ్న 9

In a moisture-content test associated with field density, the container plus wet soil weighs 42 g, the container plus oven-dry soil weighs 36 g, and the empty container weighs 12 g. What is the gravimetric water content?

A 20%. B 16.7%. C 25%. D 50%.

Question 10 ప్రశ్న 10

Which field condition most strongly favours using the core-cutter method under IS 2720 (Part 29)?

A A soft, fine-grained cohesive soil without significant gravel or hard inclusions, into which the cutter can be driven without substantial disturbance. B A dense coarse-gravel layer containing cobbles that obstruct a cutter. C A hard rock layer in which a thin-walled cutter cannot penetrate. D A loose saturated cohesionless deposit in which a clean, undisturbed cylindrical core cannot be retained.

Question 11 ప్రశ్న 11

A core cutter of internal volume 1000 cm³ has empty mass 1.10 kg and mass 3.06 kg when filled with trimmed moist soil. The soil water content is 12%. What is its field dry density?

A 1.96 Mg/m³. B 1.75 Mg/m³. C 1.65 Mg/m³. D 2.20 Mg/m³.

Question 12 ప్రశ్న 12

During a core-cutter test, the cutter is forced through a compacted layer containing oversized angular stones and the cutting edge visibly disturbs the soil. What is the best response?

A Use the nominal cutter volume without qualification because stones cannot affect the result. B Ignore the soil mass and report only the water content. C Select a more suitable applicable field-density method, such as sand replacement, and repeat the measurement. D Increase the calculated dry density by an arbitrary allowance for gravel.

Question 13 ప్రశ్న 13

In the sand-replacement method under IS 2720 (Part 28), what is the primary purpose of the calibrated dry sand?

A To determine the in-place soil water content through water absorption. B To supply the compactive effort used in the laboratory test. C To measure the weight of solids in the excavated soil without collecting them. D To determine the volume of an excavated test hole from the mass of sand filling it and the calibrated bulk density of that sand.

Question 14 ప్రశ్న 14

In a sand-replacement test, the sand-pouring apparatus contains 5.40 kg of sand before discharge and 2.82 kg afterward. The previously calibrated sand mass occupying the cone and base-plate region is 0.18 kg, and the dry sand bulk density is 1.60 Mg/m³. What is the excavated hole volume?

A 1,500 cm³. B 1,613 cm³. C 1,388 cm³. D 2,400 cm³.

Question 15 ప్రశ్న 15

A sand-replacement test yields an excavated hole volume of 1500 cm³. The collected moist soil has mass 2.70 kg and water content 12.5%. What is the in-place dry density?

A 2.03 Mg/m³. B 1.80 Mg/m³. C 1.60 Mg/m³. D 1.44 Mg/m³.

Question 16 ప్రశ్న 16

In a sand-replacement test, an operator forgets to subtract the sand held in the cone and base-plate region but uses the correct calibrated sand density. If all other measurements are correct, how is the reported field dry density affected?

A It is overestimated because the calculated hole volume is too small. B It is underestimated because the calculated hole volume is too large. C It is unaffected because the cone correction applies only to moisture content. D It becomes equal to the laboratory MDD regardless of the soil mass.

Question 17 ప్రశ్న 17

During calibration of sand used for a sand-replacement test, 2.55 kg of sand is found to occupy a calibrated container of 1500 cm³ after all apparatus corrections. What is the calibrated bulk density of the sand?

A 1.50 Mg/m³. B 1.65 Mg/m³. C 1.70 Mg/m³. D 2.55 Mg/m³.

Question 18 ప్రశ్న 18

A sand-replacement hole excavated in a loose, wet, nearly cohesionless soil suffers sidewall slumping before the sand is poured. The fallen soil remains in the hole and is not collected or weighed. Which systematic error is likely?

A The reported soil dry density will be overestimated because the sand-measured hole volume is reduced. B The reported soil dry density will be underestimated because more sand must fill the hole. C The reported dry density will be unaffected because hole wall stability matters only in a core-cutter test. D The soil water content automatically becomes zero when the walls slump.

Question 19 ప్రశ్న 19

The laboratory MDD for an earthfill is 1.90 Mg/m³ and the measured field dry density is 1.805 Mg/m³. What is the achieved relative compaction?

A 90.5%. B 105.3%. C 97.5%. D 95.0%.

Question 20 ప్రశ్న 20

A project specification requires at least 98% relative compaction using a laboratory MDD of 1.90 Mg/m³. What is the minimum acceptable field dry density?

A 1.900 Mg/m³. B 1.862 Mg/m³. C 1.805 Mg/m³. D 1.938 Mg/m³.

Question 21 ప్రశ్న 21

An earthwork specification requires both at least 95% of laboratory MDD and water content within 2 percentage points of OMC. If MDD is 1.84 Mg/m³, OMC is 12%, field dry density is 1.76 Mg/m³ and field water content is 14.5%, how should the layer be assessed?

A It satisfies both criteria because its dry density is above 1.70 Mg/m³. B It fails both criteria because relative compaction is below 95%. C It satisfies the density criterion but fails the specified moisture-content tolerance. D It satisfies moisture tolerance but fails the density criterion.

Question 22 ప్రశ్న 22

Four field density tests on the same layer give dry densities A = 1.82, B = 1.79, C = 1.83 and D = 1.81 Mg/m³. The specified minimum is 95% of laboratory MDD = 1.90 Mg/m³, and every individual test point must pass. Which location fails?

A A only. B B only. C C and D only. D All four locations.

Question 23 ప్రశ్న 23

A field sample has measured bulk density 2.10 Mg/m³ and water content 20%. Laboratory MDD is 1.90 Mg/m³, and at least 95% relative compaction is required. Which assessment is correct?

A The layer passes because bulk density 2.10 Mg/m³ exceeds MDD 1.90 Mg/m³. B The layer passes with 110.5% relative compaction. C The layer fails, because its dry density is 1.75 Mg/m³ and relative compaction is approximately 92.1%. D The layer fails because its water content must be zero when bulk density is used.

Question 24 ప్రశ్న 24

A compacted clay lift shows low dry density and water content materially above laboratory OMC. Which remedial plan is most technically sound before final acceptance?

A Add more water and assume that moisture increase always produces higher dry density. B Approve the lift on the basis that clay must be compacted wet of optimum. C Use only repeated rolling without checking whether the layer is too wet or too thick. D Condition the soil moisture appropriately, adjust lift thickness or equipment effort as needed, recompact, and retest dry density and water content.

Question 25 ప్రశ్న 25

Quality-control tests show that the upper portion of a thick granular fill lift is well compacted but its lower portion remains insufficiently dense. Which engineering action best addresses this pattern?

A Accept the lift because surface density is representative of all depths. B Reduce the loose lift thickness to a depth that the selected vibratory compactor can effectively densify, then recompact and verify the layer. C Switch off vibration because granular soils cannot be compacted by vibratory equipment. D Increase the reported relative compaction to account for the inaccessible lower portion.

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