16. Geotechnical & Pavement Flashcards

1
Q

What is the Resilient Modulus?

A

the measure of the subgrade material stiffness via the triaxial test.

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2
Q

What is the California Bearing Ratio (CBR) test?

A

An indirect measure of soil strength based on resistance to penetration (by a standardized piston moving at a standardized rate for prescribed penetration distance).

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3
Q

What is the Resistance Value (R-value) test?

A

A material stiffness test that expresses a material’s resistance to deformation as a function of the ratio of transmitted lateral pressure to applied vertical pressure.

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4
Q

What does the dynamic cone penetrometer measure?

A

The direct correlation between the strength of a soil and its resistance to penetration by solid objects.

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5
Q

What does the modulus of subgrade reaction for Richard Pavement measure?

A

The stiffness of the foundation soil

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6
Q

What are the two widely used methods for pavement design?

A

Empirical Method (1993 AASHTO guide) and Mechanistic-Empirical Method (NCHRP 1-37A)

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7
Q

What is the difference between they two methods of pavement deisgn?

A

Empirical Method is based on empirical observations; MEPDG method uses theory of mechanics.

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8
Q

What are the three major stages in the MEPDG design method

A

(1) Evaluation, (2) Analysis, (3) Stratey Selection

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9
Q

How are structual respones (stresses, strains, and deflections) calculated with MEPDG?

A

Mechanistically, based on material properties, environmental conditions, and loading charactersistics. Thus using theory of mechanics. Aka Pavement Response Model.

Input: pavement geometry, environment, material properties, traffic
Output: stress, strain, displacement

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10
Q

How are the preformace predictions calculated with MEPDG?

A

Empirical models. Aka Performance Model.

Input: stress, strain, displacement
Output: cracking, rutting

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11
Q

Causes of alligator (bottom-up fatigue) cracking.

A
  • Loss of base, subbase or subgrade support (poor drainage)
  • Stripping on the bottom of the HMA layer
  • Increase loading (unanticipated loads)
  • Inadequate structural design
  • Poor construction (inadequate compaction)
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12
Q

Causes of longitudinal (top-down) cracking for rigid pavement.

A
  • Poor lane joint construction
  • Temperature cycling
  • Reflective cracking in base layer
  • Volume changes in subgrade
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13
Q

Causes of rutting (permanent deformation).

A
  • Insufficient compaction of HMA layers
  • Subgrade rutting (as a result of inadequate pavement structure)
  • Improper mix design
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14
Q

Causes of thermal cracking (transverse).

A

Heating/cooling cycles in the asphalt. (i.e., surface cools faster and with more intensity than the core of the structure)

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15
Q

What are the distress in rigid pavement?

A
  • Bottom-Up Transverse Cracking (JPCP)
  • Top-Down Transverse Cracking (JPCP)
  • Joint Faulting (JPCP)
  • Punchouts (CRCP)
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16
Q

What are the four characteristics of pavement condition for evaluating pavement rehabilitation?

A

(1) Pavement Roughness (rideability)
(2) Pavement Distress (surface condition)
(3) Pavement Deflection (structural failure)
(4) Skid Resistance (safety)

17
Q

What is settlement?

A

Settlement by means of elastic deformation, immediate settlement.

18
Q

What is primary consolidation settlement?

A

Reduction of soil volume as a result of pore water expulsion.

19
Q

What is secondary consolidation settlement?

A

Reduction of soil volume as a result of plastic adjustment of the soil structure.

20
Q

What does compaction do to the soil?

A

Increases the density of an unsaturated soil by reducing the volume of air in the voids; instantaneous process; water content does not change.

21
Q

What does consolidation do to the soil?

A

Increase the density of a saturated soil by draining out some of the water; time dependent process; water content decreases.

22
Q

What are the purposes of ground modification (soil stabilization)?

A
  1. Increase shear strength
  2. Reduces permeability
  3. Reduces compressibility
23
Q

What are the two categories of soil stabilization?

A
  • Mechanical: blending different grades of soil to obtain required grade
  • Chemical: blending of the natural soil with chemical agents.
24
Q

Type of soil stabilization methods?

A
  • Soil Replacement: removal and replacement; displacement
  • Water removal (consolidation); wick drains/sand drains
  • Site Strengthening: deep or shallow vibratory techniques or dynamic compaction
  • Grouting or Compaction Grouting
25
Q

What is the slope of the void ratio over effective pressure called?

A

Compression index.