CE-603-C Advance Pavement Design - May 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 14 Marks
   Mention the design steps for overlay thickness design using BBD data.
   How to answer

   • Define overlay and BBD - Benkelman Beam Deflection survey
   • Steps: deflection survey, correction for temperature and seasonality, characteristic deflection
   • Design chart / IRC procedure to determine overlay thickness
   • Consideration of traffic, subgrade and existing pavement condition
2. 7 Marks
   aA cement concrete pavement 15 cm thick and 7.5 meter width has a longitudinal joint along the centre line. Design the diameter, length and spacing of the tie bars if the allowable working stress in steel is 1800 $kg/cm^2$ in tension, allowable bond strength in concrete is 24.6 $kg/cm^2$ and coefficient of friction is 1.5. Assume unit weight of concrete as 2400 $kg/m^3$.
   How to answer

   • Formula for area of steel per metre: $A_s = b \cdot h \cdot W \cdot f / (100 \cdot \sigma_s)$
   • Assume tie bar diameter and calculate spacing from $A_s$
   • Check bond length: $L = d \cdot \sigma_s / (2 \cdot \tau_b)$ with factor of safety
   • State final diameter, spacing and length
3. 7 Marks
   bDiscuss the conditions under which stresses in cement concrete pavements lead to most critical Combinations.
   How to answer

   • Define warping, frictional and load stresses in CC pavement
   • Critical combinations: summer mid-day, winter mid-night, corner/edge/interior locations
   • Explain superposition of stresses
   • Conditions for most critical stress values
4. 7 Marks
   aExplain the test procedure for determining California Bearing Ratio value of soil.
   How to answer

   • Apparatus: CBR mould, surcharge, penetration piston and loading machine
   • Procedure: sample preparation, soaking, penetration at 1.25 mm/min
   • Record load at 2.5 mm and 5.0 mm penetration
   • Calculate CBR as ratio to standard loads
5. 7 Marks
   bHow does the Benkelman Beam method contribute to the evaluation of existing pavements, and what are the key steps involved in conducting this assessment?
   How to answer

   • Purpose: measure rebound deflection for structural evaluation and overlay design
   • Equipment setup and standard truck loading
   • Procedure: probe placement, dial gauge readings, temperature correction
   • Analysis: characteristic deflection and remaining life
6. 7 Marks
   aWhat are the fundamental concepts and applications of Equivalent Single Wheels Load (ESWL), and how do they influence pavement design and performance?
   How to answer

   • Definition of ESWL and need for dual wheel load conversion
   • Concept of depth-dependent equivalency, log-log plot
   • Applications in thickness design and stress analysis
   • Effect on pavement performance and load repetition
7. 7 Marks
   bExplore the composition of flexible pavements, delineating the roles and functions of each component part within the pavement structure.
   How to answer

   • Layers: subgrade, sub-base, base, binder and wearing course
   • Functions: load distribution, drainage, skid resistance
   • Role of each component in structural capacity
   • Neat cross-section sketch of flexible pavement
8. 7 Marks
   aExplore Westergaard's stress theory and its application in analyzing stresses within rigid pavements, covering fundamental principles, assumptions and equations governing stress distribution.
   How to answer

   • Westergaard assumptions: slab on Winkler foundation, thin elastic plate
   • Interior, edge and corner load stress equations
   • Modulus of subgrade reaction $k$ and radius of relative stiffness $l$
   • Application to rigid pavement thickness design
9. 7 Marks
   bWrite down step by step procedure for design of flexible pavement as suggested by IRC.
   How to answer

   • Input parameters: traffic in msa, CBR, design life
   • IRC:37 procedure for subgrade, granular and bituminous layers
   • Use of design charts / IITPAVE for thickness
   • Steps for composition and drainage considerations
10. 7 Marks
    aEvaluate strategies for mitigating stress-related issues in rigid pavements, including reinforcement techniques, joint design and material selection and discuss their effectiveness in enhancing pavement durability and longevity.
    How to answer

    • Sources of stress: load, temperature, moisture and friction
    • Mitigation: reinforcement, dowel/tie bars, joint spacing
    • Material selection: low shrinkage, high fatigue resistance
    • Effectiveness for durability and longevity
11. 7 Marks
    bDifferentiate EASL and Design EASL and discuss how Design EASL is estimated?
    How to answer

    • Define EASL / ESAL and Design EASL concept
    • Differences: actual repetitions vs design life factored repetitions
    • Factors: traffic growth, lane distribution, vehicle damage factor
    • Steps to estimate design EASL in msa
12. 7 Marks
    aDiscuss about the following variables that influence the pavement design:

    1. i)Load variables
    2. ii)Structural variables
    How to answer

    • Define load variables: axle load, tyre pressure, repetitions, speed
    • Define structural variables: layer thickness, modulus, subgrade strength
    • Influence on thickness and performance prediction
    • Examples from IRC design approach
13. 7 Marks
    bDistinguish between "Modulus of Sub-grade Reaction" and "Radius of Relative Stiffness".
    How to answer

    • Define modulus of subgrade reaction $k$ - Winkler foundation
    • Define radius of relative stiffness $l = [Eh^3/(12(1-\mu^2)k)]^{1/4}$
    • Differences: support property vs slab-foundation stiffness ratio
    • Use in Westergaard stress and deflection equations
14. 7 Marks
    aWhy tie bars are used in CC pavement? Write the difficulties during installation of tie bars.
    How to answer

    • Function of tie bars: hold longitudinal joint, prevent separation
    • Load transfer and crack control role
    • Installation difficulties: alignment, corrosion, bond, construction delay
    • Measures to overcome difficulties
15. 7 Marks
    bDetermine the diameter, spacing and length of tie bars required for a two lane concrete pavement, 203 mm thick, 18.3 m long and 7.3 m wide with a longitudinal joint at the centre. Take, allowable tensile stress = 200 MPa; allowable bond stress = 2.4 MPa, unit weight of concrete = 25 $kN/m^3$ and coefficient of friction = 1.5.
    How to answer

    • Compute frictional force: $F = W \cdot L \cdot B/2 \cdot f$
    • Steel area and spacing for assumed diameter using $\sigma_{st}=200$ MPa
    • Bond length from $L_t = d \cdot \sigma_{st}/(2\cdot \tau_b)$
    • Final diameter, spacing and length with practical values