DESIGN OF FLEXIBLE PAVEMENTS AS PER IRC 37: 2001 .

PROBLEM 1 : Design the pavement for construction of a new bypass with the following data:

1. Two lane carriage way

2. Initial traffic in the year of completion of construction = 400 CVPD (sum of both directions)

3. Traffic growth rate = 7.5 %

4. Design life = 15 years

5. Vehicle damage factor based on axle load survey = 2.5 standard axle per commercial vehicle

6. Design CBR of subgrade soil = 4%.

Solution : 

1. Distribution factor = 0.75

2.

N =  

   365 ×( 1 + 0.075)^15 − 1) x 400x0.75x2.5

                         0.075

= 7200000

= 7.2 msa

3. Total pavement thickness for CBR 4% and traffic 7.2 msa from IRC:37 2001 chart1 = 660 mm

4. Pavement composition can be obtained by interpolation from Pavement Design Catalogue (IRC:37 2001).

(a) Bituminous surfacing = 25 mm SDBC + 70 mm DBM

(b) Road-base = 250 mm WBM

(c) sub-base = 315 mm granular material of CBR not less than 30 %

PROBLEM 2 :  Design the pavement for

 construction of a new two lane : 

Carriageway for design life 15 years using IRC method.  initial traffic in the year of completion in each direction is 150 CVPD and growth rate is 5%. Vehicle damage factor based on axle load survey = 2.5 std axle per commercial vehicle. Design CBR

of subgrade soil=4%.

Solution : 

1. Distribution factor = 0.75

2. 

 N =

        365 ×(1 + 0.05)^15−1)0.75 × 300 ×2.5

                            0.05

= 4430348.837

= 4.4 msa

3. Total pavement thickness for CBR 4% and traffic 4.4 msa from IRC:37 2001 chart1 = 580 mm

4. Pavement composition can be obtained by interpolation from Pavement Design Catalogue (IRC:37 2001).

(a) Bituminous surfacing = 20 mm PC + 50 mm BM

(b) Road-base = 250 mm Granular base

(c) sub-base = 280 mm granular material.