Question

3. Select a highway horizontal curve in your local suburb by including one site photograph. Assume a suitable radius of the curve, and design the superelevation, which might have been provided.

4. Along the highway alignment, the soaked CBR values of the soil subgrades at two different locations are 1% and 5%. Draw typical cross-sections of flexible pavement at these two locations.

Answer 1

4. Let us consider the Design of Flexible Pavement with and CBR Ranges from 1- 5%

For which as Per design the Minium CBR Range will be 2%. Such that consider 2%. ok

Let us Assume : At 2% CBR.

Four lane Express way with  Initial traffic = 400 CVPD at an growth rate = 7.5 % with design life of 15 years Assume as Vehicle damage factor based on axle load survey = 2.5 standard axle per commercial vehicle . Design as CBR of subgrade soil = 2%

Calcuclating Cumulative number of standard axles : N Value

As Per the Design Graph for Upto CBR 1 -10 %

As Per the Calculation It is coming Around 820 mm thickness of Total Layer for CBR @2% and around 620 mm For CBR @ 5%.

At CBR 2% - At N Value 7.5 (msa) - Consider as minimum - 10 (msa)

Draw as It as Sub Base 440mm -Base - 240mm - DBM - 100mm - Bitumen Coarse - 40 mm

Example: Below Image

Assign Total Thickness as 620 mm.

Draw as It as Sub Base 265 mm -Base Course -  260mm - DBM - 60mm - Bitumen Coarse - 35 mm