Highway Engineering

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👉The highway planning surveys consists:

    (i) Economic studies (Population and distribution in each village, trend of population growth, per capita income)

    (ii) Financial studies (Source of income and estimated revenue from taxation on road transport, living standards, future trends in financial aspects)

    (iii) Traffic or road studies (Traffic volume, traffic flow pattern, O and D studies)

    (iv) Engineering studies (Road location and alignment studies, Classification, Types of road in use, Maintenance problems)

👉 The stages of engineering surveys for highway locations are:

   (i) Map study

   (ii) Reconnaissance

   (iii) Preliminary surveys

   (iv) Final location and detailed surveys

👉 The following drawing are usually prepared in a highway project:

(a) Key map (Should show the proposed and existing roads and important places to be connected, the size of the plan should not exceed 22 x 20 cm.)

(b) Index map (Should show the general topography of the area, size being 32 x 20 cm)

(c) Preliminary survey plans (details of various alignment, scale: 10 cm = 1km to 25 cm = 1km)

(d) Detailed plan and longitudinal section 

(e) Detailed cross-section

(f) Land acquisition plans

(g) Drawings of cross drainage and other retaining structures

(h) Drawings of road intersections

(i) Land plans showing quarries

👉 Typical Flexible Pavement Failures:

(a) Alligator (Map) cracking

• Most common type of failure and occurs due to relative movement of pavement layer materials.
• caused by repeated application of heavy wheel loads resulting in fatigue failure or due to moisture variations resulting in swelling and shrinkage of subgrade.

                                             

(b) Consolidation of pavement layers

• Formation of ruts are mainly attributed to the consolidation of pavement layers.

(c) Shear failure and cracking

• Shear failure causes upheaval of pavement materials by forming  a fracture or cracking.

(d) Longitudinal cracking

• Due to frost action and differential volume changes in subgrade 

(e) Reflection Cracking

• observed in bituminous overlays over existing cement concrete pavements

👉Typical Rigid pavement failures:

(a) Scaling of cement concrete:

• scaling is observed in cc pavement showing overall deterioration of the concrete.

(b) Shrinkage cracks

(c) Spalling of joint

(d) Warping cracks

(e) Mud Pumping

• Mud pumping is recognized when the soil slurry ejects out through the joints and crack of cc pavements during the downward movement of slab under the heavy wheel load.