Week 4 Challenge

Question 1 - Design the abutment foundation as per IRC 6 loads. optimize the design as per irc 112.

Answer 1 - As The Given Figure Doesn't have following Points So We have to asssume Accordingly :

Assumptions :

• Abutment Shaft Height - 6.0 meter (Assumed)
• Superstructure Depth - 1.466 meter (Assumed)
• Design Discharge - 100 Cumec.
• Bed Level of Abutment - 227.250 meter (Assumed)
• Formation level - 233.691 meter (Assumed)
• Soffit Level - 232.150 meter (Assumed)
• Rock Level - 225.750 meter (Assumed) (It is Assumed that 3m below the bed level the foundation is fixed and 1.5m below from rock level as per IRC 78.)

Design of Foundations :

Question 2 - Detail the steel in shallow foundation for abutment.

Answer 2 -

Question 3 - How a shallow foundation in terms of stability,designing,construction different in flyover and in river bridge?

Answer 3 - There are some differences in shallow foundations in flyovers as compared to river bridges.

STABILITY :

• As the Stability should be checked for both the scenarios, but in flyovers there is no outer water pressure in the foundations, also the scouring near the foundation causes the sudden uplift or downward pressure in the foundations but this can only be experience in river bridges, this is the major difference between foundations in both the scenarios.

DESIGNING :

• Designing of foundations for both the cases is almost similar, but as flyovers are designed to carry heavy vehicle as well as more numbers of vehicles the foundations requirement of concrete and steel is different the concrete area of foundations used in flyovers are comparitively more, also the steel requirements are also high.
• As the Foundations in the Flyovers doesn't experience any sort of Scouring so the depth is also adequate, only the rock level and the SPT N values of the layers of rock is checked and as per IRC 78 the 1.5 meter of embedment is only required if the N Value of the rock reaches to 100 if the Depth of Rock is less and Shallow Foundation is adopted. If the Depth of the Rock is More and Deep Foundation or Pile Foundation is adopted then the SPT N values of the layers of rock is checked and as per IRC 78 the 2 times of the dia of the pile i.e. 2 x 1.2m = 2.4 meter of embedment is only required if the N Value of the rock reaches to 100.

CONSTRUCTION :

• The Construction Methodology is almost similar there is no major differences, although the flyovers are built majorly in urban portions and the construction method should be adequate and the traffic circulation should not be stopped during the construction period, proper diversion should be provided and alternate routes should be planned for the incoming traffic to reduce hindrance during the construction of the flyover.