Civil Engineering - RCC Structures Design - Discussion

I believe that this conjecture that cantilever retaining wall cannot be used for height less than 5m is logically incorrect owing to the fact that with the increase in the span of the cantilever wall, the maximum bending moment at the support will increase thereby making it necessary to increase the thickness of the wall. Even for wall of height greater than 5m, let us say 6m, the thickness of the wall required may be higher and also the base area of the wall for the stability conditions like against overturning, sliding etc. Can also be checked and the wall as overall may come out safe depending upon the design and geometry of the wall. For instance, a shear key may be provided to take into account the sliding force and similarly for overturning, the dimensions of heel and toe slab can be adjusted accordingly.

I also want to know whether there is a standard recommendation on the maximum height of a cantilever retaining wall. If yes, then kindly enlighten me about the same.

Cantilever wall are used upto 8 m, there is no restriction on the height only thing is with the increase in height bearing pressure increases and if the foundation soil is not strong then failure will occur,

Nowadays instead of RCC retaining wall, reinforced soil retaining wall are used upto a height of 100 m, in Sikkim a reinforced soil retaining wall of 100 m height is under construction.

We have gone through extensive structural design exercise for waste water treatment plants where cantilever retaining walls are mostly encountered. We found cantilever retaining walls economical upto 20' (6m). Above 6m, wall gets uneconomical.

Generally, economical up to about 25 ft in height.
Use much less concrete than gravity walls, but require more design and careful construction.
Counter fort retaining walls are more economical than cantilever walls for heights above 25 ft.

Reinforced cantilever walls have an economic height range of 1.200 to 6.000 m; walls in excess of this height have been economically constructed using prestressing techniques.

Max Hight of cantilever retaining wall 6 m if height more then 6m then counterfort retaining wall is required. Counterfort wall more efficient to reduce earth pressure.

When the height of the cantilever retaining wall is more than about 7m, it is economical to provide vertical.

Bracing system known as counter forts. So Answer D 6m.

As per my knowledge; D is correct.

Cantilever retaining wall economical for hights 6-7.5 m small to moderate height. So a/c to question 8 m correct.

Rcc cantilever retaining wall can be constructed up to 150m height if the underlying soil strata are hard enough to have the soil bearing capacity.

Cantilever retaining wall restrict up to 6 m ht.

So, option C is correct. Whereas counterfort retaining walls of more than 6m.