Allowable deflection of retaining wall

[debpriya1984]

Hi All

I am doing preliminary design of Contiguous Bored Pile wall for Crossrail project in London.The soil stratum is 1.5-2.0m thick made ground and 20-25m thick London clay.I adopted 1050mm dia pile @1150mm spacing.The retained height varies from 6.0-8.0m.I am getting 44-50mm as short term movements and 95-100mm as long term movements.There are existing Viaduct foundations near proposed retaining wall.Are there any allowable criteria for deflection and movements of retaining walls?

 

[DRC1]

There are some charts and corralations relating ground maovement to settlement, but these are approximations. the iaduct fondations will induce stress and movements of the wall willeffect the viaduct foundations. Sheeting unless it is very rigid is not a good means of foundation suport, and even then it is best for lght oads that ca tolerate a little movement. In short you should consider underpinning for the viaduct foundations.
As for deflection limits, I generally work with sheet piles or H-piles. I typically try to limit deflection to 25 mm. This not any written code, but rather due to a desire to limit secondary bending (p-delta) effects which are realy not considered in most sheeting analysis methods.

 

[palmahouse]

I recommend you read "Construction Induced Movements of Insitu walls" by Clough and O'Rourke.

 

[ruready]

We use H(in)/90 as a guide... Cant tell ya where we got it from though

 

[BigH]

Also suggest you research London Clay - and materials by Tomlinson, Schofield, Skempton, Bishop, Hutchinson - might give you insights that would prove useful. London clay is rather well understood and you should be able to find specific information rather than more general correlations/relationships.

 

[Delijosi]

Wall deflection of 0.01*retained height is acceptable. Anything higher is not. You might want to estimate roughly the ground movement as a result of the wall deflection. Use CIRIA c580. There are some tables there. This will give u the expected movement of the viaduct foundation. If the movement is not aceptable, underpin the foundation or use anchors on the wall.

 

[csd72]

Definately use the CIRIA guide as this will give you all the information you need on this.

The allowable deflection depends on what it is supporting. An old brick building maybe 20mm or less.

Also why are you looking at long term deflections? Wont you have a floor slab providing permanent support?

 

[VoyageofDiscovery]

If you are supporting a rail, then rail movement criteria set by your rail authority will limit all your movements.

HTH