Failures in Raft Foundation bridges with some probable solutions

 

Failures in Raft Foundation bridges

I have observed many Raft Foundation Bridges in Maharashtra which have failed, 

I have tried to make an Animation to demonstrate the failure mechanism as shown in below video

Picture 1:- Its vented Paved-dip having similar foundation system to that of Raft, Common observed phenomenon is, 

Scouring --> Downstream side

Silting  --> Upstream side.

The Silting on Upstream in Pipe culvert is due to several reasons such as

1) Inadequate slope to pipe from Upstream to downstream side

2) Blocking of pipes due to sticks, Plastic material etc

I have tried to solve this problem up to certain extent as demonstrated in video below.

If we observed carefully the actual problem of Failure is Failure of Transportation of bed material (Clay, Silt, Sand, Gravel, Pebbles etc.). To solve this problem we may provide through RCC pipes from upstream to downstream with steep slope so that bed material will not stuck in pipe and material can be transferred from upstream to downstream easily.