Sheet Pile Design - Causeway with Tire Pressures as Strip Loads, Retained by SSPs, and Faced with Concrete Blocks

[TymProkopovych]

Hello Community! It is my first time posting here, and I hope I can get some help with this interesting sheet pile case.

I am evaluating a proposed causeway by a marine contractor that utilized sheet piles to retain a roadway embankment. I have attached a sketch of my analysis model for reference. At first, I neglected any resisting effect from the concrete blocks (around 1x1m), and determined the required penetration depth using Teng's simplified method for cantilever sheet piles on granular soils. The result was a total sheet pile length of around 15m, which does not sit well with the contractor, as they want to avoid splicing (for lengths beyond 6m).

Hence, I would like to clarify if:
1) I may use the concrete block facing to aid in reducing the sheet pile length (i.e. by resisting the lateral pressures acting on the full height of its side)?
2) If that is the case, how will it modify my initial analysis considering the usual setup of cantilever sheet piles (where the unbackfilled side doesn't have any resisting element)?

Thank you so much!

 

[HTURKAK]

At least you can consider the concrete blocks as surcharge and increase the passive thrust accordingly. Your sketch shows passive thrust is triangular .

 

[jayrod12]

Depending on the soil, a 2:1 embedded to exposed doesn't seem that crazy to me. Then again I'm living in an area with clay as far as you can dig, so our capacities are pretty low.

I would think you'd have to get geotechnical engineer buy in on using the blocks for anything.

 

[TymProkopovych]

At least you can consider the concrete blocks as surcharge and increase the passive thrust accordingly. Your sketch shows passive thrust is triangular .

Hi thanks so much for the input. The tricky part is drawing the surcharge distribution for a seemingly triangular/trapezoidal concrete mass. I haven't been able to find any resource of surcharge loading on retaining systems besides line and strip(rectangular) surcharge. Can you provide a resource?

 

[TymProkopovych]

Depending on the soil, a 2:1 embedded to exposed doesn't seem that crazy to me. Then again I'm living in an area with clay as far as you can dig, so our capacities are pretty low.

I would think you'd have to get geotechnical engineer buy in on using the blocks for anything.

Hi thanks for replying. I agree however the contractor would want to avoid lengths greater than 6m thus the exploration of options.

 

[EireChch]

The blocks are acting as a berm to the wall. It would be far to conservative to not consider any support from them. I can see why the contractor wouldnt be happy. Pick up a copy of CIRIA c760 and read the section on berms and how to consider them in your analysis.

 

[TymProkopovych]

The blocks are acting as a berm to the wall. It would be far to conservative to not consider any support from them. I can see why the contractor wouldnt be happy. Pick up a copy of CIRIA c760 and read the section on berms and how to consider them in your analysis.

Thank you for replying. I think I found your resource and was led to this approach: https://www.icevirtuallibrary.com/doi/10.1680/geng.2008.161.1.39


However, is the θc or tan(45+Φ/2) still valid for a concrete block berm?

 

[EireChch]

yes, still applicable. The theta c angle is a function of the passive soils friction angle. The berm above is completely separate to it. It could be concrete, rubber tyres etc, all we are concerned with is the weight it provides.

 

[TymProkopovych]

yes, still applicable. The theta c angle is a function of the passive soils friction angle. The berm above is completely separate to it. It could be concrete, rubber tyres etc, all we are concerned with is the weight it provides.

Alright thank you very much!