shoring design principle results

[tre5205]

I want to ask fellow shoring engineers out there. It seems there are advantages and disadvantages to the limit equilibrium method, numerical methods, and the p-y method(soil interaction) for doing shoring design.

My question is that i have seen slightly different results for each method more so that the p-y method and numerical integration methods are closer but how does one feel comfortable that in reality they all work? They have been proven to work so i guess the results you get with either are going to be slightly different than the real world results if you will.

Does anyone have some input on this?

Thanks

 

[TDAA]

I think it is similar to establishing a bearing capacity for a footing. You can use some easy methods and get 3000psf, or you can go through a more detailed analysis including capacity and settlement and perhaps get 3200psf. The difference in this case is pretty minimal, and both fall below the actual value due to factors of safety.

Now, if the difference was quite large, I would look into what may be wrong.

 

[DRC1]

I primarily use limit equilibrium and have started to get into p-y analysis and Ensoft's p-y wall. Limit equilibrium is more of an Ultimate strength approach. If you fully develop the driving stress, by it active or at rest, how much full developed depth of passive pressure, assuming a rigid wall, do you need to resist that driving pressure. Then the required stiffness for the wall is computed. With P-y analysis the driving force is resisted by the available stiffness of the soil and the stiffness of the wall. Thus from my perspective, Traditional limit equilibrium is akin to ultimate strength of the soil system, where as p-y analysis is more like allowable stress design. Thus for the same wall in the same soil, you would expect to get somewhat different answers.

 

[RFreund]

Are there any good references specifically on this subject (the limit equilibrium method, numerical methods, and the p-y method(soil interaction) for doing shoring design)? Design manuals, codes, or texts? We don't do alot of earth retention or atleast not big earth retention but we may in the future and I'd like to research this topic a little more.

EIT

 

[tre5205]

Thanks for the replys- those make sense.