6 min sol (Geotech) Problem 19

[Road Guy]

alright for the life of me I cant figure out why the horizontal active presure is treated as a surcharge pressure below the phreatic surface extending as a rectangular pressure distribution to the base of the wall

actually I get the rectangular part, but how can the above and below be equal? Since the Ht for the above is 8' and the Ht below = 7?

Page 37 of the solution (both equal to 306???)

I am cool with the rest of the solution, but I would have hosed that part..

 

[EL Nica PE]

The horizotal surcharge is in dependant of height. Surchage = Delta P.

Kind of as a settlement calculation.

 

[Road Guy]

I guess in this particular solution it throws me off that they dont include any of the information from below the water table, only above. maybe I need to learn what surcharge really is...

 

[GTScott]

I thought that problem was much more complicated when I looked through their solution. They break it up kinda funny, IMO. If you would like, I can rework it my way and post it.

-GT

 

[3gorgesdam]

Please provide with full question and your answer if you can. Thanks.

 

[Road Guy]

if you can scan it as a pdf they post easily.

it would be much appreciated..

 

[GTScott]

No problem...in studying for the Geo PM I was planning to do walls tomorrow. I will just work that one a bit neater for you.

 

[GTScott]

Sorry I forgot about this...I will try to workk it up this morning into logical steps. These problems are time consuming and not something I would *expect* to see in the AM, from what I have heard.

 

[GTScott]

Alright, I tried to break this into the steps you would use for any wall. The thing they throw at you on this one is the water table. If you just had a dual layered profile this would not have been as tricky. However, the water table causes you to have to use bouyant unit weight.

Good luck with my handwriting...this is me trying to write neat.

The problem took me seven minutes along with writing out the commentary.

-GT

Multilayered w/ WT Retaining Wall - #19

 

[3gorgesdam]

I worked the problem out even though I don't have the original problem, with solution I can tell the backfill is horizontal and grainular material. That is why ka can be obtained from a simplified equation.

I liked the notes on the sides, coz I did forget about R1B, the rectangular portion. Also, it is good to seperate water and soil since soil need to be ajusted using Ka factor but water doesn't need.

Thanks for posting.