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Civil PE Sample Exam (Lindeburg) #81


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#1 milwaukee-geotech

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Posted 26 March 2011 - 10:14 PM

I have a question regarding the calculations in this problem (#81 Pile Settlement). Am I wrong but shouldn't the unit weight of layer 1 and 2 below the water table be the saturated unit weight and not the unit weight given. this changes initial stress calculation and I obtain the wrong answer. the solution takes layer 1 below the water table at (19kn/m3 - 9.81) shouldn't it be (19 * 1.28)= 24.32 kn/m3 for the saturated unit weight giving you (24.32 - 9.81) = ---etc.



I'm just not a fan of the Lindeburg sample problems vs. DAS and Knowles books and the NCEES sample exams.

#2 chess5329

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Posted 27 March 2011 - 01:19 AM

QUOTE (milwaukee-geotech @ Mar 26 2011, 03:14 PM) <{POST_SNAPBACK}>
I have a question regarding the calculations in this problem (#81 Pile Settlement). Am I wrong but shouldn't the unit weight of layer 1 and 2 below the water table be the saturated unit weight and not the unit weight given. this changes initial stress calculation and I obtain the wrong answer. the solution takes layer 1 below the water table at (19kn/m3 - 9.81) shouldn't it be (19 * 1.28)= 24.32 kn/m3 for the saturated unit weight giving you (24.32 - 9.81) = ---etc.



I'm just not a fan of the Lindeburg sample problems vs. DAS and Knowles books and the NCEES sample exams.


I'm agree with you milwaukee!

I think we have to take this types of problems as what they are just " practice problems", also ppi should stop making confusing problems that only confuse the exam taker. Don't forget this time we have a complete guide NCEES has provide, just take a look to this and you'll see they just provide "Y" (total unit weight) and if this is below water table you just calc. for (Yb); I think they're improving. Of course this doesn't mean forget to check for a different unit when they provide other soil properties.

just my 2 pennys!

#3 milwaukee-geotech

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Posted 28 March 2011 - 02:19 PM

I realized my error in this problem as I thought more about it. Came down to the symbolism that 6 min solution uses compared to what I was used to see.




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