Breadth Consolidation Vs Settlement

[crazypavement]

I am getting stuck in this part of my studies. I am not sure how to differentiate between what questions they might ask in the AM about soil consolidation and foundation settlement. Will they just mix these two up? or will the foundation settlement not require to calculate soil consolidation within the settlement calculations. The NCEES practice exam just highlights consolidation as a quantity problem and settlement as a conceptual question. There is little information on the CERM about how to differentiate between these two as well just compression and recompression idexes and over consolidation index with the consolidation equations. 

Also are there any good reference for immediate settlement and secondary compression settlement? I am stuck in studying these. 

 

[crazypavement]

"as well just compression and recompression idexes and over consolidation index with the consolidation equations. " I wanted to say, they just cover compression and recompression idexes and over consolidation index with the consolidation equations.

 

[Patrick1441 PE]

I would be prepared to calculate foundation settlement and not just assume it will be a conceptual or a look-up question.  The foundation would be the source of the increase in vertical stress on the soil and you'd solve it using the same method as any other primary consolidation problem, possibly requiring the 2:1 Method or something similar to estimate the increase in stress within a clay layer.  I don't believe you will need to worry about secondary consolidation settlement on the breadth exam.  You should focus on the Primary Consolidation and Primary Consolidation Rate sections in the CERM.

 

[crazypavement]

I would be prepared to calculate foundation settlement and not just assume it will be a conceptual or a look-up question.  The foundation would be the source of the increase in vertical stress on the soil and you'd solve it using the same method as any other primary consolidation problem, possibly requiring the 2:1 Method or something similar to estimate the increase in stress within a clay layer.  I don't believe you will need to worry about secondary consolidation settlement on the breadth exam.  You should focus on the Primary Consolidation and Primary Consolidation Rate sections in the CERM.

Awesome, yeah that is what I was thinking. I was just curious if I should focus on anything else. Thanks for the help, you eased my mind. 

 

[Patrick1441 PE]

Awesome, yeah that is what I was thinking. I was just curious if I should focus on anything else. Thanks for the help, you eased my mind. 

No problem!  That's what this site is for.  Best of luck.

 

[Ranger88]

I would be prepared to calculate foundation settlement and not just assume it will be a conceptual or a look-up question.  The foundation would be the source of the increase in vertical stress on the soil and you'd solve it using the same method as any other primary consolidation problem, possibly requiring the 2:1 Method or something similar to estimate the increase in stress within a clay layer.  I don't believe you will need to worry about secondary consolidation settlement on the breadth exam.  You should focus on the Primary Consolidation and Primary Consolidation Rate sections in the CERM.

Pat,

when would you use  2:1 via 60 degree method for calculating increase of stress in a clay layer?

-Bruce

 

[geomane]

They will more than likely give the method to determine the increase in vertical effective stress, as they do in the NCEES Exams. If they do not, use a couple of methods including the Boussinesq Charts and use your judgment to come to the final answer.

The 2:1 Method is typically used to calculate the increase in vertical effective stress beneath a pile group; however, this will not show up on the morning section.

 

[Patrick1441 PE]

I happened to mention the 2:1 method because it was used in a School of PE example problem that covered foundation settlement.  I actually took the construction depth exam and not geotechnical, so I'd hate to lead you too far down the wrong path about which method is best in which situation.  From what I could tell, though, most breadth exam problems could be solved in one step.  The one step in the exam might be step 3 of a more complicated method, with steps 1 and 2 provided for you already and the missing value for step 4 being the answer you're selecting.  They might provide all of the information you would need to solve the entire method as a distraction too, so you have to be careful to read the question thoroughly!

In the context of a consolidation/settlement problem, I'd guess that you would either calculate the increase in vertical stress or the primary consolidation but not both in the same problem.  I only took the exam once, though, so take that advice with a big grain of salt as anything is possible from exam to exam I'm sure.  The problems can get more complicated in the afternoon, too, of course.