Settlement of Pile Group

[Yue]

I need to calculate the settlement of pile group I found that some geotechnical publications said based on "equivalent raft concept", the total load is carried by a "equivalent raft" located at a depth of 2/3pile length and assumed the load spread from the perimeter of pile group at a slope of 1 horizontal to 4 vertical. Below the raft the load is spread as a slope of 1 horizontal to 2 vertical. Could anyone explain how the 1:4 and 1:2 were defined.

Also I found some books does not consider the "equilvalent raft". The total load spread at a slope of 1:2 begin at the depth of 2/3 pile length. Which one is better for the calculation of pile group settlement?

 

[sjhgeotech]

The 60-degree method is the one that I am familiar with. Calculate the area of the pressure influence at the mid-layer of the settling clay using a 60-degree projection from horizontal at 2/3rds of the pile length.

Das's book has some more information on this.

 

[jdonville]

The FHWA driven pile manual (HI-97-013) has diagrams and recommended methods to use depending on the soil profile assumed. Unfortunately, one of the text pages (9-122) describing the methodology was scanned incorrectly for the PDF version on the FHWA website. I have managed to parse the text and have a word file with my best shot at the correct text. I will try to send to SlideRuleEra and ask him to post on his site (with lots of other goodies) shortly. Let me know if anyone wants/needs it sooner.

Jeff


Jeffrey T. Donville, PE
TTL Associates, Inc.

http://www.ttlassoc.com

The views or opinions expressed by me are my own and do not necessarily reflect the views or opinions of my employer.