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Reduction in pile capacity for Bored cast insitu Piles

 
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john_jeevan
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Joined: 14 Jun 2011
Posts: 7

PostPosted: Thu Nov 22, 2018 12:42 pm    Post subject: Reduction in pile capacity for Bored cast insitu Piles Reply with quote

Sir,
In a soil investigation report for a project recommendations were we follows;
pile dia 500mm; Capacity; 780kN
     -do-  600mm;    -do-      1130kN
     -do-  700mm;    -do-      1530kN

Along with that it was specified like;
" Possibility of buckling of piles up to a depth of 13.5m due to insufficient lateral support( avg. N value less than 1) and corresponding reduction in pile capacity is to be considered during design of piles"

Hello sefians, can anybody guide me how to calculate the reduction in pile capacity during the design of piles
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VPandya
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Joined: 09 Nov 2009
Posts: 825

PostPosted: Thu Nov 22, 2018 5:25 pm    Post subject: Give your Final Foundation Reactrions to Soil Consultant and he gives you design capacities Reply with quote

Dear ER. John Jeevan ,
In U.S.A. soil report is done by a LICENSED  GEOTECH  ENGINEER who Signs and Seal the project Soil Report . We in USA gives our final Foundation Reactions to the Geotech. Consultants and he/she gives me type of foundation for the project ( Must meet requirements of Governing  Building like IBC 2015 on Foundations ) :

Spread Footings  or Raft Foundation or Pile Foundation ( Friction Piles or End bearing piles ) .

We license Structural Engineers will never take responsibility of figuring  out what you are trying to figure out . Your question relates to expertise in Geotechnical Engineering not Structural Engineering .  


Regards.

Vasudeo Pandya  P.E.
Structural Engineer
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ykalamkar
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Joined: 26 Jan 2003
Posts: 108
Location: Nagpur

PostPosted: Fri Nov 23, 2018 7:22 am    Post subject: Reply with quote

Dear Er. john_jeevan,

Piles shall be designed as column. In this case pile will be as long column and eccentricity due to slenderness will have to add along with the minimum eccentricity. This may result to high percentage of reinforcement. Instead, you can reduce the load to reduce the reinforcement.
Also, Loads on piles shall be vertical load (tension/compression) along with the lateral load. Point of fixity shall be worked out by soil consultant and should be provided to you. You can apply spring support at point of fixity level and calculate the reinforcement in the pile. You may require heavy reinforcement in cases where point of fixity is very deep....
Yogesh Kalamkar
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abhy_vivek
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Joined: 26 Jan 2003
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PostPosted: Fri Nov 23, 2018 11:47 am    Post subject: Re: Reduction in pile capacity for Bored cast insitu Piles Reply with quote

Dear John,

   What type of structure are you designing (building / bridge / jetty . . )? Which area / city the structure is located (Delhi / Kolkata / Jammu / Pune . . .)? type of strata (sand / silt / clay / rock at depth) ? What is length of pile planned ?  what are site characteristics (on land / in water / shore)

From the partial information you have given - it looks like the top strata is weak. Please check if 'N' value is so less then there may be possibility of soil liquefaction (if the structure is located in higher seismic zone) !!

As your consultant has expressed possible buckling, check possibility of using higher dia piles 800mm or 1000mm Dia piles !

Have you assessed the possibility of soil improvement using PVD / stone columns etc. ? . . . soil replacement appears slightly difficult due to larger thickness of weak strata.

Reg
Vivek Abhyankar

john_jeevan wrote:
Sir,
In a soil investigation report for a project recommendations were we follows;
pile dia 500mm; Capacity; 780kN
     -do-  600mm;    -do-      1130kN
     -do-  700mm;    -do-      1530kN

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