STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

NAOBA MEETEI · SEFI Member Joined: 29 May 2014 Posts: 1

Dear SEFI,
I am one of engineer from manipur. We have project for Long span bridge of 50m length. For that pilling of length 27m is recommended from layout. But during boring we have found hard shell at depth of 12m which we can't go further.
We are planning for open foundation but complications is that we don't want to disturb existing valley bridge(5m from new site).
My question to sefian is that which will be better
Open or increase number of pile
We mainly consider for lateral load safety. Since my state is in earthquakes high zone.
Every suggestion will be really helpful
Best regard
Naoba

VPandya · General Sponsor Joined: 09 Nov 2009 Posts: 842

Dear Er. NAOBA MEETEI,
In USA where I worked for many years  , we hire a LICENSE  GEOTECH  CONSULTANT  ( SOIL CONSULTANT ) . It his job to do necessary soil borings and recommend TYPE OF FOUNDATIONS , RAFT, SPREAD FOOTING , PILE FOUNDATION . We Structural Engineers only give FINAL FOUNDATION  REACTIONS ,   BOTH  GRAVITY ( DL ,  LL ) AND LATERAL LOADS ( WIND , EARTH QUAKE ) . License Geotech ( Soil Consultant)  , SIGH AND SEAL HIS  PROJECT  SOIL REPORT .
I am assuming that you are a Structural Engineer on the project . You hire a very experience SOIL CONSULTANT , GIVE HIM FINAL  FOUNDATION REACTIONS  and let him recommend what to do .

Let Soil Consultant  worry about it . This  is  his specialty, not yours  a Structural Engineer .

Regards.

Vasudeo Pandya P.E.
Structural Engineer

es_jayakumar · Posted: Sat Sep 14, 2019 1:27 am Post subject:

Er Naoba,
You say that hard shell was met with at 12m depth, which is found hard to penetrate further. Is this shell layer thicker and spread all along the terrain ? If so, can you terminate the pile tip socketed in this layer ? If pile tip is rested in hard stratum, I think, the end bearing resistance will be enough to make up for the reduction in the frictional resistance of shaft due to curtailing the pile length. Can you please post the bore-log chart and foundation recommendations here ?

E S Jayakumar

es_jayakumar · Posted: Wed Sep 18, 2019 1:06 am Post subject:

Er. Noaba,
Nothing is heard from you afterwards. In addition to checking the end bearing capacity of the pile in the hard shell layer, you have also to check for the sufficiency of lateral load carrying capacity of the pile, upon the truncation of its length.

E S Jayakumar