STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

kvgkrangaraju · SEFI Member Joined: 07 Aug 2008 Posts: 10

DearSirs,
Is it required to anchor the footing -(an isolated footing of a multi storeyed building) to the Rock surface when placed over rock even when the said rock is on a plain surface ?

vikram.jeet · General Sponsor Joined: 26 Jan 2003 帖子:3699

Foundations on rock are to be provided with Anchors to bind rcc footings/foundation s with underlying rock.

Though friction between rock and concrete is good/ substantial , but anchoring provides additional benefits :

(我)提供s extra safety against sliding & Overturning

(ii) It provides safety against upliftment during & after construction , in case of higher subsoil water conditions

(iii) It not only benefit foundations , but underlying rock also get stitched. Rock is very strong strata but due to presence of discontinuities , fissures, joints , shear zones , etc weaken the rock strata .
(Somebody said that ,Whereas Soil Mechanics is the study of STRENGTH of soil , Rock Mechanics is the study of WEAKNESSES IN ROCK).

Pl refer BIS Code on foundations on rock .

es_jayakumar · Posted: Fri Sep 16, 2022 2:09 amPost subject:

We have once anchored reinforcement bars into the bed rock for a Tower Foundation, for stability against overturning : //www.buonovino.com/forum/viewtopic.php?t=12949

E S Jayakumar

kvgkrangaraju · SEFI Member Joined: 07 Aug 2008 Posts: 10

Dear Sirs,
Thank You for the prompt reply.
But my doubt was-" is the anchoring required to be done even when the rock surface is plain and horizontal underneath the footing?" Is there any codal requirement to do so?

vikram.jeet · General Sponsor Joined: 26 Jan 2003 帖子:3699

Dear Er

Yes above response is a generalised one giving benefits of rock anchoring.

Please refer IS 12070 Code for design & Construction of SHALLOW foundations on rock.

Regarding anchoring ,, followingneeds to be kept in view :

As per Code ,

Foundations on rock have UNDESIRABLE EFFECTS OF SEISMIC RESPONSE .

HETEROGENEOUS NATURE OF ROCK

PRECAUTIONARY MEASURES TO BE TAKEN FOR FOUNDATION ON HETEROGENEOUS ROCKS ON SLOPES . Hence apparently rock surface appears to be horizontal in small area of this building construction zone , but bed rock profile could be in some grade / Slope .

Also please check up with Geotechnical Consultant who has given Report and foundation Recommendations.