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borewell beside footing mat

 
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jagan0819
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PostPosted: Thu Sep 20, 2018 2:24 am    Post subject: borewell beside footing mat Reply with quote

hello every one

i have designed a multistorey structure(G+5) and one of the footing mat falls close behind the wall of borewell (which is closed with soil) and i had a doubt whether to place the mat beside it or not?

pdf plan and soil report attached

regards



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es_jayakumar
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PostPosted: Sat Sep 22, 2018 4:37 pm    Post subject: Reply with quote

You have stated that the bore-well is already closed. Further, the soil below 1.50m looks very dense, the N value being >50. Hence, the possibility of movement of soil towards the well and the consequent subsidence of foundation or the shear failure of sub-soil can mostly be ruled out, I hope. Casing pipe of the bore-well, if any provided inside, will add to the stability.

E S Jayakumar
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spsvasan
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PostPosted: Sun Sep 23, 2018 12:31 pm    Post subject: Re: borewell beside footing mat Reply with quote

jagan0819 wrote:
hello every one

i have designed a multistorey structure(G+5) and one of the footing mat falls close behind the wall of borewell (which is closed with soil) and i had a doubt whether to place the mat beside it or not?

pdf plan and soil report attached

regards



Dear Er.Jagan

The drawing seems to indicate that the well is an open well and not a borewell. Please clarify

If it is an open well, what is the ring made of?

S.P.Srinivasan
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jagan0819
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PostPosted: Sat Sep 29, 2018 7:37 pm    Post subject: Re: borewell beside footing mat Reply with quote

yes sir its an open well but it is closed and ring is made of brick masonry
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spsvasan
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PostPosted: Sun Oct 14, 2018 3:21 am    Post subject: Re: borewell beside footing mat Reply with quote

jagan0819 wrote:
yes sir its an open well but it is closed and ring is made of brick masonry



Dear Er.Jagan

There can be a lateral thrust on the well lining due to the soil pressure below the adjoining footing

The unsymmetrical horizontal force on the brickwall can lead to bending moment in the brickwall. If the moment is large it can crack the well and lead to settlement of the footing.

Experts in the forum may please give their opinion as to whether this is a serious condition or not.

S.P.Srinivasan
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es_jayakumar
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PostPosted: Sun Oct 14, 2018 4:17 am    Post subject: Reply with quote

Srinivasan sir,
I hope, the predominant stress in the brick lining of the well will be hoop compression resulting from the horizontal thrust exerted by the earth beneath the footing. Brick masonry is relatively stronger in hoop compression. It may be possible to evaluate the hoop stress on the brick lining by first computing the lateral thrust using Rankine formula for EP at Rest (on conservative side) operated on the surcharge load beneath the footing.
Please provide your guidance.

E S Jayakumar
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spsvasan
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PostPosted: Sun Oct 14, 2018 1:07 pm    Post subject: Reply with quote

es_jayakumar wrote:
Srinivasan sir,
I hope, the predominant stress in the brick lining of the well will be hoop compression resulting from the horizontal thrust exerted by the earth beneath the footing. Brick masonry is relatively stronger in hoop compression. It may be possible to evaluate the hoop stress on the brick lining by first computing the lateral thrust using Rankine formula for EP at Rest (on conservative side) operated on the surcharge load beneath the footing.
Please provide your guidance.

E S Jayakumar



Dear Er.E.S.Jayakumar

In the case of uniform compression all around the brick well, the stress in the brick wall will be only hoop compression. In the case of lateral pressure due to footing load, the lateral pressure will be high near the footing and practically zero at the diametrically opposite side. Hence bending moments will develop in the brick wall. if the moment is high the wall may crack

S.P.Srinivasan
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es_jayakumar
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PostPosted: Sun Oct 14, 2018 1:15 pm    Post subject: Reply with quote

Sir,
Won't the passive EP by soil on the diametrically opposite face exert thrust in opposite direction ?

E S Jayakumar
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spsvasan
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PostPosted: Wed Oct 17, 2018 1:41 am    Post subject: Reply with quote

es_jayakumar wrote:
Sir,
Won't the passive EP by soil on the diametrically opposite face exert thrust in opposite direction ?

E S Jayakumar



Dear Er.E.S.Jayakumar

For developing passive pressure, the well has to move a bit. Will this not induce settlement of the adjoining footing?

Further, in this case also the soil pressure around the periphery of the well will be variable, leading to bending moments. in the brickwall

It is possible that the soil pressure is small and the brick wall will be able to resist the same. But, IMHO it is prudent to get an assessment of probable soil pressure from a geotechnical consultant and check the brickwall.

If anybody has provided a footing adjacent to a brickwell and it had been safe, it will give us a little more confidence

S.P.Srinivasan
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jagan0819
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PostPosted: Wed Oct 17, 2018 2:52 pm    Post subject: what would be the minimum distance of footing from bore well loacations Reply with quote

dear all

thank u for your valuable support
and i want to what would be the minimum distance of  footing edge from borewell
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