www.sefindia.org

[pradeepkr_2k2000]

Dear All,

We are doing a school construction project. 2m of earth filling is required inside the compound area to match with road outside.

Building foundations to be constructed at 1.8m below NGL and 2m filling is required above NGL

My query is which one of the below 2 options is better?

1. Filling the entire area for 2m and again excavating the building foundations for the depth of 2m+1.8m.
2. Construct foundation by excavating depth of 1.8m below NGL in the initial stage itself and later on filling for the depth of 2m for the whole area.

Please advise me which one will be better.

Regards,
Pradeep




Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com

Posted via Email

[suraj]

Dear Eng Pradeep Kumar,

You query is based on given very little information.
For any construction project, IFC drawings should be used.
Do you have the IFC drawings or you are talking based on the Information drawings?

What are the construction specifications regarding establishing formation level of the finished gropund level?
What are the levels indicated in relation to the global level or the drawing states only the adopted level?
What are the existing floor levels on the buildings existing in the neighbourhood?

There is a method to establish the site zero level or the datum level based on which the other levels are to be established for all permanent works.

The best proposal would be to adopt at ground floor level of the proposed school 450 to 750 mm above existing road level.
It is also not necessary to take down the foundation to 1800 mm deep in case the SBC allows to raise the foundations.
I remember one project in UMM Salal Qatar where we raised the foundations by 450 mm due to the availability of rock in the foundation sections.

Since, in this case, the earth work for filling is to be carried out by earth movers, in any case, first activity should be filling the area to defined levels to the 95% FD a minimum.
The foundation shall follow thereafter as usual.

Regards

[olavocarvalho]

Hi Pradeep,                  You need to cast your foundations prior to any earth filling work.
Please make sure that you check the OMC of the filling soil.
Since the building is a school building, the column spacing will be large.
Hence it would be ideal to use a 10 t. road roller to compact.


olavo carvalho

On Mon, Sep 14, 2009 at 3:26 PM, pradeepkr_2k2000 <forum@sefindia.org (forum@sefindia.org)> wrote:

[vvparmali]

Dear Pradeep,
It is always advisable that you should first construct foundation and then go for the filling. If you go for the filling first then you might have to pay more excavation cost also in such case you will have to excavate more area than normal as slopes maintained will not be stable because of loose fill. So It is better idea to construct foundation first and then go for the filling.  
If your plot area is large the you will have to go for land development first. So you need to go for the First option then. But If your plot area is not so large you can do construction of foundation first and then go for the filling.
Vijaykumar Parmali.


"pradeepkr_2k2000" <forum@sefindia.org>  
14-09-2009 16:05    Please respond to
general@sefindia.org

To
general@sefindia.org   cc
Subject
[SEFI] 2m filling




Dear All,

We are doing a school construction project. 2m of earth filling is required inside the compound area to match with road outside.

Building foundations to be constructed at 1.8m below NGL and 2m filling is required above NGL

My query is which one of the below 2 options is better?

1. Filling the entire area for 2m and again excavating the building foundations for the depth of 2m+1.8m.
2. Construct foundation by excavating depth of 1.8m below NGL in the initial stage itself and later on filling for the depth of 2m for the whole area.

Please advise me which one will be better.

Regards,
Pradeep




Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com

[jiwaji]

With the given information, the second option is preferred as
a) Extra excavation/compaction/material costs, time, effort are saved
b) May not be possible to control excavation depths easily wrt NGL as desired after filling initially all over as per the first option
Regards
Jiwaji Y Desai
DGM (C&S)
TCE Jamshedpur


"pradeepkr_2k2000" <forum@sefindia.org>  
09/14/2009 04:20 PM    Please respond to
general@sefindia.org

To
general@sefindia.org   cc
Subject
[SEFI] 2m filling




Dear All,

We are doing a school construction project. 2m of earth filling is required inside the compound area to match with road outside.

Building foundations to be constructed at 1.8m below NGL and 2m filling is required above NGL

My query is which one of the below 2 options is better?

1. Filling the entire area for 2m and again excavating the building foundations for the depth of 2m+1.8m.
2. Construct foundation by excavating depth of 1.8m below NGL in the initial stage itself and later on filling for the depth of 2m for the whole area.

Please advise me which one will be better.

Regards,
Pradeep




Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com

[ykalamkar]

Dear Pradeep,
It totally depends upon the method of compaction. If compaction is manually, then second would be done. But, if compaction is mechanically say using road roller etc... then you have to go for 1st option
Yogesh

From: pradeepkr_2k2000 [mailto:forum@sefindia.org]
Sent: Monday, September 14, 2009 3:27 PM
To: general@sefindia.org
Subject: [SEFI] 2m filling



Dear All,

We are doing a school construction project. 2m of earth filling is required inside the compound area to match with road outside.

Building foundations to be constructed at 1.8m below NGL and 2m filling is required above NGL

My query is which one of the below 2 options is better?

1. Filling the entire area for 2m and again excavating the building foundations for the depth of 2m+1.8m.
2. Construct foundation by excavating depth of 1.8m below NGL in the initial stage itself and later on filling for the depth of 2m for the whole area.

Please advise me which one will be better.

Regards,
Pradeep




Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com

Posted via Email

[sspawar]

Dear Pradeep,
Go straight for second Option:
2. Construct foundation by excavating depth of 1.8m below NGL in the initial stage itself and later on filling for the depth of 2m for the whole area.
Provided constructional mobilty is being maintained for easy reach and working.

later as per your working comfort (Like plinthbeam , tie beam, grade beam etc - at different level) filling in layers should be done.

Though your question is only related of sequence of activity - so in this respect consider this answer.
As for methodology of filling is not asked by you.
Any how you have also been come to know about that: If flooring resting directly on fill, It should be in 300mm layers and compaction test to be carried out for 95% relative field density. -----fill material should be selected ----- CBR of gradully upper layer should be higher etc ----
If it is framed structure - then no need of proper care but should be filled and compacted.
Regarding other level and other Bye laws  ---------- you shpould take care

Regards

[suraj]

Dear Engineers,

Various comments made me to think about the engineers approach while executing the works of buildings.

Should an engineer responsible to carry out the project go for what has been designed rightly or wrongly?

It is true that there is a design proof check activity & experts do that from the view point of theory & designs. Probably, out of these experts many may not even be aware of the site realities. Some of them may not be well conversant with the geotechnical engineering. Some may not be able to construe the reports rightly submitted to them.

We are deliberating on a school building. I suppose the building is a large one that can accommodate a preparatory or senior secondary school having say 25 class rooms with other facilities.

I suppose the area of the school building would be about one hectare if not more. It is definite that the school building shall be covered on about 25 to 35 % ground. It is also acceptable that the buidling shall not be more than 2.5 storey. I suppose the columns would be 5 m spacing on an average with the exception of the atrium or the ceremonial hall or auditorium possibly double height with 15 m span or more.

It also appears that the existing terrain or topography of the plot is low profile that has been said about 2 m from the road level. I consider the worst case of soil strata as clay.

Designer says to go down to 1.8 m below the natural ground level though the design specification of referring to the NGL is not a good practice. Designer should have properly surveyed the plot to fix a adoptable datum level that is missing.

Plot has to be filled 2 m & it is also true that engineered fill shall be used for the portion of the main structures while general fill shall be used for the non structural portions. The question has not directed about anything as such.

Should we agree with the designer, the depth of the foundation would be 3.8 m from the road level or the made up ground formation. Should we as design engineers agree the proposition? Should we as field engineers agree the proposition? Should we not make a question out of such consideration? Why so much in foundations?

Would we acknowledge & accept whatever is given to us?

After having done the engineerd fill & the general fill, there shall be no requirement of taking down the foundations to the indicated level.

Building shall not require SBC more than 15 T/sqm

These fills are not done loose as commented by some engineer. The fills are done in layers & are compacted to 95 to 98%. Should we accept that such layers would subside???

There would be no requirement to take the foundation to more than 1.2 M deep from the made up ground. Since the fill being granular, consolidation may not be a major issue to an extent, the construction is concerned.

Foundations definitely would be footings monolithically cast with the straps,

For this purpose, the excavation has to be done after the filling but in a massive mode & after the foundations are completed, backfill in a massive mode but in layers.

Not only, it is relevant to the fill activity but, the excavation in the made up fill shall be carried out for the building services internally as well as externally.

It is suggested that the designer be contacted & be made apprised about the deficiency in the design so that the design is given a consideration of value engineering.

It is also to my surprise that these days some engineers conceive the excavation or the backfill manually in open areas. JCB charges only 600 to 750 rupees per hour & it can work a lot in one hour. The whole building excavation after the fills, would not cost more than 10 hours.
Regards

[ibarua]

15th Sept 2009

Obviously, option #2 is preferable, because thereby you avoid excavating soil that has been filled up recently. This is the practice we always follow.

However, greater care needs to be taken for filling within the building, which needs to be consolidated with optimum moisture content to avoid settlement and consequent distress of floor finishes in the ground floor.

Indrajit Barua.

On Mon, 14 Sep 2009 pradeepkr_2k2000 wrote :

[B.S.VIRDI]

In this case first do the filling , compact the filling in layers of 300 mm each by watering and by small mechanical vibraters . Complete the filling up to required level. Do the lay out , excavate the footing up to 1.5m from filled up level as recommended by soil consultant, do take care while designing foundation in this case to consider over burden pressure.    


B.S.VIRDI