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Asked by : jaivir singh duddi, Civil Engineer-Other, punjab engineering college chandigarh
Industry : Construction
Functional Area : India
Keywords : foundation
Activity: Question posted: 04 25 2009 14:58:56 +0000, 10 answers, 17195 views, last activity 08 20 2013 19:19:56 +0000
 
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explain broadly........

 
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Rating : +3 

First the the type of expansive soil like black cotton should be modified by chemical admixtures, which is a common method for stabilizing the swell shrink tendency of expansive soils.  The advantages of chemical stabilization are that they reduce the swell shrink tendency of the expansive soils and also render the soils to be less plastic. Among the chemical stabilization methods for expansive soils, other methods like lime stabilization is most widely adopted method for improving the swell shrink characteristics of expansive soils. Lime stabilization of clays in field is achieved by shallow mixing of lime and soil or by deep stabilization technique. Shallow stabilization involves scarifying the soil to the required depth and lime in powder or slurry form is spread and mixed with the soil using a rotovator. The use of lime as deep stabilizer has been mainly restricted to improve the engineering behaviour of soft clays deep stabilization using lime can be divided in three main groups: lime columns, lime piles and lime slurry injection.

So foundations for these type of soil may be like Deep foundations, where in situations the soil at shallow depth is poor, the depth of foundation is increased till suitable soil stratum is met.  Piles and piers are examples of deep foundations. Lightly loaded structures on expansive clay such as black cotton soil, which is seen mostly in south India and more so in places nearby to Chennai, these are most susceptible for damages as a result of volume changes in the soil.  Under reamed piles are most suitable as foundation for houses in such areas. The pile with a bulb at the bottom are taken to a suitable depth and founded in a zone where seasonal moisture variation is less.

Hope this helps....Mr.jaivir



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by   Pragya Kothari, Construction-Heavy, DLF  | 04 27 2009 11:53:23 +0000
  Answer modified by     Sudarshan Kulkarni, B.Tech/B.E. student, PDJ High School, Bijapur  | 08 20 2013 19:26:46 +0000
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we r doing project on black soil regarding construction problems and characteristic. we are more concentrating on construction .               GIVE SUGGESTIONS IF UHAVE

  Answered by     somashekkhar , Construction-General Building, Sri Ranga Associaties  | 02 12 2011 23:32:45 +0000
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Somashekhar R Engineer and consultant  Hadagali bellary

in black cotton soil , excavate to the depth of 1.5 mts and see the strata what will be the sbc if its of 7 to 8 t/sqc than fill itwith sand and boulder for the depth of 0.45 mts, after construct with mormal way, lay plinth concrete with reniforcemnt

  Answered by     Mohammad Bakhsh, Consultant(Civil), Rail Vikas Nigam Limited  | 03 28 2010 05:47:58 +0000
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The soil is problematic if the free swell index is above 50%.The Indian black cotton soil shows a liquid limit varying from 40%-100%.It has high degree of expansiveness because of high percentage of montomonillonite.The varying treatment methods are available.While deciding the foundation,it should be also ensured that rain water do not find way in the foundation of buildings.I am suggesting  that you go for isolated footing/combined footing for the load requirement.In the excavated pit ,provide three layers of WEDGE SHEAR ELEMENT.Each layer of shear element shall be 25 mm thick comprising of 150mm to 200mm of basalt rock with sand and lime in proportion of 10:1.Over three layer of wedge shear element,provide PCC of 1:4:8 ratio of 100mm thick and construct footing over it.This arrangement will give you bearing capacity of 20t/sqm.I searched solution through net.

  Answered by     vinodkumar balikai, Advanced Construction Management student at NICMAR, Pune  | 03 27 2010 21:08:33 +0000
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I would go for a pier foundation where there is black cotton soil with level of water table comparatively high.

  Answered by     Vivek Singh, Project Manager, L&T  | 03 27 2010 12:20:27 +0000
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Most of us know about the use of under-reamed pile in this case. But Mallaya's point is different. It is actually low cost technique where swelling pressure is not too high or the pressure generated by the weight of the building is high. The technique is to load the foundation with a pressure higher than what is generated by swelling of soil. However do not forget to keep the shear stress taking capacity of soil before designing.

Mr. Dikshit's point is also worth noting. It is an important precaution.

  Answered by     SB DIKSHIT, STATE QUALITY MONITOR, U.P.R.R.D.A  | 07 07 2009 11:41:02 +0000
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APART FROM PILE FOUNDATION ,AT PLINTH,LINTEL AND JUST BELOW SLAB LEVEL AREINFORCED CONCRETE SHOULD BE PROVIDED,THIS IS TO AVOID UNEQUAL SETTLEMENT DUE TO EXPANSIVE SOIL.

  Answer modified by     kamalakannan , Assistant manager, Vedanta Resources  | 07 07 2009 11:04:47 +0000
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I agree with Ms/Mrs.Pragya,but still you have not said specific.for ordinary clay pile is sufficient,but for black cotton soil under reamed pile is preferred due to the expansive nature of the soil.

  Answered by     Mallaya Pandravada, GM-Project , Aditya Housing and Infrastructure Development Corporation  | 06 09 2009 10:09:26 +0000
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Ther is one more way of having the foundation in the black cotten soil as per my experience.In our case Excavation till thew depth of 2m was done and sand filling was carried out for a depth of 40cm and RCC footing isolated was given,All the column pedestals over the ffotngs were connected by the Plinth beams taking the upward soil pressure of the swollen black cotten soil  and Residential buiding was constructed above.

  Answered by     Mallaya Pandravada, GM-Project , Aditya Housing and Infrastructure Development Corporation  | 06 09 2009 10:09:26 +0000
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Ther is one more way of having the foundation in the black cotten soil as per my experience.In our case Excavation till thew depth of 2m was done and sand filling was carried out for a depth of 40cm and RCC footing isolated was given,All the column pedestals over the ffotngs were connected by the Plinth beams taking the upward soil pressure of the swollen black cotten soil  and Residential buiding was constructed above.

 
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