|
Activity:
Question posted: 04 25 2009 14:58:56 +0000,
9 answers, 5599 views, last activity
02 12 2011 23:32:45 +0000
|
|
|
|
explain broadly........
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
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
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.
I would go for a pier foundation where there is black cotton soil with level of water table comparatively high.
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.
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.
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.
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.
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.
|
|
Prime Minister Manmohan Singh said that there is "no instant solution" to bring back black money... |
|
|
823 referals
26 arguments,
386 views
|
|
|
National Seminar on Black Money was organised on May 18 , 2011 in New Delhi....The seminar was... |
|
|
79 referals
12 arguments,
506 views
|
|
|
Steel shuttering is a better option or wooden shuttering for civil engieering constrution... |
|
|
177 referals
48 arguments,
2932 views
|
|
|
|
|
|
|
|
|
reference handle only |
|
|
0 referals
0 answers,
0 views
|
|
|
|
202 referals
1 answers,
21 views
|
|
|
Construction site at South Mumbai( One of the prime locality with most of Parsi community... |
|
|
0 referals
0 answers,
0 views
|
|
|
|
|
|
|
the topics for my thesis...... |
the tests for geogrid material is needed in India........for better and fruitful results,..... |
planning is main phase for any type of project....... |