Dear Member ,
Black cotton soil is greyish black in colour , heavy clay content , It swells when wet ,shrinks when dry ,develops heavy cracks ,termed as poor soil .Approximate Safe bearing capacity is 5 to 10 tonne /sq.m .
- Bearing capacity of soil can be tested at site as per standard test procedure .
- A pit is excavated up to the strata thats needs to be tested .
- The bottom of the pit is levelled ,bearing plate is kept and load is applied .
- The load applied is normally four times the proposed design load .Settlement is recorded after every 24 hours until settlement occurs in 24 hours .
- Settlement under the test load should not be more than 20 mm .
- Loading can be done by using cement bags or sand bags of known weight .
So ,here i hope i have answered your query satisfactorily . But still I will suggest you to read more about geotech engineering texts related to bearing capacity of the soils as you may clear your basic doubts as you will work on site .
All the best !!