Civil Engineering - Soil Mechanics and Foundation Engineering - Discussion

It is internal molecular attraction which resists the shear of the material. It decreases as the moisture content decreases and is more in well-compacted clay.

So, C is right.

Cohesion is a soil property. So wouldn't it be constant ?

Secondly with increase in compactness shear strength increase as,
s = c+ sigma*tan(theta).

Well compacted clay doesn't mean that its formed by external load, it can be by natural means also.

Well compacted clay is right but to get well compaction, it will be due to external applied load. Why option D is not correct?

Answer C is correct because if we have a look on option he gave that cohesion decreases as moisture decreases actually cohesion is like a friction it increases when the moisture increases.

Then in option B he gave the same like option a there is no much difference in both but in option C it is more in well compacted clay. It is like when ever a soil is compacted the cohesion increases it is what in every soil mechanics lab we do UCC (UnConfined Cohesion test).

Answer C is correct because with well compaction with water cohesion increase.

Answers A, B and C are all correct. Theory of unsaturated soil mechanics in the the Soil Water Characteristic Curve (SWCC) shows that as gravimetric water content increases or decreases, the suction decreases or increases, respectively.

Also, different soils will present different SWCC's.

Yes answer C is correct, because it has the less inter molecular bonding & moisture content.

Sand is said to be cohesion less soil. Because it has less inter molecular bonding and moisture content also very less. But even though water content decreases in clay's, it may not be a cohesion less soil.

I think cohesion depends upon type of soil also. For example if we take sand its cohesion is zero. So we can't say anything about cohesion by using moisture content only. In option (A) and (B) we can't find which type of soil it is? in well compacted clay cohesion will be more due to decreasing in porosity.