Civil Engineering - Soil Mechanics and Foundation Engineering - Discussion

Discussion Forum : Soil Mechanics and Foundation Engineering - Section 1 (Q.No. 5)
Which one of the following statements is true ?
Clays are more porous than sands
Pressure of organic matter in a soil decreases the bearing capacity of the soil
Aluminous cement is used for foundations in soils with chemical deposits
All the above.
Answer: Option
No answer description is available. Let's discuss.
57 comments Page 1 of 6.

Santosh Kumar said:   2 years ago
Of course, Clay is more porous but quite less permeable than sand.

Vikas said:   2 years ago
Porosity is a measure of pore spaces in soil. It is a volumetric ratio. It is ratio of total volume of voids (filled with water or air) to the total aggregate volume of soil mass.

It is dependent on so many factors like texture, structure, arrangements of particles and organic content.

Clays have particles size below 2 microns and these small particles have small pores and the interconnected pores gives more voids which makes it more porous.

Sand have particles size greater than clay and these particles have small pores compared to same volume.

Hence clays is highly porous than sand. However, clays are not permeable (water can't flow easily through them because of these small pore size) and sands on the other hand offer excellent drainage properties.

When it comes to porosity, then clay is more porous than sand. This is because the grain size of clay is much smaller than sand. So inter-granular space between the individual grains is much more in case of clay than sand. But all these pores are not interconnected so the permiability of clay is poor. However the intergranular space in sand is more so it has greater perbiability.

But then again everything can happen depending on the degree of compaction and lithification.

Porosity (n) is the percentage of void (Vv) in the total volume+void (V) of a solid of earth material. According to Fetter, pg 75, in table 3. 4, Porosity ranges for sediments.

Well-sorted sand or gravel = 25-50%.

Mixed sand and gravel = 20-35%.

Clay = 33-60%.

This is according to Meinzer (1923a) ; Davis, 1969; Cohen, 1965; and MacCary and Lambert, 1962.

So, Clay should be much porous than sand thou not pretty much.

As mentioned 'the dispersive effect of the electrostatic charge present on the surface of certain book-shaped clay minerals causes clay particles to be repelled by each other resulting in relatively large proportion of void space.

Smile said:   2 years ago
As The surface area increase, proportionally the porosity also increases as the clay has more surface area than sand it is more porous.

Naresh said:   3 years ago
Clay has a flocculated structure which increases its void but the flocculated structure does not allow percolation of water.

Ziyaurahman Ansari said:   3 years ago
A) Generally in the construction field, only 3 types of cement are mostly in practice

1. Ordinary portland cement,
2. Pozollona portland cement,
3. White cement.

Viki said:   6 years ago
1. The main advantage is that it can withstand high temperatures so that it can be used in refractories, foundries and other workshops where high temperatures are involved.

2. The initial setting time is 3 hours than compared to that of PPC cement. And the final setting time of cement is 5 hours.

3. High Alumina Cement evolves great heat when setting so that these cements can be used in colder temperatures.

4. It is highly resistants to even concentrated acids and thereby it is widely used in chemical industries.

5. It sets fast and it attains a strength of 40 N/mm2 in just one day and 50 N/mm2 in three days.

Abinet said:   5 years ago
Clay soils are more porous than sandy soils. True because porosity is the ability of a material to hold water where as permeabilty is the ability of a material to allow passage of water through it.

Ganesh VG said:   6 years ago
I think porosity is the number of pores. Not the holding capacity.

Manoj said:   5 years ago
What is the relation between Porosity, permeability and capillary rise ?

Kiran said:   5 years ago
Presence of organic matter in the soil.

Not pressure of organic matter.

Post your comments here:

Your comments will be displayed after verification.