# Pore pressure due to capillary rise

1. Sep 14, 2017

### tzx9633

1. The problem statement, all variables and given/known data
Why there's no pore pressure due to capillary rise at point A and point D ? There's only pore pressure due to capillary rise at B ..
2. Relevant equations

3. The attempt at a solution
i think the author is wrong . There's should be also ore pressure due to capillary rise at A and D . Because the capillary rise can occur anywhere in the soil .

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2. Sep 14, 2017

### Staff: Mentor

3. Sep 14, 2017

### tzx9633

Huh , what do you mean ?

It's the pore water pressure due to capillary rise , u = -s(yw)(H2)

4. Sep 14, 2017

### Staff: Mentor

There is no water in the pores at A; it is above the saturation zone. At D, the pores are all fully saturated, because it is below the water table, and there is no capillary pressure there because there is no free surface (between air and water) in this zone. So the author is correct.

5. Sep 14, 2017

### tzx9633

Having said that there's capillary rise at B , means that there is free surface (between air and water) in this zone ?

I didnt see there's air at B , can you explain further ?

6. Sep 14, 2017

### Staff: Mentor

Sure.
What do the words "50% saturated" mean to you?

7. Sep 14, 2017

### tzx9633

ok , noted . Why there is no pore pressure due to capillary rise at C ?

8. Sep 14, 2017

### Staff: Mentor

At C and below, the pores are completely full of water.

9. Sep 15, 2017

### tzx9633

How do you know that there's no water at A ? How do you know that there's water at B ?

10. Sep 15, 2017

### Staff: Mentor

The figure implies that, between A and B, there is dry sand and between B and C, there is partially saturated sand. So, B is the top of the region containing water in some of the pores.