Heave Uplift force

[DaveHolder]

Hi Guys,


I am just not sure how would I work out the uplift force induced by the heave? I have ran a calculation check to find out the minimum foundation depth required when it is close to the trees.


Based on my calcs the minimum foundation depth required is 2m. Water level was 1m below the ground.

We are going to use 4m pile length, however, I am not sure how to work out the tension - uplift force on the pile?


Thanks

 

[r13]

If you place the bottom of footing at 2m below grade, then you have 1m hydrostatic uplift against your foundation. If the foundation is a pile cap, the uplift force per pile is the hydrostatic pressure times the area of the cap and divide the number of pile under it.

 

[DaveHolder]

I was thinking the same, however, I used the volume of soil cubic meter e.g 1m x 1m x 2m x density of the soil 18kN/m3.

I believe that I should of used 1m x 1m x 2m x9.81kN/m3 instead?

Thanks

 

[r13]

The hydrostatic pressure against the bottom of foundation with 1m head, p_w = ϒ_w*h = 9.81kN/m³*1m = 9.81 kN/m². And the uplift caused by the pressure, U = p_w*A_cap.