How High Must the Water Table Rise to Float an Offshore Circular Foundation?

  • Thread starter JosephR
  • Start date
In summary, the circular offshore foundation is resting 2ft below the surface of a dry sand with a void ratio of 0.5, Gs=2.7, and ϕ'=35. The foundation is loaded to a load q=qu/5. The water table, originally 10ft below the ground surface, rises while the load on the foundation remains constant. Using Terzaghi's theory, the load on the foundation before the water table rises can be computed by the equation qu = 1.3c'Nc + qNq + 0.3BγNγ. To determine the height at which the water level would have to rise to float the foundation, the equation Fq=1+
  • #1
JosephR
11
0

Homework Statement


A circular offshore foundation, with a diameter of 5ft rest 2ft below the surface of a dry sand. The sand's void ration = 0.5, Gs=2.7, ϕ'=35.
This footing is loaded to a load q=qu/5
The water table which was 10ft below the ground surface surface,now rises while the load on the foundation remains constant.

1) Compute the load on the foundation, before water table rises using Terzaghi's theory.
2) At what Height above the ground surface would the water level have to rise to float the foundation.


Homework Equations



Terzaghi's equation for circular foundation:
qu = 1.3c'Nc + qNq + 0.3BγNγ

Where q=γ*(depth of foundation)
Nc,Nq & Nγ are found using a table.

Fq=qu/γDf where Df= Embedment Depth of foundation here it's 2ft.
Fq=1+2[1+m(Df/B)](Df/B)Ku*tanϕ' Ku can be determined from a table.


The Attempt at a Solution



Here I pictured the solution and I'll post it here...

http://img253.imageshack.us/img253/4986/pb030002.jpg

http://img64.imageshack.us/img64/5879/pb030003.jpg

I just want to know if my solution is correct...Thanks in advance..
 
Last edited by a moderator:
Physics news on Phys.org
  • #2


Your solution looks correct, but it would be helpful to label your axes and provide units for your values. Also, be sure to explain your steps and assumptions clearly so that others can understand your thought process.
 

FAQ: How High Must the Water Table Rise to Float an Offshore Circular Foundation?

What is a shallow foundation?

A shallow foundation is a type of foundation that is typically used for smaller, lighter structures, such as houses or small commercial buildings. It is placed close to the surface of the ground and spreads the load of the structure over a larger area, making it suitable for areas with stable soil conditions.

What are the types of shallow foundations?

The most common types of shallow foundations are spread footings, strip footings, and mat foundations. Spread footings are used for individual columns or piers and are typically square or rectangular in shape. Strip footings are used for load-bearing walls and are longer and narrower than spread footings. Mat foundations, also known as raft foundations, are used for larger structures and distribute the load over the entire area of the structure.

How are shallow foundations designed?

Shallow foundations are designed by considering the soil conditions, the weight of the structure, and the expected loads that the foundation will need to support. Factors such as the type of soil, its bearing capacity, and the presence of water or other factors that could affect the stability of the foundation are also taken into account.

What are some common problems with shallow foundations?

Some common problems with shallow foundations include settlement, which occurs when the foundation sinks or shifts due to inadequate soil support, as well as differential settlement, which happens when different parts of the foundation settle at different rates. Other issues can include inadequate bearing capacity, soil erosion, and water infiltration.

How can I determine if a shallow foundation is the right choice for my project?

The decision to use a shallow foundation depends on several factors, including the size and weight of the structure, the soil conditions, and the expected loads on the foundation. It is important to consult with a structural engineer or foundation expert to determine the best type of foundation for your specific project.

Similar threads

How High Did Water Rise in the Squalus Diving Bell?
Replies
6
Views
3K
How High Does Water Rise in a Diving Bell?
Replies
2
Views
6K

Hot Threads

Recent Insights

Back
Top