The depth of concrete bed of the foundation depends upon A. The projection of the concrete block beyond the footing over it B. The upward soil pressure C. The mix of the concrete D. All the above

The correct answer is D. All of the above.

The depth of concrete bed of the foundation depends upon the following factors:

• The projection of the concrete block beyond the footing over it: The projection of the concrete block beyond the footing over it will determine the amount of soil that is being supported by the foundation. The more soil that is being supported, the deeper the foundation will need to be.
• The upward soil pressure: The upward soil pressure is the force that is exerted by the soil on the foundation. The higher the upward soil pressure, the deeper the foundation will need to be.
• The mix of the concrete: The mix of the concrete will determine the strength of the foundation. The stronger the concrete, the less deep the foundation will need to be.

In addition to these factors, the depth of concrete bed of the foundation may also be affected by the following:

• The type of soil: The type of soil will determine the bearing capacity of the soil. The higher the bearing capacity of the soil, the less deep the foundation will need to be.
• The depth of the water table: The depth of the water table will determine the amount of moisture in the soil. The more moisture in the soil, the weaker the soil will be and the deeper the foundation will need to be.
• The seismic activity: The seismic activity in the area will determine the amount of force that is exerted on the foundation by earthquakes. The higher the seismic activity, the deeper the foundation will need to be.
• The frost line: The frost line is the depth at which the soil freezes in the winter. The foundation must be below the frost line to prevent it from being damaged by frost heave.

The depth of concrete bed of the foundation is an important factor in the design of a foundation. The depth of the foundation must be sufficient to support the load of the structure and to resist the forces of the soil.