The correct answer is D. All the above.
The heel slab of a retaining wall is a critical component of the structure, as it bears the weight of the soil and any surcharge loads. The design of the heel slab must ensure that it is able to withstand these loads without failing.
The maximum bending moment in the heel slab is due to the following:
- The weight of the soil above it.
- The weight of the heel slab itself.
- The load of any surcharge, if any.
The design of the heel slab must take all of these factors into account in order to ensure that it is safe and reliable.
The following are some additional details about each of the factors that contribute to the maximum bending moment in the heel slab:
- The weight of the soil above the heel slab creates a downward force on the slab. This force causes the slab to bend, and the maximum bending moment occurs at the base of the slab.
- The weight of the heel slab itself also creates a downward force on the slab. This force, combined with the force from the soil, causes the slab to bend even more.
- If there is a surcharge load on the top of the soil, this will create an additional downward force on the heel slab. This will cause the slab to bend even more, and the maximum bending moment will be even greater.
The design of the heel slab must take all of these factors into account in order to ensure that it is safe and reliable.