In-ground base foundation

Question

Do not know if I’m under engineered.

4 feet in depth, individual 3000lb block to form walls (seating area), on geogrid between 6” of 1 1/2 angular stone, and on top of blackland prairie soil.. I have a dry well to hide the rain over flow.

https://gardening.stackexchange.com/questions/57669/geotechnical-engineering-classification-and-percolation

Top Yellow Seating back - recessed off 6” off; Bottom yellow block - 3000lb seating; Between Stone and base? Geogrid; Dark grey - Base; Light grey - Gravel sides Brown around sides it just undisturbed dirt.

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This is a close up of the subdivisions back filled garbage soil, never mind the irrigation we’re cutting it out next week, but we don’t want it to flood like the rain did and paused us during construction.

Answer 1

You didn't mention what is the foundation to support, a patio with deck is very different from a 2-stories building in concern of settlement tolerance.

The settlement is a function of soil bearing strength and footing area, for a concentrically loaded foundation, the bearing pressure is the total force (superimposed dead load + live load + footing self-weight) divided by the footing area, the resulting bearing pressure must not exceed the allowable bearing strength. For the dry condition, you can obtain the presumptive bearing pressure from the building code, or from the local building department provided that you know the type of the underlying soil. However, if there is the presence of groundwater near or above the bottom of the footing, you shall consult a geotechnical engineer for guidance.