: Horizontal soil pressure acting on the vertical walls, often calculated using the at-rest earth pressure coefficient Hydrostatic Pressure

Do you want me to (pick one)—

Using the Hardy Cross Method (Moment Distribution) or structural analysis software for a box frame:

This guide outlines the essential steps and calculations required for a reinforced concrete box culvert design, typically used in road and railway infrastructure to handle water flow and traffic loads.

Is the span-to-thickness ratio within industry norms (usually for top slabs)?

To avoid needing a “fix” in the first place, start with reliable sources: