Soil Structure Interaction [BC]

The soil-structure interaction group holds the springs that support the culvert. Culvert Bedding Spring carries the barrel vertically on the ground beneath the bottom slab; Culvert Backfill Soil resists the exterior walls laterally as they push into the fill beside them.

Both are compression-only by default, so the culvert bears on the ground and pushes into the backfill but is never pulled back by either.