What specific property of the soil under a road tells engineers how much weight it can hold?

The specific property of the soil under a road that tells engineers how much weight it can hold is its bearing capacity. Bearing capacity refers to the maximum pressure the soil can support without experiencing shear failure or excessive settlement. When engineers talk about the soil under a road, they typically refer to the "subgrade," which is the prepared layer of natural or imported soil directly beneath the road's aggregate base layers. The ability of this subgrade to bear the weight of the road structure and the traffic it carries is crucial for the road's long-term stability and performance. If the soil's bearing capacity is insufficient, the road will deform, crack, or collapse under load. This bearing capacity is fundamentally derived from the soil's shear strength. Shear strength is ....