Which structural weakness significantly increased the risk of landslides along ancient Roman roads built on steeply sloped terrain?

💡 Explanation

When roads were constructed on steep slopes without good drainage, increased water saturation raises pore pressure, reducing shear strength and causing catastrophic landslides. Therefore, inadequate subsurface drainage poses biggest risk, rather than the binder, compaction, or reinforcement problems, which cause surface deterioration instead of geohazards.

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