Which type of soil is most stable for road base support?

Answer: A — Granular soil

Granular soil, which consists of larger particles such as sand and gravel, is known for its excellent drainage properties and strength, making it the most stable option for road base support. The larger particle size allows for better compaction and reduces the risk of water retention, which can lead to weakening of the base. Granular soil provides a solid foundation that accommodates the weight of road traffic and resists deformation over time. In contrast, cohesive soil, while capable of providing some stability due to its finer particles and ability to retain moisture, can become unstable when wet and may lead to issues such as swelling or shrinkage. Loose sand, although granular in nature, lacks sufficient cohesion to provide solid support under load, potentially leading to shifting or settling. Organic soil, containing decomposed plant material, is the least suitable as it has low strength and can compress over time, undermining any constructed road above it. Therefore, granular soil stands out as the optimal choice for ensuring a stable and durable road base.