How do different types of subgrade soils affect pavement performance, and what stabilization techniques can be used to improve subgrade support?

Different types of subgrade soils have varying properties that significantly affect pavement performance. Well-graded granular soils, such as gravel and sand, provide good support due to their high strength, good drainage, and low compressibility. Silty soils have moderate strength and drainage characteristics but are more susceptible to frost heave. Clay soils have low strength and poor drainage and are highly susceptible to swelling and shrinking with changes in moisture content. Organic soils, such as peat and muck, are highly compressible and unstable, making them unsuitable for supporting pavements without significant improvement. Expansive soils, like some clays, swell significantly when wet and shrink when dry, causing pavement heaving and cracking. Several stabilization techniques can be used to improve subgrade support. Mechanical stabilization involves improving the soil's properties by compaction or by mixing different soil types. Chemical stabilization involves adding chemicals, such as lime, cement, or fly ash, to the soil to improve its strength, stability, and durability. Lime stabilization is particularly effective for treating clay soils, while cement stabilization is suitable for a wider range of soil types. Geotextiles and geogrids can be used to reinforce the subgrade and improve its load-bearing capacity. These materials provide tensile strength and distribute stresses, preventing soil deformation. Drainage improvements, such as installing subsurface drains or improving surface drainage, can help to reduce moisture content in the subgrade and prevent frost heave or swelling. Soil replacement involves removing the unsuitable subgrade soil and replacing it with a more suitable material. The choice of stabilization technique depends on the type of soil, the traffic loading, and the project budget. In general, a combination of techniques is often used to achieve the desired level of subgrade support.