Expansive Clay Soils

Expansive clay soils (also known as heavy, black cotton and fat clays) undergo large volumetric changes due to seasonal moisture fluctuations. They absorb water and expand (swell) when wet and crack (shrink) when dry. The cyclical or seasonal change in volume results in shear stresses causing significant lateral and vertical pressures – these slowly lead to cracking and buckling of roads and structures built over such soils. Damages and repairs from expansive clays cost billions of dollars every year.

Proven Solution

The Neoloy® based Tough-Cells hybrid reinforcement solution for expansive clay subgrade soils are proven in roadways, railways and ports around the world, from India to Canada, from Indonesia to Mexico. Upper pavement structures are almost unaffected by variable moisture in the expansive clay subgrades.

For example, in railways using the hybrid solution over weak expansive clays, track alignment measurements over lengthy periods of time show very low and even negligible settlement. Compared with parallel unreinforced track this results in a dramatic decrease in maintenance cycles and costs.

The composite hybrid solution is many times more effective and reliable than moisture barriers or subgrade processing/replacement and it is unaffected by high groundwater levels.

The solution is also applicable to foundations of light building structures constructed over expansive clays.

Unique Hybrid Solution

Neoloy Tough-Cells offer a unique, cost-effective and proven solution to expansive clay soils. The solution is based on a dual layer of Neoloy in the pavement structure on top of a “sacrificial” biaxial geogrid layer on the subgrade-pavement interface. The stiff geogrid acts as a stable working platform on the weak subgrade, which multiplies the effectiveness of the stiff Neoloy Tough-Cells reinforcement installed in the unbound granular layer (subbase or base).

The key in this solution is the Neoloy nano-polymeric alloy (NPA) material in the geocell. Neoloy is capable of sustaining large hoop stress and cyclical loading with relatively small strains, without losing its dimensional stability and therefore can maintain long-term confinement.

How it Works

The Neoloy Tough-Cells’ hybrid solution creates a unique composite behavior that exceeds the sum of its components. The combined stiff reinforced layers restrain expansive clays by reducing differential heave. The beam effect created by Neoloy Tough-Cells acts as an “I” beam or semi-rigid platform to separate the pavement structure from the clay subgrade. The result is that differential swelling of the clay (saw-tooth shaped) is “smoothed” by extending the swell amplitude to effectively restrain heaving. See published research on the Neoloy Hybrid solution.

At the same time, Neoloy reinforcement also improves the soil bearing capacity and strengthens the layer modulus, while decreasing vertical stresses and improving load distribution.

See case studies of Neoloy Tough-Cell stabilized pavements in expansive clays