Alabama ALDOT Geotextile Fabrics

Solmax DOT Standard Specification Product Chart (click image to expand)

Alabama ALDOT - Geotextile Uses

On pavement jobs, geotextile shows up first as separation and stabilization between weak subgrades and imported base. In much of Alabama, fine-grained clays and seasonally wet soils can pump into aggregate under traffic. A woven stabilization fabric (or fabric paired with geogrid on very soft ground) keeps the layers distinct and spreads load, cutting rutting and preserving base thickness. The result is a longer-lived pavement and fewer early maintenance cycles.

Where water is the enemy, geotextile acts as a filter and drainage helper. ALDOT projects routinely line underdrain trenches and wrap perforated pipes with nonwoven fabric so groundwater can enter while fines stay put. Behind retaining walls, a nonwoven filter separates the soil from the drainage aggregate, protecting the wall’s weep system from clogging. The same logic applies to edge drains and cuts in wet formations—soil stays stable, water has a path out.

At bridges, culverts, and channels, geotextile works as riprap underlayment. Before armor stone is placed, a robust nonwoven filter goes on the prepared subgrade to prevent fine soil from piping through voids in the rock under hydraulic loading. That filter function is critical at culvert outlets, causeway slopes, abutment embankments, and tidal or storm-affected coastlines. In coastal counties, the fabric also helps resist migration of sandy subgrades under wave action and storm surge.

For temporary erosion and sediment control, fabric is the backbone of several work items. Silt fence uses a woven filtration fabric to intercept sheet flow on disturbed ground, allowing sediment to settle while water seeps through. Inlet protection and ditch check details often incorporate geotextile as a filter layer to hold fines without damming water completely. Stabilized construction exits typically include a layer of nonwoven geotextile beneath coarse rock; the fabric distributes wheel loads and keeps the rock from punching into the soil, reducing track-out onto public roads.

In structures and earth-retaining systems, geotextile doubles as joint and face filters. For mechanically stabilized earth (MSE) walls—both precast panel and modular block—the designer often calls for strips of geotextile behind vertical and horizontal joints so backfill fines don’t migrate through to the face. The fabric maintains drainage while preserving the wall’s appearance and preventing loss of material.

Liner protection is another recurring use. Where geomembranes are specified—such as detention basins, lined ditches, or environmental containment—heavy nonwoven geotextile serves as a cushion under (and sometimes over) the liner to guard against puncture from angular aggregate, construction traffic, or subgrade irregularities.

Field practice ties all of this together. Crews prepare subgrades smooth, avoid wrinkles, and place overlaps generously (more on very soft ground). Fabrics are secured with pins, staples, or initial lifts of stone, then covered promptly to limit UV exposure. Selection is driven by function: woven for high tensile and separation/stabilization; nonwoven for filtration, drainage, and protection. Designers and contractors match apparent opening size (AOS) and permittivity to the project’s soils and hydraulic demands so water moves while fines stay put.

Bottom line: on ALDOT projects, geotextile isn’t a generic landscape sheet—it’s a purpose-chosen engineering layer that improves stability, controls water and sediment, protects structures, and extends pavement life across Alabama’s diverse soils and climates.

Alabama ALDOT