New Hampshire NHDOT Geotextile Fabrics

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

New Hampshire NHDOT - Geotextile Uses

New Hampshire projects span glacial tills and lakebed clays in the lowlands, coarse outwash and decomposed granite in the foothills, and steep mountain corridors in the Whites, plus a short but storm-prone seacoast. Add long freeze–thaw seasons, snowmelt surges, nor’easters, and deicing salts, and you get subgrades that can soften, pump fines, rut, scour, and settle. Geotextiles are the quiet engineering layer that helps pavements, structures, and drainage systems keep performing.

Separation and stabilization. On new lanes, shoulder widenings, and staged construction, a woven geotextile goes between native soil and granular base. It blocks fine silts and clays from migrating into the aggregate under traffic, spreads load, and preserves base thickness—especially helpful over wet shoulders, utility cuts, and thaw-weakened subgrades. Where the ground is very soft or saturated (floodplain approaches, peat pockets, or culvert diversions), crews first roll out fabric to create a working platform so trucks and pavers don’t punch through. On exceptionally weak ground, geotextile is often paired with a geogrid to add stiffness and speed construction.

Filtration and drainage. Water drives many failures in New Hampshire. Nonwoven geotextiles line underdrain and edge-drain trenches, wrap perforated pipe, and separate drainage stone from surrounding soils behind retaining walls and backwalls. Selecting the right apparent opening size (AOS) and permittivity lets water move while fines stay put, cutting off the mechanisms that clog outlets, create wet spots, and destabilize shoulders. In freeze–thaw zones, laying a nonwoven over open-graded aggregate also forms a capillary break, limiting upward moisture that fuels frost heave and weakens base layers in winter.

Riprap underlayment and scour control. Where flows concentrate—culverts, storm outfalls, river bends, lake shores, and tidal channels—geotextiles serve as underlayment beneath riprap or rock armor. A tough nonwoven filter is placed on the prepared bed or slope before stone. It prevents the subgrade from piping through rock voids during high velocities, ice-out events, snowmelt torrents, and debris-laden floods, helping the rock “lock in” and protecting embankments at bridge approaches and channel transitions. On steep banks or fluctuating water levels, seams are overlapped generously or sewn and anchored to stay continuous under shifting hydraulics.

Structures and MSE walls. NHDOT corridors include many mechanically stabilized earth (MSE) walls and grade separations. Geotextiles act as joint and face filters, tucked behind panel or block joints so backfill fines don’t migrate to the face while drainage continuity is preserved. The same concept applies at wingwalls, backwalls, utility penetrations, and around drains, where a filter layer keeps weeps functioning without trapping water.

Pavement interlayers. Asphalt-impregnated nonwoven geotextile beneath overlays improves waterproofing and slows reflective cracking—valuable where thermal cycling, studded tires in the north, and deicing chemicals accelerate pavement aging. On chip seals common to secondary routes, paving fabrics limit water intrusion into base and subgrade, extending service life with minimal added thickness.

Temporary erosion and sediment control. Geotextiles appear in silt fence, inlet protection, curb socks, and check structures. They filter runoff while trapping fines—critical for stormwater compliance on steep cuts, long medians, and urban work zones. At project entrances, stabilized construction exits typically include a nonwoven geotextile under coarse rock; the fabric spreads wheel loads and prevents stone from punching into wet soils, reducing track-out.

Liner protection and containment. Heavy nonwoven geotextiles cushion geomembranes in stormwater basins, lined ditches, salt-shed pads, and deicing-brine containment, protecting liners from puncture by angular aggregate and construction traffic.

Performance hinges on basics: prepare subgrades smooth, avoid wrinkles, overlap or sew seams as required, anchor with pins or the first lift, and cover promptly to limit UV and weathering. Selection is function-driven—woven for stabilization and tensile capacity; nonwoven for filtration, drainage, and protection—tuned to New Hampshire’s soils, hydraulics, and traffic demands.

New Hampshire NHDOT