Drainage clogging is often blamed on geotextile quality alone, but opening size, soil gradation, fine-particle migration, hydraulic gradient and construction contamination all influence long-term behaviour.
Start with representative soil data
Review gradation, fines content, plasticity and dispersivity before selecting characteristic opening size and permeability. Project-specific filtration testing may be warranted for complex soils.
Account for the hydraulic regime
Steady one-way flow, reversing water levels and high gradients do not present the same risk. Outlet capacity and downstream drainage must be checked with the filter.
Protect the filter during construction
Keep fabric and subgrade clean, prevent soil bypass at overlaps, control fill drop height and vehicle traffic, and repair damage before cover.
Project action list
What the procurement or project team should do next
Provide representative soil gradation
Define hydraulic gradient and flow direction
Specify filtration properties rather than mass alone
Approve a trial section where risk is high