Project of Drainage System and Erosion Protection in Leningrad Region, Russia: Application of Geotextile as Filter and Separation Layer

Project Background

In 2016, the Committee for Natural Resources and Environmental Protection of the Leningrad Region decided to reconstruct a drainage system along a highway section subject to groundwater flooding. To ensure long-term performance of the drainage pipe and prevent soil washout, a reliable filter and separation layer was required. A contractor won the tender for supplying geosynthetic materials and performing drainage works, and selected a professional geotextile supplier. The contractor installed approximately 25,000 square meters of needle-punched nonwoven geotextile (300 g/m²) along 3.5 km of drainage trench. The system included: filter geotextile wrapped around the drainage pipe, a protective layer over the drainage gravel, and separation geotextile between the native soil and the sand-gravel cushion.

Challenges

A specialized assessment of filtration properties and mechanical strength of the geotextile was carried out for this project. The technical specification clearly required that the geotextile be tested for water permeability, effective opening size, and tensile strength. The engineering company requested interface shear testing between the geotextile and surrounding soil, as well as long-term filtration capacity testing, to ensure compliance with clause 3.1.4 of the specification: "The interface between the geotextile and adjacent materials shall provide a friction angle of at least 10 degrees and a cohesion of at least 8 kPa, or an equivalent Mohr‑Coulomb strength parameter combination within the tested normal loads and displacements. The coefficient of permeability of the geotextile shall be at least 0.1 cm/s."

Solution

The supplier performed all required filtration and interface shear tests and submitted complete data proving that its needle-punched nonwoven geotextile significantly exceeded the specification requirements (actual friction angle 11.5 degrees, cohesion 9.8 kPa, permeability coefficient 0.25 cm/s). All test results were delivered on schedule, with no impact on the construction timeline.

The two main challenges for the supplier were the difficult logistics of delivering materials to remote areas of the Leningrad Region (lack of paved roads, high humidity) and the need to maintain progress during the prolonged autumn rainy season. To complete the work on schedule and within budget, the contractor made use of every favorable weather day, extending work shifts and laying the maximum possible area of geotextile. The supplier’s logistics department worked closely with the contractor and its freight subcontractors to ensure timely delivery of all materials to the site.