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Culemborg Geldermalson Rail Inspection Pad – RK12 Drainage Geocomposite

Project Information






RK12 Drainage Geocomposite


Scheme Overview

The Culemborg Geldermalson Line had been subject to speed restrictions due to weak soils and poor drainage for a number of years. Where a new inspection pad was to be installed adjacent to live track RK12 was specified negating the need for excavation and placement of imported drainage fill.

Inspection pads are an essential part of railway line infrastructure to provide a safe passage for pedestrians such as maintenance operatives, or in the event of a train evacuation.

On the Culemborg - Geldermalsen line project, various  methods of construction were considered. An inspection area often requires a substantial drainage layer beneath the pad; traditionally these are built using imported aggregate.

This drainage layer  is essential to prevent instability and washout of the track structure., and typically consists of a 300 - 500mm deep granular drainage layer, requiring excavation and removal of existing material followed by import and placement of new drainage stone. This is a time consuming, expensive process, and uses a lot of resources.

Track possession time for maintenance intervals can be very costly to rail network operators and cause significant disruption to timetables. Therefore any reduction in time for scheduled maintenance work can generate significant savings for the rail operator.



GEOfabrics RK12 was selected as the best option for this construction as it offered a number of benefits. RK12 is a geocomposite drainage layer that provides impressive performance in this type of application, delivering substantial discharge flows at near horizontal gradient while under compressive load.  At just 13mm thickness RK12  needs much less ground preparation and excavation compared to traditional drainage methods. In rail applications where access can be limited any reduction in volume of material movements is advantageous.

RK12 comprises a polypropylene filter geotextile bonded to an HDPE cuspated drainage core.

The geotextile filter is highly permeable to water, but prevents fines entering the drainage paths thus avoiding any reduction in hydraulic flow. By bonding the geotextile  to a drainage core there is no risk of displacement during installation or operation, and drainage paths are maintained through the  geocomposite.

The drainage core is designed to provide maximum drainage void while remaining strong enough to resist compressive loads from the cover materials.

This combination provides high capacity drainage performance in a very thin layer that is flexible enough for easy handling and installation yet robust enough to use in the most demanding civil engineering applications.



The key benefits of using RK12 here:

Speedy installation time – Minimal to no excavation required compared to traditional granular drainage systems

Improved Sustainability – Significant quantities of embodied carbon are saved through reducing imported drainage material and the associated  quarrying operations and transport

Hydraulic performance – RK12 provides high , drainage flow under load, with factory consistent, tested performance

Easy Logistics—a single load of RK12 replaces multiple loads of imported and exported aggregate, and is simply unrolled


In total 9km of RK12 was installed on the line.  RK12 is supplied as rolls. Widths and lengths can be bespoke to allow installation by machine or by hand.

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