Colbonddrain case study from Istanbul, Turkey

Soil consolidation at a city train station

Marmaray suburban rail is an essential project for Istanbul, connecting Europe with Asia under the Boshphorus and running in the heart of the city. It is crucial to connect the city’s metro network over two continents; in the future it will also connect the suburbs of Istanbul with the heart of the city.


It is a real civil engineering challenge to shore up and stabilize weaker soils in a short time frame to allow early construction on them. Using Prefabricated Vertical Drains (PVD’s) is a cost efficient solution to reach this goal and to stabilize soft soils even in 30-40 m depths.
Applying PVD’s a path is formed for excess pore-water created by the overburden. Water is drained off to the surface resulting in a stable subgrade on which construction can take place.



Colbonddrain CX 1000 vertical drain was installed in a 1.2 m raster with an average depth of 15 m to speed up soil consolidation,

Its tensile strength is higher than most wicks and the fabric is thermally bonded to the polymer core in a unique way. The core itself is distinctive because of its typical corrugated cross-section, allowing fast water discharge. Altogether it’s a thoroughly tough and durable composite with excellent drainage capacities. After soil measurements and investigation had been performed, the calculated 1.2 m installation raster and average 15 m installation depth delivered the calculated 0.9 m settlement in a 6 months time frame instead of years.



Applying PVD’s as a solution not just allowed the contractor to dramatically reduce construction time, but also delivered significant cost savings compared to other possible civil engineering solutions for stabilizing soft soils in such depths, like piling or even replacing the complete soil.Colbonddrain with its patented core and unique production method of thermally bonding the filter at the entire surface makes a thoroughly tough and durable geocomposite with excellent drainage capacities.
Colbonddrain’s high tensile strength allows faster construction and the thermally bonded filter provides a tear off free and thus safer installation. Colbonddrain is easy to handle with a roll length of 280 m and is suitable for use in all soil types. Its unique production method and its high tensile strength allows usage with all installation rig types.

Expensive and time consuming traditional methods with intensive truck and machinery demand could be replaced by installing Colbonddrain CX1000. A stable sub-grade has been created for the railway superstructure in a short time, which will serve the millions of travellers in the upcoming decades.

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