Railway Track Stabilization
In trackbed application, punched & oriented geogrids are known for the reinforcement effect on soft subgrades under railroad track. They also act as separators between the clayey formation & granular ballast, preventing the loss of ballast material in the weak formation. Geogrids provide a solution against loss of ballast combined with reduction of the ballast or sub ballast design thickness by reinforcing the ballast and distribution of axle load over a larger area. They have found their greatest use in those areas where a large amount of track maintenance has been required on an existing right-of-way as a result of poor drainage conditions, soft conditions, and/or high-impact loadings.
Common locations for the installation of a geogrid in railroad track are locations of excessive track maintenance resulting from poor subgrade/drainage conditions, highway-railroad grade crossing, diamonds (railroad crossings), turnouts, and bridge approaches.
Punched & oriented biaxial geogrids provide an extremely cost-effective solution for the reinforcement of ballast over a soft subgrade, bringing significant benefits to the railway engineer. There are two major application areas for the use of punched & oriented biaxial geogrids:
- Direct ballast reinforcement to reduce the rate of track settlement and hence reduce maintenance cycles.
- Reinforcement of a granular sub-base layer beneath the railway ballast to increase the bearing capacity of the track foundation.
- They help extend maintenance intervals by minimizing settlement
- The rate of settlement approaches that of track on a firm foundation
- The stiffening effect reduces the elastic deflections
- Reduction of the rate of permanent settlement.
- Improved rail ballast performance allows consistent high speeds to be achieved.
- Avoids the need for excavation of soft soil and replacement with thick layers of imported fill.
New Track Construction
Punched & oriented biaxial geogrids can be installed during the new track laying & gauge conversion as well as on the open lines having high traffic intensity. The laying over the new lines is much simpler with simple unrolling of the geogrid rolls manually. In some stretches mainly in railway cuttings or stretches with high water table, the geogrids can be combined with geotextile. The geogrid rolls shall be unrolled over the geotextile laid over the formation area.
In the case of new formation construction, especially the embankments, geogrids can be provided in the subgrade and subbase layers as reinforcing elements, which shall result in the increased bearing capacity and also reduction in the thickness of granular material.
Existing Open Lines (Tracks)
Punched & oriented biaxial geogrids can be installed during gauge conversion as well as on the open lines having high traffic intensity. In the case of existing lines (open lines), they can be installed with much easy & faster by having a simple attachment with Ballast Cleaning Machine (BCM) used for ballast renewal. It has be observed that the attachment with geogrid rolls do not affect the speed as well as other operations of the BCM.