This article was first published in the Access Engineering Blog here
The rehabilitation and improvement of road networks is a key strategic concern for any government as the provision of better infrastructure can significantly affect the rate of development within a nation. Sri Lankan governments over last two decades have recognised this and as a result many of our existing roads have been rehabilitated and new highway projects constructed, both of which have significantly improved logistics and commuting across the island. Even though, the government and the client of these road projects, the Road Development Authority (RDA) anticipate the significant life time of such rehabilitated roads, many unsatisfactory conditions or pre-mature failures have been observed on several of these roads. The pre-mature failures were; surface cracking, ravelling (the progressive disintegration of a hot mix asphalt layer from the surface downward), stripping of the top layer of bitumen, corrugations (a series of ripples), even base failures and more.
The task of resolving these issues should be taken on as soon as possible to reduce the rectification costs. In some cases the responsibility may fall to the contractor and then the RDA. In many cases the root cause is not identified and costly, time-consuming conventional rectification methods are adopted. However, in many foreign countries, advanced methods such as the application of geosysnthesis are being used to avoid such pre mature failures in road sections, with great success. To strengthen the base course and asphalt layers, geogrids and geocomposites can be effectively used. At present, the availability of quality soil (higher CBR (California Bearing Ratio)) is very limited and due to the strict environmental regulations by the government, there are further limitations to consider in our local context.
To work within such limitations and the associated time costs, the application of geosysnthesis has garnered huge attention from the construction industry in Sri Lanka, and Access Engineering PLC has been a pioneer in the application of this technology. Typical application of geosysnthesis includes; geotextiles, geogrids, geo nets, geo membranes, geo synthesis clay liner, geo cells and geo composites. Among them, geo grids and geo composites can be used respectively for road construction projects to improve base and asphalt construction.
The main advantages to the construction industry can be seen in, but is not limited to, the following list;
- Space saving
- Time saving
- Cost saving
- Higher construction quality control
- Technical superiority
- Material availability and quality control
- Environmental sensitivity
Geo Composite and Geo Grids used by AEPLC (P2)
Application for the Asphult and Base Layers
Different geosysnthesis products and methods have been used by various construction companies in Sri Lanka during last few years, but its application for the strengthening asphalt layers and as a substitute for sub base soil were minimal. However, Access Engineering PLC (AEPLC), with a deep understanding of the potential of geosynthesis for such applications obtained through an indepth review of associated technical literature, have been successfully used geo composites in the field, on a large scale in their road construction projects. The proper approvals were received from the approving agency; the RDA.
Thanks to the application of Geo Composites in between binder and wearing asphalt layers, the propagation and development of pre mature cracks have been stopped. Geo composites are strong enough to withstand the extra pressure created by wheel loads or any other load extending the life time of the asphalt layers. At present many road projects by different contractors deploy this application with approval of RDA. This geo composited can be used to strengthen the asphalt layers, and different classes of strength are available. The most popular amongst them being the strength class of 100 kN/m.
Due to very strict environmental conditions and unavailability of good sub base soils, both of which are critical factors for good road construction, the application of geo grids is a sound solution that has been successfully used by Access Engineering PLC.
The project called BLRP (Berei Lake Road Project), the complete sub base layer (300 mm thickness) was removed by introducing two geo grids layers. This application further enhanced the initial designs due to the underneath peat layer present in the coastal belt in the western province. There was a remarkable time saving due to this application of approximately one and half months.
Overall, the usage of geosysnthesis and its advantages have been proved, addressing all three key project constrains in the construction industry; time, cost and quality. With ever increasing strict environmental conditions and scarcity of natural materials, the requirement for the application of such geosysnthesis products will only increase in the construction industry.