During 2017 flood, major damage was caused in many parts of Gujarat including Dhanera and Tharad. Since last few years, average rainfall in these areas is increased which created the need for special design considerations for new roads such as better drained roads, sustainable erosion protection for slope embankments, scour protection for bridge abutments and piers. This NH 168 road section between Tharad–Dhanera– Panthwada is located in the north part of Gujarat where the weather is normally dry but subjected to heavy rains at times.
Problem:
Project scope included construction of a road embankment with heights varying from 3m to 6m. The slope of the road embankment is prepared with locally available soil. At stretches of higher embankment heights, 1m to 3m high RCC toe wall is provided to flatten the slope to arrive at finished slope of 1V:1.5H. Suitable slope erosion control measures were necessary on this finished slope.
Solution:
Since the soil available for construction of road embankment was silty sand and this soil is easily prone to erosion resulting in rain cuts and gully formation and may result into slope failure. Considering longer dry conditions, the vegetation growth and sustenance would involve maintenance costs. So, it was decided to adopt a solution which will be sustainable, technically superior, cost-effective and would not involve significant maintenance costs.
If the top soil of slope was covered with vegetative soil and coir mat or vettiver grass was laid to grow vegetation, it would require regular watering till grass grows and need periodic maintenance. Further, due aggregates were adopted as slope erosion control measure. This system would not require much of maintenance and compared to conventional stone pitching (300mm thick), it would save large quantum of stone requirements.
In case of concrete lining, which is a kind of costly option for this project and due to dry weather, small cracks may develop over a period of time which could result in damaged linings. This option is also a time consuming and un-economical option.
Compared to the above two alternatives, Geocell is three- dimensional confinement system, easy to install in very short time once the slope is prepared. The filling of GSB or granular soil does not
Execution on site:
- The slope surface was prepared as per the drawings. Debris and sharp objects were removed from the surface.
- Anchor trench was excavated on the top of the slope as per the given cross section drawings. • A non-woven geotextile was laid on the slope. Required overlaps were maintained for the adjacent rolls of the geotextile
- Geocell was expanded down the slope and the edges of each section were secured.
- J-Hooks were installed with proper alignment and spacing as shown in the drawings.
- Adjacent sections of geocell were connected using fasteners/ties.
- The infill material was filled into the geocell layer and compacted.
Conclusion:
The project was completed within the stipulated time meeting all the quality requirements and to the satisfaction of client/consultant.
About TechFab India Industries Ltd.
TechFab India was founded in 2003 with the objective of providing world class geosynthetic products and services to serve the needs of infrastructure development in India. From a modest beginning with the setting up of a manufacturing facility for woven geotextiles in Silvassa, we have rapidly grown to become the largest manufacturer of geosynthetics in India. Today we manufacture a wide range of products at our factories in Silvassa and Daman. TechFab In house laboratory is accredited with ISO/IEC- 17025:2005 & GRI – GAILAP
