Slope Erosion Protection Of Bridge Approach Embankment

Green Reinforced soil wall for approach to walkway at a park in Doha, Qatar

Application Slope erosion protection of bridge approach embankment on North and South Bank of Brahmaputra
Location National Highway 52B, Bridge across Brahmaputra, near Dibrugarh, Assam, India
Client NHIDCL / PWD Assam (NH Division)
Company K.K.M.B. (JV)
Size of the project 325,000 sqm of StrataWeb Geocells for North and South banks of Brahmaputra
Scope of the project Design, supply, and supervision with SW 445-100, SW 660-100

Overview Of The Project

The road and railway crossing across the Brahmaputra on National Highway-52B is located at Bogibeel, about 17km downstream of Dibrugarh in Assam (a North-eastern state in India). The location is an area of high intensity rainfall (the annual rainfall ranges from 2,300 mm to 3,800 mm). During heavy rains, the surface runoff along the embankment slopes erodes the surface soil, forming rills and gullies down the slope, which widen with more runoff. The government of India has given this project utmost importance declaring it a National project in 2007. This bridge is India’s longest Rail – cum – Road bridge spanning 4.95 kms, connecting the vital link between Assam and Arunachal Pradesh.

Challenge

The main challenge was the high volume of earthwork involved that included embankments of heights varying from 1.5m to 15m.

Prior to the work being awarded to Strata, a trial was done using various methods of slope erosion protection. The performance of all the systems was monitored over one full cycle of monsoon. Post monsoon, only the section where StrataWeb® Geocells were used, was intact.

Strata's innovative solution

Since the height of the embankment was of highest order, a technically advanced solution was needed. Strata was approached for the design of the slope system. We designed the erosion protection solution and recommended and supplied StrataWeb® Style SW 445-100, a 100mm deep system with weld spacing of 445mm. StrataWeb® is a lightweight, and strong, three-dimensional, curvilinear rhomboidal shaped, cellular confinement system. It can be used as a foundation reinforcement mat as well as an erosion control barrier for slope surfaces.

The geocell efficacy was demonstrated over a stretch of 20m where rain cuts and side-slope erosion were observed to be the highest in the flood-inundated area, along the South bank of the Brahmaputra. StrataWeb® were laid and the soil infilling was done, the local Uloo grass was then planted on them.

It is reported that ever since 2016, the site, which was continuously devastated, has shown no signs of degradation, withstanding heavy rains and floods. Conditions in June 2016, during the heavy rains and floods are highlighted in the picture.

Strata's Value addition

  • Cost-effective solution: this solution helped client to save up to 50% of the cost compared to conventional stone pitching solution
  • StrataWeb® slope erosion system is a proven robust and long-lasting solution
  • Faster execution of work due to ease of installation of StrataWeb® that also led to speed up the project