Road widening and slope restoration with geosynthetic reinforced soil slope, Nigeria

The road is of major economic value linking in Nigeria. The roadway reconstruction aims to ensure that all major communities and economic activities are linked to smooth and accessible roads in the state. After several failed attempts to rehabilitate the region, the local authority was pressured to find a technically sound solution with a limited budget that required little to no maintenance. The selected solution need not only restore the full access of the road but also the economic value of the land lost.

The primarily homogeneous, poorly consolidated soil along the route is plagued by uncontrolled surface runoff. The in-situ material is also commonly mined for use in construction, leaving land bare from the protection of native vegetation exposing the ground to more erosion by devastatingly high intensity rains.

To resolve the problems, steep slopes can be stabilized with planar polymeric reinforcing elements such as geogrids and woven geotextiles for the fortification of new and existing embankments. After thorough assessment of the ground conditions and utilizing the iterative trial and error process of the Bishop’s Slip Circle Method, the proposed design of three tiers at a height of 5m each with 1V: 0.2H slope was selected as it met the minimum performance criteria for the ACEGrid^® GG150-I reinforced soil mass. An ACEGrid^® reinforced soil slope about 80m long, 10m wide and the highest section at 15m, was constructed to reclaim the slope and provide stable usable land for the pavement and drainage rehabilitation works. This type of retaining wall system required a much shorter construction time with the use of the in-situ fills.

Geogrids and geotextiles manufactured from polyester, polypropylene is resistant to alkaline and acidic soil conditions, resistant to heat, ultraviolet light, and to degradation by bacteria or fungi in the soil. Facing elements should also be designed appropriately such that if the slope facing is designed to prevent soil erosion and allow for the face to be vegetated after it has been constructed. In addition, the reduced construction time and transportation of resources to site drastically cut down project costs securing the ACEGrid^® system as the superior economic choice. The splendid photo of this case is also chosen in Top ten of photo contest hold by IGS Young Members Committee. It's a work integrates both engineering and aesthetics.