Construction of the largest reinforced soil wall using StrataGrid™ and StrataBlock™

Location	National Highway 8 (The new NH48) – Ahmedabad-Vadodara stretch
Project	Expanding the highway from four to six lanes
Principal Client	National Highways Authority of India
Client Name	Modern Road Makers Pvt. Ltd.
Concessionaire	IRB Ahmedabad Vadodara Super Express Tollway Pvt. Ltd.
Independent Engineer	Aarvee Associates, Architects Engineers & Consultants Pvt. Ltd.
Project Size	294,900 sq.m. fascia area ; 46 structures
System Offered	Supply, design and construction of reinforced soil walls using StrataGrid™ as soil reinforcement and StrataBlock™ as fascia
Design methodology	BS 8006-1:2010(static) and FHWA-NHI-00-043(seismic)

The National Highway NH-8 (The new NH-48) extends from Mumbai to Delhi. Along the route it also connects two major cities of Gujarat, Vadodara and Ahmedabad. The National Highway Authority of India (NHAI) required that the 102.30 km stretch between Vadodara and Ahmedabad be converted from four lanes to six lanes as part of its expansion programme for NH-48. The expansion project was awarded to IRB Infrastructure Ltd., one of the largest highway developers in India in line with the BOT (Build–operate–transfer) model.

The Project included 46 crossovers where the highway traverses over internal roads of towns and villages as well as three railway crossings.

The conventional solution to support approach ramps for the crossovers would have been reinforced concrete retaining walls designed as cantilever walls or walls with counterforts. Costs of such walls for each structure would have been colossal and with 46 such structures, the project costs would have shot up with a strong impact on project economics.

In contrast, Strata advocated reinforced soil structures since they are faster to construct and cost-effective. The basic principle is to construct two parallel reinforced soil structures retaining earth backfill in between. The reinforced soil walls were constructed with locally available non-plastic soils and StrataGrid™ polyester knitted geogrids as soil reinforcement. The fascia comprised of StrataBlock™ precast segmental concrete blocks. The StrataBlock™ with StrataGrid™ system is extremely cost-effective.