Solution : SDR Nailing + Cementitious Grouting
Project : : Six-laning of Varanasi – Aurangabad section of NH-2 from Km 786.000 to Km 978.000 (Length 192.400 Km) in the state of Uttar Pradesh on Design, Build, Finance, Operate and Transfer (DBFOT) Toll basis under NHDP Phase-V
Background : India’s National Highway, NH-2, traversing from Varanasi in Uttar Pradesh to Bihar’s Allahabad, was scheduled to be expanded to a 6-lane express highway; construction of which originally started in 2014, scheduled for completion in 2016. Due to some land acquisition issues, work got stalled completely. Post some intermittent functioning, work restarted in 2022 in full earnest.
During this period of time, NHAI had altered some sections of Roads and Bridges where heights differed from the originally proposed ones. In one such structure, ROB @ Ch 788.817, height was proposed to be increased by 2 m compared to the original layout.
At this location, during the earlier construction phase, a Reinforced Soil Wall was constructed with Block Fascia up to a certain height. With the change in the proposed wall section, the same wall was supposed to carry an additional 2 m of load. While running a design check, Grids were found to be insufficient in taking this additional load, and additional strengthening had to be provided in the already constructed section so as to take care of this additional load.
During the design stage, additional layers of grouted SDRs (10000 RMTS with 5 layers of 1.2*1.2 spacing ) were planned to be installed. Design of SDR (Nail Strength as well as placement) was done to take care of the complete load of the wall in the portion where strengthening was to be done. This was done to take care of any damage to the existing Grid while driving in SDR or Grouting.
Work was carried out from the bottom of the wall, and the sequence of driving SDR was followed by their grouting. Strengthening was completed in 60 days and parallely, construction of the wall heights above the strengthened portion was also taken up.
