Revolutionary Terraforce® blocks used in constructing retaining walls for Kempegowda International Airport access road
The recently completed Terminal Boulevard, a 10-lane thoroughfare directly feeding into India’s Kempegowda International Airport in Bengaluru, underwent a significant transformation with the aid of Terraforce® blocks, provided by a longstanding member of the Concrete Manufacturer Association (CMA). Over 110,000 L12 blocks were supplied for the construction of retaining walls on both sides of the road, covering a vast surface area of 9,000m².
Expanding Terminal Boulevard and the choice of Terraforce®
Completed in November 2022, Terminal Boulevard’s expansion involved converting the existing 2+2 lanes to 5+5 lanes to accommodate a second airport terminal and cater to the expected surge in traffic. Approximately 1.2km of the road was lined with retaining walls on both sides, necessitating the use of the right retaining wall system.
The project team, led by Bangalore International Airport Limited (BIAL) officials, including Prasenjit Biswas, General Manager Landside Planning, Monnappa BC, General Manager Projects, and Prasannamurti Desai, Vice President Landscape, deliberated over various retaining wall options. Among them, the aesthetics, cost-effectiveness, and flexibility of the Terraforce system emerged as decisive factors. Not only did the Terraforce blocks allow for the planting of flowers and other vegetation, but the inclusion of hume pipes also facilitated the growth of trees. Furthermore, the Terraforce option required less soil excavation compared to alternatives like reinforced concrete or reinforced earthen walls.
Innovative solutions for complex challenges
One of the main challenges faced during the project was the inability to cut further into the embankments for the installation of geogrid reinforcement. The proximity of the upper-level roads, operational areas, and the need to support heavy loads of up to 45 tonnes for fire-brigade trucks and other vehicles necessitated an alternative approach. The solution involved utilizing soil nailing to maintain the slope stability.
The soil nailing process entailed drilling 115mm diameter holes up to 9m in length perpendicular to the embankment slope. Nails, 28mm in diameter, were then inserted into the holes and grouted with a non-shrinkable cement slurry. PVC drainage pipes, wrapped in geotextile membrane, were installed in pre-drilled holes at a slight incline to the horizontal plane, forming a grid to release entrapped water and reduce hydrostatic pressure in the embankment. Layers comprising a geodrain membrane, two layers of 8mm steel mesh, and 100mm of shotcrete were used to cover the slopes, ensuring stability and preventing soil leaching.
Precision construction with Terraforce® Blocks
The construction of the Terraforce retaining walls required meticulous planning and execution. Reinforced concrete shear-key blocks were cast to form the foundations of the walls, arresting both vertical and lateral forces acting on the Terraforce blocks. Steel rods were inserted into the hollow portion of the blocks to interlock each vertical layer of blocks, and the spaces between the block facades and the shotcrete layers were filled with lean concrete.
To adapt to the varying slope angles of the road, the bottom block rows followed the road’s slope, while the top rows were adjusted to match the required road or ground profile. Precast concrete paver blocks were used to pave the sections between the top of the Terraforce walls and the upper-level road kerbing, preventing water ingress into the retaining wall structure and the soil behind it.
An eye-catching entry point
Upon completion and with the establishment of the Metro in the center of the two access lanes, the project will truly shine. The lush vegetation and mature trees will provide a visually striking and green entry point to Kempegowda International Airport, leaving a lasting impression on visitors.
- Layout and Concept: Prasenjit Biswas, Prasannamurti Desai, Monnappa BC (BIAL) & Fred Laker (Terraforce)
- Landscape Architect: Grant Associates and Design Accord
- Engineers: Fred Laker/Terraforce, Maccaferri, Struct Geotech, Smart Minds, STUP India Pvt. Ltd
- Quantity Surveyor: BIAL Inhouse Team
- Main Contractor (Civil): Balajee Infratech & Constructions Private Limited
- Landscape Contractors: Hariyali Landscapes
- Terraforce Supplier: Prayosa Buildmat
With the successful application of Terraforce® blocks in the construction of retaining walls for Terminal Boulevard, this project stands as a testament to innovative engineering and sustainable landscaping practices. Its impact on Kempegowda International Airport’s access road will be felt for years to come.