Mohan Ramanathan, Managing Director, Advanced Construction Technologies, Chennai, gives insights into the current scenario of deep foundations in India and the need for improved adoption of Helical Screw Piles Methodology for efficient foundation construction.
Current scenario of deep foundation construction industry in India and the need for alternative pile technology
According to a rough assessment, 60 – 65% of total pile construction work in India depends on traditional bored pier construction methods involving use of bored piers and precast piles. Cast-in Piles and Driven Piles have limited use, and Continuous Flight Auger (CFA) Piles, Helical Piles, and Micropiles have been used very rarely.
The era of mid-90s saw the adoption of Bored Pier Construction all over India, because of its low cost. This technology did not require skilled manpower and hence got quickly adopted in the 90s, when India needed to make rapid progress. But, this technology being labour intensive, is also time consuming, which is not suitable for the growth of a fast paced economy. Today, Helical Screw Piles (HSP) can address the need for quick construction of housing for our rapidly growing population, as well as enabling connectivity of the business centers of the country with remote areas.
India can also be a leading platform to promote Helical screw pile construction with the right combination of local manufacturers and advancements in technology, keeping in mind the wide range of geological strata across the sub-continent.
What is Helical Screw Pile
Helical piles or anchors, are also referred to as Screw piles. They are a steel screw-in piling and ground anchoring system used for building deep foundations. They are manufactured using varying sizes of tubular hollow or solid square sections for the pile or anchor shaft. The pile shaft transfers a structure’s load onto the pile. Helical steel plates are welded to the pile shaft as per the intended ground conditions. They can be press-formed to a specified pitch or simply have flat plates welded at a specified pitch to the pile’s shaft. The number of helicals, their diameters and position on the pile shaft as well as steel plate thickness, are determined by the combined structure design load requirement, the geotechnical parameters, the environmental corrosion parameters, and the minimum design life of the structure being supported or restrained.
Advantages of HSP and their relevance in India
The fast and easy installation makes it an ideal solution for affordable housing in India for lightly loaded buildings. HSP can be used for coastal and marshy areas, and it is also best suited for Black Cotton soils which is present in about 40% of our country with expansive or shrinkage tendencies. It can replace the 40-year-old manually installed Under Reamed piles and is ideal for rural locations where concrete availability and quality is always doubtful. Moreover, it is seismically more suited than Under Reamed Piles and can be an economical solution, as it doesn’t require skilled workmen. What’s more, it requires smaller footprint area for construction with minor modifications.
India has a higher percentage of light-small structures, and low-cost structures like transmission structures, solar-green energy structures, industrial structures, tie-backs/tie-downs, etc. The Solar Industry is already using HSP in Indian projects. Our country also has pre-manufactured local system since we are one of the largest exporters of steel in the world. HSP can be quickly installed, has a flexibility to accommodate a wide range of modifications in diameter/length, and allows for immediate loading of the foundation after construction. There is lesser wastage and noise-free construction, make it suitable for urban areas. Another advantage is that it can be easily uninstalled by simply unscrewing from the ground.
Challenges in introducing HSP in India
• Lack of BIS code of Practice for HSP in India along with lag in raw material manufacturing
No Indian design guideline codes are available for helical screw piles yet, although the IS 2911 does comprise a few pile construction systems in the current version. It considers driven and bored cast-in-situ concrete piles in the Sections 1 and 2 of Part 1 and driven and pre-bored precast concrete piles in the 3rd and 4th sections of the Part 1. Still there is a need for promoting research in helical pile technology to create standard design guides. DFI of India is actively working in the formation of a helical pile committee and encouraging this technology. We need institutions like IITs and NITs to take up consultancy projects under research grants and publish papers on real projects for the industry to kick start. Number of manufacturers for Helical Screw Piles also needs to be increased for sustainable growth of the market since currently, there are no Auger Drive manufacturers in India and the drives have to be imported at very high costs.
• Owner – Contractor perspectives
Insufficient capacity and obsolete thinking of contractors coupled with unskilled workforce is creating a lag in the adoption of new technologies. Their reliance on age-old techniques and reluctance to accept new technologies has to be dealt with by promoting the benefits and training programs of helical pile construction with combined owner-contractor participation. Another important issue is the less importance given to foundation construction in overall project execution, leading to cost overburden, and poor foundation systems. Furthermore, the dependence on imports for drive tool kit for helical pile rig, leads to costly construction. This needs to be addressed by encouraging local manufacturing of the necessary tools.
• Role of the Government and associated stakeholders
Currently, the least importance is given to geotechnical investigation and to overall pile construction in government tender practices. The traditional tender practices and bid acceptance involve common pile construction technologies. There is overall lack of innovation and encouragement to bring new pile technology amongst the core decision makers. There is a need of a common platform for all stakeholders for the skill development and promotion of helical screw pile technology.
There is a need for organisation of trade shows and promotional conferences and events to bring helical pile technology to the forefront. There has to be encouragement in the academia for enhanced research activities and development of standard design practices. Standard tender practices have to be developed to encourage new pile technology in pre-bid level phase. DFI India is developing training and skill development programs for dissipation of Helical Pile Technology knowledge amongst the budding engineers. Equipment and Auger drive manufacturers, Geotech and Structural Consultants, PMCs, Hardware Manufacturers, Equipment Rental Companies and Building Owners, all have to work in sync towards a common goal for adoption of HSP.
Examples of Helical pile application
• Geological Limitations
India has the highest land to coastline area ratio in the world. Due to high humidity in coastal zones, the soil near the coastline are corrosive. Helical Pile Construction needs special anti-corrosive galvanization coating to prevent long-term corrosion in such soils. This will require special precautions during installation, not let corrosion affect the structure.
With proper optimization of productivity, quality and suitable geological strata, helical screw pile construction can be used for building new structures and offers an economical alternative to the existing pile practices in India. It can be a game changer for the major projects to be developed in the future.