A Stronger Foundation

Newer piling technologies and methods are making inroads into the Indian construction sector and helping contractors achieve a few firsts, discovers Charu Bahri. The demand for piling, drilling and deep foundation equipment is on the rise, thanks to the greater number of construction projects necessitating such equipment being rolled out. Even better news is the fact that Indian contractors are demanding not just conventional technologies but newer piling and deep foundation technologies, which is spurring the sector to unprecedented heights. New technologies As DV Brahme, Regional Manager, Mait India Foundation Equipment Pvt Ltd, points out, Indian contractors have adopted the latest global piling equipment and methods. Our clients Essar Constructions and Valecha Engineering are currently executing large-scale 'driven cast-in-situ' piles, which are still comparatively new to India. We've also had many takers for hydraulic diaphragm wall rigs, also a comparatively newer piling technique. Consequently, he expects the market for piling, drilling, and deep foundation equipment to grow by at least 20 per cent in the next six to eight months; the fact that several power plant, metro rail, highway and industrial projects are in the starting phase augurs well for the industry. Nowadays, Indian contractors are willing to invest in new technology, affirms Surajit Mukherjee, Managing Director, Suretech Infrastructure Pvt Ltd. Contractors like Kazstroyservice Infrastructure India Pvt Ltd and Valecha Engineering Ltd, each with contracts worth Rs 200 crore on hand necessitating 5,000 piles, have invested in IHC integrated piling rigs. Looking at their success, we are sure other contractors will follow suit. There's huge potential for this equipment as various projects are coming up like ports, refineries, airports, thermal, power, as well as upgrade of existing ports and airports. Speaking of integrated driven cast-in-situ piling rigs, Vidhushekhar, Manager - Purchase, Valecha Engineering Ltd, says, More than being cost-effective, the strata demand such piling. For example, where the stratum is sandy and contains clay, the chances of the sides collapsing during bored piling is high; therefore, driven piles are faster and more suitable. There is a definite cost advantage by way of time rather than materials. The time taken for such piling is much shorter than regular bored piles. Innovative applications Indian contractors are not only increasingly adopting new technology but using equipment in an innovative manner. For instance, Geo Foundations & Structures Pvt Ltd, Chennai, is using two Mait HR180 hydraulic piling rigs, each fitted with a 60-m kelly bar, to drill bores in the seabed from a moving gantry for a jetty for L&T Shipyard. The uniqueness of the process is that the gantry progresses or moves ahead inside the sea, taking the support of the bored piles made by the rig, explains Brahme. These rigs have already moved around 300 m inside the sea. Earlier, drilling in the seabed was done using hydraulic rigs but instead of a moving gantry the rigs were mounted either on a jack-up platform or floating barges. This system is at least five times faster than drilling from the gantry using conventional tripod rigs as it saves time and financial resources (owing to faster completion). To the best of our knowledge, this method with mounting the hydraulic drilling rigs on a gantry is being used for the first time in India, adds Brahme. For his part Sreedhara Narayanan, General Manager, Casagrande India, says, Casagrande's local presence established recently will allow the company to offer Indian contractors advanced technology and a wide range of equipment, including custom-made solutions to suit the demand for all kinds of geotechnical engineering, whether it is piling rigs, diaphragm wall equipment (guided and semi-guided grabs), CFA (continuous flight augers) technology, anchor drilling, micro drilling, jet grouting rigs, hydro mills, and CSM (cutter soil mixing) and displacement piles. Some of these technologies have been proposed and effectively used in notable projects such as the Delhi, Kolkata and Chennai metros, TISCO expansion, Purna river barrage, the DGNP project in Visakhapatnam for the construction of a jetty, Karaikal Port, and the Mono Rail project in Mumbai. In future, Narayanan hopes more path-breaking projects will necessitate equipment from Casagrande's acquired/JV companies that include the German HÜTTE-Bohrtechnik for drill rigs up to a weight of 25 tonne and accessories for civil engineering and geo-thermal applications; Hong Kong's HD Engineering for hard rock drilling solutions, such as the DTH (down-the-hole) technology and the reverse circulation hammer; and TEC System's CSM equipment for soil mixing, hydraulic grabs and cutter soil mixing technologies. Desirable features The maturing of the construction industry is evident from the fact that Indian contractors are increasingly adopting greener technologies, so too, as far as piling is concerned. At the outset, Brahme points out that piling is in itself an eco-friendly way of making foundations as it avoids large-scale excavation as well as back filling. This reduces fuel, and also does away with the difficulties of dumping such huge quantities of excavated material, not to mention the financial resources and time it saves. Still, equipment incorporating eco-friendly features, such as those that reduce fuel consumption during pile driving, are preferable. Mukherjee points out that the power packs of the vibro hammer consist of variable pumps; these moderate the load of the power packs on the vibro hammer and fuel consumption depending on the piling load, thus saving fuel. In addition, it also helps if piling rigs are driven by engines complying with the latest emission norms; this reduces air pollution and enhances fuel economy. Bored piling rigs, additionally Mait rigs, have a 'spin-off' facility to unload the muck from the auger, which reduces noise pollution, adds Brahme. As using less material is also eco-friendly, precise hydraulic drilling rigs make a good choice. For instance, Mait HR180 and HR130 minimise the chances of over-boring, thereby ensuring that extra concrete is not consumed. Indeed, using appropriate technologies to build stronger foundations bodes well for the construction industry and the nation as a whole. Case Study Overview of Micro Piling and Sheet Piling Project name: Galaxy Residential Apartments (high-rise apartments)Site: Kurla (East), MumbaiClient: HDIL Contractor: Builtwell ConstructionSoil conditions: Marine soil going down 6 to 7 m, thereafter soft rock at about 7 to 9 m depth Piling methods used: Indian contractors familiar with various piling methods are opting for some methods over and above others. For instance, sheet piles are commonly indicated for basement construction. But for this project, HDIL opted for micro piles of 200 mm supported by anchors to shore the roadsides while the basement was being constructed as there was less space at the site between retaining wall of basement and the road running nearby. A pneumatic drilling machine was used to bore piles of 200 mm diameter. The pile was reinforced by ISMB - 175 mm and grouted by cement and sand in the ratio of 1:1.5. Where a building length measures more than 120 m, sheet piling proves tedious, explains Jagdish Kadu, DGM (Engineering), HDIL. In any case, micro piles are easier to cast and more effective than sheet piles. For the main structure of some apartments, 600 mm dia cast-in-situ piles were cast using a rotary piling machine to a depth of 10.5 to 12 m. Sheet piling does, however, have its own merits to excavate foundations. Depending on the material used to manufacture sheet piles, they are categorised as wooden, precast concrete, pre-stressed concrete, and steel sheet piles. Steel piles are driven side by side into the ground to form a continuous wall to retain soil. The factors affecting the choice of the particular type of pile include the nature of soil, cost, ease of installation, ease of making connections and the availability of material. Case Study Overview of micro piling and sheet piling Project name: Kolkata AirportSite: KolkataPrincipal Client: Airports Authority of India Contractor: ITD - ITD Cementation India LtdSoil conditions: Predominantly silty clay with layers of medium to dense sand beyond 35 m depth Piling methods used: Hydraulic rotary rigs are predominantly used for 'bored piles' wherein the ground is bored by the rotation of tool before the pile is cast. The rotary rig size is decided by the torque requirement. Larger the torque required, heavier will be the machine. In turn, the torque is dependent on the soil condition, bore and depth of the pile. For larger diameter and depth with good soil conditions, bored piles are recommended but for smaller diameter and depth, 'driven piles' are cast in. In driven piles, 'liners' are driven in the earth with a hammer to create a hole before casting the pile. In India, bored piling hydraulic rotary rigs from Casagrande, Soilmec, MAIT, IMC, Bauer, Leibherr, etc, are in use in large numbers, says Dharmakirti Bhatta, Executive Vice President, ITD Cementation India Ltd. In general, these are reliable and maintenance-free machines and can be easily transported from one place to another. For driven piling, we use diesel, hydraulic and pneumatic hammers of different makes and sizes. To share your views on piling, write in at feedback@ASAPPmedia.com