Case Study 2: Large Diameter, Deep Bored, Cast-in-Situ Piles AFCONS Infrastructure Limited (AFCONS) executed an EPC contract for the construc- tion of a marine LNG receiving terminal for Petronet LNG Limited (PLL) at Puthuvypeen Island, Kochi, Kerala, India. The marine terminal has an approach trestle of 7.5 m x 325 m (24.6 ft. x 1,066 ft) long, 43.5 m x 18.5 m (142.7 ft. x 60.7 ft) wide, an unloading platform, seven mooring dolphins and five berthing dolphins, each of plan size 15 m x 15 m (49.2 ft x 49.2 ft). Maximum water depth was 14.3 m (46.9 ft) with very soft marine clays up to 30 m to 35 m (98 ft to 115 ft) below seabed. Bored cast-in-situ concrete piles of dia- meters varying from 900 m to 1,600 mm (35.4 in to 63 in) with lengths varying from 50.4 m to 76.4 m (165.3 ft to 244.7 ft) were to be installed as foundations for different structures. Maximum pile length below seabed was 52.75 m (173.0 ft). As the shallow water depths did not permit deployment of a jack-up platform, AFCONS decided to convert the marine piles into land piles by constructing a temporary platform using sand as fill material. Coconut tree trunks were driven to 3 m (9.8 ft) below seabed along the peri- phery to protect the working platform. Further, to minimize loss of sand, a geotex- LNG marine terminal at Puthuvypeen Island, Kochi, Kerala tile screen was installed. The platform was removed after installation of all piles. Two Casagrande B250 hydraulic rotary piling rigs were used for construction of piles. The project was successfully completed. This is probably the first time in India that 1,600 mm (63 in) diameter x 74.6 m (244.7 ft) long bored cast-in-situ piles were installed using rotary piling rigs. Case Study-3: Improvement of Fly Ash Deposit fly ash. The site selected for the expansion of Anpara Thermal Power plant in Uttar Pradesh, India, to install 2x500 MW units, was an abandoned ash pond covering an area of around 2,185 hectares (5,400 acres) with thickness of deposit varying from 3 m to 13 m (9.8 ft to 42.6 ft) depths. The consistency of the ash varied from loose to medium dense. Uttar Pradesh Rajya Vidyut Nigam Ltd (UPRVUNL) is the client. For the dry bottom feed method of Keller’s Vibrocat at Uttar Pradesh Keller Ground Engineering (I) Pvt. Ltd., India successfully demonstrated the effectiveness of stone columns, installed by dry bottom feed method, in improving the bearing capacity, enhancing the lateral capacity of piles and the mitigation of liquefaction potential of large deposits of stone column installation, Keller deployed a Vibrocat rig, which consists of a bottom- feed depth vibrator mounted on a crawler- rig. The Vibrocat has the advantage of exerting a pull-down force to improve penetration speed and hence productivity. The equipment feeds the coarse granular material to the tip of the vibrator with the aid of pressurized air. The installation method Larsen & Toubro Ltd Establishes L&T GeoStructure An important development took place recently in the Indian construction industry with the establishment of a specialist foundation company named L&T GeoStructure. The biggest engineering and construction company in India, M/S Larsen & Toubro Limited, acquired a large fleet of a variety of modern foundation equipment and established this subsidiary. Observers 20 • DEEP FOUNDATIONS • JULY/AUG 2012 consists of alternative steps of penetration and retraction. During the retraction, gravel runs from the vibrator tip into the annular space created, and is then compacted using vibrator thrusts and compressed air. About 34,000 lin m ( 111,520 ft) of 900 mm (35.4 in) diameter stone columns were installed for open foundations of improve the bearing capacity to 10 tonne/m (1.0 ton/sq ft). Similarly, to enhance the later-al load carrying capacity to 7 tonne (7.7 ton) (working load) of bored cast-in- situ piles for structures like conveyor, crusher house, etc. of the coal handling plant, 45,000 lin m (147,600 ft) of 0.5 m (19.7 in) diameter vibro stone columns were installed around the piles. Several field trials and pre- and post-treatment tests were carried out. various structures of a coal handling plant to 2 hope that this will encourage other general construction companies to start their own foundation subsidiaries. When the foundation industry has a number of reasonably large foundation companies, this should pave the way for rapid acquisition of technologies and equipment, healthy competition and rapid development of professional foundation practices.
