Major Projects Under Construction in India Bored Piling Foundation for Kochi Metro Kochi Metro is the first mass rapid transit project in a Tier-2 city in India and is the new icon of Kochi. Phase 1 of the project is approximately 27 km (16.8 mi) long, with an estimated cost of INR 5200-crore (US $870 million) and will connect Aluva to Petta in five stretches with 22 stations. The metro line will traverse viaducts supported by bored cast- in-place concrete piles with diameters of 1,000 mm (39.4 in), 1,200 mm (47.2 in) and 1,500 mm (59 in), and depths up to 50 m (164 ft). The piles have vertical load capacities ranging from 300 tonnes (661 kips) to 700 tonnes (1,543 kips). Depending on the loads, each pier may have a group of 4 to 6 piles. Keller Ground Engineering India Pvt. Ltd. is under contract to install 1,150 piles using hydraulic rotary piling rigs. Construction in the middle of narrow (7 m or 23 ft wide) roads with live traffic poses a great challenge to speed and safety with regard to movement and operation of heavy construction equipment and plants including rotary piling rigs, hydraulic cranes, stabilizing fluid plants, excavators and concrete transit millers. The subsoil consists of about 6 m (19.7 ft) of loose silty sand underlain by 15 m (49.2 ft) to 20 m (65.6 ft) of very soft to soft silty clay and lateritic deposits of sandy and silty clay up to 50 m (164 ft) deep. Stability of the pile boring is a major challenge in these soils. Based on material encountered at each pile location, permanent liners up to 10 m (32.8 ft) deep or temporary liners up to 6.0 m (19.7 ft) deep are used to stabilize the upper soils. Conducting instrumented load test with anchors Amrapali Verona Heights in Greater Noida L&T GeoStructure LLP completed the challenging first phase of a bored cast-in-situ concrete pile project at the Amrapali Verona Heights site in Greater Noida, in the state of Uttar Pradesh, India. The team installed 501 piles within the stipulated 120 days with quality and safety. Piles were installed 1,200 mm (47.2 in) in diameter and 40 m (131.2 ft) in depth through sandy strata. Other highlights of this project were the large number of tests, including 500 low strain integrity tests, 7 routine load tests, 77 crosshole sonic tests and 25 high strain dynamic tests. The subsurface comprised layers of sandy silt with gravel and fine sand. This, together with the requirement of 40 m (131.2 ft) deep piles, necessitated the selection of proper drilling fluid to prevent side collapse during drilling and to ensure frictional resistance along the shaft length to attain the required load carrying capacity. Field trials were performed to check the efficacy of the polymer fluid and to finalize the pile length. The pile borehole was observed for 12 hours while the fluid loss and borehole wall collapse were monitored. Then the instrumented test pile was cast and successfully tested for a load capacity of 750 tonnes (1,653.5 kips). To prevent collapse of the sandy strata the following precautions were taken: Piling works at Kochi Metro of 0.9 to 1.3 kg/m (0.06 to 0.08 lb/ft ) of soil to stabilize the walls of piles. The viscosity of the fluid is monitored on site using a Marsh An environmentally-friendly polymer is being used at a dosage 3 3 1.0 to 1.05 kg/m (0.062 to 0.066 lb/ft ). A continuous on-site monitoring of dosage, pH and density of the slurry is being performed. Polymer usage also allows effective recycling, easy handling and disposal, and successfully achieves a cleaner borehole. 3 52 • DEEP FOUNDATIONS • JULY/AUG 2014 funnel, and is generally maintained at 50-60 seconds at a density of 3 a) High torque Bauer BG-25 and BG-28 rigs with Kelly bar lengths of 40 m (131.2 ft) or more were used to achieve the required productivity. b) 6.0 m (19.7 ft) long casings were used to prevent major collapse near the pile cut-off elevation. c) Drilling tool advancement and extraction were performed at controlled speeds to avoid a suction effect that could lead to borehole collapse. The project team has made continuous efforts to plan all activities, optimize cycle time of various stages of execution, perform regular maintenance of plants and equipment, and conduct daily progress meetings, safety meetings, and critical reviews on each activity which enable the overall success of the project.
