Design and Construction of an Underground Metro Railway Station in Rocky Strata with Hybrid Construction Methodology at New Delhi Kundu Probal*, Sengupta Sumantra*, Gupta S.K.** *STUP Consultant Pvt. Ltd., Kolkata, India **Larsen & Toubro Limited Online published on 10 January, 2017. Abstract This paper deals with the design construction aspect of a Metro Railway underground Station in Delhi under Delhi Metro Railway project - Phase III. Proposed station building is 250 m long, 20m wide and 16.5m deep. Station is placed 2.5m below road level. Building is having three levels of slabs, namely roof, concourse and base slab. Geological formation of the zone exhibits moderately weathered quartzite rock at a depth of 6 m to 17m below ground level with silty sand topping. For ninety meter zone in the northern side where rock level is around 6m to 10.5m below GL, bottom up method of construction using soldier pile, waler beam, strut arrangement and rock/soil anchor has been adopted. Soldier piles are driven through top soil and embedded into rock over 0.5m depth. Beyond this depth rock is excavated in 1:6 slope. In one hundred sixty meter zone of the southern part of the station, starting level of rock varies from 7m to 17.5m below ground level. Method of construction adopted at this location is partly top down and partly bottom up. Diaphragm walls (D-walls) have been cast up to 800mm below concourse slab where rock level is present up to concourse slab level and 300mm into the rock level where rock profile varies from 1m to 5m below concourse slab level. In rest of the location D-wall has been embedded into the rock below base slab by 1m. Three numbers of 300mm diameter micro piles have been cast through the D-wall section with penetration up to 3m to 4m below base slab to support the structure during construction stage when roof, concourse has been cast and excavation proceeded below D-wall bottom. The base slab and bottom portion of wall of this stretch is constructed by bottom up method of construction technology and integrated with the wall already cast as D-wall. Temporary decking was avoided taking the advantage of top down method of construction. Restoration of road was done immediately after construction of top slab through which traffic was allowed. Top |