Construction Of 'Hyd Metro Rail' Viaducts A Challenge

By Aeman Fatima / Hyderabad

Construction of elevated metro rail viaduct over 80 road junctions on three metro corridors is a major engineering challenge. It is like building an equal number of flyovers over the busy traffic junctions without disrupting the vehicular traffic at the saturated junctions, Hyderabad Mero Rail managing Director NVS Reddy has said.

A traffic study conducted by LEA Associates, which has been engaged by HMR, for traffic management solutions for the intersections made the task even more challenging as the study has projected bigger obligatory spans for many junctions to take care of future traffic flow.
 Structural engineers of L&T, HMR and their specialist consultancy agencies held several rounds of discussions and came up with a technical solution to the tough engineering challenge: bridge the junctions up to a span length of 34 metres (112 feet) with segmental construction by the same launching girders which are building the metro rail viaduct.

However, junctions which have more than 34 mt of span length will have to be bridged through “in situ” construction ie, on-the-spot construction method. Of the 80 junctions, 28 have the requirement of designing obligatory spans exceeding 34 mt (112 feet) and need to be bridged by “in situ” construction.

In this method, temporary supports will be provided to the elevated concreting deck and, after tying the steel reinforcement, concreting will be done in three stages. After curing the concreted viaduct for 14 days, it will be secured by pre-stressing the inserted high-strength steel strands. Thereafter, the temporary supports will be removed.

“For allowing the traffic to pass through these junctions, a gap of about 50 feet will be left between the temporary supports, thereby giving about three lanes on each side for movement of traffic.” 

Since bridging the major junctions with in-situ construction at each junction will take four to five months, work will be taken up simultaneously at several junctions to save time. Work at Uppal Crossroads and Habsiguda junction has already begun. Reviewing the experience gained, simultaneous work at five to eight  junctions would be taken up, Reddy said.

The 28 junctions with longer obligatory spans needing in-situ construction are:

Corridor-I: Nizampet (141 ft), JNTU (148 ft), Godrej Y Jn (190 ft), SR Nagar (148 ft), Punjagutta (190 ft), KCP Jn (121 ft), Khairatabad (190 ft), Lakdikapul (148 ft), Nampally (131 ft), MJ Market (190 ft), Moosarambagh (131 ft) and Kothapet (121 ft).

Corridor-II: Parade Grounds (180 ft), Musheerabad (121 ft), Narayanaguda (121 ft), Sultan Bazar (144 ft), Kotla-e-Alijah (121 ft), Bibi Bazar (121 ft) and Shamsheergunj (121 ft).

Corridor-III: Uppal (148 ft), Habsiguda (148 ft), Alugaddabavi (131 ft), Sangeet Jn (138 ft), Paradise (138 ft), Dharam Karan  (148 ft), Yusufguda (148 ft), Madhapur PS (148 ft) and Hitec City (151 ft).