Title - Construction of Road under Bridge near Rail Nilayam by Box pushing technique

1General :This RUB is within the Secunderabad station yard limits and has been taken up as a deposit work for Greater Hyderabad Municipal Corporation, by South Central Railway. The road from Tarnaka to Sangeeth Junction is part of alternative airport road, termed as inner ring road.Due to construction of new International Air Port the traffic o­n this road has increased considerably causing severe traffic congestion.

i)Location
: Km.194 A/28-30 of SC-KZJ section.
ii)Year of Sanction.
: August 2011
iii)Sanctioned Cost.
: Rs. 17.97 Cr. ( Civil- 13.51, S&T-0.21, Elec-0.11, o­ne time maintenance– 4.15)
iv)Agency.
:Sri K.Ajay Kumar Reddy,Hyderabad.
v)Value of Agreement.
: Rs. 7.07 Cr.
vi)Scope of work
: a) 4 boxes (12.00x5.56m and 10.75m long) 43.00m long by box pushing across 5 existing lines.
b) 26.30m box cast in situ across 5 future lines.
vii)Overall progress (Physical)
: a) 2 boxes pushed, remaining 2 boxes casting in progress, will be completed by March and pushing will be taken up in March 2013.
b) Cast in situ portion will be completed by June 2013.
viii)TDC
: June 2013
2Salient features
:This RUB consists of
ØOne vent of 12.00 x 5.56m in side size and wall thickness of 1.00m (outer size 14.00 x 7.56m.)
ØEach Segment weighs 1100 metric tonnes and uses 60t of steel and 440 cum of concrete.
ØThe box is crossing 5 existing running lines and 5 future non running lines.
ØLength of the vent is 69.36m long (43.00m length pre cast by pushing technique and 26.36m length by cast in situ)
ØRCC Box with M-40 Grade concrete.
ØThrust bed of size 37.65x16.20m with M-25 grade concrete provided with 124 pin packets for pushing.
ØFront cutting shield with 25mm thick M.S. plate & 2.50m projection.
ØRear shield with 12mm thick plate all round.
ØDrag sheets are provided in 3 layers with 0.60 mm thick each.
ØPushing of segments is done with hydraulic jacks of 183t capacity.
ØDrainage arrangements being provided by GHMC.
3Quality Control :
·Testing of all materials before use and finished concrete.
·Source approval.
·Ensuring manufactures test certificate.
·Close supervision.
·Results achieved
: Strengthachieved(N/mm2)
Minimum required
Concrete M40
:50.2
40
Reinforcement steel
: 537
415
Concrete by Rebound hammer
:54.10
40
Pulse velocity in Concrete
:4233 m/sec
3200 m/sec
4Safety precautions :
vRound the clock watch man posted to ensure safety of trains.
vOne P-Way gang of 20 members with experienced supervisor stationed o­n track to attend any track disturbance during pushing.
v12000 Nos. of filled ballast, sand and moorum bags kept at site.
v100 cribs, 40 Nos. of wooden sleepers and 30 Nos. of Cl.III rails kept at site for insertion under the track.
vTrack parameters are recorded prior to box pushing and will be checked after every pushing/before passing trains.
vEnsuring cutting edge always buried in the earth.
vCenter line of box & levels are marked at front/rear end of box.
vAlignment and level of box measured daily. Any correction required is immediately carried in the next push, suitably adjusting the pressure in jacks and proper ground level.
5Constraints at the site
ØVery limited working space is available.
ØSeepage from existing underground drains.
ØObligatory points – Adjacent roads, OHE masts, signaling cables.
ØOld abandoned arch bridge, which is to be dismantled and protected during the pushing.
ØThis is a heavy built up city area. All transportation has to be done during the nights o­nly.




Innovations and Best Practices adopted in Box pushing works
The following innovations and best practices are followed which will enhance the safety of running trains and expedite the progress of the work.

1.Second cutting edge: As the size of the boxes are large, based o­n the past experience a second cutting edge has been provided 2 m from the top cutting edge and both are interconnected with stiffener plates. This will help in supporting the formation / slope in case of soft soils and emergencies.

2.Increasing the length of cutting edge: The length of the cutting edge has been increased from 1.25m to 2.50m. This will increase the stability of bank while pushing as it will give flatter slope to the cutting face of the bank.

3.Insertion of rails between sleepers before hand: To take care of any local collapse of formation ahead of cutting edge the running track was supported with cross rails in between the sleepers.One end of these rails was supported o­n the box and the other end o­n the formation with the help of wooden blocks.This will help in immediate transfer of load from the running rails to formation in case of any local sinking under the sleepers, while passing of the trains.

4.Use of turfers & Jacks: While pushing the box, there will be disturbance to the track alignment and level.The disturbance in alignment can be minimized by the use of turfers & jacks duly applying force in opposite direction.

5.Epoxy painting of box outside surfaces: The friction between the box and surrounding formation can be reduced by epoxy painting of outside surface of the box.

6.Welding additional 16 mm piece to sides of cutting edge: The friction between the box and surrounding formation can be reduced by welding a small strip of plate to the cutting edge. This will reduce the side contact area between the box and formation.

7.Welding of steel plates in front of Drag sheet rolls: Steel plates are welded in front of drag sheet rolls to prevent jamming of formation earth with drag sheets which will prevent free rolling and movement of drag sheets.