box girder bridge

PROJECT REPORTCOURSE NO-9103INTEGRATED COURSEGROUP-B OFFICERS

PROJECT

CASE STUDIES IN CONNECTION WITH WATER LOGGING DURING BOX PUSHING

UNDER THE GUIDANCE OFShri. V.B.SOOD,

PROFESSER BRIDGE

SPECIAL THANKS TOShri. A.CHANDOLIKAR, AP

Shri. N. KHARE, APW

PRESENTED BY

Shri RAGHVENDRA GUPTAXEN/C/WCG

Shri SURENDRA TARAI SEN/CSP/HQ/BBS

Shri C. K. THOMASAXEN/C/JBP.

CASE STUDY-1

� WATER LOGGING IN THE ENTIRE AREA AROUND BOX IN SANDY SOIL

CASE STUDY-2

� SKEW BOX PUSHING UNDER SKEW ROAD AS WELL AS TRACK PROBLEM DUE TO ROCK AND WATER LOGGING

CASE: 1

� A work of providing 2 x 2.5 x1.80 RCC box syphon by pushing method executed by Railways for Sardar Sarovar Narmada NigamLimited at Railway KM.107/12-13 on Bhabhar-Radhanpur section of Palanpur-Gandhidham section of Western Railway in connection with Radhanpur Branch canal.

-SALIENT FEATURES• SIZE OF THE BOX - 2X2.50X1.80 Mt.� BARREL LENGTH – 23.00 Mt.� THICKNESS OF TOP SLAB – 300 mm� THICKNESS OF BOTTOM SLAB – 300 mm� THICKNESS OF SIDE WALL – 300 mm� THICKNESS OF MIDDLE WALL – 250 mm� CUSHION – 1.50 Mt.� LENGTH OF SLOPPING BOX – 5 mt. & 6 mt. FOR

FRONT AND BACK BOXES RESPECTIVELY.

� Box pushing operation was started in the last week of june’2006 after casting of boxes in two segments of 9.0 Mt. and 14.00 Mt. respectively.

� Due to unprecedented heavy rain fall in the region, pushing operation was suspended in July after pushing of 9.0 Mt. only.

� Full monsoon period passed with speed restriction of 20 KMPH.

� The entire area submersed and water level was 2.50 Mt. above the thrust bed in August - 2006. Even in October the ground water level was 1.0 Mt. above the thrust bed.

ATTEMPTS MADE

� Various attempts were made for dewatering but sand along with water started coming in from all the directions.

� To prevent the adjoining soil from collapsing, sheet piling arrangement was resorted to, but desired result could not be achieved as the water continued to seep from upstream side of the embankment.

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� Soil of formation was ML (silt with low plasticity). In this type of soil extra pressure is required for pushing in the wet condition. It was not possible to push the box since the thrust bed was not designed for extra pressure.

� Speed restriction was prolonging and there was danger to safety, therefore there was urgent need to do something to lower the water table.

INNOVATION

� IT WAS PROPOSED TO LOWER THE WATER TABLE BY WELL POINT SYSTEM.

SCHEME

� To make the thrust bed dry and to prevent the sand coming on thrust bed, in place of dewatering, lowering of water table by well point system was adopted.

� Two generators of 65KV arranged for continuous non interrupt supply of electricity.

� Seven motors of 5KV placed at various locations of bridge.

SCHEME

� Each motor consisted of 5 nos. inlet of 40 mm. suction pipes of 3.00 mt. length having provision of sand filter in bottom one meter. Each suction pipe was bored 2.80 mt. by water jacket.

� Each motor was having an outlet pipe of 65 mm. dia. to discharge water in nearby field.

� Due to this arrangement water table was lowered. Seepage of water stopped and the area dried up. Pushing operation completed successfully within the stipulated time.

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WELLPOINT SYSTEM

WELLPOINT SYSTEM

GENERATOR SETS 5Kv

LESSONS LEARNT

� This method of lowering of water table is very effective. This can be used for fast construction in water logged area. This arrangement has been found very effective for localized lowering of water table.

� Approximately 2.5 lakhs extra expenditure towards lowering of water table.

� Contractor insisted for payment of above extra expenditure but not paid.

� It could have been avoided by proper planning during preparation of tender schedule.

CASE: 2

� A work of providing 2 x 5.5 x 4.85 RCC box by pushing method was executed by Railways at KM.618/13-14 on Viragam -Dhrangadhra section of Ahmedabad – Rajkotsection of Western Railway in connection with Dhrangadhra branch canal for M/S Sardar Sarovar Narmada Nigam Limited.

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SALIENT FEATURES� SIZE OF THE BOX 2 X 5.50 X 4.85 Mt.� BARREL LENGTH – 30.58 Mt.� THICKNESS OF TOP SLAB – 600 mm� THICKNESS OF BOTTOM SLAB – 600 mm� THICKNESS OF SIDE WALL – 500 mm� THICKNESS OF MIDDLE WALL – 450 mm� CUSHION -1.33 Mt.� DRG. WAS PREPARED BASED ON HYDRAULIC

DATA GIVEN BY M/S SSNN Ltd.

PROBLEMS ENCOUNTERED

� The alignment of the proposed canal was just below the level crossing No. 41 through which the state high way is crossing at a skew angle of 145 degree to the railway track. The alignment of the proposed canal is also crossing the railway track at an angle of 72 degree.

� Being state highway there was heavy road traffic in the level crossing and it was very difficult to close the level crossing for a long stretch

PROBLEMS ENCOUNTERED

� Due to the geographical conditions it was not possible to shift the level crossing.

� The water table of the area was very high.� During pushing operation rock strata was

encountered just below the level crossing which was not known earlier.

� The railway track and the road surface often got disturbed during pushing operation.

� The interlocking fixtures of L-Xing got disturbed during pushing operation.

SOLUTIONS

� During the pushing operation of the box, half of the road in the level crossing was closed for road traffic.

� The water table of the area was high and hence dewatering was continuously done.

� Due to the peculiarity of the location, it was not possible to excavate the rock by blasting as such excavation was done with the help of hand breakers and excavator.

CARE TAKEN

� The railway track and the road surface often got disturbed due to pushing of the box in a skew angle just below the level crossing as such need frequent attention to pass the train and the road traffic.

� Due to disturbance of the formation around the level crossing the interlocking fixture got disturbed and it could not maintained properly, as such the level crossing was converted into non-interlocked temporarily.

� Being state highway there was heavy road traffic in the level crossing, the road was blocked for half portion, the railway administration faced a lot of problem to control the road traffic.

ROCKS FOUND DURING BOX PUSHING

ROCKS FOUND DURING BOX PUSHING

WATER LOGGING DURING BOX PUSHING

INTERLOCKING ARRANGENMENT DISTURBED

LESSONS LEARNT

� Box pushing work should not start just before or during monsoon.

� Stand by generator set, jacks, power packs, pressure pipes and packing blocks should readily available.

� Minimum 1.5 mt. cushion must be ensured to avoid excess track distortion.

� Gang of minimum 10 labour with all necessary tools and plants and equipments should be available.

CONCLUSION

� Before box pushing work, proper soil investigation, proper design of thrust bed and proper planning must be done.

THANKS