Bridge No 117/1 (Viaduct 6)- Case Study.pptx

Case study of Bridge No. 117/1 (Viaduct-06) at Lonavala involves a specific scheme of restoration of bridge located in Lonavala in Maharashtra. Here’s a structured approach to understand this case study.

1. CENTRAL RAILWAY Bridge Line Organization By: Mohammad Furqan Senior Section Engineer (Bridge) Case study- Br. No 117/1 ( Viaduct -06)

2. RESTORATION WORK OF APPROACH OF BR. NO: 117/1 (VIADUCT NO. 6) BETWEEN KJT-LNL SECTION OF MUMBAI DIVISION

3. BRIEF DETAIL OF RESTORATION SITE Location Bhor Ghat  (Railway) Bridge No. 117/1 (Viaduct No -6 ), Approach on Lonavala End. Kms 117/3-4 No of Span 06 Span of 24.4 m + 01/18.3m +01/24.4m Year of Construction 1983 Between Cabin (Nagnath –Monkey Hill Cabin) Division Mumbai Zone Central Railway

4.   Geo-Location of Br.No 117/1 SE/Ghat UP/RD.  

5. Condition W arrants R estoration :- On 02/10/2019 slippage of backfill earth for a length of about 30 mts. beyond A2 abutment (LNL Side) occurred due to heavy rainfall. The slippage is about 06 m deep. Initial efforts to restore the site by filling material and also supporting toe wall etc. failed. The slippage continued . Subsequent to failure of bank and restoration effort by Earth filling it was decided to launch 26.6 m RH Girder for early restoration. However a detailed study of strata indicated that providing C.C.Crib support may turn out to be risky due to the 7.508 m depth of firm strata. The idea of insertion of temporary RH Girder was abandoned as it was realized that the construction of bridge shall become extremely complicated. It was then decided to find a permanent solution by extending the existing bridge. Finally , it was decided to provide two additional Span of 1/24.4m & 1/18.3m with depth of Hard underlying strata found out to be 07 m & 05 m below rail level at Pier (P7) & Abutment (A2) respectively. Restoration work on the section commenced from first week of October and continued up to last week of December due to which Central Railway had to cancel several train services between Mumbai and Pune and short-terminated five long-distance trains at Pune.

6. Slippage of Backfill beyond Abutment A2 Detail of work:- DATE OF AGREEMENT 29/11/2019 DATE OF COMPLETION 04/02/2020 TRACK FIT FOR RUN 25/12/2019 SANCTIONED AMOUNT 73721888.48/-

7. P ortion of about 30 mtrs behind A2 was continuously slipping as the rock profile was deep and in slope. Extremely difficult approaches (tunnel on both sides + no road + distance from Lonavala & Karjat). No space for keeping material & equipment. Transportation of machinery was greatest challenge. 70m valley and 50m hill on either side of restoration site. Picture depicting Geographical constraints of site

8. SUBSTRUCTURE

9. Technical Planning : Various option for foundation was thought of and finally it was decided to go for open foundation. Geotechnical investigation details also indicated that the rock could be available at 7-8 mtrs. For A1 and 5-6 mtrs. at A2. Subsequent to determining the type of foundation, detailed design was got prepared. In the meantime, processing of single tender was completed. Contract was finalized on single tender basis after finalizing the scheme at a cost of Rs. 73721888.48. Work order for 1/24.4+1/18.3 m span welded plate girder-25t Loading was placed at CEW/MMR.

10. PRELIMINARY ARRANGEMENTS For Transportation of material and equipment a loading depot was established at Lonavala from where shifting of Material & Machineries to site was carried out with the help of Light Engine + DBKM was organised twice daily basis. OHE masts were removed as they were infringing movement of Machineries & Poclain. Temporary Micro piling was planned to retain earth during Excavation Activity. To address the extraordinary space constraints it was decided to create about 25 meter long and 8 m wide platform. Removing OHE wire & OHE mast Track structure removed

11. Shifting of Machinery at site through DBKM Excavation & micro-piling work in progress RMC Mixers fitted upon DBKM

12. SUBSTRUCTURE Micropiling work was carried out upto Chainage 50.00 m for confining the foundation space of P7 and A2 and retaining the earth. Total 640 no’s of micropiling were done to retain earth for further sliding during excavation activity. During the day time at least two material train with material sent. Excavation work for Pier (P7) & New Abutment (A2) completed. First Pier(P7) then abutment (A2) were casted , Ready Mix Concrete of M35 Grade transported to site with the help of special DBKM fitted with RMC Mixer. Micro piling work in progress. Excavation work after micro piling

13. Concreting of footing(Abutment) Concreting Work : Ready Mix Concrete of M35 Grade was transported to site with the help of special DBKM fitted with RMC Mixer. The concrete mix was required to be designed in such a way that during transit from IOW Siding to restoration site, it should not set or harden. To counter early setting of concrete retarder of BASF Brand (Master Polyheed 8353) ha s been used. Concreting of Platform for Crane Stability

14. Photographs taken during concreting of substructure.

15. SUPER-STRUCTURE

16. Launching of Girders at desired location was done partially by Cantilever Method & partially by two no’s of 70 MT capacity Crane. The various activity involved prior to launching of superstructure are : Cranes loaded on DBKM at IOW siding @Lonavala after removing its wheel. Platform is created for crane positioning for avoiding infringement. Cranes get unloaded one by one on platform prepared at site. Loading of crane @iow yard after removing wheel . Unloading of Crane @Restoration Site.

17. Girder loading at CEW/MMR Girder Unloading at Bridge site Lowering of Girder up to rail level @ Res toration Site UNLOADING/LOADING OF GIRDER SPANS

18. The girders loaded at CEW Manmad were unloaded at site by side slewing method. Girders unloaded on a temporary staging after removing short bracings. Side Slewing was done on arrangement of two 52 Kg rails pieces keeping aside with Pushing Arrangement. Proper anchorage at hillside was provided to ensure controlled movement of girders during side slewing. Lowering of span up to rail level was done with the help of mechanical jack s. Side slewing arrangement for girder. Side slewing of girder from DBKM to CC Crib Staging.

19. LAUNCHING OPERATION OF GIRDERS: Girders were longitudinally skidded upon guard rail by pulling with the help of Turfer & Chain pulley block attached to pulling arrangement which was fixed at old A2 abutment. Girders was pulled first up to abutment (A2), then pulled until 1/3 of Girder would be propped cantilever , supported on Temporary staging of CC-Cribs. Girder was lifted with the help of crane 1 & 2 having 70MT Capacity and then placed on temporary staging near Bed Block. Girder again lifted and lowered on bed plate in proper position. Pre-Launching Position of Girder at abutment (A2) Lifting of girder by 70 MT Crane from Pre-Launching

20. End diaphragm, X-frame, lateral bracings are temporarily fixed by service bolt and finally by riveting work. Total 680 nos. of rivets we re driven only four days. Riveting work completed by Bridge/Line Organisation. Riveting

21. PROVIDING TRACK FITTINGS & FINAL ALIGNMENT First top lateral bracing rivets were driven so that P-way department can provide track structure. Further H-Beam sleepers were provided on top of the span, after that 60kg rail was laid upon sleepers. Moreover alignment, cross levels and longitudinal levels were checked and corrected. Anchor bolts were provided & grouted with cement slurry. Providing Track fittings

22. M ission Accomplished

23. Difficulties Encountered Location of the work had posed a massive challenge as the concrete required for the structure could not be prepared at the site due to lack of space. Retardant was used to slow down the setting process of concrete so that could transport it to the site. Reaching the site was difficult, as it is located between two tunnels with a deep ravine on one side and a high hillock on the other. The only way we could transport the crucial items was through the rail route. While transporting the cranes from Lonavala to Restoration Site, upon Loading on DBKM its height was infringing the overhead Electrical wires. The only remedial measure was to remove its tires as to avoid infringement inside tunnel. Progress Achieved Earlier it was estimated that the work would be completed by January 15, 2019, but department has managed to finish it ahead of time i.e 2 5 /12/2019.

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