Consultancy Report
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For official Use Only GOVERNMENT OF INDIA Hkkjr ljdkj MINISTRY OF RAILWAYS jsy ea=ky; Consultancy Report On Tilting Of Bridge No. 172 Between Swadinpur And Nalhati Stations Howrah Division : Eastern Railway Consultancy No. RDSO/2007/GE:CR-0100 March 2007 Geo-technical Engineering Directorate Hkw&rduhdh bathfu;jh funs’kky; Research Designs & Standards Organisation vuqla/kku vfHkdYi vkSj ekud laxBu Lucknow – 226011 y[kuÅ & 226011 Consultancy Report On Tilting Of Bridge No. 172 Between Swadinpur And Nalhati Stations INDEX SL Contents Page Preface 2 Synopsis 3 1. Introduction 4 2. Reference 4 3. History 4 4. Observations by RDSO team 5 5. Conclusion 5 Page 1 of 6 Consultancy Report On Tilting Of Bridge No. 172 Between Swadinpur And Nalhati Stations PREFACE This report is based on the observations made during the inspection of the bridge site by RDSO team, discussions held during inspection and relevant records collected thereon. The views expressed are subject to modifications from time to time in the light of future developments on the subject. The views do not represent the views of Ministry of Railways (Railway Board), Government of India. This report is the property of the RDSO and is meant essentially for officials use. It may not be loaned, reproduced in part or in full or quoted as an authority without the permission of Director General, RDSO. (S.K. Sharma) (Alok Kumar) Joint Director/G.E. Executive Director/G.E. Page 2 of 6 Consultancy Report On Tilting Of Bridge No. 172 Between Swadinpur And Nalhati Stations SYNOPSIS In the double line section between Swadinpur and Nalhati stations on Rampur Hat – Barharwa section of Howrah Division on Eastern Railway tilting of pier no. 2 of bridge No. 172 (9 x 18.3m + 7 x 9.15m) from km 110/9 to km 109/4 has been reported. It is a Group ‘E’ route having maximum permissible sectional speed of 100 kmph. On the request of Eastern Railway vide letter no. W(3)65/3/ RECON/BR-172, dated 09-02-07, inspection of the bridge was carried out by the team of GE Directorate, RDSO headed by Shri B. S. Rajpal, Deputy Director alongwith Shri Rawel Horo, JRE. Page 3 of 6 Consultancy Report On Tilting Of Bridge No. 172 Between Swadinpur And Nalhati Stations 1.0 INTRODUCTION - The bridge no.172 is at km 109/4 - km 110/9 over river Brahmini at Nalhati, Rampur Hat, West Bengal and is an over 100 years old early steel girder bridge. It is located on Rampur Hat – Barharwa section of Howrah division between Swadinpur and Nalhati stations in Sahibganj Loop. The bridge is having two portions, one is arch and another one is steel girder. Arch portion has total 7 spans each of 9.15 m length, four on Barharwa end and three on Rampur Hat end. Steel portion is having 9 spans each of 18.3 m length. Type of foundation is spread foundation in brick masonry. 2.0 REFERENCE - Chief Bridge Engineer/Eastern Railway/Kolkata vide his letter no. W(3)65/3/RECON/BR-172, dated 09.02.2007 requested RDSO for inspection of the bridge. Detailed field investigations between Swadinpur and Nalhati stations have been carried out by the team of GE Directorate of RDSO. 3.0 HISTORY OF PROBLEM - 3.1 Bridge no.172 at km 109/4 to 110/9 between Swadinpur and Nalhati stations on Rampur Hat – Barharwa section over river Brahmini at Nalhati is in Indo- Gangetic Alluvial Plain of Bengal basin of West Bengal. The bridge site is about 15 km from Rampur Hat. This basin is primarily constituted of sand, silt, clay and peat. Pier P2 of the above bridge has tilted during monsoon of 2006. Page 4 of 6 Consultancy Report On Tilting Of Bridge No. 172 Between Swadinpur And Nalhati Stations 3.2 The bridge had been inspected by Director (B&S)/Testing and a report of the same was sent by RDSO vide letter no. CBS/Lib. dated 04-08-06. In this report RDSO had indicated that settlement of pier had taken place due to excessive scour of sandy strata. 3.3 Howrah Division had also entrusted the same work to M/s P.K. De & Associates Pvt. Ltd., Kolkata. The report of this firm has been provided by the concerned officer of Division, i.e. Shri Budhdev Kundu, DEN/Bridge/Howrah for consideration of site observations, collection of data and remedial measures. The conclusion of this report also says that at flood, there was no soil embedment depth of pier P2 at such flood situations and that was the prime reason why the said pier P2 tilted. 3.4 Permanent restoration for the bridge work has been finalized by Eastern Railway and CRS has been approached for giving sanction for the same. CRS/EC has desired that EDBS and EDGE of RDSO or their officers should visit this site to give their opinion on the cause of settlement of the pier. It has been requested by Eastern Railway in compliance to the instructions of CRS as stated in their above-mentioned letter. 4.0 OBSERVATION BY RDSO TEAM - Based on the above inspection, opinion of Geo-technical Directorate of RDSO regarding the probable cause of settlement of the pier is as under : 4.1 The tilting of P2 pier has taken place due to its settlement of about 30 cm on the upstream side possibly as a result of cavity formed beneath the foundation of P2. At the place of excavation of river bed on the upstream face of foundation of P2, the water collected was completely got dewatered during inspection and it was found that about 200 mm deep cavity exists there beneath the foundation for about half its width. A bamboo was driven through this cavity, which penetrated without any obstacle through a length of about 3.9 m as measured by workers there at the site. 4.2 As stated by DEN/Br./HWH and AEN/Br./HWH, it is gathered that in July 2006, there was an unprecedented water discharge from the barrage under control of the State Government. It was of the order of 64000 cusecs on 11th July 2006, as measured by barrage authorities. According to AEN and DEN it might have been above 1 lakh cusecs during this period as barrage has capability of measuring only upto 64000 cusecs. It appears that vortex must have formed which finally scoured the foundation. Page 5 of 6 Consultancy Report On Tilting Of Bridge No. 172 Between Swadinpur And Nalhati Stations 4.3 It has also been observed that only P2 pier got affected out of six piers. The foundation depth of P2 pier is 3.92 m. As is evident from the bore log, the ‘N’ value corresponding to this depth is 13, which shows that the foundation of pier is laid on firm ground as per Earth Manual USBR. 4.4 By scrutinizing the test results, it is found that the Liquid Limit is 56, Plasticity Index is 32 and soil is classified as “CH” which is highly compressible clay and with increase in run-off, the safe depth of foundation got increased. 4.5 It is also worthwhile to mention here that at the time of construction of bridge, there was no barrage and hence, no additional water discharge might have been considered in the design of foundation at that time. 5.0 CONCLUSION - 5.1 In the light of information provided by the officials of Howrah Division at site and the information of geo-technical data of site collected by M/s P. K. De & Associates Pvt. Ltd., Kolkata on behalf of Eastern Railway, it is agreeable that lateral movement at foundation level of the pier P2 is due to sudden influx of water through the river Brahmini during monsoon of 2006. OFFICERS AND STAFF ASSOCIATED WITH PREPARATION OF REPORT The report has been prepared under the guidance of Shri Alok Kumar, Executive Director/Geo-technical Engineering/RDSO and Shri S. K. Sharma, Jt. Director/Geo-technical Engineering/RDSO. This report has been prepared on the basis of field inspection done by the following officials of Geo-technical Engineering Directorate :- 1. Shri B.S. Rajpal, Dy.Director/G.E. 2. Shri Ravel Horo, JRE-I/G.E. Above officials were associated in preparation of this Consultancy Report. Page 6 of 6 .