A number of projects have recently been taken up by Indian Railways for converting railway lines from meter gauge to broad gauge. Gauge conversion projects (Fig. 28.2) basically aim at providing a uniform gauge for the smooth and fast flow of traffic, which may be necessitated either due to strategic reasons or on account of operating considerations.
The main advantages of gauge conversion as well as its details are discussed in Chapter 2.
28.4.1 Execution of Gauge Conversion Projects
Details of works The fieldwork normally involved in gauge conversion projects is presented in Table 28.2.
Fig. 28.2 Gauge conversion from MG to BG
Table 28.2 Details of fieldwork for gauge conversion projects
Nature of work
Brief details of works
Engineering-cum-traffic survey; land acquisition; earthwork
for widening the formation; extension of minor bridges; extension of major bridges of PSC slabs or steel girders; permanent way work consisting of supplying and spreading of ballast and laying of rails, sleepers, and fastenings, including points and crossings, and all connected works
Conversion to high tension (HT) crossings; augmentation of power supply; wiring of new structures; modifying LT (low tension) and HT installations; shifting of floodlight masts
Erection of signals at new locations; interlocking of points; track circuiting; relay track installation; wiring and testing works
Planning of works Gauge conversion projects require detailed planning as they involve expansion, which needs to be carried out in a tight time schedule and multifarious activities such as assigning of contracts; posting and management of manpower, including supervisors and artisans, etc.; supply of track materials; and coordination between the engineering, service and telegraph, electrical, operating, and various other departments. Most of the engineering work is done by placing traffic blocks on a regular basis while the residual work is finally completed after
placing an extended traffic block of several consecutive days on the route, during which time gauge conversion works are executed on a war footing.
Manpower requirement The manpower required for the various tasks involved in a gauge conversion project is to the tune of about 80 labourers per km to ensure that gauge conversion is completed within 30 days in all respects. One PWI and one AEN should be assigned for one- and two-block sections, respectively, for the continuous monitoring of the progressing work to ensure the requisite quality control. The contractor should also engage at least two competent supervisors per block section in addition to the trained permanent way mates appointed for each gang.
Speed potential Two rounds of packing by light off-track tampers such as phooltas or chinese tampers are required to make the track fit for a speed of 50 km/h. This is further supplemented by two more rounds of packing using heavy on-track tie tamping machines for making the track fit for a speed of 100 km/h.
Economy measures Gauge conversion projects are capital intensive and adequate financial resources have to be mobilized to meet these ambitious targets. The Railway Ministry has, therefore, taken a decision that all schemes of gauge conversion are to be carried out in the most economical way. By cutting down the cost of gauge conversion in various ways, the Railways plan to carry out gauge conversion works at an economical cost of Rs 6 to 7 million per km as against the normal cost of Rs 9 to 10 million per km, thereby saving about 30 to 40% on the initial cost. The guidelines to be followed in this regard are the following.
(a) The maximum permissible speed on the converted BG section need not be more than what was previously specified for the MG section.
(b) The facilities required at the stations should not be more than what has already been provided except that the loop length should be 686 m.
(c) The length of the platform at those stations that currently serve as stops for mail/express trains should be just enough for accommodating l6 coaches. If the existing platform needs to be extended, the extended portion should be constructed at rail level. On suburban sections, the length of the platform should be enough for 12 coaches. At important stations, the platform length should be sufficient for no more than 22 coaches with added provisions for future expansion to include 26 coaches.
28.4.2 Civil Engineering Works of Gauge Conversion Projects
Engineering-cum-traffic surveys The survey is done to examine the technical feasibility of the proposal and the economical aspects of the same.
Land acquisition The land requirement for converting the track from MG to BG is assessed and, if necessary, extra land is acquired as per the existing procedure laid down in the Land Acquisition Act.
Earthwork Earthwork is done on either side of the existing formation of a singleline track to increase its width from 4.88 m (16 ft) to 6.10 m (20 ft) in the case of embankments and from 4.27 m (14 ft) to 5.49 m in the case of cuttings.
Bridges and culverts The existing bridges and culverts are extended to suit the BG formation and to conform to the standards adopted for BG sections. The extension of these bridges is properly planned to ensure the minimum dislocation of traffic.
Track linking Track linking involves the following operations.
Unloading of track material Track material such as rails, sleepers, and fastenings are taken from the base depot to the work site and unloaded at the final location. Preliminary works such as boring and adzing of sleepers, proper matching of rails, and drilling of holes in the rails are planned in advance.
Interlacing of sleepers Wooden sleepers are best suited for gauge conversion projects, if available. They are interlaced with the existing sleepers of the track and the two are spiked together.
Arrangements of men and materials The deployment of manpower, including the supervising staff, is planned in detail so that the conversion of the track from MG to BG is achieved with minimum interruption of traffic. Normally 50 to 100 men per km work are required on the track during a traffic block. In addition, the work of skilled artisans such as blacksmiths is also required for track conversion. All track material, including fittings, are properly organized and arranged at the site. Tools and equipment such as augers and drills, Jim Crows, crowbars, rail tongs, sleeper tongs, and spanners are also arranged in adequate quantities.
Traffic blocks Traffic is suspended on the railway line for a period of 15 to 30 days depending upon the length of the track to be dealt with, so that the work of gauge conversion can be carried out at one stretch. During a traffic block, traffic is diverted on alternate routes or trans-shipped onto road vehicles.
Linking the new track During the traffic block, the existing rails are removed and new rails placed in what is to be their final position on the BG track. The new sleepers are also placed in their proper position and the rails are spiked to the sleepers as per BG requirements. The track is properly levelled and aligned and traffic is allowed on the new line at a restricted speed after obtaining the sanction of the commissioner of railway safety.
Ballasting and packing An adequate quantity of ballast is then put in the track and the track is properly packed. The speed restrictions are gradually relaxed as the stability of the track improves.
Both passenger and goods traffic is increasing at a very fast rate on Indian Railways. Therefore, the construction of new lines or the doubling of the existing single-line tracks becomes important. The latter is brought about through extensive gauge conversion projects, which involve land acquisition, earthwork, construction of bridges and station buildings, and many other activities. The project should be planned and executed following the standard norms to ensure that the trains run safely.
1. Using a sleeper density of n + 6, determine the number of sleepers required for constructing a BG railway track that is 768 m long, if the length of the rail is 13 m.
2. Describe the principal operations involved in the plate laying method used extensively in India.
3. Define plate laying and give an elaborate description of the same.
4. You are placed in charge of a plate laying operation for the construction of a BG railway track. Give a detailed and step by step account of how you would carry out the work to achieve the desired result.
5. A 5-km-long BG main line straight track with CST-9 sleepers and duplex joint sleepers is to be constructed. Estimate the total quantity of track material required with respect to 90 R rails and a N + 5 sleeper density.
6. Discuss briefly the factors affecting track alignment and describe in brief the methods one would adopt to align a railway track in a region where a heavy gradient is unavoidable. Using a sleeper density of N + 5, determine the number of sleepers required for constructing a railway track of a length of 640 m on a BG section.
7. Work out the quantities of the various track materials required for laying a single-line BG track for a length of 1 km. Make suitable assumptions for all the other data that may be required.
8. Briefly discuss the various steps involved in the construction of a new BG railway line.
9. Write notes on (a) doubling of a railway line (b) gauge conversion project.