INTRO: The infrastructure on Japan’s oldest high speed line has gradually been improved to allow operation at 270 km/h, with curve realignment, the introduction of composite sleepers and improved standards for maintenance work. Plans are being drawn up to strengthen major structures from 2017

Dr-Eng Masaki Seki

Head of Track Maintenance & Civil Engineering Research *

Central Japan Railway

IN OCTOBER, a step-change in the level of service on Japan’s pioneering Tokaido Shinkansen will see all trains operating at 270 km/h. Experience with running an increasing proportion of trains at this speed since 1992 has allowed JR-Central to fine-tune its infrastructure monitoring and maintenance procedures to ensure there will be no deterioration in performance or ride quality. The 38-year old line is now used by more than 285 trains a day, carrying over 120 million passenger journeys a year.

The 515 km line was the pioneer for Japan’s high-speed network. Almost one-third of the line is carried on reinforced concrete viaducts, with 230 km on embankment and 45 km in cutting. The standard viaducts are built as 24m long three-span sections. Ballasted track is used on 495 route-km, with 60 kg/m continuous welded rails.

The Tokaido Shinkansen is internationally renowned for its punctuality. Following the establishment of the JR companies in 1987, the average delay per train has been less than 1min in every year except 1990, and the figure in 2002 was just 22sec. As there has been no change to the hardware since JNR days, the improvement can be put down to issues such as employee awareness and education. It is the culmination of daily efforts to improve maintenance levels, manage the facilities better, and eliminate human error.

Changes to the track maintenance strategy have concentrated on improving ride quality by minimising the vibration of vehicle bodies and focusing on track irregularities with a relatively long wavelength. New and improved track materials have been introduced, and the supporting structure reinforced. The inspection regime has been revised, and preventive countermeasures have been taken against small deformations which were shown up by the inspection results.

Speed through curves

When the line speed was raised in 1992, the area of greatest study was the raising of speed through curves. It is not possible to run at 270 km/h through curves with a radius below 3500m. The Tokaido Shinkansen has 2500m radius curves at around 50 locations, which were acceptable for the original design speed of 210 km/h, but now prevent trains from running at 270 km/h on more than about one-third of the line.

Increasing the speed through these curved sections to 250 km/h was considered sufficient to meet the planned journey time reductions. When the line was built, the maximum cant was designed at 200mm, which would allow 250 km/h running given an allowable steady-state acceleration of 0·1g. At the time the riding comfort standard for standing passengers on conventional lines was 0·08g, which was used as a general guideline. Raising this threshold to 0·1g seemed acceptable, and was confirmed by running tests.

Reinforcement of the track structure after 1993 has seen a significant improvement in ride comfort compared to the levels achieved before 1987. Relaying with 1500m long continuous welded rails reduced the number of fishplated joints, although the use of longer rails required the introduction of specialist handling equipment. A spin-off benefit was a reduction in the amount of maintenance needed for 10m chord management (below), thus reducing the overall cost.

Other measures included the introduction of new sleepers on the steel bridges with non-ballasted track sections, which total approximately 20route-km. Conventional wooden sleepers have been replaced by a harder synthetic composite material offering a lower life-cycle cost and reduced track deviation. The expansion joints and glued insulated joint designs have been changed to smooth the joints, and the elasticity of the track pads has been reduced to give a stiffer track form, accompanied by the introduction of double spring rail fasteners. Much of the ballast has also been renewed.

Track improvement works ahead of the launch of Nozomi services in 1992 included the track realignment over lengths of several hundred metres to prevent hunting. All curves were surveyed down to 1mm with a geometry correction unit, using poles as alignment markers. Around 320 km was surveyed in this way. Rail welding faults were corrected at no less than 6900 sites.

A Speno rail grinding car was later acquired to condition the railhead surface to reduce wheel load fluctuation at higher speeds. Grinding is now done twice a year in residential areas, and after every 40 million gross tonnes elsewhere. Typically 0·3mm is removed each time, requiring four passes with the machine.

Chord management

The quality of track on the Shinkansen network has traditionally been determined by taking regular measurement of irregularities over each 10m chord, using the high speed inspection train.

Target values for the maximum deviation were set at 7mm in the vertical direction and 4mm horizontally. These were based on the results of tests prior to the start of service, recordings from the measurement train, and the practical results of track maintenance work. These are designed to meet the ride comfort target values of 0·25g for vertical motion and 0·20g for lateral motion.

The start of 270 km/h operation highlighted a problem with long-wavelength track irregularities greater than 10m. Frequency analysis of vibration with the Series 100 trainsets revealed a dominant frequency near 1·4Hz that corresponded to the car body yawing. At 270 km/h this is equivalent to a wavelength of approximately 54m. Wavelengths of 40 to 60m related to car body yaw frequencies of 1·9 to1·3Hz.

Tests were conducted to determine the actual line irregularity values corresponding to lateral motions of 0·2g for each wavelength, and the value for a 40m wavelength was found to be 4·5mm. So even if the track irregularity was kept to 4mm using conventional 10 m chord management, an irregularity of 10mm or more might remain over a 40m length.

Therefore 40m chord management was added from 1991, with strict maintenance target values - 6mm for horizontal irregularity, and a finishing standard limit of 3mm. This level of accuracy could no longer be achieved manually, so the number of multiple-sleeper tampers was greatly increased. The net result was a ride comfort at 270 km/h roughly equivalent to the level formerly achieved at 220 km/h. Thanks to mechanisation, manual tamping could be reduced, leading to cost savings. This enabled more to be invested in reinforcing the track structure such as rail replacement and ballast renewal.

A ’40m chord P value’ was also established, modelled on the P value used on conventional lines as an index to represent average ride comfort per km of track. On introduction in 1992 the P value ranged from 13 to 17, but it has improved annually until now it has reached about 3.

Automated inspection

In 2001 a new-generation high speed inspection train was put into service on the Tokaido and Sanyo Shinkansen, known popularly as Dr Yellow II, and by the railway as T4 (RG 4.99 p219). More advanced than its predecessor, it was developed from the Series 700 trainset, and is able to operate at 270 km/h. Measurement runs are undertaken on each section of line every 10 days.

The test train’s track geometry car uses two bogies and an asymmetrical chord measurement method, in place of the versine method performed by the previous track geometry car which required three bogies. A laser beam under the vehicle floor acts as a reference line to enable diagnosis of track condition at full line speed.

All recorded data is stored on computer, and used to plan maintenance strategies and generate work orders. Work reports from the maintenance staff are also entered into the computer and the repaired track is checked again by T4 on its next run.

An ultrasonic test train also operates over the line twice each year to inspect the rails for defects. This is backed up by visual inspection and hand-held ultrasonic testers. Rail defects are ranked in three categories: A for observation only, B for replacement within six months, and C for replacement within 10 days.

Devolved management

As part of changes to the maintenance system introduced from 1995 onwards, the number of track maintenance depots was doubled, halving the amount of line for which each is responsible. There were previously 10 depots with 50 staff each, responsible for up to 70route-km, with two smaller groups of eight people covering half of the section. The depots have now been split into 20 separate units with about 30 people each, responsible for an average of approximately 25route-km (Table I).

At the same time, the Track Maintenance Section head office empowered each track maintenance depot to budget for maintaining the tracks in their area, and set their own work programme. The depot manager is now responsible for everything in his charge, bringing a considerable boost in morale and motivation.

Track maintenance and repair have been brought together into a single Inspect-Analyse-Plan-Do-Test cycle, with the local teams and contractors working closely together. The contractors have their own office at each depot, and have terminals connected to the SMIS maintenance planning computer system so that they can share data. The local depot management is responsible for supervising both railway employees and contractors’ staff, thereby engendering a better team spirit. Groups of five railwaymen are responsible for daily inspection and maintenance of each 5 km section, and liaise with the contractors’ engineers for repairs to their section.

The revised track repair approvals process starts with the General Manager notifying each depot of the overall policy for the year ahead. The maintenance budget is based on the level of assets, trains run and local line speed, and is thus constant year-on-year. But each local depot must investigate its tracks, plan what repair works are needed, and set a repair budget. Lump-sum contracts are awarded to the main contractors for a fixed level of repair work, after which the local management is responsible for supervising the work done, and conducting the final inspections.

Ageing structures

The Tokaido Shinkansen is now approaching its 40th anniversary, and questions have been asked about the soundness of the civil engineering structures. The line is now carrying almost five times as many trains each day as it did when it opened, although the latest rolling stock has cut the maximum axleload to 70% of that on the original trains.

Given proper maintenance, we do not expect that large-scale repair or reinforcement work will be needed for the moment. However, there are some concerns that any deterioration that does emerge may be concentrated over a relatively short period, since the whole line was built within five years, using simple standard structures, which have since been subjected to repeated loading by standard trainsets.

It is important to recognise that an appropriate level of depreciation needs to be set aside to fund renewal. JR-Central purchased the Tokaido Shinkansen infrastructure from the government in 1991 at a price which did not reflect its historic cost. Around half of this can be attributed to the value of the land, which does not depreciate, and the other half to the structures. However, using a standard depreciation rate may not put aside the huge sums that would be needed for total replacement if the assets were left untouched. Advanced planning for asset renewal is particularly important.

I have been engaged in facilities management of the structures for many years, and I believe the best approach is to inspect them regularly and undertake appropriate repairs whenever necessary. For example, improvements have been made to reflect modern seismic protection standards, such as the fitting of steel jackets around the concrete support columns.

In recent years efforts have been made to establish an inspection system, review the in-house rules, and introduce new inspection techniques. These include detailed visual examination, stress measurement, magnetic testing and even the acquisition of railway-owned helicopters to undertake aerial inspection and detect any displacement of physiognomy in the various river basins. A rail-mounted visual recording car has been acquired to inspect the tunnel linings.

A preventative maintenance regime was put in place to act on the inspection results. Four Structures Management Offices were set up, working closely with the four inspection centres and the five or six track maintenance depots in each area (Table I).

A Structure Survey Committee including outside experts was established in 1988 under the chairmanship of Emeritus Professor Yoshiji Matsumoto of Tokyo University. This committee studies inspection methods, sets guidelines for repair and reinforcement standards, and carries out regular investigations.

In 1997 the committee reported that ’given proper maintenance, the need for large-scale replacement should not arise for some time’, which it suggested could be as much as 20 years. We plan to begin reinforcing several of the major structures against fatigue and deterioration after another 15 years, starting in 2017. As the cost of this work is expected to be very high, a reinforcement fund is being accumulated every year.

Studies are also underway to develop repair methods that will not affect the operation of trains, and to set up an improved regime for maintaining the structures properly against fatigue and deterioration.

BYLINE: * Dr-Eng Masaki Seki joined JR-Central as a supervisor responsible for structural maintenance on the Tokaido Shinkansen, becoming General Manager of the Track & Structures Department in 1996. He headed the Property & Procurement Management Department in 2000-02, before taking responsibility for developing new maintenance strategies and preparations against natural disasters, as Manager of the Technology Planning Team and the Track Maintenance & Civil Engineering Team in the JR-Central Research & Development Institute.

CAPTION: ABOVELEFT: The T4 high speed test train (Dr Yellow II) inspects each section of the line every 10 days, at up to 270 km/h

ABOVE: Composite sleepers have been introduced to reduce the transmission of noise and vibration on steel bridges and cut maintenance requirements

CAPTION: Self-propelled tower wagons are used to inspect the interior of tunnels on the route

CAPTION: Regular railhead conditioning with this Speno grinder helps to ensure a smooth ride and reduce wheel loading fluctuations for operation at 270 km/h

CAPTION: Regular monitoring of stresses is part of a package of measures being put in place to maintain and extend the life of the ageing structures on the Tokaido Shinkansen

TABLE: Table I. Tokaido Shinkansen infrastructure maintenance depots

Depot Length Structures route-km Management Office

Oi - Tokyo

Tokyo 14·3 "

Shin-Yokohama 24·0 "

Shonan 25·2 "

Odawara 21·3 "

Atami 20·2 "

Mishima 16·0 Shizuoka

Shin-Fuji 20·0 "

Shizuoka 38·6 "

Kakegawa 43·4 "

Hammamatsu 23·0 "

Toyohashi 40·4 Nagoya

Mikawa-Anjoh 34·2 "

Nagoya 26·4 "

Gifu-Hashima 29·9 "

Maibara 49·1 "

Rittoh 28·4 Kansai

Kyoto 27·6 "

Torigai 16·1 "

Shin-Osaka 10·1 "

Gérer la maintenance sur leTokaãdo Shinkansen

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