The Great East and JR Group Response Preparing for Major

Norimichi Kumagai

Introduction and there was still major damage when viaducts collapsed in the Great Earthquake (1995)(Figure 1). In the Mid To assure reliable transport railway operators must always Earthquake, a tunnel roadbed suffered be prepared for natural disasters. The Great East Japan upheaval, viaducts were damaged, and a Earthquake on 11 March 2011 and subsequent tsunami derailed. Although damage differs depending on whether the caused huge damage. Although the earthquake was Richter epicentre is in an ocean trench or inland, every possible type Magnitude 9.0, there were no railway related casualties of damage must be covered if railways are to assure safety. and damage to railway structures from the earthquake In the recent Great East Japan Earthquake, the main itself was relatively minimal. Structural damage was light damage to railway infrastructure included shattered viaduct due to the lessons learned from the 1995 Great Hanshin Earthquake and 2004 Mid Niigata Prefecture Earthquake. However, there are still Figure 1 Minimizing Damage to Railways from Mega-earthquakes issues remaining in dealing with large earthquakes. This article explains What should we learn from past earthquakes? efforts by the Railway Technical Research Institute (RTRI) to minimize damage caused by large earthquakes in the future.

Characteristics of Earthquake Damage and Lessons from Past Great Hanshin Earthquake (1995) Mid Niigata Prefecture Earthquake (2004) Earthquakes

The large earthquakes that strike Figure 2 Damage from Great East Japan Earthquake 2011 Japan have damaged railways in the past. Damage to embankments The Great East Japan Earthquake typically caused broken poles and cracked viaduct supports with some ground was recorded after the Great Kanto liquefaction at stations. Despite the size of the earthquake, the damage was not as bad as expected although coastal lines were hard hit by the tsunami. Earthquake (1923), Tonankai Earthquake (1944), and Fukui Viaduct damage Broken poles Ground liquefaction Earthquake (1948). Liquefaction was reported in the Niigata Earthquake (1964) and Tokachioki Earthquake (1968). As railway speeds increased systematic research on aseismic countermeasures for embankments and concrete structures started in earnest. However, the viaducts of the as-then-unopened Tohoku Shinkansen were damaged by the Secondary damage from aftershocks Ceiling collapse in stations Damage from tsunami Miyagiken-oki Earthquake (1978),

Japan Railway & Transport Review No. 60 • Oct 2012 34 The Great East Japan Earthquake and JR Group Response

columns, secondary damage from aftershocks, collapsed Figure 3 Broad Slip Caused by 2011 Earthquake and broken electric poles, bridge girders and embankments 44˚ washed away in the ensuing tsunami, damage to stations, and liquefaction under foundations (Figure 2). Excluding the 43˚ tsunami damage, the main earthquake shock did not cause catastrophic damage such as viaduct collapses as occurred 42˚ in the Great Hanshin Earthquake because countermeasures to shear failure of columns and bridge collapse had been 41˚ taken following that disaster. 40˚ Fault Slip

Characteristics of Great East Japan 39˚ Max. 23 m Earthquake Seismic Waves Epicentre 38˚ The Great East Japan Earthquake epicentre was in an offshore ocean trench and three large plate movements 37˚ along a 500-km (Figure 3) plate edge caused an enormous tsunami. Figure 4 shows the seismic acceleration and 36˚ frequency spectrum at two selected locations. Data from 35˚ the Great Hanshin Earthquake and Mid Niigata Prefecture SN 500 km×EW 200 km Earthquake are given for comparison. There were more 34˚ than two acceleration peaks and the continuous shaking Characteristics of the 2011 Great East Japan Earthquake33˚ Reference: Prof. Yagi,Tsukuba Univ. 32˚ 137˚ 138˚ 139˚ 140˚ 141˚ 142˚ 143˚ 144˚ 145˚ 146˚ 147˚ 148˚

Figure 4 Characteristics of Great East Japan Earthquake

This earthquake had a long continuation time and large acceleration compared to past quakes

3000 Tsukidate Great East Japan 2000 103 1000 Earthquake 2 0 10

-1000 (gal*sec) 101

(Inter Plate Earthquake) Acceleration (gal) -2000 -3000 Fourier Amplitude 100 0 100 200 0.1 0.5 1 5 10 2000 Shiogama 3 1000 10 2 0 10 -1000 (gal*sec) 101 Acceleration (gal) -2000 Fourier Amplitude 100 0 100 200 0.1 0.5 1 5 10 Time (sec) Frequency (Hz)

2000 3 Great Hanshin 1000 10 2 Earthquake 0 10 -1000 (gal*sec) 101 (Near-Source Earthquake) Acceleration (gal) -2000 Fourier Amplitude 100 0 100 200 0.1 0.5 1 5 10 2000 3 Mid Niigata Prefecture 1000 10 2 Earthquake 0 10 1 -1000 (gal*sec) 10

(Near-Source Earthquake) Acceleration (gal) -2000 Fourier Amplitude 100 0 100 200 0.1 0.5 1 5 10 Time (sec) Frequency (Hz)

35 Japan Railway & Transport Review No. 60 • Oct 2012 lasted more than 3 minutes. Compared to the other two Conventional embankments have low resistance to earthquakes, the acceleration was large and the peak shaking, erosion, and flooding in large earthquakes and frequency was high at about 5 Hz, which was very different tsunamis. Moreover, large soil volumes are needed to from the natural frequency of railway viaducts (2 Hz) and build high seawalls. To overcome these problems, RTRI possibly explains why damage to viaducts was minimal. developed the Reinforced Railroad/Road with Rigid Facing (RRR) construction method in which reinforcing material is Resisting Large Earthquakes and Tsunami layered in the embankment and covered by a nearly vertical concrete facing as shown in Figure 9. Such structures Research and development on how to resist damage remained undamaged in the Great Hanshin Earthquake. The from large earthquakes is split into three fields: aseismic method could be applied to seawalls, and we plan to verify design countermeasures; securing safe running; and early its resistance to large tsunamis in the future. detection. Countermeasures aim to improve earthquake resistance so structures are not destroyed. Securing safe running characterizes train behaviour in an earthquake to prevent derailing. Early Detection and Warning System slows Figure 5 Countermeaures to Mega-quakes and stops trains before the main shock strikes. These are represented in Figure 5. 1. Aseismic Structural Design

Improving Structural Seismic Resistance Anticipating seismic motion Anticipating responses of structures and tracks RTRI summarized the various aseismic technologies in the Improving seismic performance of structures form of a technical proposal in December 2011 to support restoration and recovery of railways damaged by the Great East Japan Earthquake. Figure 6 shows the technologies 2. Securing Safe Running for regions hit by the tsunami. Figure 7 shows technologies Anticipating behavior of running trains during earthquakes to make existing railway facilities more earthquake resistant. There are more than eight aseismic technologies depending Preventing derailment on the structure and location of installations, including viaducts, embankments, bridges, and stations. The technical 3. Early Detection & Warning System proposal also considers how to reduce construction costs Stop operation by using Early Earthquake Detection and and time. Warning System

Seismic Resistance of Bridges and Figure 6 Reconstruction Methods in Tsunami-hit Areas Embankments Reinforced track with rigid facing Integral bridge with The weak points of bridges geosynthetic-reinforced soil in earthquakes and tsunamis Embankment are the bridge girder supports Geotextile and the embankments, Breastwork which are easily swept away. The geosynthetic- reinforced soil (GRS) integral bridge overcomes these weaknesses by bonding bridge girders, facings, and embankments into a single structure using concrete (Figure 8). These structures Seawall against tsunami have double the seismic resistance of conventional structures.

Japan Railway & Transport Review No. 60 • Oct 2012 36 The Great East Japan Earthquake and JR Group Response

Figure 7 Aseismic Reinforcement of Existing Structures

Reinforcement of Knee brace damper for Anti-angular Damper-brace for old bridge over-track bulding rotation device railway viaduct

Seismic reinforcement of existing structures

Reinforcement of pivot Soil nailing of Arch-shaped steel Soil nailing of bearing embankment plate for RC frame retaining wall

Figure 8 Construction Process and Experimental Bridge Figure 9 Reinforced Soil Wall and Application for Seawall

In the integral bridge with geosynthetic-reinforced soil (RRR-GRS), The Reinforced Railroad with Rigid Facing-Method (RRR) has proven the bridge frame is built after the embankment is constructed. high seismic performance in the Great Hanshin Earthquake. In 2011, RRR was used for reconstruction of damaged sea walls.

Embankment

Construction of embankment Geotextile Breastwork

Completion

Completion Experimental bridge at RTRI 6850 14750 6850 1500 1500 2000 900 12950 900 2000

0 JR line affected by Great Hanshin 0 0 0 5 0 9 8 5 Earthquake in 1995 30 1 8 1 : 1 900 1 0 5 0 7 0

3 February 2011 00 3 00 3 0 0 9 2000 1350 1350 2000 Sea Wall Before constructing concrete facing

This sea wall was damaged by a typhoon in July 2007.

37 Japan Railway & Transport Review No. 60 • Oct 2012 Figure 10 Fundamental Behaviour of Vehicle at Rocking Derailment

Lower centre rolling motion (less than 0.8 Hz) Higher centre rolling motion (greater than 1.3 Hz) First First Centre of rolling Third Third

Body Body

Truck Truck Wheelset Wheelset

Centre of rolling (Freq. 2.0 Hz, Half amplitude 85 mm) (Freq. 0.5 Hz, Half amplitude 370 mm)

Figure 11 Vibration Test using Shinkansen Bogie (Large-scale Vibration Test Machine)

Excitation pattern: Sinusoidal wave (Freq. 0.5 Hz, Half amplitude: 330 mm) Actuators Half carriage body

Bogie

Shaking table (5 m × 7 m) • Maximum surcharge load 50 tonnes • Maximum acceleration ±2000 gal ExamplesThis test machine of was Running financially supported Safety in part byLimit the Ministry Based on Results of Vehicle Dynamics• Maximum Simulation displacement 1000 mm (Half amplitude) of Land, Infrastructure, Transport and Tourism.

Figure 12 Examples of Running Safety Limit Based on Results of Vehicle Dynamics Simulation

Shinkansen vehicle (speed: 240 km/h) Overturning Rocking derailment Jumping derailment 700 Derailment: relative lateral displacement between wheel and rail is 600 larger than ±70 mm. 500 Initial position +70 mm -70 mm 400 New vehicle Dangerous 300 200 Old vehicle Wheel Tread 100 Safe 0 Half amplitude of lateral excitation (mm) 0 0.5 1 1.5 2 2.5 3 Rail Frequency of lateral excitation (Hz)

Shinkansen Behaviour in Earthquakes When performing numerical analysis of vehicle dynamics, it is important to perform detailed analysis of the varying To prevent trains derailing and injuring passengers, RTRI dynamics of vehicles and to accurately calculate the has analyzed the detailed behaviour of rolling stock vibration of viaducts and tracks. We have shown that seismic during seismic motion. We rely mostly on numerical vibration is amplified when propagating from the ground to simulations to analyze vehicle dynamics and then perform tracks on viaducts. We have also been able to model the vibration experiments on shinkansen bogies to validate jumping movement of wheels on vibrating rails. the simulations. Moreover, we have evaluated the running Seismic derailment is very different from climbing-wheel safety of specific rolling stock types to propose measures derailment. In shinkansen carriages, the wheels and body to make them harder to derail when running at high speed. roll in phase and sway gently when the lateral vibration

Japan Railway & Transport Review No. 60 • Oct 2012 38 The Great East Japan Earthquake and JR Group Response

Figure 13 Examples of Anti-deviation Facilities after Derailment (JR East)

Solution on track: L-shape guide Solution on track: Improved tapers Rail fall prevent facility

Guides track after derailment

Taper Axle-box Bolt Tie plate Train direction L-shape guide

Figure 14 Examples of Anti-derailment Facilities (JR Central)

Solution on track: Anti-derailment guard Solution on track: Ballast stopper Solution on track: Anti-deviation stopper Prevents derailment caused by rolling motion Prevents collapse of ballast Prevents deviation from track

Guards stop motion of wheelsets

frequency of rails is about 0.8 Hz or less. However, when where the probability of derailment is high. The lower area is the lateral vibration frequency of rails is about 1.3 Hz or broader for new rolling stock models than for older models, more, the wheels and the body roll out of phase and sway indicating the better safety of new models. However, these violently. In this situation, the wheel flanges and rails impact diagrams do not account for misalignment at boundaries of violently. Derailment is called rocking derailment when these structures and bend angle. disturbances occur in combination caused by complex waves including many frequency components (Figure 10). Technical Measures to Secure Safe Running To improve simulation accuracy, we shook an actual shinkansen bogie in the parallel direction to the sleepers JR Companies, RTRI, the Ministry of Land, Infrastructure, under a load equivalent to that of a train body (Figure 11) Transport and Tourism (MLIT), and other participants have using a vibration tester with a maximum load of 50 tonnes, held study meetings, the Council for anti-derailment measures maximum excitation stroke of 1 m, and maximum vibration for shinkansen, to propose countermeasures to shinkansen acceleration of 2000 gal. derailment since the Mid Niigata Prefecture Earthquake. The measures include adjustment of vehicle springs, dampers, and Running Safety Boundary Diagrams stoppers along with installation of new derailment prevention guards. In the event that carriages do derail, a method has One reason for simulating derailments is to create running been proposed to prevent them deviating greatly from the safety boundary diagrams (Figure 12) by plotting rail rails. Simulations and experiments were conducted on each of vibration amplitudes for vibration frequencies of 0.3 to 3 Hz these measures, and railway operators have selected specific just before a carriage derails. The diagrams help identify measures based on consideration of improvements to safety. basic vehicle running safety versus seismic motion and JR East adopted a measure to prevent carriage deviation can compare the effects of different vehicle characteristics by combining L-shaped guides and rail overturn prevention and running conditions on running performance. In Figure devices (Figure 13). JR Central adopted a measure combining 12, the two lines show the running safety boundaries for derailment prevention guards and deviation prevention two types of shinkansen rolling stock. The area under the stoppers (Figure 14). The two companies adopted different lines is where derailment does not occur. The area above is measures due to structural differences where one has tracks

39 Japan Railway & Transport Review No. 60 • Oct 2012 Figure 15 Simulation of Train Motion on Railway Long-Span Bridges during Earthquake

Seismic wave of Mid Niigata Prefecture Earthquake applied to viaducts and bridges

Figure 16 Earthquake Disaster Prevention System

1960 1970 1980 1990 2000 2010

1965~ 1982~ 1998~ 2004~ Mechanical Electric Compact Earthquake Disaster Seismograph Seismograph UrEDAS Prevention System

Coastline Earthquake 2006~ Detection System JMA Earthquake 1992~ Early Warning UrEDAS System

Mechanical Seismograph Seismic Observation Station Earthquake Disaster Prevention System

with many slab roadbeds and viaducts while the other has Development and Introduction of tracks with many ballasted sections and embankments. New Early Warning Seismometers

Effects of General Simulation Trains must decelerate and stop quickly in an earthquake to prevent damage. Following the 1964 opening of the Tokaido To assess the safety of shinkansen rolling stock running Shinkansen, systems were equipped with seismometers on various structures, previous actual seismic vibrations in 1965 to stop trains in an earthquake (Figure 16). As are used as simulation input waves. For example, inputting shinkansen speeds increased, RTRI developed the Urgent the ground seismic waves observed during the Mid Niigata Earthquake Detection and Alarm System (UrEDAS) using the Prefecture Earthquake recreated the behaviour when the first early P-wave vibrations to quickly estimate the earthquake shinkansen derailed (Figure 15). In this test, the rolling stock epicentre and magnitude, evaluate the expected size of the behaviour included numerical simulation of the effects of main shock (S-waves), and stop trains. A newer earthquake rail angular bending at structural boundaries. At large-scale early warning system was developed in 2004 reducing the seismic motion, general simulation to analyze the behaviour time to estimate the distance from the epicentre and the of wayside equipment from the ground to the track surface magnitude and giving more time to stop the trains (Figure 17). and the behaviour of the rolling stock is very effective in Today, more than 180 seismometers of the new system are setting and assessing measures to secure safe running. installed along coasts and railway lines across Japan.

Japan Railway & Transport Review No. 60 • Oct 2012 40 Principle of P-wave Warning

The Great East Japan Earthquake and JR Group Response

Figure 17 Principle of P-wave Warning

Issue P-wave warning for damage area corresponding to magnitude

S-wave Damage area (Main Motions) corresponding to P-wave magnitude

1~2 sec Issue warning before S-wave arrival

Epicentre • Estimate epicentre distance Δ, azimuth Θ, magnitude • Estimate damage area from epicentre and magnitude Θ M Δ P-wave Accuracy is essential for estimating epicentre distance, Railway azimuth, magnitude Coastline Seismograph (Railside Seismograph)

Figure 18 Characteristics of P-wave Motion

Comparison of amplitude increase of initial P-wave with other records (gal) 7 *Average of amplitude increase These measures seem to have proved of records with hypocentral 6 distance 150 km ±10% effective against the recent giant Great East Japan Earthquake. However, some previous 5

on Average of M7.0 records i t measures were inadequate and new issues 4 P-wave 2011 Earthquake (M=9.0) came to light. Arrival 3

ical Accelera In countering tsunami, we especially t

Ver 2 Average of M6.5 records need methods for assessing hardware enhancements as well as measures for 1 Average of M6.0 records guiding people to safety before the tsunami 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 (s) arrives. Methods for assessing damaged Time railway structures are also needed. Placement of seabed seismometers in addition to shoreline seismometers might be effective for earlier earthquake detection. Characteristics of 2011 Earthquake and But further risk-management techniques including risk P-wave Warning Detection assessment methods must be developed to conduct measures in a prioritized and effective manner. In the Great East Japan Earthquake, the P-waves and S-waves were detected almost simultaneously, which means that the P-wave early warning was not very effective. To clarify the characteristics of these seismic waves, the average values for seismic waves from past earthquakes at almost the same distance from the epicentre were compared with the 2011 earthquake (Figure 18). The start of the P-wave acceleration in 2011 was much gentler than past earthquakes. At present, we do not know if this phenomenon is unique to very large earthquakes. However, if the P-wave acceleration is gentle, the magnitude is underestimated. We are now beginning to study better methods for quickly estimating earthquake parameters. Norimichi Kumagai Dr. Norimichi KUMAGAI is a Vice President of Railway Technical Future Efforts Research Institute. He Joined JNR in 1976 and worked on planning of new rolling stock. In 1987 he joined RTRI as a General Manager Japanese railways and railway researchers have developed of Brake Control Laboratory and High-Speed Rail Project. He earthquake countermeasures based on past earthquakes. was consecutively Executive Director in charge of R&D, and Vice President. He earned his PhD degree in Tohoku University in 2004.

41 Japan Railway & Transport Review No. 60 • Oct 2012