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Shin-Kodaira Station

Coordinates: 35°43′51″N 139°28′14″E / 35.73083°N 139.47056°E / 35.73083; 139.47056
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JM32
Shin-Kodaira Station

新しん小平こだいら駅えき
Shin-Kodaira Station, September 2019
General information
Location2-1960 Ogawa-chō, Kodaira-shi, Tokyo 187–0032
Japan
Coordinates35°43′51″N 139°28′14″E / 35.73083°N 139.47056°E / 35.73083; 139.47056
Operated by JR East
Line(s)JM Musashino Line
Distance7.4 km from Fuchūhommachi
Platforms2 side platforms
Other information
StatusStaffed
WebsiteOfficial website
History
Opened1 April 1973
Passengers
FY201911,448
Services
Preceding station Logo of the East Japan Railway Company (JR East) JR East Following station
Nishi-Kokubunji
JM33
towards Fuchūhommachi
 Musashino Shin-Akitsu
JM31
towards Ōmiya
Kunitachi
JC18
towards Hachiōji
Nishi-Kokubunji
JM33
towards Fuchūhommachi
 Musashino Line Shin-Akitsu
JM31
towards Kaihimmakuhari or Tokyo
Location
Shin-Kodaira Station is located in Tokyo
Shin-Kodaira Station
Shin-Kodaira Station
Location within Tokyo
Shin-Kodaira Station is located in Japan
Shin-Kodaira Station
Shin-Kodaira Station
Shin-Kodaira Station (Japan)

Shin-Kodaira Station (新しん小平こだいら駅えき, Shin-Kodaira-eki) is a passenger railway station located in the city of Kodaira, Tokyo, Japan, operated by East Japan Railway Company (JR East).

Lines

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Shin-Kodaira Station is served by the Musashino Line between Fuchūhommachi and Nishi-Funabashi, with some trains continuing to Tokyo via the Keiyō Line. It is 7.4 kilometers from Fuchūhommachi.

Station layout

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The station consists of two side platforms serving two tracks, and is located in a cutting between the 4,381 m long Higashimurayama Tunnel to the north and the 2,562 m long Kodaira Tunnel to the south.[1]

  • View of the sub-surface station platforms, May 2010
    View of the sub-surface station platforms, May 2010
  • View looking toward the Kodaira Tunnel from Platform 1, May 2010
    View looking toward the Kodaira Tunnel from Platform 1, May 2010
  • View looking toward the Higashimurayama Tunnel from Platform 1, May 2010
    View looking toward the Higashimurayama Tunnel from Platform 1, May 2010

Platforms

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1 JM Musashino Line for Nishi-Kokubunji and Fuchūhommachi
2 JM Musashino Line for Musashi-Urawa, Shim-Matsudo, Nishi-Funabashi, Tokyo, and Kaihimmakuhari

History

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The station opened on 1 April 1973.[1]

October 1991 flood

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The area had received record-setting rainfall since August 1991: 394mm in August[2] (the sixth-highest August total in history), 447mm in September (the second-highest September total in history, and the fourth-highest in any month). In October, 200mm of rain had already fallen by the 11th, the day of the incident, due to a front associated with Typhoon 21.

By the middle of September, groundwater was leaking from the retaining walls around the northern part of the platform. At around 11:45pm on October 11th,[fn 1] after 95mm of rainfall from Typhoon 21 within the previous 24 hours, a 120-meter length of the station structure had bulged upward by up to 1.3 meters.[fn 2] Gaps of up to 70cm opened in the retaining wall seams, and sediment-laden groundwater began pouring in at up to 8 tons per minute.[3] Some residents of the surrounding area had to evacuate due to the appearance of sinkholes. Because the incident happened late at night, however, no trains were running.

Attempts to drain the water using a large number of submersible pumps were unsuccessful, as the pumps could not keep up with the influx. To lower the groundwater level, eight deep wells were drilled, and 8 tons of water per minute were discharged into the sewer system. This still proved insufficient, so 11 more wells were drilled, increasing the discharge rate to 15 tons per minute, and the water was instead discharged into the Karabori River, 2km away from the station.

By the middle of November, the groundwater had subsided enough for construction to reach full speed, and by December 11th, the station was restored.[4] At first, restoration had been expected to take 6 months, but in view of the Musashino Line's importance for freight transportation, construction was expedited and carried out around the clock. Restoration was completed in about one month.

JR East incurred an estimated 3.5 billion yen[5] worth of damage from the incident.

Cause

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The station is a U-shaped structure made of reinforced concrete. Half of its depth is embedded within the Musashino gravel stratum, underneath the Kantō loam on the surface. Within the Musashino gravel, the groundwater level varies greatly with rainfall. On the day of the flood, the groundwater had risen to less than 3m below the surface, its highest level in 75 years.[6]

The Musashino Line runs north-south through the area, and acts as a dam against the west-east flow of groundwater. The structure experienced buoyancy from the rising water. The northern part of the station is uncovered and thus the weakest part of the structure, and incurred the most damage.

Prevention

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As part of the station's restoration, measures were taken to prevent a reoccurrence of the disaster even in high-groundwater conditions.

To counteract the structure's buoyancy, earth anchors were driven down through the platforms and the Musashino gravel stratum. Drainage equipment and strain sensors were installed within the retaining walls. After the groundwater subsided, a 1m upward bulge remained in the station's U-shaped concrete structure. Around the bulge, the bottom of the structure was cut out, the slab track was replaced with ballasted track, and a steel frame was added above the platforms to support the retaining walls.[7] More than half of the station's structure was rebuilt during the operation.

South of Shin-Kodaira Station, the Kunitachi Branch Line runs in a tunnel even longer than the Kodaira Tunnel, obstructing the west-to-east flow of groundwater. This effect caused frequent inundation in the town of Nishi-Koigakubo, in Kokubunji, but it was reduced by the measures JR East took to protect Shin-Kodaira from flooding.[8]

Diversion during line closure

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During the two months it took to restore service, the Musashino Line operated in two segments:[4][9] between Tokyo or Shin-Narashino and Shin-Akitsu, and between Nishi-Kokubunji and Fuchūhommachi. Substitute buses operated between Shin-Akitsu and Nishi-Kokubunji, stopping at Shin-Kodaira.[4][9] This created chronic congestion in the towns of Kumegawa and Koigakubo, along Tokyo Metropolitan and Saitama Prefectural Route 17, and meant that it could take around an hour to travel between two stations. As a result, many passengers instead walked to Akitsu Station, took the Seibu Ikebukuro Line to Tokorozawa, then the Seibu Shinjuku Line to Higashi-Murayama, then the Seibu Kokubunji Line[fn 3] to Kokubunji, and finally the JR Chūō Line to Nishi-Kokubunji. Since alternate transportation was available, commuter passes were not extended.[9]

Although there is a connecting track from the Musashino Line to the Seibu Ikebukuro Line at Shin-Akitsu,[fn 4] and the remains of a connecting track between the Seibu Kokubunji Line and the Chūō Line at Kokubunji,[fn 5] no special service was operated through the Seibu Railway. There was a plan to introduce a temporary connecting passageway between Shin-Akitsu and Akitsu stations,[10] but it was dropped amid opposition from local merchants, who feared it might become permanent.[10]

Freight trains were rerouted via the Yamanote Freight Line, the Hachikō Line, and others, but spare capacity was limited,[11] and other lines they ran on (the Chūō Line, Jōban Line, and Sōbu Main Line) had operational restrictions as well.[fn 6] 28 of the normal 113 freight trains were suspended throughout the Musashino Line closure, and others were substituted with trucks.[11]

Passenger statistics

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In fiscal 2019, the station was used by an average of 11,448 passengers daily (boarding passengers only).[12] The passenger figures for previous years are as shown below.

Fiscal year Daily average
2000 9,326[13]
2005 10,496[14]
2010 11,146[15]
2015 11,429[16]

Surrounding area

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See also

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Footnotes

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  1. ^ According to the October 12, 1991 Nikkei Shimbun evening edition. Other sources give the time of the incident as 11:15pm or 11:30pm.
  2. ^ The uplift reached its maximum in the following days, eventually reaching up to 2 meters.
  3. ^ The Kokubunji Line normally operated 4-car trains during the daytime, but switched to operating 6-car trains all day during the diversion period.
  4. ^ This track is sometimes used to move equipment to and from the Seibu Tamagawa Line
  5. ^ The track was removed when the JR part of Kokubunji Station was converted to two island platforms.
  6. ^ The Yamanote Freight Line was full (the Musashino Line had been built to bypass it). The Hachikō Line was single-track and included an unelectrified section, so little of it was usable. The Chūō Line carried many limited express and rapid trains and thus would have required high-speed freight locomotives. The Jōban Line would have required dual-voltage locomotives to go beyond Toride. The Sōbu Main Line had a tight schedule, single-track branch lines, and partially incompatible signaling.

References

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  1. ^ a b Kawashima, Ryozo (February 2011). 日本にっぽんの鉄道てつどう 中部ちゅうぶライン 全線ぜんせん・全ぜん駅えき・全ぜん配線はいせん 第だい１１巻かん 埼玉さいたま南部なんぶ・東京とうきょう多摩たま北部ほくぶ [Railways of Japan – Chubu Line – Lines/Stations/Track plans – Vol 11 Southern Saitama and Northern Tama Tokyo]. Japan: Kodansha. p. 14/58. ISBN 978-4-06-270071-9.
  2. ^ 観測かんそく史上しじょう1～10位いの値ね Japan Meteorological Agency, weather statistics
  3. ^ JR武蔵野線むさしのせん新しん小平こだいら駅えきの浮うき上あがり（社）しゃだんほうじんTokyo Geotechnical Consultants Association, Technical Note No.30
  4. ^ a b c "ＪＲ武蔵野線むさしのせん、あす始発しはつから運転うんてんを再開さいかい　災害さいがい復旧ふっきゅう工事こうじに３０億おく円えんも". 毎日新聞まいにちしんぶん（朝刊ちょうかん／社会しゃかい）. 毎日新聞社まいにちしんぶんしゃ. 11 December 1991. p. 26.
  5. ^ 平成へいせい３年ねん災害さいがい別べつ公益こうえき事業じぎょう等とう被害ひがい集計しゅうけい表ひょう Tokyo Metropolitan Construction Bureau
  6. ^ 1991年ねん秋あきに発生はっせいした武蔵野台むさしのだい地ちにおける地下水ちかすい位いの異常いじょう上昇じょうしょうについて Hosono Yoshizumi, Groundwater Technology (1993)
  7. ^ 三好みよし好こう三さん; 垣本かきもと泰宏やすひろ (1 February 2010). 武蔵野線むさしのせんまるごと探さがせ見み. JTBパブリッシング. pp. 34-36.
  8. ^ ＪＲ武蔵野線むさしのせん引込線ひきこみせんトンネルの地下水ちかすいを野川のがわに導水どうすい Tokyo Metropolitan Bureau of Environment
  9. ^ a b c JR東日本ひがしにっぽん課長かちょう・水沢みずさわ洋ひろし (30 October 1991). "［気流きりゅう］「不通ふつうの日数にっすう分ぶん定期ていき券けん延長えんちょうを」にお答こたえします". 読売新聞よみうりしんぶん（朝刊ちょうかん）. 読売新聞社よみうりしんぶんしゃ. p. 12.
  10. ^ a b "西武せいぶ線せんとの連絡れんらく通路つうろに「待まった」　不通ふつうの武蔵野線むさしのせん（リポート多摩たま）". 朝日新聞あさひしんぶん（朝刊ちょうかん）. 朝日新聞社あさひしんぶんしゃ. 17 November 1991. p. 東京とうきょう地方ちほう版ばん.
  11. ^ a b "不通ふつう１か月げつ、貨物かもつにも影響えいきょう　う回かいも限界げんかい、毎日まいにち28本ほん運休うんきゅう--JR武蔵野線むさしのせん". 毎日新聞まいにちしんぶん（朝刊ちょうかん／社会しゃかい）. 毎日新聞社まいにちしんぶんしゃ. 18 November 1991. p. 27.
  12. ^ 各駅かくえきの乗車じょうしゃ人員じんいん (2019年度ねんど) [Station passenger figures (Fiscal 2019)] (in Japanese). Japan: East Japan Railway Company. 2020. Retrieved 2 August 2020.
  13. ^ 各駅かくえきの乗車じょうしゃ人員じんいん　（2000年度ねんど） [Station passenger figures (Fiscal 2000)] (in Japanese). Japan: East Japan Railway Company. Retrieved 2 September 2014.
  14. ^ 各駅かくえきの乗車じょうしゃ人員じんいん　（2005年度ねんど） [Station passenger figures (Fiscal 2005)] (in Japanese). Japan: East Japan Railway Company. Retrieved 2 September 2014.
  15. ^ 各駅かくえきの乗車じょうしゃ人員じんいん　（2010年度ねんど） [Station passenger figures (Fiscal 2010)] (in Japanese). Japan: East Japan Railway Company. Retrieved 2 September 2014.
  16. ^ 各駅かくえきの乗車じょうしゃ人員じんいん　（2015年度ねんど） [Station passenger figures (Fiscal 2015)] (in Japanese). Japan: East Japan Railway Company. Retrieved 2 September 2020.
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