In case of tunnels being deformed, hindrances may occur more severely in railway tunnels than in other tunnels. Examinations and reconstructions of deformed tunnels had been performed by J. N. R., hitherto. Shimokuno tunnel: In consequence of measuring mainly earth pressure behind the lining over a long period before and after reconstruction, some behaviours of earth pressure could be observed as follows:

  1. Accumulation of earth pressure behind the deformed lining when it was protected by steel supports,

  2. responses of earth pressure to the progress of reconstruction works, and

  3. accumulation of earth pressure after reconstruction. This method of examination was applied in Usami tunnel and others. Through these experiences and considerations on them an idea was obtained: that examinations of deformed tunnels should be made by pressure cells of lining itself or by load cells of protective supports themselves to estimate acting load. In the case of lwakake tunnel load cells were planted at the base of steel supports which had steel packings for fastening. Meanwhile, seasonal effects of earth pressure on deformed tunnels were also observed.


La deformation des tunnels ferroviaires est plus dangereuse que les autres. Le Chemin de Fer Japonais a etudie tunnels deformes et les a reconstruits. Shimokuno tunnel: D'après la mesure pendant long temps, notamment, en ce qui concerne le pourtour d'un revêtement, avant et après sa reconstruction les pressions ont ete observees d'avoir des caracteristiques suivantes:

  1. Accumulation des poussees sur le revêtement, s'il serait supporte par soutènements,

  2. fluctuation des poussees avec progrès de la reconstruction et

  3. accummulation des poussees après reconstruction. Les processus sont appliques aussi pour Usami tunnel. Conclusion qui sont tenu compte des experiences et considerations sont ainsi; pour l'etude des tunnels deformes, le revêtement ou soutènement doit être considere entièrement comme un extensometer. Dans Iwakake tunnel, les mesures sont effectuees sous des pieds des cintres metalliques avec remplissages metaliques. Fluctuations des poussees avec saisons sont aussi observees.


Die Umformung eines Tunnels ist besonders unvollkommener bei Eisenbahnen als bei anderen. Bis heute hat die japanische Eisenbahn mehren solchen Tunneln untersucht und rekonstruiert. Shimokuno Tunnel; Durch den lang duarnden Erddruckmessungen, die hauptsachlich hinter der Tunnelauskleidung bevor und nach der Rekonstruierung durchgefuehrt wurden, wurde folgendes festgestellt.

  1. Zunahme des Erddruckes auf der Tunnelauskleidung, wenn er durch Stahlbogen verstàrkt wurde,

  2. Schwankung des Erddruckes mit Fortschritte der Rekonstruierungsarbeit und

  3. Zunahme des Erddruckes nach der Rekonstruierung. Eine ahnlicbe Untersucbung wurde auch in Usami Tunnel vergenommen. Aus Erfahrungen und Überlegungen konnte die Folgerung gezogen werden, daβ bei Untersuchung eines schlechten Tunnels die Tunnelauskleidung oder der Einbau als eine Druckdose betrachtet werden sollte. In Iwakake Tunnel wurden Druckdose unter den Stahlbogenfueβen mit eisernen Packungen angebracht. Die Erddruckschwankung wurde nach Jahreszeit auch beobachtet.


The term «deformed tunnel» is applied to a tunnel whose inside sectional dimension differed from the original state caused by external forces or other activities and whom countermeasure as protective supports or reconstruction was necessitated. Deformed tunnels can conveniently be classified by causes which induced to them the deformation as follows.

  1. Deteriorated: deterioration of material of the lining, according to long term after construction or use of bad materials, be remarkable.

  2. Deformed: inside sectional dimension be differed from the originals.

  3. Destroied: lining materials be destructed, and

  4. Defective: defects, such as leakage water or mud pumping in road bed depend on the conditions of construction, be existed. For instance, a tunnel whose inside sectional area became insufficient for new operation of large-sized car or electrification is also contained in this item. Long term measurings, examinations and reconstructions concerned the deformed tunnels have been performed by Japanese National Railways hitherto. Behaviours of the earth pressure acting on the deformed tunnelsare described in this paper.

2. Measurements in early stage
2.1. Shimokuno tunnel

Shimokuno tunnel, which is located in the Kisugi-line connecting Matsue to Bingo-Ochiai, was constructed about 35 years ago (1931–4). The tunnel, whose lining was customarily consisted of an arch with precast concrete blocks and of a side wall of concrete in situ, was deformed by the external forces. One of places, where deformation was most hardly occured, corresponded unexpectedly to a section with invert concrete. Destruction of the lining was remarkably occured where the altered porphyrite intruded into granite mass and the reconstruction was then performed over a length of 177 meters from 1958.1 to 1959.3. Although the deformation with a maximum sectional reduction as much as 33 centimeters was observed obviously to be in progress, a greater part of them was presumed to have already occured in time soon after the construction.

2.1.1. Before construction(1958.3 -1958.10) [1]

Earth pressure, whose development is shown in Fig. 1, had been measured for about 7 months preceding the reconstruction. Earth pressure seems to show naturally increasing and decreasing or restoration and release.

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