Japan Railway & Transport Review No. 61 (p30-p39)
Breakthrough in Japanese Railways 11
Advances in Geological Surveying for Railways in Japan
|Start of Geological Surveying in Japan|
The opportunity provided by modern Western geological studies to Japan came in the form of surveying for mineral resources in the late 19th century from the end of the Edo period (1603–1867) to the early Meiji period (1868–1912). American geologists William Blake and Raphael Pumpelly were recruited together with Japanese counterparts by the shogunate in 1861 to survey the mineral and coal resources of southern Hokkaido.
|Start of Geological Survey of Japan|
A section in charge of lumber and ore was established in Japan’s Ministry of Home Affairs in 1874, and collection of unusual rocks and minerals from across Japan was also initiated. In 1878, an imperial geological surveying agency was established by Naumann and Tokyo University Associate Professor Tsunashiro Wada. That agency developed into the ministry’s Department of Geology.
|Nobi Earthquake and seismology|
The magnitude (Mj) 5.8 Yokohama Earthquake of 1880 did not cause major damage, but caused great shock among residents of the foreign settlement in Yokohama. British Professor John Milne at the Imperial College of Engineering (a forerunner of the Tokyo University’s Faculty of Engineering) founded the Seismological Society of Japan as the world’s first academic group dedicated to the study of earthquakes and started full-scale research into them.
| Figure 1: Geological Sketch of Yezo Island, Japan (1876)
Figure 2: Geological Measurements near Jizo Pass (1885)
Photo: Milne Seismometer (National Important Cultural Property) (1894) (National Museum of Nature and Science)
|Start of hazard geology|
|In Japan, where weather-related disasters such as typhoons occur regularly along with earthquakes, the relationship between weather and geological phenomena was the early focus of study. Surveys on these phenomena were promoted by the Imperial Earthquake Investigation Committee
In 1901, Tokyo Imperial University Professor Kotora Jinbo, who had surveyed denuded land in Yamanashi, Ishikawa, and Shizuoka prefectures under contract to the Imperial Earthquake Investigation Committee, published a report in The Journal of the Geological Society of Japan, advocating the necessity for geological surveys. Jinbo further stressed that geologists would need to cooperate more closely with civil engineers, stating that knowledge in areas such as ground collapse and weathering of rock is imperative for civil engineers, and that geologists should bear this in mind.
The magnitude (Mj) 7.9 Great Kanto Earthquake that struck the southern Kanto region on 1 September 1923 was the worst natural disaster Japan ever faced, with close to 100,000 people dead and 44,000 missing. The government immediately established the Imperial Capital Reconstruction Agency and started reconstruction, including about 800 bore surveys to identify the ground structure under the capital region. The survey results were released in 1929 as a report on geological surveys of Tokyo and Yokohama, which was subsequently used in civil engineering and architectural construction, disaster prevention planning, etc.
Aerial photography, which had advanced along with aircraft development, was put to use in tasks such as identifying disaster areas in the Great Kanto Earthquake, but this kind of technology was still used mostly for military purposes. The Ministry of Railways first tried using aerial photography to survey lines in 1932 with the cooperation of the army. In 1937, it used six aircraft with photographic equipment and pilots to start independent line surveys using aerial photography. Approximately 5000 km of rail lines had been surveyed using aerial photography by the end of WWII, but aerial photography was suspended in 1943 due to the war. All documents were destroyed at the end of the war, so none passed down to history, but this did provide an opportunity for aerial photography to be used in surveys for civil engineering construction works.
|Tanna Tunnel and geological surveying|
|Construction of the Tanna Tunnel on the Tokaido main line started in 1918 and was one of the world’s most difficult projects in the history of tunnel construction. With works often disrupted by cave-ins and floodings due to distensible geology and large volumes of groundwater, the tunnel was not completed until 1934.
Tokyo Imperial University was commissioned to perform a survey for construction of the Tanna Tunnel, and predicted large volumes of spring water. However, construction went forward without gaining a clear conclusion from the geological factors. The tunnel was in danger of non-completion and was criticized by overseas tunnel engineers as a reckless endeavour. As a result, the Ministry of Railways hired geological experts in 1923 to its conduct own geological surveys.
When surveying for a railway across the Kanmon Straits, bridge and tunnel proposals were compared, with geological surveys involving boring being conducted in 1919. Such geological surveys by boring were already common in mining, but at last came into popular use in civil engineering with geological surveys for the Tanna Tunnel and the Tokyo Subway (part of the Tokyo Metro Ginza Line today), which started operation in 1927.
|Photo: Railway Damage due to Nobi Earthquake (Nagaragawa Bridge) (1891) (Dr. Hiki’s collection of Kyoto University)
Photo: Railway Damage due to Great Kanto Earthquake (1923) (Author’s Collection)
Figure 3: Tanna Basin Fault and Groundwater Survey Chart (1934)
Figure 4: Tanna Tunnel Boring Geological Survey (1934)
Figure 5: Kanmon Undersea Tunnel Geological Map (1939)
Photo: Preliminary geophysical prospecting Test by Ministry of Railways’ Geotechnical Committee (1933) (RTRI’s Collection)
|Formation of Ministry of Railways Geotechnical Committee|
|The Ministry of Railways recognized the importance of geological surveys in reflections on the difficulties with the Tanna Tunnel construction, setting up its Geotechnical Committee in 1930. At the time, new concepts in new soil mechanics were being established in Europe by the likes of Karl von Terzaghi, Wolmar Fellenius, and Albert Atterberg. Swedish State Railways, in particular, organized its Geotechnical Commission and achieved great results in areas such as disaster geology.
Such knowledge from abroad was introduced to Japan through various means such as activities of the Ministry’s Geotechnical Committee, greatly influencing the country. The Committee, along with outside people such as researchers from Tokyo Imperial University, started studies to apply geological knowledge to engineering. The purpose of the Committee was stated as being to ‘survey and research the characteristics of soil in a scientific and engineering-based manner for conducting construction, maintenance, improvement and other work for national railways lines, and to execute construction appropriate for the condition of the particular location, and contribute to construction cost reduction and safety for lines.’ The Committee established study groups on design and building methods for structures, etc., based on geological surveys, and it tirelessly conducted activities such as bibliographic surveys, holding of study groups, testing commissioned by outside entities, and consulting, until 1938.
The Committee put much effort into practical use of elastic prospecting, electrical prospecting and other geophysical prospecting methods and into development of testing methods to identify the physical properties of soils and rock, thereby establishing the foundations of today’s engineering geology. Geophysical prospecting technologies, such as elastic prospecting, had already been used in mining by the 1920s, but the first attempts to use these technologies for railways were electrical prospecting in surveying the foundations for the Chuo main line Tamagawa River Bridge in 1930 and elastic prospecting for the Tanna Tunnel in the same year.
Such results were applied later to construction of the Kanmon Undersea Tunnel, but the Ministry of Railways’ engineers were sent overseas or transferred to tasks such as construction of underground bunkers and other defensive facilities as the war intensified. This situation continued until the end of the war.
|Postwar Reconstruction and Geological Surveying|
|Start of Railway Technical Research Institute’s Geological Research Laboratory
Advancement in geological surveying for railways was halted for a time due to WWII but the need for geological surveying grew rapidly with the postwar recovery. Railways and roads, and water resource facilities such as dams and large irrigation canals were being built at a rapid pace.
Demand increased for construction of railways along with postwar reconstruction, so Japanese National Railways (JNR) launched the Geological Research Laboratory at its Railway Technical Research Institute (RTRI) in April 1955. The geological consulting industry had not sufficiently developed at the time, so the Laboratory primarily conducted its own surveys. The first job was a geological survey for the Hokuriku Tunnel then in planning. It conducted bore surveys, electrical prospecting, elastic prospecting, and hydrogeological surveys, establishing the foundations for later tunnel geological surveys.
Railway disasters and geological surveying
JNR set up a landslide experimental station at Nou on the Hokuriku main line in 1948 and started activities such as general monitoring using measuring devices and model experiments. A committee on countermeasures against disasters on the Dosan Line was later established by JNR in response to the 1962 slope disaster on the line between Tosa-Iwahara and Toyonaga, with experts from inside and outside the company coming together to perform analyses. The committee identified levels of disaster risk from the cause and effect relationship between geological structure and slope disasters. It also accomplished results such as extraction of broken terrain by deciphering aerial photos.
Aerial photographs were put to full-scale use for slope disasters from 1970 with creation of a grading chart to evaluate degree of soundness. Multispectral photographs were used from 1972 in an attempt to more accurately extract the terrain of slope disasters. These results were published in 1978 as a study group report on methods of deciphering aerial photographs, and anuals were created for methods of deciphering disaster terrain and interpreting the results of deciphering.
Railway construction and geological surveying
Seabed geological surveying was conducted in 1960 using deepsubmersibles for the Seikan Tunnel, which had been under survey from the 1950s. Other methods included bore surveys, elastic prospecting, electrical prospecting, and physical and chemical ests. Thanks to these, the seabed geology of the Tsugaru Strait was almost completely known by about 1962.
Ra i lway c o n s t r u c t i o n a n d improvement works expanded in the 1960s with Japan’s rapidly growing economy, andgeological survey work also eventually broadened wi t h s hin ka nse n c o ns t ru ct i o n projects. Standard specifications for geological surveying were thus established by JNR in 1969, and a framework for conducting geological surveys was put in lace ahead of civil engineering construction.
For railway tunnel construction in particular, the New Austrian Tunnelling Method (NATM) was introduced in the late 1970s as a replacement for the conventional sheet piling method.
NATM rapidly became commonplace as a flexible construction method that is well-matched to Japan’s complex and varied eological conditions.
Moreover, quantitative assessment of ground based on rock engineering became possible due to factors such as identification of ground deformation behaviour, use of mine workface observation records, and application of numerical analysis technologies, such as FEM. NATM gained prominent status in the railways field as the standard method of tunnelling in mountains with the 983 establishment of the NATM design construction guidelines by JNR.
Interest in deep underground spaces increased from 1987 with the skyrocketing cost of land in urban areas, promoting technical development for deep underground railway tunnels.
Rock mass classification for railways had started around 1942 with the creation of simple rock classification charts for slopes, but more quantitative assessment methods were needed with the spread of geological surveying methods. A classification of rock conditions for tunneling was created in 1966 based on previous tunnel surveys and accumulation of knowledge from construction, with rock mass strength broken down into seven levels, based on rock type and elastic wave velocity (Table 1).
This classification is the basis of the later rock mass classification, and with the establishment of the 1983 NATM design onstruction guidelines, a six-level rock mass strength classification was made based on rock type and elastic wave velocity and ground strength comparisons.
Standard support patterns according to individual rock mass classifications were presented, and tunnel design and construction was conducted in a more streamlined manner thanks to these guidelines.
| Figure 6: Geological Survey Chart on Dosan Line (1964)
Photo: Seikan Undersea Tunnel Construction (1983) (Japan Railway Construction Corporation)
Table 1: Classification of Rock Quality for Railway Tunnel Construction (1970)
Photo: Railway Damage due to Great East Japan Earthquake (2011) (JR East)
There was little interest in geological surveying during
early railway construction in Japan, and almost no detailed
surveys based on scientific knowledge were performed.
Dr. Shigeru Onoda is an associate director in the information management division at Railway Technical Research Institute RTRI).
He joined Japanese National Railways (JNR) in 1979 after graduating Nihon University. In 1987 joined RTRI as a researcher of Geotechnical Engineering and Disaster Prevention Laboratory. He took charge of development of reinforcement and repair methods of railway tunnels.
He earned his doctorate at Tokyo University in 1998. And he is a specialist in the history of a railway civil engineering heritage now.