Geotechnology Basic Survey

with Associate Prof. C. T. Oguchi, Saitama University.

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What kind of geology is Taya's cave dug in?



Geotechnology Basic Survey
​with Saitama University
埼玉大学大学院 理工学研究科

埼玉大学 小口千明 准教授
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  • データ精査の結果から、洞門密閉改修の必要性を定泉寺へ提言。

  • 公益財団法人東日本鉄道文化財団より密閉洞門改修事業の助成を受託。

We are proceeding with engineering investigation with the cooperation of laboratory of Associate Professor Oguchi of Saitama University to verify the soil quality etc. of the cave.

  • Based on the results of the data review, we suggested the necessity of renovation to the sealed gate to Josenji Temple.

  • We entrusted a grant from the East Japan Railway Culture Foundation for the sealed gate renovation project.

Geological field survey
​地盤地質 現地確認


We spend a lot of time studying the "layer breaks" and "shell fossils" that can be considered in the cave. We are also observing the geology of the neighborhood.



With the permission of Josenji Temple, we sampled at two locations in the cave, brought the samples back to the laboratory, and conducted various laboratory tests.

Cave temperature and humidity monitoring


We have installed data loggers at seven locations inside and outside the cave to monitor weather conditions inside the cave and monitor temperature and humidity once per hour.

Thermostat photography survey



Whether we can visualize the temperature, we conducted a study survey using a thermostat camera.

The temperature of the passage space and the wall of the cave were measured. We tried to shoot if we could catch the time change of the subtle temperature change in the cave with video shooting. The result was so small a change that we couldn't get a good video of the temperature change over time.  

Equipment cooperation: Yokohama City.

Destructive testing


We conducted a pressure test at Saitama University using materials sampled from inside the cave with the permission of Josenji Temple. We also conducted a dry and wet repeated inspection to understand the weathering conditions of the ground.

Non-destructive testing


We also carry out non-destructive inspection inside the actual cave. We take care not to damage the pattern on the cave wall, and we carry out wall repulsion and ultrasonic transmission tests.

Analysis of surface precipitated phases in the cave


On the surface of the wall of the cave, it has fixed a variety colored materials. These deposits have been transformed into the surface by the rainwater and groundwater that have fallen on the surface of Satoyama over the years, and have appeared on the surface. We analyze these precipitates and investigate what kind of components are coming out.