Professor Hiroshi Niki's research group at the Graduate School of Literature and Human Studies, Osaka City University explored the area around the main enclosure of Osaka Castle during the Toyotomi Hideyoshi era, which sleeps in the ground, using a Swedish sounding survey.For the first time, I confirmed the foundation of the castle tower, which I could only know from pictures, and clarified the height and spread of the area around the main enclosure.
Osaka Castle, built by Toyotomi Hideyoshi in 1583 (Tensho 11), is positioned as the starting point of the modern castle, but after the fall of the castle by the summer camp, Tokugawa filled the entire castle with thick mounds. Since Tokugawa Osaka Castle was built on top of it, Toyotomi's Osaka Castle was completely buried underground.Currently, it cannot be confirmed at all on the ground.In addition, since Osaka Castle is currently designated as a national special historic site, the implementation of excavation surveys is severely restricted even for academic purposes, and the actual situation has not been clarified very much.
Therefore, Professor Niki's research group adopted a method called the Swedish sounding survey.This is to measure the strength of the load required to penetrate the stratum by inserting the screw (diameter about 3 cm) attached to the tip of the metal rod (rod) vertically into the ground by a machine.By analyzing this strength, the height of the ground surface estimated to be during the Toyotomi period can be obtained.Also, if the screw hits a stone in the stone wall, it cannot be inserted, so it is possible to know the position and height of the stone wall.
By this survey, the surface of the outer shell on the north side of the castle tower of Toyotomi Osaka Castle was physically confirmed for the first time, and it was found that the altitude was 30 m.In addition, it was confirmed for the first time that the exact position of the foundation part of the turret-like structure on the south side of the main gate "Mikado Yakura" of Toyotomi Osaka Castle's Tsumenomaru and the height of the foundation part was about 4.5m (remaining). bottom.
Other findings and details of the research will be reported at the Osaka Historical Society Conference to be held on June 2019, 6.In the future, the research group will continue to elucidate the actual situation of Toyotomi Osaka Castle while continuing the Swedish sounding survey and incorporating other exploration methods such as electrical exploration, surface wave exploration, and microtremor array exploration.
