Study on preservation of the stone historic remains in cold regions

点击翻译按钮获取中文摘要

In Hokkaido there are several historic remains, which were bult on the bedrock. In this study present author investgated Temiya Cave, Otaru city. The carvings on the wall of the cave of Temiya were found as one of the most important historic remains in Hokkaido. That cave was excaveted its inlet about 100 years ago. Since that time the carvings on the cave wall have been damaged, as the carvings were exposed to the severe cold climate, and frost stattering has occurred on the wall. The present author conducted on-the-spot investigations measuring temperatures at various points at the site to preserved the cave and carvings. The numbers of freezing-thawing cycles were counted at several points both inside and outside of the cave based on the results of temperature measurements. If rocks of the wall freeze and thaw at temperaures fluctuating between the maximum of +4ﾟC and the minimum of -4ﾟC,the rocks tend to break up. The numbers of freeze-thaw cycles counted in this critical temperatu … More re range were six in total during the observed period in 1994-95 winter season.Meanwhile, rock specimens were sampled from the bedrock of the cave and their frost resistances were tested in the laboratory. Besides, the effective porosity and the velocity of ultra-sonic wave propagation through the specimens were measured. These results indicate that this type of rock is very frost susceptible under conditions in which water is sullied to it. Some of the specimems were treated by the synthetic resin call SS-101. Then they were subjected to freezing-thawing cycles with water supply in the cold chamber. As a result, no damage occurred too them. Based on the field investigations and laboratory experiments, the most effective methods were suggested by the author for the preservation of the cravings on the wall.In addition of the field investugation, the author evaluated the empritude of local climate to cause frost damage of stone remains. The relation between the breaking of porous stone and the amplitude of the temperature change was examined using a tertiary tuff (Ohya ishi). The author defined the day when the temperature changed greater than -4ﾟC-+4ﾟC as a possible day for frost damage of the stone remains to occur by freezing-thawing cycles. Climate data from October 1983 to May 1984 were examined at 838 points in Japan. The area having large number of days when one must be cauti on againt frost damage is the northern part of Kanto district. The climate of this area is however, usually dry in winter, so frost damage would not occur unless a stone remain has a supply of water. Less