1:45 PM - 3:15 PM
[O11-P104] Reproduction of Dish Structure by Water Tank Experiment using a Transformer and Discussion of Formation Process
Keywords:Dish Structure, Impermeable Layer, Transformer, Colored Sand, Degree of Solidarity
Abstract
A Dish Structure is a lamination that is found in silt and sandstone layers, and has an upward concave shape.
In this study, a reproduction experiment was carried out in a water tank, and by adjusting the water flow with a transformer, it was possible to observe the water hole that occurs during the formation of the Dish Structure. First, a seepage flow wells up from the bottom of the stratum, and when the pressure and amount of water are appropriate, a water hole is formed in the stratum. When the water hole collapses, the water rises diagonally upward, and a structure that appears to be a Dish Structure was confirmed from the trace of its path.
Objective
The formation process of the Dish Structure has been discussed, and Tsuji and Miyata (1987) showed the process (Fig. 1). The purpose of this study is to reproduce the Dish Structure in a tank and to elucidate the conditions necessary for its formation.
Experimental Methods
After filling the water tank with about 15 cm of water and quartz sand, the stratum was compacted with a stick, and after leaving it for a few hundred percent, about 5 mm of quartz sand was added to create an impermeable layer. After that, another 5mm of colored sand was added. Then, about 15 cm of quartz sand was added again and left to settle for several hours (Figures 2-1 and 2). Finally, water was injected into the tank using a motor to check the structure formed inside and to see how the colored sand (Figure 3) moved in the tank.
Consideration
Throughout the experiment, I was able to confirm the plate-like structure several times. The use of a transformer allowed the water to flow in slowly, and we were able to observe the water moving diagonally upward (Figure 4-3). When colored sand was spread on the impermeable layer, it basically remained in place (Figures 4-1 and 4-2), but there were places where it moved upward due to the influence of water, suggesting that the impermeable layer is responsible for stopping the water hole to some extent.
Conclusion
The possible factors involved in the formation of the Dish Structure are “the speed of water flow” and “the degree of solidification of the strata,” both of which require appropriate pressure.
Acknowledgments
I would like to thank Mr. Satoshi Fujimura of Exploreground for his help in making the water tanks used in the experiments.
I thank Mr. Kenichiro Hisada of Bunkyo University for his cooperation in conducting the fieldwork in Nakaminato.
References
・Tsuji, T. and Miyata, Y. (1997). Explanation of the term “Porphyry Structure”. Journal of Sedimentology, No.45, 59-63.
・Tsuji, T. and Miyata, Y. (1987). Deformation structures in sandstone formations due to fluidization and liquefaction: An example and experimental study of the Nichinan Group, Miyazaki Prefecture, Japan. Geological Magazine, 1987, Vol. 93, No. 11, p. 791-808_3
・Wada, E. (2019). A Study on the Formation Process of the Dish Structure -An Example of the Dish Structure in the Misaki Formation, Miura Peninsula-.
・Yukino B. and Wada, K.(2021). A Study on the Formation Process of the Plate Structure. The 128th Annual Meeting of the Geological Society of Japan, Junior Session.
・Sato, M. and Kamada, Y. (2023). Study on the reconstruction and formation process of the plate-like structure. Japanese Geological Society 130th Annual Meeting, Junior Session.
A Dish Structure is a lamination that is found in silt and sandstone layers, and has an upward concave shape.
In this study, a reproduction experiment was carried out in a water tank, and by adjusting the water flow with a transformer, it was possible to observe the water hole that occurs during the formation of the Dish Structure. First, a seepage flow wells up from the bottom of the stratum, and when the pressure and amount of water are appropriate, a water hole is formed in the stratum. When the water hole collapses, the water rises diagonally upward, and a structure that appears to be a Dish Structure was confirmed from the trace of its path.
Objective
The formation process of the Dish Structure has been discussed, and Tsuji and Miyata (1987) showed the process (Fig. 1). The purpose of this study is to reproduce the Dish Structure in a tank and to elucidate the conditions necessary for its formation.
Experimental Methods
After filling the water tank with about 15 cm of water and quartz sand, the stratum was compacted with a stick, and after leaving it for a few hundred percent, about 5 mm of quartz sand was added to create an impermeable layer. After that, another 5mm of colored sand was added. Then, about 15 cm of quartz sand was added again and left to settle for several hours (Figures 2-1 and 2). Finally, water was injected into the tank using a motor to check the structure formed inside and to see how the colored sand (Figure 3) moved in the tank.
Consideration
Throughout the experiment, I was able to confirm the plate-like structure several times. The use of a transformer allowed the water to flow in slowly, and we were able to observe the water moving diagonally upward (Figure 4-3). When colored sand was spread on the impermeable layer, it basically remained in place (Figures 4-1 and 4-2), but there were places where it moved upward due to the influence of water, suggesting that the impermeable layer is responsible for stopping the water hole to some extent.
Conclusion
The possible factors involved in the formation of the Dish Structure are “the speed of water flow” and “the degree of solidification of the strata,” both of which require appropriate pressure.
Acknowledgments
I would like to thank Mr. Satoshi Fujimura of Exploreground for his help in making the water tanks used in the experiments.
I thank Mr. Kenichiro Hisada of Bunkyo University for his cooperation in conducting the fieldwork in Nakaminato.
References
・Tsuji, T. and Miyata, Y. (1997). Explanation of the term “Porphyry Structure”. Journal of Sedimentology, No.45, 59-63.
・Tsuji, T. and Miyata, Y. (1987). Deformation structures in sandstone formations due to fluidization and liquefaction: An example and experimental study of the Nichinan Group, Miyazaki Prefecture, Japan. Geological Magazine, 1987, Vol. 93, No. 11, p. 791-808_3
・Wada, E. (2019). A Study on the Formation Process of the Dish Structure -An Example of the Dish Structure in the Misaki Formation, Miura Peninsula-.
・Yukino B. and Wada, K.(2021). A Study on the Formation Process of the Plate Structure. The 128th Annual Meeting of the Geological Society of Japan, Junior Session.
・Sato, M. and Kamada, Y. (2023). Study on the reconstruction and formation process of the plate-like structure. Japanese Geological Society 130th Annual Meeting, Junior Session.