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[O08-P42] The relationship between particle size and the growth of frost columns
Keywords:frost columns, soil, capillary phenomenon, environment
Introduction
I live in a snowy country, so I have grown up in an environment where there are frost columnswhen winter approaches. I thought it was just a phenomenon caused by the drop intemperature, but one day I was looking at data from Weather News and found that frost columnswere not observed in much of western Japan, but were observed in southern Kyushu. As Icontinued reading the data, I found that volcanic ash was the cause, and that frost columnswere formed on the Shirasu Plateau in southern Kyushu and on the Kanto Loam Layer in theKanto region. I hypothesized that the size of the particles may have an effect on the growth offrost columns.
Purpose
According to Kanemitsu, the frost column causes a number of problems. The first is that theprocess of frost column formation pushes up water, cutting off plant roots and affecting cropgrowth during the winter months. Second, the water pushed up by the formation of the frostcolumn can cause hillsides and slopes to collapse. Third, the melting of the frost column canlead to slush, which is caused by the accumulation of water as ice on the surface layer of thefrost column. This study will help to clarify the relationship between particle size and the size of the growing frost column, which may provide clues to solving the above problems. For example,if it is found that larger particles can suppress the growth of the frost column, it may be possibleto increase the size of particles within the range of crop growth to make crop growth more stableduring the winter.
Theory
In this experiment, frost column growth was considered from the viewpoints of soil physics and fluid dynamics. According to previous studies, capillary action plays a role as a pseudo-tubebecause gaps are generated between soil particles and these gaps are continuous within thesoil, resulting in the generation of capillary force. The height of the water table h(m) raised bycapillary force , assuming that the surface tension is T(Jm^-2) , the contact angle is θ(rad), the density of the liquid is ρ(kmg^-3) , the gravitational acceleration is g(ms^-2), and the radius of the tube is r(m), it is expressed by
h=(2Tcosθ)/(ρgr)
However, in this experiment, wettability, such as contact angle, was not considered because the samples were wetted beforehand. Therefore, the equation used is
h=(2T)/(ρgr)
Hypothesis
I hypothesize that the smaller the particles, the more the frost columns grow. As a theoretical value, I think that it depends on the minimum radius of the tubes that are pseudo generated between the particles, and using Descartes' circle theorem, I formulate the following equation.
h=(6+4･3^1/2)T/(ρgr)
Method
In the past, Kanemitsu has succeeded in generating frost pillars using quartz crystal powder, a material used in Japanese painting. Quartz crystal powder is numbered, and the larger the
number, the larger the particle size. The quartz crystal powder white has the smallest particles.
Therefore, four types of quartz crystals (5, 7, 9, and white) were used in this experiment. The
particle sizes were measured using a microscope and were as table 1. Based on this data, the
theoretical values were calculated as table 2. The experiment was also conducted with the
apparatus shown in the attached figure. (Fig. 1) The experiment was conducted by placing the
apparatus shown in the figure in a freezer and waiting for 2 hours, after which it was removed
and the length of the growing frost columns was measured. This process was decided upon
because the device was able to function properly when preliminary experiments were actually
conducted using soil.
Result
After 10 experiments, the results were as shown in Graph 1.
Consideration
There was a trend that the smaller the particle size, the larger the size of the growing frost
column, and the correlation was also positive. However, when compared to the theoretical
values, a large discrepancy and the fact that no frost columns were produced at the crystal end
5 occurred. Therefore, taking advantage of the fact that frost columns were produced when the
experiment was verified with actual soil, the experiment was conducted again based on a new
sample made by mixing a certain amount of quartz crystal powder with actual soil. The results
are shown in Graph 2. In this experiment, the soil containing white quartzite should have
produced the most frost columns, but the results were different. Therefore, the hypothesis was
not fully supported, but some of the results were considered supported. For further
development, I would like to increase the number of samples and actually use volcanic ash to
study particle size and frost column growth.
Bibliography
Please see separate figure for references.
I live in a snowy country, so I have grown up in an environment where there are frost columnswhen winter approaches. I thought it was just a phenomenon caused by the drop intemperature, but one day I was looking at data from Weather News and found that frost columnswere not observed in much of western Japan, but were observed in southern Kyushu. As Icontinued reading the data, I found that volcanic ash was the cause, and that frost columnswere formed on the Shirasu Plateau in southern Kyushu and on the Kanto Loam Layer in theKanto region. I hypothesized that the size of the particles may have an effect on the growth offrost columns.
Purpose
According to Kanemitsu, the frost column causes a number of problems. The first is that theprocess of frost column formation pushes up water, cutting off plant roots and affecting cropgrowth during the winter months. Second, the water pushed up by the formation of the frostcolumn can cause hillsides and slopes to collapse. Third, the melting of the frost column canlead to slush, which is caused by the accumulation of water as ice on the surface layer of thefrost column. This study will help to clarify the relationship between particle size and the size of the growing frost column, which may provide clues to solving the above problems. For example,if it is found that larger particles can suppress the growth of the frost column, it may be possibleto increase the size of particles within the range of crop growth to make crop growth more stableduring the winter.
Theory
In this experiment, frost column growth was considered from the viewpoints of soil physics and fluid dynamics. According to previous studies, capillary action plays a role as a pseudo-tubebecause gaps are generated between soil particles and these gaps are continuous within thesoil, resulting in the generation of capillary force. The height of the water table h(m) raised bycapillary force , assuming that the surface tension is T(Jm^-2) , the contact angle is θ(rad), the density of the liquid is ρ(kmg^-3) , the gravitational acceleration is g(ms^-2), and the radius of the tube is r(m), it is expressed by
h=(2Tcosθ)/(ρgr)
However, in this experiment, wettability, such as contact angle, was not considered because the samples were wetted beforehand. Therefore, the equation used is
h=(2T)/(ρgr)
Hypothesis
I hypothesize that the smaller the particles, the more the frost columns grow. As a theoretical value, I think that it depends on the minimum radius of the tubes that are pseudo generated between the particles, and using Descartes' circle theorem, I formulate the following equation.
h=(6+4･3^1/2)T/(ρgr)
Method
In the past, Kanemitsu has succeeded in generating frost pillars using quartz crystal powder, a material used in Japanese painting. Quartz crystal powder is numbered, and the larger the
number, the larger the particle size. The quartz crystal powder white has the smallest particles.
Therefore, four types of quartz crystals (5, 7, 9, and white) were used in this experiment. The
particle sizes were measured using a microscope and were as table 1. Based on this data, the
theoretical values were calculated as table 2. The experiment was also conducted with the
apparatus shown in the attached figure. (Fig. 1) The experiment was conducted by placing the
apparatus shown in the figure in a freezer and waiting for 2 hours, after which it was removed
and the length of the growing frost columns was measured. This process was decided upon
because the device was able to function properly when preliminary experiments were actually
conducted using soil.
Result
After 10 experiments, the results were as shown in Graph 1.
Consideration
There was a trend that the smaller the particle size, the larger the size of the growing frost
column, and the correlation was also positive. However, when compared to the theoretical
values, a large discrepancy and the fact that no frost columns were produced at the crystal end
5 occurred. Therefore, taking advantage of the fact that frost columns were produced when the
experiment was verified with actual soil, the experiment was conducted again based on a new
sample made by mixing a certain amount of quartz crystal powder with actual soil. The results
are shown in Graph 2. In this experiment, the soil containing white quartzite should have
produced the most frost columns, but the results were different. Therefore, the hypothesis was
not fully supported, but some of the results were considered supported. For further
development, I would like to increase the number of samples and actually use volcanic ash to
study particle size and frost column growth.
Bibliography
Please see separate figure for references.