Variation of the physical properties of Kanumatsuchi for depths and regions

Abstract

It is recently found that Kanumatsuchi is problem soil due to increment of earthwork with the advance of agricultural use. We investigated the properties of Kanuma pumice stratum and the physical organization of Kanumatsuchi from a view point of agricultural use. Kanumatsuchi consists of pyroclastics originated from Akagi volcano(Gunma prefecture), and its main component is weathered pumice grain of which the diameter is about 2 ~20mm. Taking Kanumatsuchi to pieces,they are classified into four components :(l)Weathered pumice,(2)Small grained pumice,(3)Imogolite,(4)Volcanic gravel.After natural moisture ratio o›j,dry weight ratio a. and specific gravity Gs of each component are determined,moisture ratio (a›i'),void ratio(e / )and porosity (n1’) for the whole Kanumatsuchi are caluculated by the following equations. ω1’＝αiωi　ω”＝ωn-∑ωi’ ei’=G・(αi/Gi)ei　e”=en—∑ei’ n1’= ei'/ (1+en) 　n”= nn—∑ni’ Where the mark(' )andC ) represents respectively inside value and outside one of pumice grains (Weathered pumice and small grained pumice)for the whole Kanumatsuchi. Degree of saturation of pumice grain Si and one among pumice grains S。are caluculated by the following equations. S i= ωi Gi=ei　S0＝ω”Gs/ei” As the result,the following facts become clear. (1) Value of solid phase,liquid phase and gaseous phase are respectively 11.8〜13.5%,61.4〜74.5%, 12.5 〜26.5%. (2) On natural condition, quantity of mositure(〇)//n)and quantity of void(ω1'/ωn)in weathered pumice is respectively 85.3〜95.9% and 71.9〜90.1% to the whole quantity. (3) Degree of saturation in weathered pumice grain(S Jis respectively high value(80.6~97.9%). (4) Degree of saturation among pumice grains is 16.6〜60.5% and quantity of moisture among pumice grains to the whole quantity is relatively low value(2.2〜9.7%)