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No.25 (1978/12) >

 
Title :乾湿繰返しによる島尻層泥岩における 2,3 の物理的性質の変化(農業工学科)
Title alternative :Variations in some physical properties of Shimajiri mudstone due to alternate drying and wetting (Department of Agricultural Engineering)
Authors :小宮, 康明
新城, 俊也
Authors alternative :Komiya, Yasuaki
Shinjo, Toshiya
Issue Date :1-Dec-1978
Abstract :乾湿繰返しによる泥岩の物性変化を明らかにするために, 未風化島尻層泥岩に室内乾燥湿潤サイクルを与え, 各サイクル毎に2,3の物理的性質を調べ, 次の結果を得た。1.未風化泥岩は乾湿繰返しにより顕著に細粒化する。2.細粒化過程はおよそ3段階に分けられる。第1段階では(乾湿1サイクル)泥岩は方向性を有するクラックにより主に大きなレキ大の団粒に分解される。第2段階では(乾湿2サイクルから8サイクル付近まで)レキ大の団粒, 砂大の団粒に無数のクラックが生じ, 主に砂大の団粒とシルト大の団粒が生じる。第3段階では(乾湿9サイクル付近以降)主にシルト大の団粒の粘土化が始まる。3.乾湿繰返しにより塑性限界はほとんど変化を示さないが, 液性限界は顕著に変化する。乾湿8サイクル付近まで液性限界は細粒化に反映されて増大するが, 乾湿9サイクル付近以降では土粒子の疎水化に反映されて減少する。4.乾湿繰返しを受けた泥岩の水浸含水比は乾湿13サイクル付近でピークを示し, その時の含水比は自然含水比のおよそ3.5倍で, 液性指数は1.6に増大する。5.乾湿繰返しにより泥岩構成土粒子は疎水化する。その要因は乾燥時の粘土粒子の再団粒化と水浸時のリーチング作用に求められそうである。
This study is to know the variations in some physical properties due to alternate drying and wetting, that is a physical weathering process, on unweathering Shimajiri mudstone that outcrops the central and southern parts of Okinawa Island. the samples were alternately air-dried at room temperature during 4 days to 7 days and wetted under approximately free swell condition, and then some physical tests were carried out after each dry-wet cycle. The results are summarized as follows : 1. The unweathered mudstone is slaked and disintegrated due to dry-wet cycles. The process of disintegration may be distinguished approx. 3 stages as follows : (1) at 1 cycle, mudstone is mainly divided into some large gravel sized aggregates by laminal and oniony cracks. (2) from 2 cycles to 8 cycles, sand and silt sized aggregates are mainly produced by the breakdown of gravel sized aggregates. (3) after 9 cycles, the original silt sized aggregates may be dispersing. 2. The plastic limit values are scarcely affected due to dry-wet cycles however the liquid limit values are varied with a number of dry-wet cycles, that is, they gradually increase due to the breakdown of aggregates until 8 cycles and slowly decrease with decreasing affinity of soil particles to water after 9 cycles. 3. The water content and liquidity index values after wetted increase until approx. 13 cycles and decrease after 14 cycles. The maximum values of water content and liquidity index are approx. 100% and 1.6 respectively. 4. The decrease of affinity to water may be caused not only by the re-aggregating in the process of drying, but also by the leaching action in the process of wetting.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/4205
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.25 p.295 -305
Appears in Collections:No.25 (1978/12)

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