報告書番号

U90024

タイトル（和文）

膨潤性土質材料の物理質的性質と締固め特性

タイトル（英文）

PHYSICAL PROPERTIES AND COMPACTION CHARACTERISTICS OF SWELLING SOILS

概要 （図表や脚注は「報告書全文」に掲載しております）

従来，土の膨潤特性は建設工事に対し悪影響をもたらしていることが多い。しかし，最近では高レベル放射性廃棄物地層処分システムで処分坑を埋戻す材料（緩衝材）や超軟弱地盤の改良材に膨潤性土質材料を利用しようとする考えがある。このような状況において，膨潤性土質材料の基本的な物理諸特性の把握も含め，その締固め特性や膨潤特性および熱特性についての評価が急がれている。本報告では，膨潤性土質材料として一般に普及しているベントナイトを用いて膨潤性土質材料の新しい物理試験方法の提案を行い，さらにベントナイトを含む各種粘土の静的締固め試験を行い，粘土の締固め特性について調査している。その結果，信頼性の高いベントナイトの物理試験方法の提案と基本的な物理定数が得られた。また塑性限界を導入した粘土の最大乾燥密度と最適含水比の算定式を提案した。

概要 （英文）

RECENTLY,EXPANSIVE SOILS HAVE ATTRACTED ATTENTION AS BACK FILLING (BUFFER) MATERIALS FOR REPOSITORIES FOR HIGH-LEVEL NUCLEAR WASTE,AND AS IMPROVEMENT MATERIALS FOR EXTREMELY SOFT GROUND.HOWEVER,SINCE VERY LITTLE IS KNOWN ABOUT THEIR PHYSICAL AND MECHANICALCHARACTERISTICS,IT IS NECESSARY TO CLARIFY THEIR SWELLING,COMPACTION AND THERMAL CHARACTERISTICS. FOR THIS PURPOSE,VARIOUS INDEX TESTS AND A SERIES OF STATIC COMPACTION TESTS WERE PERFORMED USING SEVERAL TYPES OFSWELLING SOILS TO INVESTIGATE THE RELATIONSHIP BETWEEN THE FUNDAMENTALPHYSICAL PROPERTIES AND THE COMPACTION CHARACTERISTICS. THE FOLLOWING CONCLUSIONS WERE DRAWN. (1) SINCE ORDINARY TESTING METHODS PRESCRIBED BY JIS ARE DIFFICULT TO USE FOR EXPANSIVE SOILS,NEW METHODS WERE PROPOSED TO OBTAIN RELIABLE VALUES FOR SPECIFIC GRAVITY GS,GRAIN SIZE DISTRIBUTION AND LIQUID/PLASTIC LIMITS WL,WP. SOME REPRESENTATIVE VALUES ARE PRESENTED FOR VARIOUS CLAYS INCLUDING BENTONITE. (2) STATIC COMPACTION TESTS SHOWED THAT THE COMPACTION CHARACTERISTICS OF CLAYS ARE STRONGLY DEPENDENT ON THE PLASTIC LIMIT WP. (3) FROM THESE EXPERIMENTS,IT WAS SHOWN THAT THE MAXIMUM DRY DENSITY RHO DMAX AND OPTIMUM WATER CONTENT WOPT ARE STRONGLY DEPENDENT ON BOTH THE PLASTIC LIMIT WPAND THE COMPACTION PRESSURE P. USEFUL EQUATIONS ARE PROPOSED TO SELECT MATERIALS AND TO ESTIMATE THE APPROPRIATE COMPACTION PRESSURE P REQUIRED TO ACHIEVE THE MAXIMUM DRY DENSITY RHO DMAX.

報告者

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