報告書番号

382012

タイトル（和文）

泥岩の力学的特性に関する研究（その２）クリープ特性

タイトル（英文）

A STUDY OF MECHANICAL PROPERTIES OF MUD STONE (2) -CREEP CHARACTERISTICS-

概要 （図表や脚注は「報告書全文」に掲載しております）

筆者らは泥岩の力学的性質について調べてきたが，本研究もその一部を成すものである。今回は排水条件を変えて三軸圧縮クリープ試験を行い，クリープ変形および強度について，既に実施した三軸圧縮試験結果と比較しながら考察を行った。その結果，次のことが明らかになった。クリープ時の体積変化はせん断特性と非常に似通っており，有効応力の概念に基づけば説明することができる。したがって，この観点からクリープ変形および強度を議論した。クリープ変形を記述するには力学的意義が不明確ではあるが，実験式で十分説明しうる。また，クリープ強度については，ひずみ速度を媒介として破壊時間と強度を結びつけることによって長期の強度が推定可能であり，簡便な推定式を提案した。

概要 （英文）

THIS REPORT CONSISTS OF A PART OF THE RESEARCH, WHICH THEME IS STRENGTH AND DEFORMATION CHARACTERISTICS OF THE TERTIARY DEPOSIT OF MUD STONE. IN THIS REPORT LONG-TERM STRENGTH AND DEFORMATION CHARACTERISTICS ARE INVESTIGATED SYSTEMATICALLY BASING ON THE CONCEPT OF EFFECTIVE STRESS. ADOPTED TEST CONDITION WAS THAT DEVIATORIC STRESS WAS CONSTANT IN TEST, AND A LOT OF TESTS WERE PERFORMED OVER THE WIDE CONFINING PRESSURE RANGE. THE OBTAINED MAIN CONCLUSIONS ARE AS FOLLOWS: 1.CREEP DEFORMATION:(1)FOR THE HEAVILY OVER-CONSOLIDATED CONDITION, CREEP SHEAR STRAIN AND CREEP VOLUMETRIC STRAIN CAN BE EXPRESSED BY ANEXPERIMENTAL EQUATIONS AND VOIGT MODEL FORMED BY 5-ELEMENTS, AND THEN CREEP POISSON S RATIO IS CONSTANT WHEN DEVIATORIC STRESS IS COMPARATIVELY SMALL.(2)FOR THE LIGHTLY OVER-CONSOLIDATED CONDITION,THE RELATION BETWEEN CREEP STRAIN AND ELAPSED TIME DIFFERS FROM THAT FOR THE HEAVILY OVER-CONSOLIDATED CONDITION, AND SO TIME EFFECT IS COMPLICATED. 2.CREEP FAILURE:(1)WHEN THE RELATIONS BETWEEN STRAIN RATE AT STEADY CREEP STATEAND CREEP RUPTURE TIME ARE PLOTTED ON LOG-LOG SCALE PAPER FOR HEAVILY OVER-CONSOLIDATED MUD STONE, THE RELATION IS LINEAR AND ITS INCLINATION ANGLE IS NEARLY EQUAL TO THAT OF CLAYS.(2)IF FAILURE CRITERIA IS EXPRESSED IN TERMS OF COEFFICIENT OF THE POWER AND ONE OF THE TWO PARAMETERS IS CONSTANT, THE RELATION BETWEEN ANOTHER PARAMETER AND LOG-SHEAR STRAIN RATE AT STEADY CREEP STATE GIVES ESSENTIALLY STRAIGHT LINE.(3)THE RELATIONS OBTAINED IN THE WAY DESCRIBED ABOVE, HOLD THROUGH THE MEDIUM OF SHEAR STRAIN RATE, AND AGREE WITH THAT OF TRIAXAL COMPRESSION TESTS. SOIF WE ELIMINATE THIS VARIABLE FROM TWO EQUATIONS, THE RELATION BETWEENMAXIMUM STRENGTH AND RUPTURE TIME IS OBTAINED FOR OVER-CONSOLIDATED MUD STONE.

報告者

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