Drying induced deformation of anisotropic soft sedimentary rocks: experimental measurements and shrinkage modelling

• Material Type: 博士論文
• Title: Drying induced deformation of anisotropic soft sedimentary rocks: experimental measurements and shrinkage modelling
• Author/Editor: ILLANKOON, MUDIYANSELAGE THILINI NUWANRADHA ILLANKOON
• Author Heading: ILLANKOON, MUDIYANSELAGE THILINI NUWANRADHA ILLANKOON
• Publication Date: 2016
• Publication Date (W3CDTF): 2016
• Alternative Title: 異方性を示す堆積軟岩の乾燥変形特性：実験と収縮モデル
• Periodical title: 博士論文（埼玉大学大学院理工学研究科（博士後期課程））
• Degree grantor/type: 埼玉大学
• Date Granted: 2016-09-23
• Date Granted (W3CDTF): 2016-09-23
• Dissertation Number: 乙第237号
• Degree Type: 博士(工学)
• Conferring No. (Dissertation): 乙第237号
• Text Language Code: eng
• Subject Heading: Drying test; Shrinkage; Mudstone; Koetoi formation; Wakkanai formation; Radioactive waste disposal; Horonobe Underground Research Laboratory; Steady state; Transient state; Pore size distribution; Transversely isotropic rock; Tage tuff; Elastic wave velocity; Dynamic modulus; Saturation; Shrinkage estimation; Elastic modulus; Capillary stress
• Target Audience: 一般
• Note (General): type:text; This study concentrate on drying experiments on anisotropic soft sedimentary rocks with the aims of (i) understanding the drying-induced deformation of argillaceous rocks, (ii) investigating the effect of anisotropy on drying deformation and (iii) simulating drying experiment in a laboratory scale specimen. Drying induced deformation is a well-known coupled process of deformation and moisture transfer within a porous material. It is important to investigate and simulate the drying shrinkage behaviour to overcome engineering issues associated with desaturation of clay bearing soft sedimentary rocks, which are porous and low in strength. Recent researches on high level radioactive waste disposal in clay bearing sedimentary formations emphasized the importance of understanding the drying-induced deformation characteristics of rocks in predicting the excavation damaged zone (EDZ) which is not desirable for the long-term safety of geological disposal, but is inevitable in underground ventilated galleries. Therefore, a better knowledge of the mechanisms of desaturation-resaturation of the clay rocks is needed for further understanding of the hydro-mechanical properties of EDZ as well as for the prediction of the stability of structures associate with them.Horonobe sedimentary rock, which is considered as a potential host rock for the geological disposal by the Japan Atomic Energy Agency was tested to achieve the first objective. The deformation behaviour during desiccation was examined by measuring weight and strain in twenty two cylindrical mudstone specimens cored from successive formations of Koetoi and Wakkanai at Horonobe Underground Research Laboratory, Japan. Porosity, bulk density, grain density, ultrasonic wave velocity, Equotip hardness and tensile strength of cores were determined to clarify the drying behaviour of Horonobe sedimentary rock with extraction depth. The recorded data showed a clear decrease in weight change rate with porosity in both formation specimens. Mercury intrusion porosimetry (MIP) results indicate that the Wakkanai formation contains a high volume of smaller pores (which can generate strong capillary pressure) than the Koetoi formation. Regardless of having a high volume of smaller pores, Wakkanai formation specimens in the 237 - 437 m depth interval experienced the lowest maximum shrinkage. Measured properties and scanning electron microscope observations revealed that a strong framework/cementation limited shrinkage evolution of the cores from the 237 - 437 m depth interval. Thus, the deformation behaviour of Horonobe sedimentary rock depends not only on its pore structure, but also on the strength of its framework/cementation.Further experiments conducted on Koetoi formation revealed that the strain measuring method, drying environment and drying technique have no effect on the water retention properties and the deformation behaviour. Hence, the transient state drying technique (which consumes less experimental time than the steady state drying technique) was identified as the most suitable experiment technique to study the drying induced deformation behaviour of low porous mudstones.The deformation behaviour of Tage Tuff during desiccation was investigated to achieve the second objective. Strain as well as compressional (P) and shear (S) wave velocities were measured concurrently in a set of cylindrical Tage Tuff specimens cored across and along the bedding plane. Saturated specimens were prepared in one-dimensional drying conditions and dried in 50℃, 50% relative humidity environment. Strain, P wave velocity and dewatering rates were sensitive to the degree of saturation as well as measured direction with respect to the bedding plane. Rapid increase in shrinkage as well as P and S wave velocities in below 35% saturation level occur due to the desiccation-driven hardening of Tage tuff. Different height specimens (5 cm and 3 cm) exhibit similar final shrinkage, shrinkage evolution behaviour and wave velocity variation patterns during drying. Moreover, sensitivity of P wave velocity variation pattern with saturation according to the bedding direction gives an insight into the understanding of the water/air distribution within a transversely isotropic rock during desiccation. Engineering constants of Tage tuff were calculated using measured ultrasonic wave velocities and density during drying experiment. Results revealed that the drying process strengthen the Tage tuff.Obtained results for Tage tuff were used to simulate drying induced deformation behaviour with the aim of achieving third objective. Existing micromechanical model which was used to analyse the drying shrinkage behaviour of concrete was adapted and modified to model the shrinkage behaviour of Tage tuff during drying at 50 ℃ and with 50% relative humidity. Shrinkage estimation was done by assuming a linear elastic relationship between capillary stress and shrinkage. According to wave velocity measurement results, the elastic parameters during drying are not constant. Hence, the elastic modulus for capillary stress was assumed to be varying with saturation and was estimated by back calculations. Moreover, the pore size distribution (PSD) determined by the MIP was used to represent the pore structure of Tage tuff. Results indicate that the MIP determined PSD can adequately represent the shrinkage evolution of Tage tuff. Moreover, the elastic modulus due to capillary stress follows 1-tanh relation with the drying shrinkage. However, the estimated elastic modulus for capillary stress indicates lower values and dissimilar behaviour when compared with P and S wave velocity calculated elastic parameters. Furthermore, it is necessary to consider the effect of surface tension changes during desaturation when applying proposed calculations in actual situations.; ABSTRACT ................................................................................................................................................ iACKNOWLEDGEMENTS ...................................................................................................................... iiiTABLE OF CONTENTS ........................................................................................................................... vLIST OF FIGURES .................................................................................................................................. viiiLIST OF TABLES .................................................................................................................................... xiiiCHAPTER 1 ............................................................................................................................................... 11.1 Objectives and study procedure ............................................................................................ 21.2 Previous studies ....................................................................................................................... 41.3 Phenomenological description of moisture transfer in argillaceous rocks ...................... 61.4 Outline ...................................................................................................................................... 7CHAPTER 2 ............................................................................................................................................... 92.1 Introduction ........................................................................................................................... 102.2 Materials ................................................................................................................................. 122.2.1 Location and geological background of Horonobe URL site ...................................... 122.2.2 Details of tested cores ....................................................................................................... 132.3 Drying experiment ................................................................................................................ 152.3.1 Specimen preparation and experimental setup ............................................................ 152.3.2 Results of drying experiments ......................................................................................... 172.3.3 Mass variation with time ................................................................................................. 212.3.4 Strain evolution with time ............................................................................................... 232.3.5 Shrinkage evolution with degree of saturation ............................................................. 262.3.6 Visual observation of existing cracks ............................................................................. 282.4 Effect of the drying environment and the strain measuring method on drying induced deformation ............................................................................................................................ 282.4.1 Strain measurement using triaxial strain gauge ........................................................... 292.4.2 Strain measurement using laser displacement meter .................................................. 312.4.3 Shrinkage-saturation relation .......................................................................................... 322.5 Effect of drying process on drying induced deformation ................................................ 332.5.1 Experiment procedure ...................................................................................................... 342.5.2 Results and discussion ..................................................................................................... 342.6 HDB10 bore hole steady state drying experiments .......................................................... 372.6.1 Experiment procedure ...................................................................................................... 382.6.2 Results and discussion ..................................................................................................... 392.7 Mercury intrusion porosimetry ........................................................................................... 452.7.1 Specimen preparation ....................................................................................................... 452.7.2 Porosity and pore size distribution of each core ........................................................... 462.8 Other tested physical properties .......................................................................................... 472.8.1 Grain density test .............................................................................................................. 472.8.2 Ultrasonic wave velocity measurement ......................................................................... 472.8.3 The Equotip hardness test ................................................................................................ 482.8.4 Brazilian test ....................................................................................................................... 482.9 Discussion ............................................................................................................................... 492.9.1 Physical property variation with depth ......................................................................... 492.9.2 Relation of pore size distribution and incremental volumetric strain ....................... 542.9.3 Strength-shrinkage relation of Horonobe sedimentary rock ....................................... 572.9.4 Explanation of Horonobe sedimentary rocks’ hydromechanical behaviour with schematic diagrams ........................................................................................................... 592.10 Summary and conclusion ..................................................................................................... 61CHAPTER 3 ............................................................................................................................................. 633.1 Introduction ............................................................................................................................ 643.2 Materials and methods ......................................................................................................... 663.2.1 Specimen characteristics ................................................................................................... 663.2.2 Specimen preparation ....................................................................................................... 673.2.3 Experimental techniques .................................................................................................. 673.2.3.1. Deformation measurement during drying ..................................................................... 673.2.3.2. Ultrasonic wave velocity measurement during drying .............................................. 683.2.3.3. Mercury intrusion porosimetry ......................................................................................... 693.3 Experimental results and discussion................................................................................... 693.3.1 Deformation behaviour during desaturation ................................................................ 693.3.2 Ultrasonic wave velocity characteristics during desaturation .................................... 723.3.3 Mass variation behaviour during drying ....................................................................... 763.3.4 Effect of specimen height on drying experiments ........................................................ 773.3.5 Porosity and pore size distribution ................................................................................. 773.4 Determination of the complete set of engineering constants .......................................... 783.4.1 Generalized Hook’s law for a transversely isotropic rocks ......................................... 783.4.2 Determination of the stiffness matrix ............................................................................. 793.4.3 Variation of stiffness constants of Tage tuff with saturation ....................................... 823.4.4 Variation of engineering constants of Tage tuff with saturation ................................ 823.5 Summary and conclusion ..................................................................................................... 84CHAPTER 4 ............................................................................................................................................. 854.1 Introduction ........................................................................................................................... 864.2 Shrinkage estimation............................................................................................................. 874.2.1 Theories .............................................................................................................................. 874.2.1.1. Novelty of the present calculations .................................................................................. 874.2.1.2. Pore structure of Tage tuff .................................................................................................. 874.2.1.3. Shrinkage of Tage tuff due to drying ............................................................................... 884.2.1.4. Elastic modulus for capillary stress (Es) ......................................................................... 894.2.1.5. Back calculations .................................................................................................................... 904.2.2 Results ................................................................................................................................. 904.2.3 Discussion .......................................................................................................................... 924.2.3.1. Capillary pressure comparison .......................................................................................... 924.2.3.2. Comparison of elastic modulus for capillary stress with calculated elastic parameters ................................................................................................................................ 944.2.3.3. Role of surface tension of liquid water during drying ............................................... 954.3 Summary and conclusion ..................................................................................................... 95CHAPTER 5 ............................................................................................................................................. 975.1 Drying induced deformation of argillaceous rocks: Experimental measurements of mudstone extracted from two successive formations in Horonobe underground research laboratory ................................................................................................................ 975.2 The effect of anisotropy on drying deformation: Drying experiments on Tage tuff, a transversely isotropic pyroclastic sedimentary rock ........................................................ 985.3 Simulate drying experiments in a laboratory scale specimen: Shrinkage estimation of Tage tuff during drying ........................................................................................................ 995.4 Conclusions and perspectives.............................................................................................. 99REFERENCES ........................................................................................................................................ 102PUBLICATIONS ................................................................................................................................... 107; 主指導教員 : 長田昌彦
• DOI: 10.24561/00010442; https://doi.org/10.24561/00010442
• Persistent ID (NDL): info:ndljp/pid/10959031; https://dl.ndl.go.jp/pid/10959031
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• Collection (particular): 国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文; https://dl.ndl.go.jp/collections/A00014
• Acquisition Basis: 博士論文（自動収集）
• Date Accepted (W3CDTF): 2017-10-02T17:34:20+09:00
• Date Created (W3CDTF): 2017-07-19
• Format (IMT): application/pdf
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• Periodical Title (URI): http://dx.doi.org/10.24561/00010442; http://id.nii.ac.jp/1586/00010442/
• Data Provider (Database): 国立国会図書館 : 国立国会図書館デジタルコレクション; https://dl.ndl.go.jp

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2023-09-05 再収集