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Author Name: 羽柴公博
Showing 1-20 results out of 33 results found
  • Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2020 Volume 136 Issue 1 1-7
    Published: January 31, 2020
    Released: January 31, 2020
    JOURNALS FREE ACCESS

    Time dependence, probability distribution, and size effect have been investigated by many researchers and are still important issues in rock engineering. These seem to be different characteristics of rock but were found to be closely related to each other through laboratory tests with rock specimens in recent studies. In this paper, the theoretical aspects on the time dependence, probability distribution, and size effect of rock strength were explained, and some of the theoretical results were compared with the previous experimental results. The theoretical formulae based on the rate process theory that represent the failure progression of rock were introduced, and their relation to the theories of visco-elasticity and visco-plasticity was described. The exact solutions of the loading-rate dependence of strength and the creep lifetime were derived from the formulae and were compared with the experimental results of andesite. In addition, the exact solutions of the probability distribution of strength and creep lifetime and their relation to the statistics of extremes were described; the exact solutions of the size effect of strength and creep lifetime and their relation to the comminution theory were also described. The authors clarified what issues have been or have not been verified in previous studies and presented the subjects of future investigation.

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  • Minami KATAOKA, Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2018 Volume 134 Issue 3 41-45
    Published: March 31, 2018
    Released: March 30, 2018
    JOURNALS FREE ACCESS

    It is known that the rock strength increases with an increase in loading rate. Many studies on the loadingrate dependence of rock strength have been performed under two environments, namely water-saturated and airdried conditions, and the loading-rate dependence has not been investigated well under the conditions of various water saturations observed in situ rock masses. In addition, the quantitative relation between the loading-rate dependence and water saturation has not been examined. In this study, the uniaxial compression test of Sanjome andesite under various water saturations was carried out and the dependence of the strength on the loading rate and water saturation was investigated. The test was performed with alternating two loading rates and the strength corresponding to each loading rate was determined from a single specimen. The test results show that the strength increase with a ten-fold increase in loading rate is almost the same under various water saturations and that the strength increases with a decrease in water saturation. Based on the test results, the theory to explain the dependence of the strength on the loading rate and water saturation was suggested. The variation in the strength was discussed to validate the theory.

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  • Keita IWANO, Junichi NAGAE, Katsunori FUKUI, Kimihiro HASHIBA
    Journal of MMIJ
    2018 Volume 134 Issue 2 22-30
    Published: February 01, 2018
    Released: February 27, 2018
    JOURNALS FREE ACCESS

    Because blasting is a quite efficient and economical excavation method, it has been widely applied to tunnel excavation especially in hard rock. However, this method is rarely used to the tunnel site close to residential houses due to its environmental impact such as vibration and noise. Nowadays, the advanced electronic detonator, which was widely used in overseas mine site, was introduced to the tunnel site in Japan. This electronic detonator with accurate delay time (=ignition time difference between consecutive holes) has a potential to mitigate blasting vibration. In the past, many studies to lower the blasting vibration had been conducted and in some of them, several ways of simulation were implemented and the relations between vibration mitigation and arrangement of delay time were proposed. In this study, based on the past achievement and blasting test the authors had carried out, the appropriate method to determine the optimum delay time was proposed. In the case of electronic detonator in which each hole has different ignition time, the methods using autocorrelation and frequency analysis were found to be good expectation of delay time to lower the vibration. Also, in the case of conventional electric detonator in which ignition time has dispersion, the relation between vibration and ignition time dispersion was calculated, and the proper way to lower the vibration was proposed. This study gives practical method to set appropriate ignition time to lower blasting vibration.

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  • Kimihiro HASHIBA, Katsunori FUKUI, Masahiro KOIZUMI
    Journal of MMIJ
    2017 Volume 133 Issue 9 223-229
    Published: September 25, 2017
    Released: September 27, 2017
    JOURNALS FREE ACCESS

    Rock drills were developed about two hundred years ago, and hydraulic percussion rock drills are about half-century old. Performance and efficiency of rock drills have been increased by a number of researchers and engineers. Percussion energy was dramatically increased with changing the power source from pneumatic to hydraulic pressures; rods and rod joints were improved to endure the high percussion energy; carbide button bits were developed for hard rock drilling. This paper reviewed the previous studies and future issues on the drilling processes with hydraulic percussion rock drills. Studies on the stress wave propagation in rods and rod joints were based on theoretical and graphical methods and recently on numerical simulation. Studies on the interaction between a button bit and rock included crack propagation in rock, force-penetration relationship during drilling, and bit wear. Studies on the factors affecting drilling efficiency and drilling rate made a transition from simple to precise numerical simulations. Finally, important future issues were presented for the further progress of hydraulic percussion rock drills.

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  • Keita IWANO, Junichi NAGAE, Katsunori FUKUI, Kimihiro HASHIBA
    Journal of MMIJ
    2017 Volume 133 Issue 6 123-131
    Published: June 01, 2017
    Released: June 19, 2017
    JOURNALS FREE ACCESS

    Although blasting is a quite efficient and economical excavation method, it is rarely applied to tunnel projects close to residential areas due to its environmental impacts, especially with regard to vibration and noise. Two key controls used to mitigate the occurrence of noise and vibration due to blasting are the use of small instantaneous explosives charges and the use of precise delay times to initiate the blast design sequence. An advanced electronic detonator, which has its precision of 0.01% of designed delay time and has made it possible to achieve precise initiation control in blasting, was introduced and used in a tunnel construction site in Japan. Testing of the delay times during blasting was carried out, the test results revealed the specific features and performance of the detonator to control the blasting vibration especially within a short distance of the tunnel face. In previous studies, several ways of simulating blasting waveforms were used. One of these, the Monte Carlo method, in which the production wave was reproduced by superposing a single wave had the potential to give good predictions of the production waves that might occur. Therefore, in this study, a similar way of simulating production waves was carried out. Section peaks in the production waveforms correspond with the detonation of each blasthole. These section peaks were found to follow the Weibull distribution, even though the section peaks might be influenced by amount of explosives, drill alignment, and geological inhomogeneity etc. More detailed simulation with consideration of difference in travel time and the change of the Weibull parameters with distance gives further precise results compared with the real production waves. This study leads more precise method of predicting production waves and of optimum blasting design.

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  • Minami KATAOKA, Tianshu BAO, Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2017 Volume 133 Issue 6 107-115
    Published: June 01, 2017
    Released: June 06, 2017
    JOURNALS FREE ACCESS

    The effect of water on the mechanical properties of rocks, such as strength and Young's modulus, has been investigated in many studies. To understand the mechanism of the effect of water on the mechanical behavior of rocks, not only these mechanical properties but also the stress-strain curve, which is one of the most basic data showing the mechanical behavior, should be focused on, and the change of the stress-strain curve with the different water conditions is needed to be known. In this study, the effect of water saturation on the uniaxial compressive strength and the stress-strain curve of rocks was investigated. The uniaxial compression test with alternating loading rate was performed using Sanjome andesite, Tage tuff, Kimachi sandstone and Akiyoshi marble. Inada granite was used for the uniaxial compression test with constant loading rate. The tests were conducted under various water conditions: oven-dried, vacuum-dried, air-dried, air-dried for one day, immersed in water and watersaturated conditions. The test results showed that the stress-strain curve of the andesite, tuff, sandstone and granite changed with the water saturation. On the other hand, the effect of water saturation on the stress-strain curve of the marble was not observed. From the test results, the increase in strength due to decrease in water saturation was discussed. A shift of the peak strength point with the water condition change was investigated, and the relation between the stress-strain curves under the different water conditions was considered based on it.

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  • Kimihiro HASHIBA, Katsunori FUKUI, Motoki SAKAGAMI, Shogo SANUKI
    Journal of MMIJ
    2016 Volume 132 Issue 8 144-151
    Published: August 01, 2016
    Released: August 31, 2016
    JOURNALS FREE ACCESS

    In the CERCHAR abrasivity test for rocks, to understand the wear process of styli is important for the appropriate setting of test conditions and for the estimation of bit wear in in-situ rock excavation. In this study, the wear process of a stylus was estimated from both the stylus vertical displacement measured during the test and the groove depth measured after the test. The results showed that the stylus wear during the test can be traced with a simple calculation of the measured values for the two high abrasive rocks, Inada granite and Iwaki sandstone. In those tests, the styli were worn flatly. The calculation was corrected for the other medium to low abrasive eight rocks, because the measured groove depth was not thought to be completely consistent with the penetration depth of the stylus. Comparing the results of the nine rocks with the exception of the granite, the stylus wear continued for longer sliding distance in the tests for higher abrasive rock. It was found from the results of the granite that the mineral constitution affected the wear process of the stylus. In addition, this paper discussed the relation of the CAI (CERCHAR Abrasivity Index) and its variation to the stylus wear process and the rock hardness. On the basis of the results, points of attention in the CERCHAR test were described.

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  • Yingzong LIANG, Kimihiro HASHIBA, Katsunori FUKUI, Masahiro KOIZUMI, Toshio MATSUDA
    Journal of MMIJ
    2016 Volume 132 Issue 8 129-136
    Published: August 01, 2016
    Released: August 27, 2016
    JOURNALS FREE ACCESS

    Computer simulation of percussive rock drilling requires appropriate numerical models for the interactions among the drill body, rod, rod joint, bit, and rock. In this study, the impact penetration of a bit into rock was investigated for the modeling of the bit-rock interaction. Impact penetration tests on Inada granite were carried out with six rod-bit configurations which were composed of four kinds of button bits and two kinds of rods. In the calculation of force-penetration curves from the measured rod strains, the bit model constructed from the acoustic impedance was simplified, and the empirical data correction method proposed by the authors was applied to all the rod-bit configurations. The force-penetration curves for the six rod-bit configurations showed that the bit force in loading phase was approximately proportional to the square of the penetration. The curves in unloading phase had a linear relation between the bit force and the penetration. The final penetration of each blow had a linear relation with the maximum penetration, and the measured borehole depth was proportional to the maximum penetration. The effect of rod diameter on the force-penetration curves was not obviously observed. On the other hand, the bit force corresponding to the same penetration increased and the specific energy decreased with an increase in bit diameter or in the number of button tips on the bit. These findings will contribute to the improvement of the accuracy in the simulation of percussive rock drilling.

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  • Kimihiro HASHIBA, Kazuo TANI, Tetsuji OKADA, Suguru SHIRASAGI, Yasuki OIKAWA, Naruki WAKABAYASHI
    Journal of MMIJ
    2016 Volume 132 Issue 1 7-13
    Published: January 01, 2016
    Released: January 16, 2016
    JOURNALS FREE ACCESS
    Compared to uniaxial or triaxial compression tests on rocks, direct tension tests on rocks are not common in practice. As is well known, the reasons are because underground rock masses are usually under compressive stress state and/or because the direct tension test on rock is rather difficult and time-consuming. However, the direct tension test is important to understanding mechanical characteristics of rocks under tensile stress state. Moreover, the number of case examples requiring accurate tensile strength of rock is recently increasing in rock engineering. This paper summarized the methods and points of attention for the direct tension test on rock, based on the previous studies and the authors' experiences. The direct tension tests on rock have adopted a variety of specimen shape, loading apparatus and testing conditions. This paper presented some important factors affecting the deformation and failure of rocks under tensile stress state. The relations of the direct tensile strength to the other mechanical properties, such as the Young's modulus, the elastic wave velocity and the compressive strength, was discussed. The rock tests related to the direct tension test were explained: tension test using centrifugal action, tension test under confining pressure, dynamic tension test and in situ tension test on rock masses. This paper introduced the authors' ongoing standardization activity for the direct tension test on rock.
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  • Kimihiro HASHIBA, Yingzong LIANG, Katsunori FUKUI, Masahiro KOIZUMI, Toshio MATSUDA
    Journal of MMIJ
    2015 Volume 131 Issue 1 9-16
    Published: January 01, 2015
    Released: January 01, 2016
    JOURNALS FREE ACCESS
    To improve the performance and efficiency of rock drills, it is essential to understand the penetration behavior of a bit into rock. However, studies on the impact penetration with a button bit, which is commonly used for percussive drilling of hard rock recently, are insufficient. In previous studies, large fluctuations were observed in a force-penetration curve calculated from rod stresses measured during percussive drilling, and therefore precious force-penetration curves could not be obtained. In this study, a calculation method was examined to preciously obtain a force-penetration curve from impact penetration tests. The results of numerical simulation showed that the fluctuations can be caused by the mismatch between the product and calculation model, and that the precious forcepenetration curve may be obtained with subtracting the bit force in a free end test from that in an impact penetration test. The suggested method was applied to the measured results of impact penetration tests with granite conducted by Fukui et al. (2010), and improved force-penetration curves were obtained. The method proposed in this study can be adopted to in-situ rock drilling, and contribute to the development of the bit suited to each rock type.
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  • Seisuke OKUBO, Yang TANG, Jiang XU, Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2014 Volume 130 Issue 10_11 473-478
    Published: October 01, 2014
    Released: October 02, 2015
    JOURNALS FREE ACCESS
    Variation of rock strength has an important role in designing the various rock structures. Though strength in uniaxial stress state such as uniaxial compressive strength has been well investigated up to now, the strength in complicated stress state such as triaxial compressive or shear strength has been studied only to very limited extent because of its difficulty in experimental works. For example, variation of shear strength should be studied under various normal stresses and then many specimens are necessary. In this study, direct shear tests of red shale were conducted under the normal stress from 1 to 6 MPa. A special care was taken to make as many specimens as possible from the limited sample rock, and total number of 397 specimens were tested. It was found that the variation of Δτ, which is the difference between the shear strengths measured in testing and calculated with the regression line, did not depend on normal stress. The obtained failure criterion and variation of strength for the red shale were discussed comparing the envelope of rock stress which was reported previously and the results of other rocks in various testing conditions.
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  • Seisuke OKUBO, Hailong ZHANG, Jiang XU, Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2014 Volume 130 Issue 8_9 428-433
    Published: August 01, 2014
    Released: August 01, 2015
    JOURNALS FREE ACCESS
    There are many research results on creep and relaxation aiming at investigating the time-dependent behavior of rock. However, rock mass around gateways in mines or underground structures deforms accompanied with both stress and strain change. Fukui et al. (1992) proposed the generalized relaxation test where both stress and strain change keeping the ratio between them constant. In this study, computer simulation was carried out to explain their results. The non-liner Maxwell model was used in the simulation and the calculated results well coincided with the experimental results except those in high stress level in which strain/stress rate were considerably larger than the calculated results.
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  • Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2014 Volume 130 Issue 5 146-154
    Published: May 01, 2014
    Released: May 13, 2015
    JOURNALS FREE ACCESS
    To design underground structures and estimate their stability, it is essential to understand mechanical behaviors of rock and applicability of constitutive equations not only in compression but also in tension. In this study, the non-linear visco-elastic constitutive equations proposed by the authors in compression were applied to the behaviors in uniaxial tension. The deformation characteristics and mechanism in uniaxial compression and tension under dry and wet conditions were investigated by comparison of the mechanical properties and the constants in the equations. It was found that three non-linear visco-elastic constitutive equations can reproduce the stress-strain curves in uniaxial tension for Sanjome andesite in dry and wet, Kawazu tuff in dry and wet, and Inada granite in dry condition. Time-dependent behaviors of Sanjome andesite in dry condition such as loading-rate dependency and creep can be also reproduced with the same equations. Because the calculated results of unloading curves were not consistent with the testing ones, the new constitutive equation combining the previous ones was proposed. The testing results showed that strength degradation by water is larger in tension than in compression and that initial Young's modulus in tension is nearly equal to the slope of unloading curves in the pre-failure region in compression. Relationship of the constants in the constitutive equations under various testing conditions was discussed. The exponents representing the stress dependency of strain rate in transient creep were calculated with the constants in tension, and found to be consistent in the three constitutive equations under dry and wet conditions.
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  • Kimihiro HASHIBA, Katsunori FUKUI, Yutaka SUGITA, Masanori SANADA
    Journal of Nuclear Fuel Cycle and Environment
    2014 Volume 21 Issue 2 75-82
    Published: December 01, 2014
    Released: January 31, 2015
    JOURNALS FREE ACCESS
      Diatomaceous earth and siliceous rock are widespread in the areas along the Sea of Japan in Hokkaido Prefecture, Akita Prefecture, Noto Peninsula and Oki Islands. To construct underground structures in the siliceous rock mass, it is essential to understand its mechanical properties. In this study, siliceous mudstone of the Wakkanai formation obtained from the deep underground in Horonobe, Hokkaido was applied to various laboratory tests; uniaxial compression test, Brazilian tension test, drying shrinkage test and the test to investigate the time dependent behavior and strength recovery. The testing results showed that water has a huge effect on the deformation and failure of the siliceous mudstone; when the specimen is air dried in room temperature, the axial shrinkage strain reaches 0.9% and the strength is twice larger than that in wet condition. It was found that the siliceous mudstone exhibits the same degree of time dependent behavior and strength recovery as other rocks such as tuff and sandstone.
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  • Seisuke OKUBO, Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2013 Volume 129 Issue 10_11 635-641
    Published: October 01, 2013
    Released: November 01, 2014
    JOURNALS FREE ACCESS
    In the previous paper, based on the summarized experimental results, long-term strength (failure criterion at extremely low loading-rate) was proposed. The simplest form of the long-term strength was σ1 = 3 where σ1 and σ3 were major and minor principal stresses, and constant 'a' varied from 2 to 6 depending on rock. For validation of the proposed failure criterion, rock stresses were plotted on σ1 and σ3 diagram. It was found that 86 data except one were plotted under the line (σ1=4σ3). After the previous paper was published, Okubo et al. conducted push-in test in which a failed rock sample was compacted in a steel cylinder. The envelope of Mohr's stress circles through the test were approximated byτ= 0.7. Under this curve, it was considered that strength of the failed sample was recovered up to a certain extent. More than 150 data of rock stresses were newly added to examine the long-term strength. It was found that almost all Mohr's circles were plotted under the curve τ = 2σ0.7. This was the better result than the previous one, σ1=4σ3. As stated in the previous paper, it is reasonable to consider that, in relatively stable rock mass, rock stress is maintained at a certain value lower than a long-term strength. If so, this result supports the validity of the newly proposed long-term strength, τ = 2σ0.7.
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  • Seisuke OKUBO, Kimihiro HASHIBA, Katsunori FUKUI, Qingxin QI
    Journal of MMIJ
    2013 Volume 129 Issue 8_9 569-576
    Published: August 01, 2013
    Released: October 21, 2014
    JOURNALS FREE ACCESS
    Only the very limited knowledge has been known concerning the mechanical properties of coal under uniaxial tensile stress which are very important factors in coalmines. In this study we carried out uniaxial tension tests on coal, with particular attention to find the most appropriate constitutive equation for the sample coal. Three constitutive equations were chosen and tested, among which two had been proposed by the authors and one was newly proposed in this study. Coal showed high sample-to-sample scatter in strength and Young's modulus, however, relatively small scatter in the normalized stress-strain curves in the pre-failure region. All three constitutive equations were found to represent the complete stress-strain curves in reasonable accuracy. This result presents a successful application of the authors' constitutive equations to the coal behavior under uniaxial tensile stress. Once these equations are determined, they can be incorporated into FEM software to investigate various time-dependent behaviors of coal and aid in the efficient design of coalmines and the prevention of coalmine disasters.
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  • Kimihiro HASHIBA, Katsunori FUKUI
    Journal of MMIJ
    2013 Volume 129 Issue 8_9 553-558
    Published: August 01, 2013
    Released: October 21, 2014
    JOURNALS FREE ACCESS
    To estimate long-term deformation and stability of underground structures, it is indispensable to understand time-dependency of rock sample and rock mass. Previous experimental and theoretical studies showed that rock strength was proportional to the 1/(n+1)-th power of loading-rate and creep lifetime was inversely proportional to the n-th power of creep stress, where n was a constant depending on rock type and testing environment. The smaller value of n, the larger time-dependency of rock, which suggests that n can be a useful index of time-dependency. This paper introduced three loading and a creep testing methods to obtain the value of n, and showed their results in uniaxial compression, uniaxial tension and Brazilian tension tests for 38 rocks in the country and overseas. Many rocks showed smaller values of n under water-saturated than air-dried condition. The value of n was proportional to strength under water-saturated condition or low confining pressure, but not under high confining pressure under which failure was more ductile. Rock mass classification systems considering time-dependency of rock were examined as an application of testing data on design or construction of underground structures. An index n was implemented in four classifications, RMR, Q, GSI and RMi, and their proposed equations indicated that rating decreased with an increase in duration of use of structures or in degree of time-dependency of rock mass.
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  • Kimihiro HASHIBA, Katsunori FUKUI, Nobuyuki OKAMOTO, Yukihiro MIZUOCHI
    Journal of the Society of Materials Science, Japan
    2014 Volume 63 Issue 3 244-249
    Published: March 15, 2014
    Released: March 20, 2014
    JOURNALS FREE ACCESS
    Seafloor hydrothermal deposits have been found to be widespread in the waters off Okinawa Island. Since Japan currently depends heavily on foreign mineral resources, it is expected that such deposits will be developed in the near future. To assist with the design and manufacture of mining and crushing machinery and ore transportation equipment, in this study the mechanical properties of seafloor hydrothermal deposits were investigated. Tests were carried out on the strength, hardness and abrasiveness of boring cores and block samples of the deposits. The average uniaxial compressive strength was found to be between 20 and 60 MPa, the CERCHAR abrasiveness index was between 1 and 2, and the Mohs hardness was between 4 and 6. In uniaxial compression tests, in which a specimen was crushed up to 20% of its initial height, size of debris was a little smaller than tuff, andesite and sandstone. The specific energy calculated with the boring data was found to be closely related to the mechanical properties of the hydrothermal deposits, and its distribution beneath the seafloor was determined from some boring data. The results obtained in this study provide important guidelines for the development of mining techniques for seafloor hydrothermal deposits.
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  • Seisuke OKUBO, Katsunori FUKUI, Kimihiro HASHIBA
    Shigen-to-Sozai
    2002 Volume 118 Issue 12 737-744
    Published: December 25, 2002
    Released: October 29, 2013
    JOURNALS FREE ACCESS
    A constitutive equation of variable compliance type had been proposed by Okubo in 1987. The equation is simple and its parameters are relatively easy to obtain. The equation can be applicable to creep of rock, however, experimental result in primary creep region in which strain rate is decreasing with time does not conform well to the calculated result.
    Recently Okubo and Fukui (2002) proposed a constitutive equation especially focusing on low stress level creep. In this study, old one proposed in 1987 and new one proposed in 2002 are combined to extend an applicable range of the constitutive equation of variable compliance type.
    For validation of the proposed constitutive equation, calculated results are compared with the experimental data by Okubo and Nishimatsu (1986) and Fukui et al. (1992, 1993), and it can be said that experimental results in uniaxial compression can be well simulated by the proposed equation. The equation is also tested against the creep performed in uniaxial tension and possible applicability of the equation to tensile stress field is discussed.
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  • Seisuke OKUBO, Katsunori FUKUI, Kimihiro HASHIBA
    Shigen-to-Sozai
    2002 Volume 118 Issue 3,4 165-170
    Published: 2002
    Released: October 29, 2013
    JOURNALS FREE ACCESS
    In soil mechanics, a transparent tri-axial vessel is frequently used, however, in rock mechanics, a metal vessel has been used to withstand higher confining pressure. In this study, a transparent vessel made of an acrylic acid resin with tensile strength of 75 MPa was designed and manufactured for tri-axial compression test under confining pressure up to 10 MPa.
    Every component of the vessel was designed with safety factor more than four. Paying special attention to safety, confining pressure was increased over the designed value until its failure. The confining pressure at the failure was more than 55 MPa and daily use at 10 MPa was considered to be safe. It was also revealed that an annular transparent tube made of an acrylic acid resin did not break into pieces, but only a vertical crack was extended.
    Preliminary tri-axial tests were conducted for Tage tuff and Dotan that were deformed easily under the confining pressure. Many photographs were taken by a digital camera, and vertical and lateral deformations / strains were read out successfully.
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