Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
48 巻, 4 号

• 西村 強, 木山 英郎, 藤村 尚
1999 年 48 巻 4 号 p. 323-328
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
The numerical methods of analysis can provide useful information for engineering in rock. One of the most important components of these methods is the mathematical description of a relationship between stress and strain. For example, the response which is typified by relatively brittle behavior becomes apparently ductile as the confining pressure is increased. Strain may be larger to reach failure, which is particularly observed in soft rock. In such cases, numerical methods should be formulated referring to the frame of large strain theory which can explain a result of material rotation.
This paper describes a formulation of FLEM (Flow Element Method) for large deformation analysis of continua. An analytical area is divided into conceptual sub-sections. The explicit time-marching scheme of the equation of motion is adopted to get displacements of the centroid of the section. The basic idea of this method has originated from DEM (Distinct Element Method). Another sub-division into individual elements of finite size is prepared to calculate forces acting to the centroid. This procedure is based on FEM (Finite Element Method).
A two-dimensional elastic block subjected to end-displacement in a plain strain condition was simulated by FLEM incorporating the Jaumann-rate. The same problem was analyzed by FEM to check the FLEM simulations. The results obtained in this paper are as follows. (1) This method can be applied to quasi-static problems by which the damping factor and the time increment are set to be the optimum values. (2) The objective stress-rate plays an important role in large deformation analysis. However, the response of the external shear stress acting on the block to shear deformation indicates an unrealistic curve, further development of appropriate laws involving material rotation or a new procedure must be needed.
• 大西 有三, 陳 光斉
1999 年 48 巻 4 号 p. 329-333
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
In this paper, the application of Discontinuous Deformation Analysis (DDA), a powerful numerical method, to the simulation of rock mass failure problems has been discussed. It has been shown that the failure along discontinuous surfaces can be easily simulated by use of the method based on the Mohr-Coulomb failure criterion. For the failure (separation) of an individual block, we suggest that dense artificial meshes are made within the block, and the same strengths of the block itself are assigned to the cohesion, friction and tensile parameters of the artificial discontinuous surfaces. Then, the same algorithm as for the general discontinuities can be adopted.
The new approach has been successfully applied to the simulation of a huge rock collapse at Toyohama tunnel, a very sad accident happened in Hokkaido in Feb., 1996. The collapse picture obtained from the simulation is quite in agreement with that from the spot. It is the first time that the progressive failure processes of the event are re-shown in detail. We believe that the simulation is very helpful on investigation of the failure mechanism and process, which can provide useful knowledge for preventing such kind of events in future.
• 稲田 善紀, 木下 尚樹
1999 年 48 巻 4 号 p. 334-340
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
The authors have been proposed and discussed temporary storage of high and low temperature materials in openings excavated in rock mountain. Here, high temperature materials means such as heated water which is produced by surplus heat from garbage burning plants, while low temperature materials means such as LNG, LPG, frozen food etc. In this case, as the storage quantity of heated water, LNG and LPG will change with these use continually, rock masses around openings to store these materials will receive effects of thermal hysteresis of high and low temperatures. Therefore, obtaining the strength and deformation characteristics of rock affected by the thermal hysteresis becomes important for discussing the stability of the openings. In this study, strength and deformation characteristics of granite and tuff were examined after undergoing thermal hysteresis of high and low temperatures. From the results, it was found that the decreasing ratio of strength and deformation of rocks decrease with the increasing number of thermal hysteresis, and it is supposed that the value will converge to a constant value.
• 楠見 晴重, 金田 俊哉, 西田 一彦, 上枝 和司
1999 年 48 巻 4 号 p. 341-345
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
Hydromechanical behaviour of rock masses is influenced in a decisive way by the presence of joints. It is largely responsible for the seepage occurring through the rock mass and is the most sensitive elements with respect to deformation under stress changes. Hydromechanical studies of fractured rock masses must therefore pay special attention to the role of joints and to correct assessment of their properties.
In this paper, an experimental study was carried out in granite specimens included a single joint with the purpose of obtaining the hydromechanical properties under hydrostatic stress conditions. The test results are then presented and analyzed, and the relationship between the roughness of joint surface and hydromechanical properties are discussed.
• 芦田 讓, 真田 佳典, 式森 孝好, 中内 啓雅
1999 年 48 巻 4 号 p. 346-350
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
In the present paper, using elastic and electro-magnetic reflected waves, the algorithm for imaging the subsurface structure by use of equi-travel time planes are proposed and applied to the data for forward prediction survey from tunnel face and the detection of buried pipes.
(1) In the case of looking forward prediction from tunnel face, the new configuration of source and receiver are proposed.
(2) In the case of looking ahead from the radar sensor attached at the top of drilling rod, the algorithm of velocity analysis is proposed in order to determine the velocity distribution in the forward structure.
Judging from the present studies, it was concluded that the reflectors with any dip in looking ahead from tunnel face are reconstructed accurately by use of the proposed configuration and the locations of buried pipes were detected those locations with high accuracy.
• 二宮 正, 花崎 紘一, 塚田 和彦, 保岡 哲治
1999 年 48 巻 4 号 p. 351-356
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
A horizontal jet grout forepiling method reinforced by steel pipe is one of the useful pre-supporting systems in excavating a tunnel in weak ground. However, the dimension of the grouted column forming forepiles has not been measured and controlled during the executing operation, though it is important to estimate its dimension for the quality assurance and cost management in tunnel construction.
In this paper two new methods for estimating the diameter of a grouted forepile are proposed; One is the indirect method by measuring and controlling the replacing rate of soil with the grouting material. Another is the direct method by measuring the electrical resistance of the grouted material along the forepile by means of an electrical potential technique.
• 水戸 義忠, 若林 成樹, 平野 勇, 菊地 宏吉
1999 年 48 巻 4 号 p. 357-364
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
It is well-known that shear strength of rock mass is strongly affected by shear strength of rock joint. In this study, direct shearing tests of artifitial joints, which had been presented with referring the actual joint surface roughness, have been carried out before and after grouting, in order to clarify grouting influence of rock joint properties on joint shear strength improvement by grouting. The test results shows that the cohesion of joint can be improved by grouting, but the friction angle can not be done in the case that the mating of joint planes is constant. The rolls of joint roughness, persistence, filling, aperture and wall strength are discussed based on the test results. It is clear that Joint roughness, persistence and filling play very important roll on the improvement of joint cohesion.
• 井上 忠信, 久保 司郎
1999 年 48 巻 4 号 p. 365-375
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
• 小南 金洋, 兼子 佳久, 北川 和夫
1999 年 48 巻 4 号 p. 376-380
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
The purpose of the present study is to investigate the grain boundary (GB) structures of low angle [001] symmetrical tilt boundaries by means of the molecular dynamics (MD) simulations. The misorientation angles θ of the model copper bicrystals were set from 2.9° to 14.3° ({100} GB plane) and from 64.0° to 86.1° ({110} GB plane). The misorientation angles θ ranged from 64.0° to 86.1° correspond to the deviation angle Δθ from 3.9° to 26.0°, where the Δθ is a deviation angle from the single crystal state. After the relaxation at GBs by the MD calculation, it was recognized that some low-angle GBs were composed from arrays of a/2 ‹110› lattice dislocations as predicted from the widelyknown dislocation array model of a low angle GB. The GB structures of the {110} boundary plane were the arrays of a/2 [110] dislocations. On the other hand, a/2 [110] and a/2 [110] dislocations were alternately arranged along the {100} GB. The GBs with large deviation angles from a single crystal state contained another structure that is different from the a/2 ‹110› dislocation. The ranges of the deviation angle where the GBs are represented exclusively by the a/2 ‹110› dislocations depended strongly on the geometry of the GB plane. The critical deviation angles Δθc for the {100} and {110} GB planes were 8.8° and 22.6°, respectively. The average distances between the dislocations in these boundaries were sensitive to both the misorientation angle and the GB plane. The average dislocation distances obtained at the MD simulations agreed with those calculated from the dislocation array model of a low angle boundary with a good accuracy.
• 中谷 彰宏, 北川 浩, 下川 智嗣
1999 年 48 巻 4 号 p. 381-386
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
Recently, nanometric surfacing of microcomposite material has been required for the high performance and precision of electronic parts. In this paper, the grinding of the microcomposite material which consists of the materials of different mechanical property, such as hardness or stiffness is studied to find an available grinding condition. As our main interest is focused into the dependence on the mechanical properties of constructed materials, a molecular dynamics simulation is carried out on 2-dimensional model by using a simple atomic interaction. The dependence of surface roughness on grinding velocity and grinding depth is investigated and the distribution of atomic stress and grinding force are evaluated. The main results are as follows. The irreversible movements of dislocation from the hard material to the soft material across the interface were observed and the dislocations which caused residual stress were trapped in the soft material. The bending of the hard material was observed in grinding process. The grinding force ratio almost did not depend on the mechanical properties of composite but only depended on the geometrical relation between composite and abrasive grain.
• 岩佐 正明, 青山 博, 服部 敏雄
1999 年 48 巻 4 号 p. 387-391
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
The delamination propagation behaviors of FRP/Metal double lap adhesive joints under cyclic loading were analytically and experimentally examined. The stress singularity parameter and energy release rate were analyzed for each delamination length by FEM stress analysis. The FEM analysis shows that stress is higher at the corner than the center of the double lap adhesive joints. Secondaly the delamination propagation rates measured under cyclic loading shows that the delamination propagation rates can be estimated both by the range of stress singularity intensity and the energy release rate range. Finally the fatigue life of FRP/Metal double lap adhesive joints is found to be mostly determined by delamination process.
• 南谷 林太郎, 初田 俊雄, 島津 ひろみ, 笠井 憲一
1999 年 48 巻 4 号 p. 392-397
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
Liquid perfluorocarbon coolant Fluorinert® FC-72 for electronic devices has high thermal stability and low chemical reactivity. However, the presence of water in FC-72 at less than 10wt ppm has been shown to appreciably increase copper corrosion. In the present study, the corrosion mechanism under low solubility of water in FC-72 was investigated by chemical analysis, water volume measurement, and corrosion testing. It was found that FC-72 liberates no decomposition products in temperatures below 100°C and copper corrosion depends on liquid temperature, dissolved water, and oxygen. In FC-72, copper specimens were corroded by wet oxidation at temperatures of 50, 70, and 85°C and by both wet and dry oxidation at 100°C. Copper corrosion was induced when dissolved water in FC-72 was increased to more than 8wt ppm. However it was reduced when oxygen in FC-72 was decreased to less than 25ml/L. Dissolved water in FC-72, as in air, equilibrates with adsorped water on copper surface. Therefore, the mechanism of copper corrosion in FC-72 is the same as that in air. It is considered that the mechanism for FC-72 can be extended to explain corrosion behavior in almost all inert coolants.
• 門前 亮一, 岡本 智宏, 久世 卓矢, 三浦 博己
1999 年 48 巻 4 号 p. 398-402
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
Bi-doped Cu bicrystals with various [001] and [011] twist boundaries have been tensile tested at room temperature and 543K. The fracture stress and fracture strain depend strongly on the misorientation angle and tensile temperature. The difference in the degree of embrittlement among different grain boundaries is more significant at 543K. The fracture stress and fracture strain at 543K against misorientation curves display some clear peaks; θ=23°(Σ13A), 28°(Σ17A), 37°(Σ5) and 44°(Σ29A) for [001] boundaries and θ=50°(Σ11), 59°(Σ33C), 71°(Σ3) and 83°(Σ57B) for [011] boundaries. For the two types of grain boundary, a good correlation is found between the degree of embrittlement and grain-boundary energy. A higher-energy boundary is more brittle and fractures more easily with a lower tensile stress. The fracture stresses of [001] boundaries are greater than those of [011] boundaries.
• 芳我 攻
1999 年 48 巻 4 号 p. 403-409
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
A super hybrid material plate built up from some aluminum alloy sheets and unidirectional FRP sheets is a kind of new composite material with many excellent mechanical properties. An optical fiber is an excellent sensor that has a wide range of application. It can be embedded into FRY structures so easily that it has become very important constituent material to create smart material and structures. The author succeeded in embedding the optical fiber into the super hybrid material plate. It was found out that several dB of right transmission loss increased when a fatigue crack tip crossed the optical fiber. After that, the transmission loss gradually increased with an increase of crack length. Therefore, to detect an arrival of a crack tip at the position of the embedding optical fiber and to monitor propagation of the crack tip after the arrival became possible by monitoring right transmission loss of the embedding optical fiber.
• 6. 新しい測定技術
吉岡 靖夫, 林 眞琴, 佐々木 敏彦
1999 年 48 巻 4 号 p. 410-415
発行日: 1999/04/15
公開日: 2009/06/03
ジャーナル フリー
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