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ROMAN D. HRYCIW, MASYHUR IRSYAM
1993 Volume 33 Issue 3 Pages
1-13
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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The behavior of cohesionless soil around rigid plane ribbed inclusions during shear was investigated. The experimental program included monitoring of individual sand grain movements during plane strain shearing and mapping of zones of dilation, contraction aud maximum shear strain. The parameters of study included rib geometry aud spacing, soil density, grain shape, grain size and number of shearing cycles. The rib spacing proved to be a particularly important parameter as it controlled the development or lack of development of a passive soil zone ahead of an advancing rib. The initial soil density determined the volumetric straining and the peak load transfer. Beyond the first half-cycle of shearing, both dense and loose sands exhibited similar behavior. Carbowax solidification techniques were also employed to characterize the failure surfaces and to determine localized changes in void ratio in the intrarib region.
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LUIS E. VALLEJO
1993 Volume 33 Issue 3 Pages
14-27
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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Stiff clays and shales forming part of earth dams contain cracks in their structure. Cracks develop in these materials during and after the construction of the dams. It has been suggested that hydraulic fracturing after the first reservoir filling causes the growth of the cracks that develop into continuous channels through which concentrated water leaks take place. Current methods of analysis of crack propagation in earth dams assume that the cracks grow when water pressures on the walls of the cracks become greater than the dam stresses acting normal to the walls of the cracks. Current methods of analysis do not take into consideration the effect on crack propagation of any shear stresses that could act parallel to the plane of the cracks. In the present study, a theoretical approach for the interpretation of crack growth in earth dams is presented. This is a new approach and it is based on Linear Elastic Fracture Mechanics theory. Using this theory crack propagation and interaction in earth dams are studied considering not only the water pressures and normal stresses acting on the cracks but the effect of any shear stresses as well.
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MASAYOSHI SHIMIZU, TOSHIYUKI TABUCHI
1993 Volume 33 Issue 3 Pages
28-39
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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Unconfined compression tests with the measurement of suction and CIU triaxial compression tests were carried out on a remolded and reconsolidated sample to evaluate whether the effective stress behavior in the unconfined compression tests could be explained through the results from the triaxial tests. It is shown that : effective stress paths in unconfined compression tests are very similar to those in triaxial tests; and unconfined compressive strengths can be predicted well by using those relationships between A
f and the overconsolidation ratio and alternatively between the ratio of the undrained strength to the consolidation stress and the overconsolidation ratio obtained from triaxial tests.
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MICHIYO SUGAI, MINORU MATSUO
1993 Volume 33 Issue 3 Pages
40-53
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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The ultimate bearing capacity of steel pipe piles consists of skin friction and end resistance, and it is highly desirable that it be estimated independently during the pile driving procedure. Such an estimation becomes possible by using the method based on wave theory. The main objective of the present study is to provide a probabilistic method for pile driving control, in which the skin friction term and the end resistance term are independently estimated. The paper presents following the two results : Firstly, indices of ultimate bearing capacity to stop pile driving are determined based on reliability analysis. The ultimate bearing capacity, which is needed to stop pile driving, should be changed to about 80.0(%) to 120.0(%) of the value in a usual design method, according to the ratio of the skin friction term to the ultimate bearing capacity. Secondly, a method is introduced based on Bayes' theorem, in which information obtained from in-situ pile loading tests is applied to the proposed reliability analysis. For friction piles, the ultimate bearing capacity, which is needed to stop pile driving, should be changed to about 40.0(%) to 120.0(%) of the standard value in the case where in-situ loading tests are not available. This should be in accordance with the observed set-up value of skin friction of six to one in the in-situ pile loading tests, respectively.
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KATSUHIKO ARAI
1993 Volume 33 Issue 3 Pages
54-67
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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This paper develops a numerical procedure for calculating the active earth pressure against a retaining wall, which allows consideration of the movements of retaining wall and backfill soil. The limit equilibrium analysis, which has been the principal concept for designing geotechnical structures, has the deficiency that the analysis cannot necessarily consider soil-structure displacements at failure. The design technique for overcoming this deficiency may have to provide a definite collapse mode like a potential slip surface, because the stability analysis subjected to a final collapse mode will keep on playing a major role in engineering practice. The proposed procedure assumes 1) Mohr-Coulomb and Coulomb yield criteria respective for backfill soil and friction interface, 2) fundamental non-associated flow rules related to the yield criteria, and 3) elastic-perfectly plastic stress-strain relationship. The procedure uses the initial stress method in FEM, and a set of yield stresses in each finite element is determined so as to minimize the total plastic work, because the procedure tries to solve the active earth pressure problem without considering the loading history. By use of these assumptions, the procedure enables to produce a definite failure region like a collapse mode supposed in the limit equilibrium analysis. The problem formulation based on these assumptions discloses an important property of Coulomb friction interface that the stresses on the interface are rather insensitive to varying some factors when keeping the initial stresses constant. The validity of the proposed procedure is verified by applying the procedure to several hypothetical case studies, where comparisons are made with Coulomb method, and where many important aspects in the earth pressure problem are clarified.
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GUIDO GOTTARDI, ROY BUTTERFIELD
1993 Volume 33 Issue 3 Pages
68-79
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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Estimation of the bearing capacity of a shallow footing subjected to both inclined and eccentric loads is usually based on well-known limit-equilibrium solutions which apply linear superposition to a problem that is highly non-linear. This paper concerns an alternative approach using "interaction diagrams" to relate the different loading components at failure. Such curves define a region inside which all allowable load combinations must lie. They can be obtained experimentally as the failure envelope of a series of load tests. A comprehensive experimental programme, using a new three-dimensional, small-scale physical model, has been carried out at the University of Padua to determine the form of such diagrams for a very dense sand. The experimental rig as well as the test programme-in which the loading path was the only variable parameter-is briefly described. Failure conditions in all three loading component planes are analysed and very simple expressions are found to interpret the experimental data in an acceptable way. In the H-M/B plane, where the sign of the eccentricity is important in relation to the direction of the horizontal load, a new, interesting geometrical form of failure envelope has been revealed. All the planar interaction diagrams investigated appear to be load-path independent and therefore provide a rational way of studying the load capacity of such footings.
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C.F. LEUNG, H-Y KO
1993 Volume 33 Issue 3 Pages
80-91
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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The research reported herein is concerned with the centrifuge model testing of piles socketed in soft rocks having uniaxial strengths below 12 MPa. Gypsum cement was employed as the pseudo-rock to obtain the desirable range of rock strength. Aluminium tubing with a roughened surface having an equivalent structural stiffness as that of a solid concrete pile was used to simulate the piles. By comparing the centrifuge model test results with those obtained from conventional small-scale models, the latter will overpredict the ultimate unit shaft resistance as the magnitude of friction mobilized along the pile socket depends upon the confining pressure and lateral stiffness of surrounding rocks in the rock socket. In general, the shaft and base resistances obtained from the centrifuge test results agree with predictions from existing design methods whose formulations are derived from load tests on piles in the field. The second part of the research work is to examine the effect of weakness planes in the rock mass on pile capacity. It is noted that for piles having major weakness planes below their base, very little base resistance can be mobilized.
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SATOSHI YAMASHITA, SHOSUKE TOKI
1993 Volume 33 Issue 3 Pages
92-104
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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In order to examine the effects of fabric anisotropy on the relationships between the cyclic triaxial and torsional shear strengths, a series of cyclic undrained triaxial and torsional shear tests was performed on three kinds of sands made by three different sample preparation methods. The test results showed that the cyclic undrained strengths varied with sample preparation methods. In particular, the effects of sample preparation methods were clearly observed in the triaxial test. The relationships between the cyclic triaxial and torsional shear strengths also varied with sample preparation methods. In addition, it was found that the effects of fabric anisotropy due to the difference in the sample preparation methods appear in the axial deformation and the developed pore water pressure characteristics during the cyclic triaxial test. In order to evaluate quantitatively the effects of fabric anisotropy on the relationships between the cyclic triaxial aud torsional strengths, new index parameters were introduced, which express the degree of the anisotropy of specimens. Consequently, it was indicated that there exists a unique rule between these parameters and the ratio of torsional strengths to triaxial strengths.
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MARTE GUTIERREZ, KENJI ISHIHARA, IKUO TOWHATA
1993 Volume 33 Issue 3 Pages
105-117
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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This paper presents an elastoplastic constitutive model for the deformation of sand during loadings involving rotation of principal stress directions. The model employs a plastic potential formulation that allows for the dependency of flow on the stress increment direction and a stressdilatancy relation that incorporates the effects of the non-coaxiality of the principal stress and principal plastic strain increment directions. The continuous plastic deformation of sand during principal stress rotation at constant shear stress level is allowed for in the model by using a very small elastic region in the stress space. In the deviatoric stress space, an associated flow is employed to model the dependency of yielding on the stress increment direction. Hardening behaviour is modelled using discrete surfaces of equal plastic hardening modulus which are allowed to move with the stress point during loading. To model cyclic effects, the plastic hardening modulus is allowed to stiffen during loading depending on the amount of accumulated normalized plastic shear work. The model is used to simulate the deformation of hollow cylindrical sand specimens subjected to rotation of principal stress direction.
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MASASHI KAMON, SUPAKIJ NONTANANANDH, TAKESHI KATSUMI
1993 Volume 33 Issue 3 Pages
118-129
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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The utilization of wastes as construction material is one of the most desirable strategies to solve environmental problems caused by the generation of wastes. There are only a few researches that have discussed the utilization of slag derived from stainless-steel industry. Stainless-steel slag, which is simply disposed of, is one kind of electric furnace slags which exhibit the expansion phenomenon associated with water absorption. The objective of this study is to illustrate the effective utilization of stainless-steel slag as ground materials by solidification. Strength and durability characteristics of stainless-steel slag hardened by stabilizers were investigated experimentally. It has been shown that the Carbonated-Aluminate Salts can be used effectively in stabilizing this slag. The addition of kaolin clay as a pre-mixed admixture to raw materials improves the hardening effect considerably and the durability of materials, and the durability characteristic of stabilized mixtures depends on the curing condition, especially drying method. It is recommended that the hardened stainless-steel slag examined in this study can be applied as road (subbase course) materials.
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KATSUHIKO ARAI
1993 Volume 33 Issue 3 Pages
130-138
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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This note proposes a numerical procedure in which both deformation modulus and Mohr-Coulomb strength parameters are back-calculated from a load-displacement response monitored in the field. The back-analysis of nonlinear constitutive parameters contains the difficulty that most nonlinear constitutive models employ stress as the fundamental variable to govern the change in deformation modulus and to specify the yield criterion, and that the stress is little sensitive to the change in deformation modulus. This difficulty is easily solved by applying the initial strain method for nonlinear stress-strain analysis, because the stress calculated by the method does not directly depend on the tangent modulus of rigidity. By combining a hyperbolic stress-strain equation, FEM based on the initial strain method and mathematical programming technique, the procedure allows to correct unknown soil parameters until the difference between calculated and monitored load-displacement curves decreases sufficiently. The proposed procedure is applied to some hypothetical case studies of in-situ testing and its validity is verified. The result indicates an important role of the initial stresses within subsoil, because the effects of friction angle and cohesion can be evaluated separately, only when the confining pressure exceeds a certain value.
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DOV LESHCHINSKY, SABINA CHOWDHURY
1993 Volume 33 Issue 3 Pages
139-145
Published: September 15, 1993
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The main objective of this paper is to compare safety factors obtained from Morgenstern-Price, Janbu and Spencer methods with the factors calculated from the modified variational approach (Leshchinsky and Huang, 1992a). Such comparison is essential since there is no mathematical proof that the variational analysis indeed yields a minimum and thus, physically produce significant results. The safety factors compared well, indicating the variational analysis is on a par with acceptable existing rigorous methods. Availability of a user-friendly computer code may make the variational analysis useful to practicing engineers. However, its greatest potential at the moment is in 3-D applications; i.e., unlike other methods, its extension to 3-D is straightforward.
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Akira Mori, Masahito Tamura, Hideo Komine, Yuji Ogawa
1993 Volume 33 Issue 3 Pages
159-169
Published: September 15, 1993
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Yu-long Zhang, Makoto Kato, Rokuro Yasutomi
1993 Volume 33 Issue 3 Pages
170-179
Published: September 15, 1993
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Keizo Ugai
1993 Volume 33 Issue 3 Pages
180-186
Published: September 15, 1993
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Masaki Kitazume, Tomohiro Ikeda
1993 Volume 33 Issue 3 Pages
187-195
Published: September 15, 1993
Released on J-STAGE: February 29, 2008
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