Research Achievements - Original paper -

A simple equation for calculating the isochrone

IGARASHI Masaru, OIKAWA Hiroshi, OGINO Toshihiro

Scientific and technical reports of Faculty of Engineering and Resource Science,Akita University ( Akita University )  ( 30 ) 15 - 23   2009.10  [Refereed]

Research paper (journal)   Single author

A simple yet approximately accurate formula is developed for calculating the degree of consolidation Uz at depth z . The formula was obtained by fitting of various functions to the actual Uz - z curves. Based upon this investigations, the Weibill distribution curve which provided a best-fit to the actual Uz - z curves was selected as a proposed equation. Using proposed equation, the degree of consolidation Uz can be easily calculated with less than 3% error.

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Shear modulus of peat soil at small strain measured by laboratory bender element and cyclic loading test

OGINO Toshihiro, TAKAHASHI Takayuki, OIKAWA Hiroshi, MITACHI Toshiyuki, TSUSHIMA Masaki

Japanese Geotechnical Journal ( The Japanese Geotechnical Society )  4 ( 1 ) 125 - 133   2009  [Refereed]

Research paper (journal)   Single author

Shear modulus of peat soil from Akita, Japan is evaluated and discussed in this paper. Bender element and triaxial cyclic loading tests are performed on disturbed and undisturbed specimens. Three techniques for travel time determination on bender element test proposed so far are applied on each specimen to discuss the resulting error on shear modulus evaluation. Estimated <i>G</i>-&sigma; relationships show that the difference of shear modulus between cyclic loading and bender element tests is practically negligible and that the value of shear modulus is approximately 25% less than those from overseas or domestic reports. It is also described that structural anisotropy of peat soil caused by the fiber orientation has little influence on shear modulus in contrast with on shear strength.

DOI CiNii Research

Influence of Deviatoric Yield Curve upon Plastic Deformation Behaviour in Soil

MORITOKI Hitoshi, OIKAWA Hiroshi, OGINO Toshihiro, IGARASHI Masaru

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ( The Japan Society of Mechanical Engineers )  74 ( 747 ) 1432 - 1440   2008.11  [Refereed]

Research paper (journal)   Single author

So far, as a yield criterion on a deviatoric plane, Mises criterion has been widely used in soil as well as in metal in the prediction of plastic deformation behaviour. However, the criterion similar to Mohr-Coulomb fits well in soil rather than Mises criterion. Then, in our simulation of deformation behaviour, we took up the criterion obtained from the stress state at fracture and referred to the experimental results given by Lade & Duncan to estimate the deformation behaviour. In their experiment, compression tests were performed within the range from one dimensional compression to equi-two dimensional compression. On the criterion, <I>J</I><SUB>2</SUB> is represented as a function of <I>J</I><SUB>3</SUB> where<I> J</I><SUB>2</SUB> and <I>J</I><SUB>3</SUB> are the second and the third invariants of deviatoric stress respectively. In this paper, first, the method for including the criterion into analysis is introduced. Second, the strain developments in these compression processes are simulated and compared with the experimental values. The results in simulation are not always agree with experimental ones. However, stable limits in these compressions are situated nearly on a straight line (a critical line) in the yield plane composing of hydrostatic pressure and equivalent deviatoric stress. Third, we examine what criterion gives good correlations between simulation and experiment. The dependence of <I>J</I><SUB>2</SUB> on <I>J</I><SUB>3</SUB> in the criterion is similar on the whole to that obtained from the fracture state, but in detail, the difference is admitted between them.

DOI

Shear characteristics of over consolidated peat in constant volume ring shear test

IGARASHI Masaru, OIKAWA Hiroshi, OGINO Toshihiro, TSUSHIMA Masaki

Japanese Geotechnical Journal ( The Japanese Geotechnical Society )  3 ( 3 ) 175 - 186   2008  [Refereed]

Research paper (journal)   Single author

Undrained shear characteristics of normally and over consolidated remolded peat are investigated using constant volume (CV) ring shear apparatus. Followings are shown in this paper. That is, the shear stress _&tilde; displacement curve in CV ring shear test shows a peak shear stress which enable us to decide the undrained shear strength &tau;_MAX of peat. Shear displacement at failure depend largely on both consolidation pressure &sigma;₀ and over consolidation ratio OCR, but it has a unified relationship with void ratio ^<i>e</i>. The initial part of shear stress _&tilde; displacement curve can be approximated by a hyperbolic curve, and the stress shown by the asymptote is in proportion to &tau;_MAX. The relationship between &tau;_MAX and &sigma;₀ did not pass the origin even if sample was normally consolidated, and shear strength ratio obtained from CV ring shear test was smaller than that obtained from the triaxial compression test. The angle of shear resistance in CV ring shear test was also smaller than that in triaxial compression test. Unprecedented shape was observed in stress pass where the stress pass after peak strength did not converge on a envelope.

DOI

Shape of Yield Curves on a Deviatoric Plane in Soil

MORITOKI Hitoshi, OIKAWA Hiroshi, OGINO Toshihiro, IGARASHI Masaru

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ( The Japan Society of Mechanical Engineers )  73 ( 729 ) 619 - 625   2007.05  [Refereed]

Research paper (journal)   Single author

The failure criterion examined using fracture state says that Mohr-Coulomb criterion is more appropriate to soil than Mises criterion. The important aspect which must be confirmed in the examination of the criterion is that the stress state at fracture are situated on a critical straight line in primary yield relation showing the dependency between equivalent deviatoric stress and hydrostatic pressure. Moreover, the equivalent deviatoric stress must be representative of the magnitude and shape of the yield curve on a deviatoric plane. Therefore, the critical straight line is also affected by failure criterion itself. Such mutual dependency makes it complicated to find out the relevant yield criterion. For the discussion of the yield criterion, we used the data obtained in the compression tests performed by Reades & Green and by Lade & Duncan. First, on the assumption that fracture stress points are situated on the critical line in the primary yield relation, the shape of yield curve on the deviatoric plane is examined. Then, the curve shape is represented with the relation between <I>J</I><SUB>2</SUB> and <I>J</I><SUB>3</SUB> where <I>J</I><SUB>2</SUB> and <I>J</I><SUB>3</SUB> are the second and the third invariant of deviatoric stress respectively. Second, the equivalent stress is defined using the curve shape relation. Third, it is confirmed that fracture points in primary yield relation are located on the straight line when based on the equivalent stress defined

DOI CiNii Research

A Proposal for Predicting Plastic Deformation Behaviour in Soil

MORITOKI Hitoshi, OIKAWA Hiroshi, OGINO Toshihiro

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ( The Japan Society of Mechanical Engineers )  72 ( 718 ) 872 - 879   2006.06  [Refereed]

Research paper (journal)   Single author

In the prediction of deformation behaviour of soil, it is important to specify the inherent properties of the soil itself, although it is needless to say that appropriate constitutive equations must be applied in its analytical treatment. As the inherent properties there are the shape of yield curve and hardening characteristics. The yield curve represents the relation between the hydrostatic pressure and the equivalent deviatoric stress in the process of plastic deformation. On the other hand, the hardening characteristics correspond to the yield curve expansion accompanying with plastic deformation. These inherent properties are independent of the loading manner to be assigned to the soil. In this paper, the yield curve and the hardening characteristics are specified referring to the deformation behaviours on one of loading paths. Then, they are applied to the prediction of deformation behaviour on the other loading paths. In the results obtained, the difference of behaviours could be shown reasonably between loading paths, but they were numerically imperfect in comparison with the experimental observation. However, the method makes it possible to predict the plastic behaviour on the basis of the material characteristics referred.

DOI CiNii Research

SHEAR WAVE VELOCITY BY TSP APPLIED BENDER ELEMENT TEST IN SAND

OGINO Toshihiro, OIKAWA Hiroshi, MITACHI Toshiyuki, TSUSHIMA Masaki, NISHIDA Kohta

Doboku Gakkai Ronbunshuu C ( Japan Society of Civil Engineers )  62 ( 1 ) 169 - 174   2006  [Refereed]

Research paper (journal)   Single author

A method of identifying the impulse response by TSP(time stretched pulse) is applied to bender element test. From a series of experiments with sand, it is shown that the impulse response of bender element test system can be given by this method and the received wave form closely resembles to that obtained in the case square input wave is transmitted. Two kinds of shear wave velocity, for travel time and for phase difference in frequency domain (phase velocity), are obtained from impulse response. It is observed that shear wave velocity for travel time is close to that given by square input wave. Phase velocity, on the other hand, changes with frequency, and strong dispersion of velocity dependence on frequency is implied.

DOI CiNii Research

Boundary Condition Disturbed in Shear Banding Analysis by Rudnicki and Rice for Pressure Sensitive Materials

MORITOKI Hitoshi, OIKAWA Hiroshi, OGINO Toshihiro

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ( The Japan Society of Mechanical Engineers )  71 ( 706 ) 928 - 935   2005.06  [Refereed]

Research paper (journal)   Single author

Rudnicki and Rice invistigated the localization of deformation into a shear band resulted from an instability in constitutive description of homogeneous deformation in pressure sensitive dilatant materials. Their analytical method has been used very often for the prediction of shear banding in soil. In their analysis the equilibrium is considered between multiple solutions in the perpendicular direction to a shear band, but the essential requirement is ignored that these multiple solutions are under identical boundary condition. This paper shows concretely the disturbance of boundary condition appeared in the onset of instability in their method. This disturbance results in the fact that their method cannot give useful prediction for ductile fracture in soil.

DOI

Vibration properties of self-monitoring bender element

Nishida Kohta, Ogino Toshihiro, Mitachi Toshiyuki, Kawaguchi Takayuki

Proceedings of the Japan National Conference on Geotechnical Engineering ( The Japanese Geotechnical Society )  39 ( 0 ) 271 - 272   2004  [Refereed]

Research paper (journal)   Single author

DOI

EVALUATION OF DEFORMATION CHARACTERISTICS OF SOIL BY BENDER ELEMENT TEST

OGINO Toshihiro, MITACHI Toshiyuki, TSUSHIMA Masaki, OIKAWA Hiroshi

Doboku Gakkai Ronbunshu ( Japan Society of Civil Engineers )  2003 ( 743 ) 135 - 145   2003  [Refereed]

Research paper (journal)   Single author

Damped free vibration and resonance of soil are observed by using bender element system. Shear modulus and damping ratio are evaluated in two ways by applying the theory of resonance. Based on the test results on NSF-clay and Akita peat, it is shown that shear modulus can be estimated properly and is larger than that in case that the travel time is defined by the peak of receive wave on usual bender element test. In addition, it is also shown that damping ratio from these methods is almost coincident with that past report. It is proposed that bender element test can be performed in three ways; above two and an usual methods, so that information on damping ratio as well as shear modulus is given.

DOI

Consolidation and Strength Characteristics of Peaty soil under VacuumConsolidation

Ogino Toshihiro, Shiono Toshiaki, Oikawa Hiroshi, Igarashi Masaru

Proceedings of the Japan National Conference on Geotechnical Engineering ( The Japanese Geotechnical Society )  38 ( 0 ) 341 - 342   2003  [Refereed]

Research paper (journal)   Single author

DOI

EFFECT OF ANISOTROPIC CONSOLIDATION ON RESIDUAL EFFECTIVE STRESS AND UNCONFINED COMPRESSIVE STRENGTH OF HIGHLY ORGANIC SOIL

TSUSHIMA Masaki, MITACHI Toshiyuki, OGINO Toshihiro

Doboku Gakkai Ronbunshu ( Japan Society of Civil Engineers )  2003 ( 743 ) 235 - 240   2003  [Refereed]

Research paper (journal)   Single author

Simulation test for the process from sampling to unconfined and triaxial compression tests on undisturbed highly organic soil are performed with different anisotropic consolidation stress condition. The influence of anisotropy of consolidation stress on residual effective stress and unconfined compressive strengths are examined. From the test results, it is found that the unconfined compressive strengths decrease with the degree of consolidation stress anisotropy. It is also found that the unconfined compressive strengths of highly organic soil obtained from the tests of different anisotropic consolidation stress can be reasonably corrected by applying a simplified method which is formerly proposed by the authors.

DOI

<Original Papers>Shear Characteristics of Highly Organic Soil Obtained by Ring Shear Tests

TAKAHASHI Takayuki/OGINO Toshihiro

Scientific and technical reports of Faculty of Engineering and Resource Science,Akita University ( Akita University )  ( 23 ) 81 - 85   2002.10  [Refereed]

Research paper (journal)   Single author

In this paper, two types of direct shear tests; direct shear box test and ring shear test, are performed in constant volume or constant pressure condition on highly organic soil or clayey soil in order to evaluate their strength characteristics. Strength characteristics from these tests are compared with results of other tests such as triaxial compression tests and effects on strength characteristics due to test method or shear condition are discussed. In the results of the series of these tests, it is shown that these kinds of direct shear tests can contribute to obtain proper value of strength characteristics for highly organic soil and are enough effective in not only clayey soil but also highly organic soil.

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STRENGTH CHARACTERISTICS OF HIGHLY ORGANIC SOIL OBTAINED BY DIRECT SHEAR TESTS

OGINO Toshihiro, OIKAWA Hiroshi, TSUSHIMA Masaki, MITACHI Toshiyuki

Doboku Gakkai Ronbunshu ( Japan Society of Civil Engineers )  715   277 - 285   2002.09  [Refereed]

Research paper (journal)   Single author

In this paper, it is examined whether the type of direct shear tests can be applied to highly organic soil to evaluate strength characteristics in the laboratory. A series of shear box tests and ring shear tests are performed on a remolded samples. Based on the test results, strength characteristics of peat soil obtained from direct type shear tests are discussed comparing with those on clay soil. Direct type shear test data are also compared with those by consolidated undrained triaxial tests. It is concluded that direct type shear tests provide more reliable strength parameters on highly organic soil than triaxial or unconfined compression tests. Practical usefulness of the direct type shear test, especially shear box test, is also suggested for the determination of the strength parameters of highly organic soils.

DOI

Multiplicity of Deformation and Shear Band Mode in Soil

MORITOKI Hitoshi, OIKAWA Hiroshi, OGINO Toshihiro

Journal of applied mechanics ( Japan Society of Civil Engineers )  ( 5 ) 283 - 294   2002  [Refereed]

Research paper (journal)   Single author

The volumetric change accompanying with plastic shear deformation causes the dependency of q on p where p and q respectively represent the hydrostatic pressure and equivalent deviatoric stress in yielding. Their dependency is called yield curve or yield function. For predicting yield curve the following assumptions are set up. Yield curves expand similarly in shape with plastic deformation and yield function plays as a plastic potintial. Basic yield curve is determined which gives a basic shape in similary expansion of yield curve. Using experimental results obtained under plane strain compression tests, we predict the basic yield curves. The basic yield curve has a limit over which yield curve cannot expand in (p, q) space. We call it expanding limit. First, it is examined whether plastic instability arises or not in plane strain compression tests, but its occurrence is denied consequently. Next, we show that multiple deformation rate can exist at the expanding limit. Hence, the onset of bifurcation is predicted at the expanding limit and the mode of shear plane is determined based on the concept of a characteristic plane. These predictions agree reasonably well with reported experimental observations.

DOI

DEFORMATION AND STRENGTH CHARACTERISTICS OF COHESIVE SOIL OBTAINED BY CONSOLIDATED CONSTANT VOLUME DIRECT SHEAR TEST - Measurement of Elastic Shear Modulus by Bender Elements -

OGINO Toshihiro, MITACHI Toshiyuki, SHIBUYA Satoru, OIKAWA Hiroshi

  673   15 - 26   2001.03  [Refereed]

Research paper (journal)   Single author

PROMOTION OF SECONDARY COMPRESSION OF PEAT BY HEATING

OIKAWA Hiroshi, OGINO Toshihiro

Doboku Gakkai Ronbunshu ( Japan Society of Civil Engineers )  673 ( 673 ) 183 - 188   2001.03  [Refereed]

Research paper (journal)   Single author

Laboratory oedometer tests were conducted to investigate the effects of heating on promotion of secondary compression of peat. From the test results, it was confirmed that the rate of settlement of peat in the range of secondary compression was increased drastically by heating. Effect of heating on settlement promotion is incredibly larger for peat than for clay. After cooling the specimen, resettlement followed by small rebound was observed. The rate of resettlement, however, was so small that the long term compression tendency of peat could be reduced upon cooling

DOI CiNii Research

Dependency of Shear Deformation Behaviour in Soil upon Shape of Yield Curve

MORITOKI Hitoshi, OIKAWA Hiroshi, OGINO Toshihiro

Journal of applied mechanics ( Japan Society of Civil Engineers )  4 ( 4 ) 239 - 249   2001  [Refereed]

Research paper (journal)   Single author

The volumetric change accompanying with plastic shear deformation causes the dependency of <I>q</I> on <I>p</I> where <I>p</I> and <I>q</I> respectively represent the hydrostatic pressure and the equivalent deviatoric stress in yielding. Their dependency is called yield curve or yield function. In geomechanics Cam-clay and cap models have been frequently used as yield curve. In the last report we examined the shapes of yield curve based on the deformation behaviour observed in the published experiments where a parallel piped specimen was compressed under plane strain condition or a cylindrical specimen was extended in axial direction increasing confining pressure. In many cases the shape of yield curve were different from those in Cam-clay and cap models. In this paper the inverse prediction is discussed where the deformation behaviour is predicted according to the yield curve and hardening charcteristics obtained in the last report. First, the method of the inverse treatment is proposed, and then the comparison is made between predicted behaviour and the observed one. On the whole the inverse prediction is successful, but an abnormal prediction arises in the case that the term &fnof;<SUB>r</SUB>+&alpha; tends to zero or to be negative where &fnof;<SUB>r</SUB>;, represents the ratio of compressive volumetric strain rate to distortional strain rate and a is the hardening ratio constant. So far geomechanics has been developed under the condition of &alpha;=0. In such framework the abnormal prediction can be brought about at positive volumetric strain rate, and so introducing of hardening ratio constant must be considered. Stress point (<I>p</I>, <I>q</I>) moves with progressive deformation. Under plane strain compression the stress point approaches to the critical state line with the increase of deformation, and finally reaches to it. It is proved that the movement of stress point always stops on the critical state line regardless of the hardening characteristics of deforming soil.

DOI CiNii Research

Deformation and strength characteristics of cohesive soil obtained by consolidated constant volume direct shear test.:Measurement of Elastic Shear Modulus by Bender Elements

OGINO Toshihiro, MITACHI Toshiyuki, SHIBUYA Satoru, OIKAWA Hiroshi

Doboku Gakkai Ronbunshu ( Japan Society of Civil Engineers )  2001 ( 673 ) 15 - 26   2001  [Refereed]

Research paper (journal)   Single author

Shear modulus <i>G</i> of clayey soil at small strain level is discussed in this paper. The authors developed a new direct shear apparatus which is equipped with loadcells inside wall of the shear box and a pair of bender elements (BE) at the top and bottom plates so that mean effective stress &sigma;<i>_m</i>&prime; and shear modulus <i>G</i> can be evaluated during consolidation and shear processes of consolidated constant volume direct shear test. Based on the test results, the relationships among void ratio <i>e</i>, mean effective consolidation stress &sigma;<i>_m</i>&prime; and shear modules <i>G</i> are compared with the relationships among <i>e</i>, &sigma;<i>_m</i>&prime; and Young's modulus <i>E</i> measured by cyclic triaxial loading. A simple equation is proposed based on the observed relationships and it is also shown that the change of <i>G</i> during and after drained creep is due to the combined effects of development ar deterioration of soil structure and change of void ratio. Strong dependency of shear modules <i>G</i> measured by BE during constant volume direct shear test on the effective mean stress &sigma;<i>_m</i>&prime; is also found and the relationship between shear strength and shear modules <i>G</i> is discussed.

DOI

Residual effective stress and unconfined compressive strength of overconsolidated highly organic soil.

OGINO Toshihiro, TSUSHIMA Masaki, MITACHI Toshiyuki

Doboku Gakkai Ronbunshu ( Japan Society of Civil Engineers )  2001 ( 673 ) 195 - 200   2001  [Refereed]

Research paper (journal)   Single author

A series of test simulating the process from sampling to unconfined and UU triaxial compression tests for overconsolidated highly organic soil are performed. The influence of residual effective stress change on unconfined compressive and UU triaxial strength are examined, and a method for predicting in-situ strength from the relationship between residual effective stress and unconfined compressive srength is proposed. From the test results, it is found that strengths obtained from unconfined compression test with suction measurement can be reasonably corrected to estimate in-situ undrained strength by applying proposed method.

DOI