Integrated Geotechnology Institute Ltd.

Shinjuku, Japan

Integrated Geotechnology Institute Ltd.

Shinjuku, Japan
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Chiaro G.,University of Wollongong | Chiaro G.,University of Tokyo | Koseki J.,University of Tokyo | Sato T.,Integrated Geotechnology Institute Ltd.
Soils and Foundations | Year: 2012

This study focused on the role which static shear plays on the large deformation behavior of loose saturated sand during undrained cyclic loading. A series of undrained cyclic torsional shear tests was performed on saturated Toyoura sand specimens up to single amplitude shear strain exceeding 50%. Three types of cyclic loading patterns, i.e., stress reversal, intermediate and non-reversal, were employed by varying the initial static shear level and the cyclic shear stress amplitude. The observed types of failure could be distinguished into liquefaction (cyclic and rapid flow) and residual deformation by comparing both monotonic and cyclic undrained behavior. It was found that the presence of initial static shear does not always lead to an increase in the resistance to liquefaction or strain accumulation; they could either increase or decrease with an increasing initial static shear level depending on the type of loading pattern and failure behavior. In addition, according to the failure behavior which the specimens exhibited, three modes of development of large residual deformation were observed. © 2012 The Japanese Geotechnical Society.


Ezaoui A.,CETE LYON DLA | Tatsuoka F.,Tokyo University of Science | Maeda Y.,Central Nippon Expressway | Sasaki Y.,Chiba Prefectural Office | Duttine A.,Integrated Geotechnology Institute Ltd
Soils and Foundations | Year: 2016

The yielding of compacted moist cement-mixed gravelly (CMG) soil, subjected to arbitrary loading histories with two stress variables, is studied by means of non-standard drained triaxial compression tests. A non-linear three-component model is modified to describe the elasto-viscoplastic property affected by ageing and shear yielding-associated damage. The development of the inviscid yield locus (YL) is formulated based on the interactive double-yielding mechanism that comprises (i) the bounding mechanism controlled by "inviscid YL, YB" and (ii) the frictional mechanism controlled by "inviscid YL, YF". Each inviscid YL is determined as an inner envelope of a given set of YB and YF that have developed by ageing and shear yielding and have been affected by damage. As the inviscid YL approaches the peak strength line, the shape changes in association with a decrease in the effect of YB and an increase in the effect of YF. The size and shape of the respective YLs in total stresses (i.e., measured effective stresses) are different from those of the corresponding inviscid YLs due to the viscous effects. The total stress-strain relation for a given loading history is obtained by accounting for the viscous effects from the inviscid stress-strain relation, which is obtained from the basic inviscid stress-strain relation accounting for the effects of ageing and damage. It is shown that this model can properly simulate the development of YL for a wide variety of loading histories applied along various stress paths. © 2016 Japanese Geotechnical Society.


Wahyudi S.,University of Tokyo | Koseki J.,University of Tokyo | Sato T.,Integrated Geotechnology Institute Ltd. | Chiaro G.,University of Canterbury
International Journal of Geomechanics | Year: 2016

Following major earthquakes that occurred in New Zealand (2010-2011) and Japan (2011), soil multiple liquefaction, or reliquefaction, regained major attention in the field of geotechnical earthquake engineering. Not only can liquefaction occur multiple times at the same site, but the devastation caused by reliquefaction is often more severe than that triggered by the first liquefaction. In this study, to address this issue and provide new insights into reliquefaction mechanisms, a series of cyclic simple shear tests was conducted with the use of a newly developed stacked-ring shear apparatus. In the multiliquefaction tests, subsequent liquefaction stages were applied to a single Toyoura sand specimen sheared at different levels of maximum shear strain double amplitude (γ DAmax), from 2% to 10%. Tests results showed that: (1) the increase in soil density during the postliquefaction reconsolidation stages had only a minor effect on sand resistance against multiple liquefaction; (2) the extent of γ DAmax significantly influenced sand resistance against multiple liquefaction; and (3) the major impact of γ DAmax was a change in the soil fabric during multiple liquefaction, as confirmed by image analysis results. © 2015 American Society of Civil Engineers.


Wang H.,University of Tokyo | Koseki J.,University of Tokyo | Sato T.,Integrated Geotechnology Institute Ltd. | Chiaro G.,University of Canterbury | Tan Tian J.,University of Tokyo
Soils and Foundations | Year: 2016

Over the past several years, the International Maritime Organization (IMO) has become increasingly concerned about the liquefaction of unsaturated solid bulk cargo (e.g. iron ore fines) during maritime transportation. This concern has arisen due to several accidents including the capsizing of vessels. In addition, although the resistance against liquefaction of ordinary unsaturated soils is higher than for saturated soils, possible key parameters governing the liquefaction resistance of unsaturated soils (RL,unsat) have not yet been clearly identified. Therefore, in this study, undrained cyclic loading tests of saturated and unsaturated iron ore fines and two sandy soils were conducted using a triaxial apparatus to reveal the liquefaction behavior of iron ore fines and to find the key parameters governing RL,unsat. Through comparisons, it was found that the liquefaction behavior of iron ore fines is similar to that of sandy soils. The degree of saturation and potential volumetric strain, which have been proposed as the governing parameters of RL,unsat, were examined based on experimental data obtained in this study and by other researchers. It was shown that neither of the two parameters correlate with the liquefaction resistance ratio (LRR), a ratio of RL,unsat to the liquefaction resistance of the saturated soils (RL,sat) with a unique relationship, especially when considering soils with considerable fines content. Following the concept of potential volumetric strain, which considers the compressibility of pore air in the unsaturated soils, volumetric expansion due to the reduction in confining pressure during cyclic loading is further considered, and a new index, the volumetric strain ratio (Rv) is proposed in this study. According to the experimental data obtained in this study, Rv exhibits a much better correlation with LRR than the two former parameters. © 2016 Japanese Geotechnical Society


Enomoto T.,Japan National Institute for Land and Infrastructure Management | Koseki J.,University of Tokyo | Tatsuoka F.,Tokyo University of Science | Sato T.,Integrated Geotechnology Institute Ltd
Geotechnique | Year: 2016

In order to investigate creep failure behaviour of gravelly soils in the field, a series of triaxial compression tests was conducted on large-scale natural gravelly soil samples. The samples were retrieved by means of a new method using thick, water-soluble, polymer solutions from two tunnel excavation sites in Japan. Creep failure behaviour was evaluated by performing drained sustained loading at prescribed stress states during otherwise monotonic loading at a constant loading rate. Rate-dependent behaviour was also evaluated by stepwise changing vertical strain rate many times during otherwise monotonic loading at a constant strain rate. The observed viscous properties including creep failure behaviour were simulated by a non-linear three-component model taking into account the effects of particle characteristics on the viscous property parameters. The viscous property parameters evaluated for this simulation were compared with those of reconstituted granular materials obtained by previous studies. Shear moduli during the creep failure process, which were measured by the dynamic method, were also analysed. © 2016, ICE Publishing. All rights reserved.


Enomoto T.,Japan National Institute for Land and Infrastructure Management | Koseki J.,University of Tokyo | Tatsuoka F.,Tokyo University of Science | Sato T.,Integrated Geotechnology Institute Ltd
Soils and Foundations | Year: 2015

The creep failure behaviour of three reconstituted sands exhibiting various viscous property types was evaluated by large-, medium- and small-scale drained triaxial, and medium-scale drained unconfined compression tests. The creep characteristics were evaluated by performing sustained loading during otherwise monotonic loading at a constant loading rate. Creep failure and Isotach viscous stress-strain behaviour were observed with well-graded Miho sand compacted heavily under the optimum water content condition. Creep failure of saturated and air-dried Toyoura sand exhibiting TESRA viscosity was observed at the nearly peak stress state. Degradation of the shear modulus of Toyoura sand during creep failure process was measured by the dynamic method. Creep failure did not occur with air-dried Albany silica sand exhibiting P&N viscosity. It was experimentally shown that the stability against creep failure was higher in order of P&N, TESRA and Isotach viscosities. The creep behaviour of various viscous property types was well simulated by the non-linear three-component model taking into account the effects of particle characteristics on the viscous property parameters. © 2015 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.


Kiyota T.,University of Tokyo | Koseki J.,University of Tokyo | Sato T.,Integrated Geotechnology Institute Ltd
Soil Dynamics and Earthquake Engineering | Year: 2013

With the spread of performance-based design concepts in geotechnical earthquake engineering, conducting a practical and accurate analysis for estimating the liquefaction-induced ground deformation has become important. However, there is a difficulty in setting relevant parameters of liquefied soil that would be employed in the analysis because experimental investigations on large deformation behaviour of liquefied soil are still limited. Therefore, in order to investigate the liquefaction-induced ground deformation characteristics, a series of undrained cyclic torsional shear tests was performed by using a modified torsional shear apparatus that is capable of achieving double amplitude shear strain up to about 100%. The tested materials were saturated Toyoura sand, two kinds of in-situ frozen samples having different geological ages and their reconstituted samples. The in-situ samples were retrieved from Pleistocene deposits. In all the undrained cyclic torsional shear tests, cyclic mobility was observed and the double amplitude shear strain approached 100%, irrespective of the different initial conditions of the specimens. A limiting value of double amplitude shear strain to cause strain localization, which would be linked to the maximum possible liquefaction-induced ground deformation, was evaluated based on the change in the deviator stress during the undrained cyclic torsional loading. The limiting value was found to increase with decrease in initial values of small strain shear moduli which were evaluated by dynamic measurement. In addition, we measured tangent shear moduli at the limiting state as well as after strain localization, and evaluated a reduction ratio of shear moduli due to liquefaction, which would be employed in the ALID framework. These characteristics measured by such large strain liquefaction tests would be useful in estimating the maximum liquefaction-induced ground deformation. © 2013 Elsevier Ltd.


Araki H.,University of Tokyo | Koseki J.,University of Tokyo | Sato T.,Integrated Geotechnology Institute Ltd.
Soils and Foundations | Year: 2016

A rammed earth technique is a traditional architectural technique to build soil structures by compacting geo-materials in a form. In this study, tensile strength properties of rammed earth materials and effects of test conditions are evaluated by conducting direct tension tests and splitting tests on several specimens. It is inferred from the result of these test that the direct tension test should be used to evaluate tensile strength of a layer interface, while the splitting test might evaluate the strength related to the tensile strength inside a compaction layer. When rammed earth structures are constructed, the results from the experiments indicate that it is important to scarify interfaces during compaction in order to prevent reduction and variation of the tensile strength of the layer interfaces. The tensile strength of the rammed earth specimens made of compacted soils without lime increased with the decrease in their water contents. The tensile strengths of the specimens represent 5.0-12.5% of corresponding values of unconfined compression strength at the same water content range. The tensile strength of rammed earth specimens made of lime-mixed soil was in the range of 15-20% of the corresponding unconfined compression strength at 28 days curing. In the series of cyclic tensile loading test, no significant reduction of tensile strengths was observed even after undergoing the cyclic loading history. © 2016 Japanese Geotechnical Society.


Kiyota T.,University of Tokyo | Sato T.,Integrated Geotechnology Institute Ltd
Soils and Foundations | Year: 2010

In order to investigate liquefaction-induced ground displacement, we conducted a series of undrained cyclic torsional shear tests on saturated Toyoura sand using a modified torsional apparatus capable of applying and measuring double amplitude shear strain up to about 100%. The limiting value of double amplitude shear strain, at which strain localization appears during undrained cyclic loading tests, was evaluated from the test results with reference to the change in the deviator stress during liquefaction. The limiting strain values, which increase with a decrease in the relative density of the specimen, were found to be consistent with the maximum amounts of liquefaction-induced ground displacement observed in the previous shaking table model tests and most of the relevant case studies. This feature is reasonable considering the reduction in the mobilized cyclic shear stress in liquefied soil due to the degradation of the shear resistance. As long as the liquefied soil layer remains in uniform deformation, these limiting strain values may be used in estimating the maximum amount of liquefaction-induced ground displacement.


De Silva L.I.N.,University of Moratuwa | De Silva L.I.N.,University of Tokyo | Koseki J.,University of Tokyo | Wahyudi S.,University of Tokyo | Sato T.,Integrated Geotechnology Institute Ltd.
Soils and Foundations | Year: 2014

In order to describe the volumetric behavior of soil subjected to shearing, a relationship that deals with the ratio of plastic strain increments to stress ratio (i.e. a stress-dilatancy relationship) is required in addition to the stress-shear strain relationship. In view of the above, stress-dilatancy relationships during cyclic torsional shear loadings were experimentally investigated in the current study. Based on the experimental results, a bilinear non-unique stress-dilatancy model was proposed for stress controlled drained cyclic torsional shear loading. The stress-dilatancy relationships during virgin loading and subsequent cyclic loading were modeled separately by considering the effects of stress history (over-consolidation or normal consolidation). Then the volume change of Toyoura sand specimens subjected to cyclic torsional shear loading was simulated by combining the simulation of stress-shear strain relationship with the proposed stress-dilatancy relationships. It was observed from the comparison of the experiment results with the simulation of volumetric strain that, after combining with accurate modeling of stress-shear strain relationship, the proposed stress-dilatancy relationship can reasonably simulate the volumetric behavior of sand subjected to various drained cyclic torsional shear loadings. © 2014 Japanese Geotechnical Society.

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