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Page 1: Numerical analysis on crushing stress of sand in ...scientiairanica.sharif.edu/article_1994_58b5869e726b29fd67cd4d809d... · The simple crushing model proposed by Yao et al. [24]

Scientia Iranica A (2015) 22(5), 1755{1764

Sharif University of TechnologyScientia Iranica

Transactions A: Civil Engineeringwww.scientiairanica.com

Research Note

Numerical analysis on crushing stress of sand inconstitutive model with particle crushing

Y. Wua;� and H. Yamamotob

a. Graduate School of Science and Engineering, Yamaguchi University, Ube 7558611, Japan.b. Graduate School for International Development and Cooperation, Hiroshima University, Higashi-Hiroshima 7398529, Japan.

Received 9 March 2014; received in revised form 26 October 2014; accepted 28 January 2015

KEYWORDSParticle crushing;Crushability;Constitutive model;One dimensional test;Triaxial compressiontest.

Abstract. Estimation of crushing stress is important to understand the crushingmechanism and shear strength of granular material. One simple constitutive model usingthe reference crushing stress had been proposed for describing the variation in strengthand deformation behavior of sand before and after particle crushing occurrence. Theprediction capacity of the constitutive model is examined for representing the variationin mechanical behavior of relative high crushable sand. This study presents the parametricanalysis on the reference crushing stress and examines its e�ect on the mechanical behaviorof Cambria sand. Numerical results demonstrate that peak stress ratio increases andcontractive behavior becomes less obvious with larger reference crushing stress. The stressratio and dilatant ratio at failure with variable reference crushing stresses and con�ningpressures are also demonstrated. Predicted results indicate that reference crushing stressis basically dependent on the inherent feature and type of sand but has some relationshipwith the ultimate strength of a single particle. The linear relationship between the referencecrushing stress and the yield stress decided in one dimensional compression test has beenobtained on the logarithmic plot. The reference crushing stress can be applied as onee�ective strength index for sand in macro viewpoint.c 2015 Sharif University of Technology. All rights reserved.

1. Introduction

Particle crushing occurs once external force overcomesits inherent material strength. It had been observedand con�rmed in a series of laboratory experiments [1-4]. The e�ect of particle crushing on shear behaviorcan be understood as a decrease in positive dilatancy,which causes a decrease in the shear strength of sandsimultaneously [5,6]. The strength and deformationbehavior of sand is signi�cantly a�ected by particlecrushing occurrence. The coarse granular material

*. Corresponding author. Tel.: +81-836-85-8363;Fax: +81-836-85-9301E-mail addresses: [email protected] (Y. Wu);[email protected] (H. Yamamoto)

such as rock�ll similarly displays obvious crushablecharacteristics [7-9]. It is signi�cant to evaluate thestress level at which the particles of granular mate-rial are crushed in infrastructure construction [10-13].Study on the estimation of crushing stress for granularmaterial had attracted many researchers' attentions.Di�erent de�nitions and forms of the crushing stresswere adopted in corresponding to the types of exper-iment. Single particle strength had been used as anindex to describe the crushing strength of a single grainin micro viewpoint by many researchers [13-16]. It ex-pressed the average tensile stress or force on the singlegrain without lateral con�ning reaction. Marketos andBolton [17] investigated the crushing stress of particleusing statistical processing. However, estimation ofthe crushing stress for specimen of assembled grains

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not the individual particle is quite important in bothexperimental and �eld practical aspects.

The crushing stress in macro viewpoint and itsrelationship with the relevant from of crushing stressin micro viewpoint needs further investigation. Justas the yield stress decided from the compression curvefor specifying the crushing stress in one dimensionalcompression test which is commonly recognized as asimple method to examine the compressive and crush-ing features of granular material [18-21], it is necessaryto clarify such kind of crushing stress for assembledgrains subjected to more complex stresses. Triaxialcompression test is an e�ective alternative to examinethe mechanical behavior of assembled grains subjectedto variable stress states and paths. Some constitutivemodels considering particle crushing had been estab-lished but a limited number of them directly introducedthe crushing stress into the elasto-plastic theory.

Explanations of granular material behavior com-bining the critical state concept have been adoptedby some researchers [22,23]. One constitutive modelfor sand using the concept of reference crushing stresshad been proposed by Yao et al. [24] to representthe variation in strength and deformation at di�erentcon�ning pressures. It is necessary to understandthe relationship among the di�erent forms of crushingstresses in macro viewpoint under various loadingpatterns and con�rm the rationality of the utilizationof reference crushing stress for describing the strengthfor sand in triaxial test. To examine the predictioncapacity of the constitutive model over a wide range ofsand with di�erent crushability, the constitutive modelis validated by comparing the predicted values withexperimental results for Masado and Cambria sand at�rst.

This study presents a parametric study aboutthe e�ect of the reference crushing stress on the peakstrength and deformation behavior of Cambria sand.Predicted results demonstrate that the peak stressratio increases and contractive behavior becomes lessobvious with larger reference crushing stress. Thepeak stress ratio at failure decreases and dilatant ratioat failure increases with increasing mean stress. Thereference crushing stress expresses the linear relationwith the yield stress decided in one dimensional com-pression test for �ve kinds of sand on the logarithmicplot. Therefore, the reference crushing stress can beapplied as an e�ective strength index for sand in macroviewpoint and estimated from the experienced equationobtained in this study.

2. Constitutive model for sand with particlecrushing

In recent decade, several constitutive models had beendeveloped using elasto-plastic theory to include the

characteristics of particle crushing. Daouadji et al. [25],Daouadji and Hicher [26] proposed a constitutive modeland its enhanced version taking into account theparticle breakage and proved its new theory on a basisof laboratory tests. Kikumoto et al. [27] also discussedthe crushing behavior of sand with the revised Severn-Trent sand model based on the critical state theory.The grain size distribution was chosen as a parameterin model. The simple crushing model proposed byYao et al. [24] could predict both positive and negativedilatancy of sand at failure and the variation in peakstrength under di�erent con�ning pressures. Thereference crushing stress pc is directly integrated withthe expression of the hardening parameter, H, of theconstitutive model. The evolution of characteristicstate curve as well as failure state curve in the model issimultaneously a�ected by it. The constitutive modelis successfully proved to predict the crushing behaviorof soil in surrounding of pile tip [28,29].

2.1. Theory of the constitutive model withparticle crushing and its referencecrushing stress

The constitutive model is one of the members ofmodi�ed Cam-clay model family. It is established byintroducing the uni�ed hardening parameter, H, anda reference crushing stress pc. The uni�ed hardeningparameter, H, in Eq. (1) is capable of predicting bothof the positive and negative plastic volumetric strain"pv.

H =ZdH =

ZM4c

M4f

M4f � �4

M4c � �4 d"

pv; (1)

Mc = M�ppc

�n; (2)

Mf = M�ppc

��n: (3)

The critical state line M involves two curves on thep� q plane in Figure 1. Straight lines AB, CD and EF

Figure 1. The Mf and Mc curves on p� q plane.

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Y. Wu and H. Yamamoto/Scientia Iranica, Transactions A: Civil Engineering 22 (2015) 1755{1764 1757

denote di�erent stress paths at low, medium and highinitial con�ning pressures, respectively. p indicatesmean stress, while q means deviatoric stress. � = q=pis the stress ratio. The characteristic state curve Mc,in Eq. (2) is the di�erentiating curve of volumetricvariation from contraction to expansion. Namely,the volume contracts continually provided that thestress ratio below Mc:Mf in Eq. (3) is the dividingline of material failure and takes the same value asthe peak stress ratio. The indicia n is the materialcoe�cient. Two curves start from the original pointO and intersect at point D subsequently more again.The reference crushing stress pc is corresponding tothe point by drawing the straight line from the non-zero point perpendicular to the p-axis. The predictiontheory of the constitutive model for volumetric varia-tion is explained as follows. Path AB (low con�ningpressure); the volume initially contracts from A to Kand expands in phase KB. Paths CD and EF (mediumand high con�ning pressures); stress path reaches thecharacteristic state curve, Mc, and the failure statecurve, Mf , simultaneously or later than that. Onlythe volumetric contraction is predicted.

The description of the constitutive model is re-viewed and its tensor form for �nite element analysisis speci�ed in detail by Wu et al. [30]. The determi-nation method of the reference crushing stress, pc, isexplained as the example of Cambria sand. Experimentresults indicate that both of the stress ratio, qf=pand �(d"v=d"a), become the constant value when theCambria sand is at failure under di�erent con�ningpressures. Besides, connecting the points at the failurestate in the qf=p and �(d"v=d"a) plane provides astraight line as shown in Figure 2. On the linearrelation between these two ratio values, the elasticdeformation part is ignored. The stress ratio at criticalstate, M , can be determined when the volumetricstrain increment is zero, �(d"v=d"a) = 0. Utilizing

Figure 2. The relationship between qf=p and �(d"v=d"a)at di�erent con�ning pressures.

Figure 3. The relationship between ln(Mf ) and ln(p).

the above linear relationship, we can determine M andthen make rearrangement of Eq. (3), obtaining Eq. (4).

lnMf = �n ln p+ n ln pc + lnM: (4)

According to the relationship between the failure statecurve, Mf , and the mean stress, p, under di�erentcon�ning pressure, we can draw the line in Figure 3to express the relationship between ln(Mf ) and ln(p).n is the gradient of the straight line, then we can decidethe exact value of pc.

"ev = Ce��

pxpa

�m��popa

�m�; (5)

"pv = (Ct � Ce)��

pxpa

�m��popa

�m�: (6)

It had been revealed by Nakai [31] that the linearrelation between the elastic volumetric stain, d"ev, orplastic volumetric stain, d"pv and (p=pa)m, for granularmaterial could be obtained based on the experimentalresults on Toyoura sand in Eq. (5) and Eq. (6). Herein,pa is the atmosphere pressure. m is a coe�cient forsand. Swelling index, Ce, and compression index, Ct,can be determined from the isotropic loading-unloadingtest. Poisson ratio, v, is assumed to be 0.3. There areseven parameters in the constitutive model in total.Six of them can be determined using the conventionalisotropic and triaxial compression tests.

The constitutive for sand with particle crushingis established based on the critical state theory. Thestress-dilatancy equation of this model is the same asthat of modi�ed Cam-clay model. The yield functionof constitutive model for sand with particle crushing isgiven in Eq. (7).

f =Ct�Cepma

��(2n+ 1)p2n

cM2 � q2

p+p2n+1

� m2n+1� pmo

��H = 0; (7)

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where po is the initial mean stress. Crushing modeltakes the associated ow rule, so that plastic potentialfunction is identical to the yield function.

2.2. Validation of constitutive model for highcrushable sand

The constitutive model had been veri�ed for describingthe mechanical behavior of Toyoura sand in triaxialcompression test considering particle crushing. Ac-tually, many infrastructures are constructed on therelative crushable sand especially in coastal region.Therefore, it is necessary to examine the predictioncapability of the constitutive model for high crush-able sand. The numerical values from constitutivemodel are compared to the experimental results foranother two kinds of relative high crushable sand inthis study. The positive dilatancy of sand specimensin triaxial compression test disappears at con�ningpressure as 200 kPa, 1000 kPa and 4000 kPa forMasado, Cambria and Toyoura sand, respectively [32-34]. The criterion for evaluating the crushability ofsand in this study is simply employed by comparingthose con�ning pressures in triaxial test. Hence,Masado, Cambria and Toyoura sand are regarded asthe high, medium, and low crushable sand. Ta-ble 1 shows the physical property for Masado andCambria sand. The determination method of thereference crushing stress for Masado is the same asexplained for Cambria sand. The seven parametersof constitutive model for both of the Masado andCambria sand are shown in Table 2. Figure 4 rep-resents the experimental and predicted relationshipbetween stress ratio and axial strain under varyingcon�ning pressure from 60 kPa to 400 kPa in triaxialcompression test for Masado. Prediction agrees wellwith the measured results except that the con�ningpressure is at low level. The predicted peak stressratio exhibits the decreasing tendency as the con�ningpressure is increased. The constitutive model predictsthe dilatancy from negative to positive at con�ningpressure as 60 kPa and 100 kPa, and only the negativedilatancy at con�ning pressure as 200 kPa and 400 kPain Figure 5. The constitutive model is capable of

Figure 4. Experimental and predicted relationshipbetween stress ratio and axial strain (Masado).

Figure 5. Experimental and predicted relationshipbetween volumetric strain and axial strain (Masado).

representing the variation in deformation behavior andstrength reduction for high crushable sand at relativelow stress.

The numerical and experimental relationship be-tween the stress ratio and axial strain for Cambriasand is displayed in Figure 6. The peak strengthgradually reduces from 3.8 to 2.5 as con�ning pressure

Table 1. Physical properties for two kinds of sand.

Name of sand Speci�c gravity emax emin d50 (mm) Relative density (%)

Masado 2.62 0.967 0.491 0.760 90

Cambria sand 2.65 0.792 0.503 1.620 60

Table 2. Parameters of constitutive model with particle crushing for two kinds of sand.

Name of sand Ce Ct m pc (MPa) M n v

Masado 0.00637 0.01494 0.8 0.412 1.80 0.1782 0.3

Cambria sand 0.00640 0.00970 0.5 1.200 1.36 0.1132 0.3

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Figure 6. Experimental and predicted relationshipbetween stress ratio and axial strain (Cambria sand).

Figure 7. Experimental and predicted relationshipbetween volumetric strain and axial strain (Cambriasand).

is increased from 0.25 MPa to 8 MPa. The predictedresults of constitutive model exhibit dilatancy fromnegative to positive at con�ning pressures as 0.25 MPaand 0.5 MPa, and only negative dilatancy at con�ningpressures as 1 MPa, 2 MPa, 5 MPa and 8 MPa inFigure 7. Cambria sand displays markedly contrac-tive behavior at high con�ning pressure and predictsvolumetric strain attaining to 12% in compressionside.

The constitutive model is proved to be capable ofpredicting the mechanical behavior of high and mediumcrushable sand over a wide range of con�ning pressures.It is noted that the reference crushing stress varies withthe kind of sand and expresses some correlation withthe peak strength of sand. To investigate the e�ectof reference crushing stress on its mechanical behavior,the parametric study on the reference crushing stresspc is performed.

3. Numerical study on the reference crushingstress of Cambria sand

3.1. Parametric analysis of reference crushingstress pc

The parametric study on the reference crushing stresspc is carried out on Cambria sand. Cambria sandhad been testi�ed by Yamamuro and Lade and hiscollaborators [3,20,35] to investigate its compressionand crushing features. The reference crushing stresspc varies from 0.9 MPa to 1.8 MPa with the incrementof 0.3 MPa. Other six parameters are kept as constantin the parametric analysis. The predicted mechanicalrelationship is expressed at con�ning pressure increas-ing from 0.25 MPa to 8 MPa in corresponding to theloading condition in triaxial test. The gradient ofthe failure state curve Mf decreases as the referencecrushing stress becomes small. Oppositely, the gradientof the characteristic state curve Mc increases as thereference crushing stress decreases.

Owing to the completion of numerical analysiswith reference crushing stress pc as 1.2 MPa, onlypredicted relationship between the stress ratio andaxial strain using the reference crushing stress 0.9 MPa,1.5 MPa and 1.8 MPa are shown in Figure 8(a), (b)and (c). The predicted peak stress ratio increasesas the reference crushing stress pc becomes larger atthe same con�ning pressure. The peak stress ratio isaround 3.75 at con�ning pressure of 0.25 MPa with pcas 0.9 MPa, while it reaches 4.2 at con�ning pressureof 0.25 MPa with pc as 1.8 MPa. Numerical resultsshow that the initial tangent modulus of stress-straincurve increases as the con�ning pressures increase.The predicted relationship between volumetric strainand axial strain when reference crushing stress takesvalue as 0.9 MPa, 1.5 MPa and 1.8 MPa is displayedin Figure 9(a), (b) and (c). The positive dilatancybecomes remarkable as the reference crushing stresspc increases. It is summarized that the constitutivemodel adopting high reference crushing stress predictslarger peak stress ratio and less contractive volume.Reference crushing stress can be applied to be an indexto describe the strength of assembled grains in macroviewpoint. It is noted that the scope between thepredicted maximum volumetric expansion strain andmaximum volumetric contraction strain is not a�ectedby the reference crushing stress level.

3.2. The e�ect of reference crushing stress onmechanical behavior of Cambria sand

Figure 10 displays the predicted stress ratio at failureplotted against the mean stress when the referencecrushing stress pc is 0.9 MPa, 1.2 MPa, 1.5 MPa and1.8 MPa, respectively. The stress ratio at failure Msfsigni�cantly decreases with the increasing mean stress.The sand almost loses one third of the total strength

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Figure 8. Predicted relationship between stress ratio andaxial strain for Cambria sand with di�erent referencecrushing stresses.

as the entire loading is applied. The progressivestrength reduction is explained as the particle crushingand rearrangement in the specimen. However, thedecreasing tendency and degree of strength at failure isless dependent on the reference crushing stress pc. Inaddition, the stress ratio at failure slightly increasesas the reference crushing stress pc becomes large.However, the in uence of reference crushing stress on

Figure 9. Predicted relationship between volumetricstrain and axial strain for Cambria sand with di�erentreference crushing stresses.

the variation in the initial tangent modulus of stress-strain curve is minimal.

Figure 11 shows the predicted dilatant ratio atfailure �(d"v=d"a) plotted against the mean stress asthe reference crushing stress varying from 0.9 MPa to

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Figure 10. Relationship between stress ratio at failureMsf and mean stress.

Figure 11. Relationship between dilatant ratios at failure�(d"v=d"a) and mean stress.

1.8 MPa. The dilatant ratio �(d"v=d"a) increases fromthe negative value to positive value with the increasingmean stress. As seen in Figure 11, the dilatantratio at failure decreases reversely as the referencecrushing stress pc is increased. It is believed thatconstitutive model adopting larger reference crushingstress is believed to be di�cult for being crushed.The predicted negative dilatancy for constitutive modelwith larger reference crushing stress is smaller underthe same loading condition.

3.3. The e�ect of con�ning pressure onmechanical behavior of Cambria sand

Figure 12 demonstrates the predicted stress ratioat failure Msf plotted against the reference crush-ing stress pc. Con�ning pressure is increased from0.25 MPa to 4 MPa. Predicted results show thestress ratio at failure Msf slightly increases as thereference crushing stress increases. The stress ratio atfailure under each con�ning pressure exhibits almostthe similar increasing tendency and rate. It is noted

Figure 12. Relationship between stress ratio at failureMsf and reference crushing stress pc.

Figure 13. Relationship between volumetric strain("v)0:15 and reference crushing stress pc.

that the reduction of stress ratio at failure with increas-ing con�ning pressure exhibits decreasing tendencycompared to the incremental of con�ning pressure.

The relationship between the volumetric strainat failure ("v)0:15 and the reference crushing stressis shown in Figure 13. The volume strain at failure("v)0:15 is de�ned as the value of volumetric stain "vwhen the axial strain is 0.15 in this study. The decreas-ing tendency of volumetric strain at failure is predictedwith the increasing reference crushing stress pc. Thevolumetric strain at failure increases as the con�ningpressure becomes large. The increasing tendency ofvolumetric strain at failure ("v)0:15 becomes slowercompared to the increment of con�ning pressure.

4. Relationship between the reference crushingstress and the yield stress in onedimensional compression test

One dimensional compression test is commonly per-formed to examine the crushing characteristics of sand

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Figure 14. The yield stress (�v)y in the compressioncurve of one dimensional compression test for silicasand [15].

for simplicity. The compression curve always displaysthe obvious yield point as the applied vertical stressis increased on silica sand as shown in Figure 14.The yield point is related to the threshold stressfor particle crushing when subjected to not only theone dimensional compression but also the isotropicpressures. The curve almost becomes the straight lineafter the yield point. The stress on the vertical stressaxis in corresponding to the yield point is called theyield stress (�v)y.

To examine the relationship between the referencecrushing stress in triaxial compression test and thatin one dimensional compression test, the referencecrushing stress pc and yield stress (�v)y on the loga-rithmic plot for �ve kinds of granular material expressa linear relationship in Figure 15. The same sandspecimens are prepared in both triaxial compressiontest and one dimensional compression test. The

Figure 15. Relationship between yield stress (�v)y in onedimensional compression test and reference crushing stresspc in constitutive model.

Table 3. Reference crushing stress, pc, and the yieldstress, (�v)y, in one dimensional compression for sand [15].

Name of sandReference

crushing stresspc (MPa)

Yield stress(�v)y(MPa)

Silica sand (0.18-2.0 mm) 2.040 11.20

Aio sand 1.220 5.26

Chiibishi sand 0.965 3.26

Toyoura sand 5.850 17.46

Masado 0.412 2.23

specimens used for the triaxial compression test andone dimensional compression test are prepared at thesame initial relative density. The values for thesetwo kinds of crushing stresses are listed in Table 3.The yield stresses for �ve kinds of sand in one di-mensional compression test are measured by Nakataet al. [12]. It is seen that the reference crushingstress pc is smaller than the yield stress (�v)y in onedimensional compression test for the same kind sand. Itis explained that the signi�cant shear stress in triaxialcompression test causes the particle to be crushed inearly time at relative low stress level. It is shownthat the reference crushing stress pc and the yieldstress (�v)y are the minimum for the Masado andmaximum for the Toyoura sand. The di�erence of thereference crushing stress pc for di�erent kinds of sandis basically dependent on the mineral composition ofmaterial. The main reason for the di�erence between(�v)y and pc is that reference crushing stress pc doesnot represent the actual crushing stress in triaxialcompression test but a strength parameter a�ecting thefailure state curve during the entire loading process.It is well known that the crushing failure of grain isgreatly a�ected by the con�ning pressure in triaxialcompression test. While the con�ning pressures in theone dimensional compression test is proportional to thevertical stress. The crushing of sand grains in onedimensional compression test is mainly resulted fromthe compressive stress among particles. It indicatesthat the reference crushing stress could be applied asone strength index for sand in triaxial compression testjust as the yield stress in one dimensional compressiontest. Meanwhile, the reference crushing stress couldbe estimated based on the experienced relationshipestablished in Figure 15.

5. Conclusions

The constitutive model with reference particle crushinghas been applied to predict the mechanical behaviorof high and medium crushable sand. The constitutivemodel can predict the dilatancy from negative topositive at low con�ning pressure and only the negative

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dilatancy at high con�ning pressure. To investigate thee�ect of reference crushing stress, pc, on the mechanicalbehavior of sand, a series of parametric study onpc for Cambria sand is conducted. The variationsin stress ratio and dilatant ratio at failure are alsodiscussed in consideration of the in uences of referencecrushing stress and con�ning pressure. pc is not thespeci�c ultimate strength of the particle when particlecrushing occurs in triaxial test but is dependent on theultimate strength of a single particle to some degree inmacro viewpoint. The major �ndings of the study aresummarized below:

1. The constitutive model with reference particlecrushing is veri�ed to be applicable to a wide rangeof sand with di�erent crushability. The constitu-tive model is capable of describing the mechanicalbehavior of relative high crushable materials andexpressing the extremely large volumetric strainunder high con�ning pressure for medium crushablesand.

2. The predicted peak stress ratio increases as thereference crushing stress, pc, becomes larger at thesame con�ning pressures level. The positive dila-tancy becomes remarkable as the reference crushingstress, pc, increases. It is noted that the scopebetween the predicted maximum positive strain andmaximum negative strain is not a�ected by thereference crushing stress level.

3. The stress ratio at failure Msf signi�cantly de-creases with the increasing mean stress. Theprogressive strength reduction is explained as theparticle crushing and rearrangement. The dilatantratio increases from the negative value to positivevalue with the increasing con�ning pressure. Thedilatant ratio at failure decreases reversely as thereference crushing stress, pc, is increased.

4. The reference crushing stress, pc, for assembledgrains in macro viewpoint and the yield stress,(�v)y, in one dimensional compression test on thelogarithmic plot expresses a linear relationship for�ve kinds of sand. The di�erence of the referencecrushing stress, pc, for di�erent kinds of sand isbasically dependent on the mineral composition ofmaterial. The reference crushing stress can beestimated from the experienced equation. Thereference crushing stress, pc, could be applied asone strength index for sand in triaxial compressiontest just as the yield stress in one dimensionalcompression test.

Acknowledgments

This research is supported by the scholarship of theMinistry of Education, Culture, Sports, Science andTechnology, Japan.

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Biographies

Yang Wu, currently, is the postdoctoral fellow ofGeotechnical Engineering Laboratory at YamaguchiUniversity. He received a BS degree in Civil Engineer-ing from Shenyang Jianzhu University in 2008, MScand PhD degrees in Geotechnical Engineering fromHiroshima University in 2010 and 2013, respectively.His research interests include the constitutive model ofgranular material, numerical analysis of pile, labora-tory test on sand crushing and constitutive model ofmethane hydrate bearing sand.

Haruyuki Yamamoto received his PhD of Geotech-nical Engineering from Hiroshima University in 1982.He is, currently, the Professor at Hiroshima University.His research �eld covers a wider range of Geotech-nical Engineering. It includes development of imageanalysis of soil behavior and constitutive laws of soils,environmentally-friendly and economical methods forthe construction of foundations, static and dynamicanalysis of soil-bag.