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This study addressed the characteristics of lateral pile-soil interactions in coral sand foundation using a series of direct shear, triaxial, and model pile tests. Through the comprehensive analysis of the stress state of the coral sand around pile, it was found that the soil resistance is mainly dominated by frontal squeezing resistance. Accordingly, the framework of the modified p-y model was determined, namely the function type, exponents of depth term, and the mark of entering the plastic state. The modified p-y model adopts a normalized dimensionless form, and it is composed of the first nonlinear segment represented by the power function and the plastic state at large displacements represented by a straight line. The final p-y model was calibrated using the results of the model pile test. Subsequently, the validity of the modified p-y model was verified by the experimental results of this study and other researchers. The soil reactions and pile responses predicted by the modified p-y model were in a reasonable agreement with the measured data. Finally, the modified p-y model was compared with the existing p-y models, thus confirming its rationality and applicability. Key words: coral sand, p-y curve, direct shear test, triaxial test, model pile test, Introduction Pile foundations are commonly used to resist the lateral loads applied to structures (Luan et al. 2020a, 2020b). To date, several approaches are available to determine the behavior of [...]

Asphalt's self-healing properties demonstrate the capability to partially or even fully restore the damage caused by external loads, which could be improved using innovative modifying materials. In this study, the impact of nanoclays on asphalt performance grading (PG), complex shear modulus, and self-healing properties are investigated on a laboratory scale. The intrinsic healing phenomenon of the analyzed binders is measured using a two-piece healing test. Prepared by high shear mixing, the modified binders containing different dosages of two types of organo-modified montmorillonites were evaluated in this paper. In addition to the Superpave PG, the dispersion method's effectiveness was analyzed using a scanning electron microscope. This study indicates that nanoclays improve the high-temperature performance grade of the binder, while they do not hinder the low-temperature performance. Finally, nanoclay-modified binders showed higher shear strength and improved self- healing properties compared to the unmodified binder. Key words: nanoclay-modified asphalt, self-healing, complex shear modulus, two-piece healing test, Introduction Over 90% of paved roads in the United States and Canada are constructed using asphalt concrete (Urban and Takamura 2002; Ahmed and Hossain 2020). Climate change and the ever-increasing [...]

Fine-grained marine sediments often contain gas bubbles that can cause many geotechnical problems. This soil has a composite structure with gas bubbles fitting within the saturated soil matrix. The gas cavity has a detrimental effect on the soil stiffness and strength when they are filled with undissolved gas only. The gas cavity can be filled with gas and pore water due to 'bubble flooding'. Bubble flooding has a beneficial effect on the soil stiffness and undrained shear strength because it makes the saturated soil matrix partially drained under a globally undrained condition. A critical state constitutive model for gassy clay is presented that accounts for the composite structure of the soil and bubble flooding. The gas cavity is assumed to have a detrimental effect on the plastic hardening of the saturated soil matrix. Some of the bubbles can be flooded by pore water from the saturated soil matrix, which leads to higher mean effective stress of the saturated soil matrix. Consequently, both soil stiffness and strength increase. Only one new parameter is introduced to model the detrimental effect of gas bubbles on plastic hardening. The model has been validated by the results of three gassy clays. Key words: gassy clay, critical state, constitutive model, undrained shear strength, pore pressure. Les sediments marins a grain fin contiennent souvent des bulles de gaz qui peuvent causer de nombreux problemes geotechniques. Ce sol a une structure composite avec des bulles de gaz s'inserant dans la matrice du sol sature. La cavite gazeuse a un effet nefaste sur la rigidite et la resistance du sol lorsqu'elle est remplie uniquement de gaz non dissous. La cavite gazeuse peut etre remplie de gaz et d'eau interstitielle en raison de l'inondation des bulles. L'inondation par bulles a un effet benefique sur la rigidite du sol et la resistance au cisaillement sans drainage, car elle permet a la matrice de sol saturee d'etre partiellement drainee dans une condition globalement non drainee. Un modele constitutif d'etat critique pour l'argile gazeuse est presente, qui tient compte de la structure composite du sol et de l'inondation des bulles. La cavite gazeuse est supposee avoir un effet nefaste sur le durcissement plastique de la matrice du sol sature. Certaines des bulles peuvent etre inondees par l'eau interstitielle de la matrice du sol sature, ce qui entraine une augmentation de la contrainte effective moyenne de la matrice du sol sature. Par consequent, la rigidite et la resistance du sol augmentent. Un seul nouveau parametre est introduit pour modeliser l'effet nefaste des bulles de gaz sur le durcissement plastique. Le modele a ete valide par les resultats de trois argiles gazeuses. [Traduit par la Redaction] Mots-cles : argile gazeuse, etat critique, modele constitutif, resistance au cisaillement sans drainage, pression interstitielle., 1. Introduction Submarine soils with free gas bubbles are widely seen in the seabed throughout the world (Hong et al. 2017; Gao et al. 2020; Sultan and Garziglia 2014). Gas [...]

Fully softened shear strength mobilized in first-time slope failures, introduced by Skempton in 1970, corresponds to a random edge-face arrangement and interaction of clay particles in an entirely destructured fabric of stiff clays and clay shales. A series of triaxial compression tests was conducted on reconstituted normally consolidated specimens of 15 stiff clay and clay shale compositions. Based on the laboratory results an empirical correlation for secant fully softened friction angle, [Please download the PDF to view the mathematical expression], was developed for clay compositions with plasticity index in the range of 10%-250%, in effective normal stress range of 10-700 kPa. The laboratory measurements confirm an empirical equation for fully softened shear strength in terms of parameters [[[[phi]'.sub.fs].sup.100.sub.s] and [m.sub.fs]. The field application of secant fully softened friction angle was examined by stability analyses of 63 first-time slope failures in 38 geologic materials. These include 45 slope failures with a segment of observed slip surface at residual condition and the back-scarp mobilizing fully softened shear strength, and 18 slope failures with entire observed slip surface at fully softened condition. The back-calculated fully softened secant friction angles for first-time slope failures are in good agreement with [Please download the PDF to view the mathematical expression] correlation based on laboratory tests. Key words: fully softened shear strength, stiff clays, clay shales, first-time slope failures. La resistance au cisaillement entierement ramollie mobilisee dans les ruptures de pente initiales, mise en evidence par Skempton en 1970, repond a une disposition aleatoire des bords et a une interaction des particules d'argile au sein d'un assemblage completement destructure d'argiles rigides et de schistes argileux. On a realise un ensemble d'essais de compression triaxiale de 15 compositions d'argiles rigides et de schistes argileux sur des echantillons reconstitues et normalement consolides. Les resultats de laboratoire ont permis d'etablir une correlation empirique pour l'angle de frottement secant entierement ramolli, [Please download the PDF to view the mathematical expression] pour des compositions d'argile presentant un indice de plasticite de 10-250 %, dans une plage de contraintes normales effectives de 10-700 kPa. La recherche en laboratoire confirme une equation empirique pour la resistance au cisaillement entierement ramollie en termes de parametres [[[[phi]'.sub.fs]].sup.100.sub.s] et [m.sub.fs]. On a examine comment l'angle de frottement secant entierement ramolli peut etre applique sur le terrain en effectuant des analyses de stabilite de 63 ruptures de pente initiales dans 38 materiaux geologiques. Parmi celles-ci, 45 ruptures de pente avec un segment de la surface de glissement observee a l'etat residuel et l'escarpement arriere mobilisant la resistance au cisaillement entierement ramollie, et 18 ruptures de pente avec toute la surface de glissement observee a l'etat entierement ramolli. Les valeurs retro-calculees des angles de friction secants entierement ramollis pour les ruptures de pente initiales sont en bon accord avec la correlation [Please download the PDF to view the mathematical expression] basee sur des essais en laboratoire. [Traduit par la Redaction] Mots-cles : resistance au cisaillement entierement ramollie, argiles rigides, schistes argileux, ruptures de pente initiales., Introduction The urgent need for the introduction of fully softened shear strength (Skempton 1970) followed the Skempton (1964) recommendation of residual shear strength for the long-term stability of stiff fissured [...]

In this study, the small-strain shear modulus of a calcareous sand was investigated by conducting bender element tests on both horizontal and vertical planes. The effects of sample preparation method, stress path and stress history on the developing of void ratio, the parameters in the modified Hardin Equation, and the stiffness anisotropy were examined. The test results show that the moist tamping samples have the least void ratio variation among the five samples. The void ratio recovery in effective horizontal stress [[sigma]'.sub.h] = 100 kPa tests is higher than that in the effective vertical stress [[sigma]'.sub.v] = 100 kPa tests. The samples prepared in the dry state have lower stiffness than those prepared in the moisture state, which is not influenced by the anisotropic stress state. The stiffness anisotropy induced by the sample preparation method is significant under anisotropic consolidation. In [[sigma]'.sub.h] = 100 kPa tests, the stiffness ratios at the end of the unloading stage are lower than the initial values at the loading stage, which is not found in the [[sigma]'.sub.v] = 100 kPa tests, meaning that the stress history and stress path could affect the stiffness anisotropy and eliminate the impact of fabric anisotropy. Key words: small-strain shear modulus, anisotropic consolidation, bender element, stiffness anisotropy, sample preparation method. Au cours de la presente recherche, on a etudie le module de cisaillement a petite deformation d'un sable calcaire en realisant des essais sur elements flexibles dans des plans horizontaux et verticaux. La methode de preparation des echantillons, la trajectoire et l'historique des contraintes ont ete examinees pour determiner le taux de vide, les parametres de l'equation de Hardin modifiee et l'anisotropie de la rigidite. Selon le rapport d'essai, les echantillons de bourrage humide presentent la plus faible variation du taux de vide parmi les cinq echantillons. Le rapport de vide recupere dans les essais a contrainte horizontale effective [[sigma]'.sub.h] = 100 kPa est plus eleve que dans les essais a contrainte verticale effective [[sigma]'.sub.v] = 100 kPa. De plus, les echantillons prepares a l'etat sec presentent une rigidite plus faible que ceux prepares a l'etat humide, independamment de l'etat de contrainte anisotrope. Sous une consolidation anisotrope, la methode de preparation des echantillons induit une anisotropie de la rigidite significative. Au cours des essais [[sigma]'.sub.h] = 100 kPa, les rapports de rigidite a la fin de la phase de dechargement sont inferieurs aux valeurs initiales de la phase de chargement, ce qui n'est pas le cas dans les essais a [[sigma]'.sub.v] = 100 kPa, indiquant que l'historique et la trajectoire des contraintes pourraient affecter l'anisotropie de la rigidite et eliminer l'impact de l'anisotropie du tissu. [Traduit par la Redaction] Mots-cles : module de cisaillement a faible deformation, consolidation anisotrope, element de flexion, anisotropie de la rigidite, methode de preparation des echantillons., Introduction Small-strain shear modulus G0 is an important mechanical parameter in geotechnical engineering, reflecting the deformation resistance of soil subjected to static and dynamic small-amplitude shear loadings. The factors affecting [...]

A series of direct simple shear (DSS) tests were carried out on a non-plastic sandy silt lead-zinc-silver tailings to develop a relationship between undrained shearing behaviour and density for contractive states. The critical state line was also obtained through triaxial compression tests to enable the DSS tests to be viewed in a critical state framework and allow comparison with in situ testing. It was found that the gravimetric water content (GWC) used to tamp the specimens had a significant effect on the resulting undrained strengths when attempting to achieve dense states--with higher GWC giving lower strength at a given density than a lower GWC. Intact and slurry deposited (SD) samples were also tested to access denser states without inducing tamping-related stresses. These showed a more consistent trend with the loose-tamped specimens, and with other data from the literature. Plausible explanations as to the causes of the increased strength of dense-tamped samples were obtained through estimating potential preconsolidation stresses and 'locked in' horizontal stresses that may occur from dense tamping. The importance of these observations on the development of density-strength profiles in engineering practice was outlined. Key words: laboratory testing, sample preparation, shear strength, mine tailings. Une serie d'essais de cisaillement simple direct (DSS) a ete realisee sur des residus de plomb-zinc-argent limoneux non plastiques afin de developper une relation entre le comportement de cisaillement non draine et la densite pour les etats de contraction. La ligne d'etat critique a egalement ete obtenue par des essais de compression triaxiale afin de permettre aux essais DSS d'etre consideres dans un cadre d'etat critique et de permettre une comparaison avec les essais in situ. Il a ete constate que la teneur en eau gravimetrique (TEG) utilisee pour tasser les specimens avait un effet significatif sur les resistances non drainees resultantes lorsqu'on tente d'obtenir des etats denses--une TEG plus elevee donnant une resistance plus faible a une densite donnee qu'une TEG plus faible. Des echantillons intacts et deposes en boue (SD) ont egalement ete testes pour atteindre des etats plus denses sans induire de contraintes liees au compactage. Ces echantillons ont montre une tendance plus coherente avec les specimens non tasses et avec d'autres donnees de la litterature. Des explications plausibles quant aux causes de l'augmentation de la resistance des echantillons compactes ont ete obtenues en estimant les contraintes potentielles de preconsolidation et les contraintes horizontales << verrouillees >> qui peuvent se produire lors d'un compactage dense. L'importance de ces observations sur le developpement des profils densite-resistance dans la pratique de l'ingenierie a ete soulignee. [Traduit par la Redaction] Mots-cles : essais en laboratoire, preparation des echantillons, resistance au cisaillement, residus miniers., Introduction The direct assessment of tailings properties from in situ test data such as the cone penetration test (CPT) presents a number of challenges in current engineering practice. For example, [...]

The wheel tracking test (WTT) has been extensively used for laboratory characterization of permanent deformation of hot mix asphalt (HMA). However, the fully-confined setup of the device is unable to capture the tertiary zone where shear deformation takes place. This makes the permanent deformation resistance characteristics of HMA difficult to analyze. Hence, a modified wheel tracker (MWT), with unconfined lateral sides along the wheel tracking direction was utilized in this study, which can capture the tertiary flow (referred to as the flow number (FN)). The dynamic creep test, which yields FN, is a common laboratory test which has the ability to characterize permanent deformation considering the shear behavior. The study investigated the relationship of the MWT and the dynamic creep test utilizing the permanent deformation and permanent microstrain data from the respective tests. A novel parameter, FN-Index was explored. The permanent deformation parameters derived from the MWT were well correlated with the dynamic creep test. The MWT showed promising repeatability for the FNs. Key words: wheel tracker, permanent deformation, dynamic creep, flow number (FN), FN Index. L'essai a l'orniereur a ete largement utilise pour la caracterisation en laboratoire de la deformation permanente de l'asphalte melange a chaud (<>). Toutefois, la configuration entierement confinee du dispositif ne permet pas de capturer la zone tertiaire ou la deformation par cisaillement a lieu. Cela rend les caracteristiques de resistance a la deformation permanente de HMA difficiles a analyser. Par consequent, un orniereur modifie (OM), avec des cotes lateraux non confines le long de la direction de l'orniereur et qui peut capturer le flux tertiaire (appele le numero de flux (<>), a ete utilise dans cette etude. L'essai de fluage dynamique, qui donne le FN, est un essai de laboratoire commun qui a la capacite de caracteriser la deformation permanente en tenant compte du comportement de cisaillement. L'etude a examine la relation entre l'OM et l'essai de fluage dynamique en utilisant les donnees de deformation permanente et de microdeformation permanente des tests respectifs. Un nouveau parametre, l'indice FN, a ete explore. Les parametres de deformation permanente derives de l'OM etaient bien correles avec le test de fluage dynamique. L'OM a montre une repetabilite prometteuse pour les FN. [Traduit par la Redaction] Mots-cles: orniereur, deformation permanente, fluage dynamique, numero de flux (<>), indice FN., 1. Introduction Permanent deformation in the form of rutting is a common mode of failure in flexible pavements (Abed and Al-Azzawi 2012). While the stress conditions and the pavement layer [...]

The authors would like to thank the discussers for their interest in our paper (Ng et al. 2021). They questioned the reliability of the measured damping ratio (D) and shear [...]

The authors conducted an experimental study to investigate the influence of sesquioxide composition of unsaturated compacted lateritic soils on the shear modulus (G) and damping ratio (D) using a Drnevich [...]

The rheological properties of cellulose diacetate (CDA) with different intrinsic viscosity (IV) and different concentration in acetone solutions were studied at low and high shear rates. The zero-shear viscosity increased and the structural index increased, when the IV of CDA was increased or the acetone solution concentration was increased. Evidence suggested that a sulfate structure may be forming. It is shown that the increase of hemicellulose and sulfur content is associated with an increase of chain entanglements between CDA molecules and the abnormal increase of solution zero-shear viscosity. At a high shear rate, the correlation curve between inlet pressure drop and solution concentration obtained by Bagley method analysis shows an inflection point, which appears to be the critical concentration at which the cellulose diacetate molecular chains in the solution form a long range entangled elastic network. After the concentration exceeds a certain range of above critical points, the entanglement of the molecular chains in the solution is significantly enhanced. The zero shear viscosity inflection point concentration calculated by the rheological curve with low shear velocity and the inlet pressure drop inflection point concentration calculated by the capillary rheological calculation have good consistency. KEYWORDS cellulose diacetate, chain entanglement, solution rheology, 1 | INTRODUCTION The properties of polymer materials can affect the rheological properties of the solution, including viscosity, non-Newtonian index, etc. Viscosity is a measure of the internal friction of [...]

The risk posed by seabed instability is of increasing significance as offshore activities including oil and gas developments continue to expand in this century. Many studies have considered runout of debris flows resulting from submarine landslides and potential impact on offshore infrastructure. However, initiation of slab failure resulting from shear band propagation (SBP) at the onset of a landslide has received less attention, although it is of key importance for estimating the scale and consequences of landslides. The present paper explores arrest of SBP as well as global slab failure above the shear band. The complete evolution of a submarine landslide from shear band initiation, propagation, slab failure, and arrest of SBP is observed through large-deformation finite element (LDFE) modelling. Governing equations for both dynamic and quasi-static SBP are established and solved, with results showing good agreement with the LDFE results. Lower limits for the final shear band length and for global slab failure are proposed for cases with high strain-rate dependency of shear strength, where shear band propagation is quasi-static; upper limits are proposed for cases without rate effects where the behaviour is dynamic. Key words: failure, landslides, shear strength, slopes, offshore engineering. Les risques poses par l'instabilite des fonds marins sont de plus en plus importants, car les activites d'exploitation de mer, y compris les developpements petroliers et gaziers, continuent de prendre de l'ampleur au cours de ce siecle. De nombreuses etudes ont pris en compte le debordement des coulees de debris resultant des glissements sous-marins et l'impact potentiel sur les infrastructures d'exploitation de mer. Cependant, l'initiation de la rupture de la plaque resultant de la propagation de la bande de cisaillement (PBC) au debut d'un glissement a recu moins d'attention, bien qu'elle soit d'une importance capitale pour estimer l'echelle et les consequences des glissements. Le present article explore l'arret de la PBC ainsi que la rupture de la plaque globale au-dessus de la bande de cisaillement. L'evolution complete d'un glissement sous-marin a partir de l'initiation de la bande de cisaillement, de la propagation, de la rupture de la plaque et de l'arret de la SBP est observee grace a une modelisation par elements finis de grandes deformations (<< LDFE >>). Les equations determinantes pour la PBC dynamiques et quasi statiques sont etablies et resolues, les resultats montrant un bon accord avec les resultats par LDFE. Des limites inferieures pour la longueur finale de la bande de cisaillement et pour la rupture globale de la plaque sont proposees pour les cas ou la vitesse de deformation depend fortement de la resistance au cisaillement, ou la propagation de la bande de cisaillement est quasi statique; des limites superieures sont proposees pour les cas sans effets de taux lorsque le comportement est dynamique. [Traduit par la Redaction] Mots-cles: echec, glissements, resistance au cisaillement, pentes, ingenierie d'exploitation de mer., Introduction Instability of submarine or subaqueous slopes is ubiquitous throughout the world, including much studied examples such as the giant Storegga landslide that occurred 8200 years ago in the North [...]

A series of undrained monotonic and cyclic triaxial tests were performed on silica sand at two initial densities and different confining pressures from 0.1 to 5 MPa to investigate their shear response and crushing behaviour. The influence of particle crushing on the undrained shear strength and pore-water pressure was examined. To clarify the evolution of particle crushing, undrained monotonic and cyclic tests were terminated at several distinctive stages and sieving analysis tests were subsequently performed on the tested specimens. In the undrained monotonic test, specimens exhibited remarkable dilation behaviour and experienced no apparent particle crushing at low confining pressures. An increase in the mean stress suppressed the dilatancy due to a faster increase of the pore-water pressure, giving rise to the occurrence of particle crushing. In the undrained cyclic test, a higher confining pressure and cyclic stress ratio resulted in a much higher relative breakage. At a specific cyclic stress ratio, the relative breakage increased as the cyclic loading progressed. The confining pressure and shear strain amplitude played a significant role in controlling the evolution of particle breakage. The correlation between the relative breakage and plastic work for specimens under isotropic consolidation, undrained monotonic, and cyclic loadings has been validated experimentally. Key words: undrained shear behaviour, particle crushing, phase transformation state, cyclic stress ratio, plastic work. Une serie d'essais triaxiaux monotones et cycliques non draines ont ete effectues sur du sable de silice a deux densites initiales et differentes pressions de confinement de 0,1 a 5 MPa, pour etudier leur reponse au cisaillement et leur comportement d'ecrasement. L'influence des particules de broyage sur la resistance au cisaillement et de pression de l'eau interstitielle a ete examinee. Pour clarifier revolution du broyage des particules, des essais monotones et cycliques non draines ont ete executes a plusieurs etapes distinctes et des essais d'analyse de tamisage ont ensuite ete effectues sur les echantillons testes. Dans l'essai monotone non draine, les echantillons presentaient un comportement de dilatation remarquable et n'ont eprouve aucun ecrasement de particule apparent a des pressions de confinement faibles. Une augmentation de la contrainte moyenne a supprime la dilatance due a une augmentation plus rapide de la pression de l'eau interstitielle, ce qui donna lieu a l'apparition de broyage de particules. Dans l'essai cyclique non draine, une pression de confinement et le rapport cyclique de contrainte superieurs ont conduit a un rapport de rupture beaucoup plus eleve. A un rapport specifique de contrainte cyclique, la rupture relative a augmente alors que le chargement cyclique a progresse. La pression de confinement et l'amplitude de cisaillement de deformation ont joue un role important dans le controle de revolution de la rupture des particules. La correlation entre la rupture relative et le travail plastique pour les echantillons sous la consolidation isotrope, les chargements monotones et cycliques non draines avaient ete valides experimentalement. [Traduit par la Redaction] Mots-cles: comportement au cisaillement, particules de broyage, etat de transformation de phase, rapport cyclique de stress, travail plastique., Introduction Particle crushing of granular material has attracted many researchers in the past half century (Vesic and Clough 1968; Miura and O-Hara 1979; Miura et al. 1984; Hardin 1985; Hagerty [...]