Cyclic Deviator Stress Research Articles

Dynamic characteristics of compacted landfill waste material from cyclic triaxial tests

This study conducted a series of cyclic and monotonic triaxial tests on reconstituted landfill waste material from a closed landfill site in Sydney, Australia, to assess its dynamic behaviour under various testing conditions. Specifically, the effects of cyclic deviatoric stress, loading frequency, and effective confining stress on the cumulative plastic axial strain, resilient modulus, and damping ratio under undrained cyclic loading conditions were investigated. Results indicated that the plastic deformation, resilient modulus, and material damping are significantly influenced by dynamic stress and confining stress, with a lesser impact from loading frequency. Notably, as the number of loading cycles increased, the cumulative plastic axial strain and resilient modulus exhibited an increase, whereas the damping ratio decreased. Furthermore, increasing cyclic deviatoric stress led to an increase in both cumulative plastic axial strain and damping ratio, while an increase in confining stress resulted in a decrease in these parameters. Conversely, the resilient modulus showed an increase with rising cyclic deviatoric stress and confining stress. The influence of loading frequency on cumulative plastic axial strain and resilient modulus was minor, and its effect on the damping ratio was rather negligible. The study observed that initial loading cycles caused rearrangement and reorientation of waste components and the mobilisation of fibres with tensile forces as loading progressed, suggesting that these landfill waste samples behaved comparably to fibrous soil with randomly distributed fibres. Through nonlinear regression analysis, an empirical relationship for cumulative plastic axial strain incorporating cyclic deviatoric stress, confining stress, number of cycles, and frequency was derived. This research contributes valuable insights into the behaviour of compacted landfills as railway subgrades, providing a foundation for informed decision-making in the design of transport infrastructure over closed landfill sites.

Investigation on shakedown response-behavior of thawed subgrade soils under long-term traffic loading

The shakedown state of the subgrade is crucial for the sustainable design and long-term stability evaluation of pavement structures. In order to characterize the plastic deformation and shakedown behavior of subgrade soil in seasonal frozen regions, cyclic triaxial tests were conducted on the thawed subgrade soil after seven cycles of freeze-thaw. The influences of the numbers of cycle loading, the amplitude of cyclic deviator stress, and the confining stress were considered variables. The evolution features of accumulative plastic strain, accumulative plastic strain rate, and critical dynamic stress were experimentally analyzed. Based on the shakedown theory, the ensuing discoveries were that the accumulative plastic strain response-behavior of thawed subgrade soil was typically divided into plastic shakedown, plastic creep, and incremental collapse under the long-term cyclic loading. Furthermore, the shakedown standard for thawed subgrade soil was also proposed based on the evolution of the accumulative plastic strain rate. The critical dynamic stresses can be obtained by the proposal formula to determine the different plastic deformation ranges.

Strength, deformation, and environmental impact assessment of cement stabilized mine overburden soil

Mine haul roads are the unpaved roads that are constructed from the overburden materials obtained from the mining operations and are used for the movement of heavily loaded dumpers and trucks. The haul roads constructed from this overburden material shows continuous distress in the form of over ruts, potholes, and shear failures, creating major issues in the movement of dumpers. In the present research study, an experimental investigation was conducted based on mechanistic empirical design to evaluate the strength-deformation characteristics, durability, and environmental emissions of cement stabilized overburden soil of a local mine. The unconfined compression tests were conducted at cement dosages varying from 1 to 6% of dry soil mass and increase in the unconfined compressive strength were examined at different intervals of time until 28 days of the curing period. In the case of static triaxial tests, the enhancement in undrained shear strength and elastic modulus of stabilized specimens was determined in comparison to the untreated specimens, whereas in cyclic triaxial tests, the reduction in permanent deformations and increase in resilient modulus were evaluated under different confining pressures and cyclic deviatoric stresses. An empirical model has been proposed to predict the long-term rutting of overburden under repeated loading. The proposed model is based on the behaviour of various parameters, such as applied cyclic deviatoric stress, number of load repetitions, loading frequencies, and on the permanent deformation characteristic of mine overburden soil. In addition, durability and environmental sustainability aspects of the treatment has also been studied to determine the optimal dose of cement.

Effect of Moisture Content on the Permanent Strain of Yellow River Alluvial Silt under Long-Term Cyclic Loading

The Yellow River alluvial silt has unique engineering properties and is unstable when encountering moisture. The mechanical properties of silt subgrade can be impaired by the increase in moisture content due to rainwater infiltration, which has a negative effect on traffic safety. To further reveal the influence of moisture content on the deformation characteristics of silt, a series of monotonic and cyclic triaxial tests were conducted on the alluvial silt with different moisture contents. The development law of cyclic accumulative permanent strain and the effects of moisture content, cyclic deviator stress and confining pressure on the axial permanent strain of silt were explored. The study shows that the static strength of silt decreases with the increase in moisture content, and the attenuation of static strength is mainly caused by the decrease in cohesion due to the reduction in matric suction. The permanent strain rises linearly with the increase in moisture content and cyclic deviator stress, and decreases with the increase in confining pressure. An empirical model for predicting the permanent strain of silt under long-term cyclic loading considering the effect of moisture content was established. Compared with the test data and other existing models, the established model has easier obtained parameters, higher prediction accuracy and better applicability.

Effect of variable confining pressure on the long-term cyclic behaviour of calcareous sand: experimental observation and microstructural interpretation

Subgrade soils are exposed to simultaneous cyclic deviatoric stress and variable confining pressure (VCP) caused by traffic loading. However, the effect of VCP on cyclic behaviour is still debated and no attempt was made to investigate its effect on calcareous sand. In this study, high-cyclic triaxial tests with a wide range of mean effective stress, cyclic stress ratio ( ζ), and VCP amplitude were conducted to understand the effect VCP on the long-term cyclic behaviour of calcareous sand. The results demonstrate that VCP has a considerable effect on the accumulated axial strain ([Formula: see text]) and shakedown behaviour of calcareous sand, both of which depend greatly on the stress levels. At a low ζ, the effect of VCP on the [Formula: see text] and plastic shakedown behaviour is insignificant, where the application of VCP tends to slightly promote the [Formula: see text]. However, at a high ζ, [Formula: see text] decreases significantly with an increase in the VCP amplitude. For different ζ, the damping ratio increases and resilient modulus decreases significantly as VCP amplitude increases. Moreover, microscopic observations of pore size distribution were obtained through nuclear magnetic resonance tests, and were analysed to discover the microstructural mechanism highlighting how VCP affects cyclic behaviour.

Assessment of cyclic deformation and critical stress amplitude of jointed rocks via cyclic triaxial testing

Jointed rock specimens with a natural replicated joint surface oriented at a mean dip angle of 60° were prepared, and a series of cyclic triaxial tests was performed at different confining pressures and cyclic deviatoric stress amplitudes. The samples were subjected to 10,000 loading-unloading cycles with a frequency of 8 Hz. At each level of confining pressure, the applied cyclic deviatoric stress amplitude was increased incrementally until excessive deformation of the jointed rock specimen was observed. Analysis of the test results indicated that there existed a critical cyclic deviatoric stress amplitude (i.e. critical dynamic deviatoric stress) beyond which the jointed rock specimens yielded. The measured critical dynamic deviatoric stress was less than the corresponding static deviatoric stress. At cyclic deviatoric stress amplitudes less than the critical dynamic deviatoric stress, minor cumulative residual axial strains were observed, resulting in hysteretic damping. However, for cyclic deviatoric stresses beyond the critical dynamic deviatoric stress, the plastic strains increased promptly, and the resilient moduli degraded rapidly during the initial loading cycles. Cyclic triaxial test results showed that at higher confining pressures, the ultimate residual axial strain attained by the jointed rock specimen decreased, the steady-state dissipated energy density and steady-state damping ratio per load cycle decreased, while steady-state resilient moduli increased.

Investigation on crushing behavior and cumulative deformation prediction of slag under cyclic loading

This investigation aims to explore the crushing behavior and cumulative deformation of slag under cyclic loading by both cyclic triaxial simulation tests through PFC5.03D and in-situ vibration tests. The particle crushing index Kg was proposed to characterize the evolution of particle crushing of slag. The negative exponential Mechanics-Empirical model (M-E) was summarized to predict the cumulative deformation of slag and validated by in-situ vibration tests. Three crushing types for slag particles are observed: rupture, breakage, and surface grind, respectively. The Kg increases with increasing confining pressure, frequency, and cyclic deviatoric stress. The Kg exhibits a linear correlation with the accumulated strain under the same confining pressure, and the confining pressure would inhibit the accumulated strain. The rebound modulus of slag decreases with the dynamic strain. The normal contact force mainly exists in the vertical direction under various loading settings, and the maximum rotates toward the axial direction with the increasing cyclic deviatoric stress. The trend of the settlement predicted by the M-E model is similar to that of the measured by the vibration test, but the prediction is more conservative on the safe side than that measurement.

Postcyclic Stiffness Behaviors of Laterite Clay under Various Conditions

The changes in mechanical behaviors of soils after cyclic loading will lead to the generation of additional settlements. The postcyclic stiffness characteristics of soils are usually analyzed by using conventional cyclic triaxial tests, in which only cyclic deviator stress is applied under undrained conditions; however, the cyclic variations of both axial stress and horizontal stress under traffic loading were observed. Moreover, the pore water was permitted to drain under cyclic loading. Therefore, cyclic triaxial tests under partially drained conditions were performed to investigate the postcyclic stiffness characteristics of remolded laterite clay. The influences of variables, such as the cyclic deviator stress, number of cycles, cyclic confining pressure, and degree of reconsolidation, were evaluated. The postcyclic elastic modulus increases as the cyclic deviator stress, number of cycles, and degree of reconsolidation increase, while it decreases as the cyclic confining pressure increases. Nevertheless, the ratio of the postcyclic elastic modulus with and without cyclic confining pressure decreases as the cyclic confining pressure increases; the postcyclic elastic modulus ratio of the degree of reconsolidation to without reconsolidation increases linearly with the increasing degree of reconsolidation. Based on the result, an empirical formula for the postcyclic elastic modulus, considering the effects of both cyclic confining pressure and the degree of reconsolidation, was proposed. The predicted results match the measured data well, indicating that the formula is valid for the prediction of the postcyclic elastic modulus of laterite clays after cyclic loading.

Partially-drained deformation properties of anisotropically overconsolidated clay by triaxial tests with cyclic confining pressure

The subgrade clay in situ may be anisotropically overconsolidated, the traffic-induced dynamic stress field on the subgrade clay can be simulated more accurately by the simultaneous application of cyclic axial stress and cyclic confining pressure by the VCP test, and the partially drained condition represents a more appropriate field scenario for the cyclic response of subgrade clays under long-term traffic loading. To mimic the coupling of the above factors, this study performed a large number of cyclic triaxial tests on a overconsolidated clay in partially drained condition. The ratio of the radial consolidation stress to vertical consolidation stress (K), cyclic stress ratio (CSR) and the ratio of cyclic deviatoric stress amplitude to cyclic mean principal stress amplitude (ηampl) are proposed, and their effects on the partially-drained permanent and resilient deformation behaviors of saturated clay are investigated. Test results show that the increase of consolidation-induced anisotropy (i.e., the decrease of K) leads to a remarkable increase of permanent axial strain, while it induces a first slight growth and then a decrease of permanent volumetric strain. Based on the shakedown theory, the allowable cyclic stress ratio separating the shakedown ranges of metastable and stable is determined, and it is unrelated to either K or ηampl. The effects of ηampl on the permanent axial strain are related to the shakedown range, and a uniform linear relationship is established between the permanent volumetric strain and cyclic mean principal stress amplitude. The anisotropically overconsolidated clay produces stiffness hardening in partially drained condition, in which the increase of both CSR and ηampl promote the hardening. It is suggested the prediction and control of subgrade clay settlement in engineering practice should consider all the factors involved in this study.

Influence of cyclic deviator stress and consolidation degree on permanent strain of “under-consolidated” marine sediment

Rapid rates of clay sedimentation produce a highly hazardous marine foundation condition: “under-consolidated” marine sediments. Numerous traffic infrastructure facilities have been constructed on this type of clay. In this study, a series of original cyclic oedometer tests were performed to investigate the drained long-term permanent strain of soft marine clays. The stress–strain relationships and permanent strain accumulations of the clay specimens were evaluated and compared under different cyclic stress ratios (CSR s) and consolidation degrees (U s). First, when CSRs increased, the total strain also increased; however, its rate of increase decreased at higher CSR values. Thereafter, we derived a new threshold value as the upper boundary of the CSR for pavement designs on soft clay foundations. When the CSR was below this threshold value, the accumulated permanent strain increased rapidly with an increase in the CSR; when the value was surpassed, the strain accumulated slowly and was approximately linear as the CSR increased. Finally, equations for predicting the long-term permanent strain of under-consolidated clays were established. The findings of this study will serve as a useful technical reference for researchers and engineers in the field of land reclamation, thereby helping ensure the safety and durability of current and future public infrastructure facilities constructed on such lands.

Experimental investigation for vibration characteristics of jointed rocks using cyclic triaxial tests

Jointed rock specimens with planar, sawtooth and natural replicated joint types with a dip angle of 60° were prepared, and a series of cyclic triaxial tests were performed at different confining pressures and cyclic deviatoric stress amplitudes subjected to 10,000 loading cycles to evaluate their effect on dynamic properties of the jointed rock specimen. Analysis of the test results indicated that the level of confining pressure and cyclic deviatoric stress amplitude along with the type of the joint had a significant influence on the dynamic characteristics of the jointed rock samples. With increasing confining pressure, the maximum residual axial strain attained decreased, while they increased with cyclic deviatoric stress amplitude for all the joint types. Jointed rock specimens subjected to cyclic loading responded with higher resilient moduli at higher confining pressures, while increasing cyclic deviatoric stress amplitude resulted in reduced resilient moduli. Furthermore, a higher confining pressure corresponded to a lower dissipated energy and damping ratio, while a higher cyclic deviatoric stress amplitude corresponded to a higher dissipated energy and damping ratio. With increasing number of cycles, the residual axial strains attained by the samples showed an increasing trend, especially during the initial phase of deformation. The resilient moduli illustrated a decreasing trend with number of cycles whereas dissipated energy and damping ratio showed a prompt decreasing trend within the first few cycles and then stabilised for all the joint types. Empirical relationships for the steady state resilient moduli and steady state damping ratio were developed through nonlinear regression analysis which incorporated the influence of confining pressure, applied cyclic deviatoric stress amplitude, shear strength and joint friction angle.

The effect of adding rubber crumbs on the cyclic permanent deformation of waste mixtures containing coal wash and steel furnace slag

Among the numerous studies into the dynamic loading behaviour of rubber crumbs–soil/waste mixtures, the main focus is on how the content of rubber crumbs ([Formula: see text]) affects the damping ratio, shear modulus and total deformation. However, research into the influence of [Formula: see text] on the permanent strain rate ([Formula: see text]) and the deformation mechanism under repeated loading is very limited. In the current study, the cyclic deformation response for waste mixtures of steel furnace slag (SFS), coal wash (CW) and rubber crumbs (RC) is analysed and the test results reveal that [Formula: see text] has a significant influence on the initial [Formula: see text] and the slope of the permanent axial strain rate line, whereas cyclic deviator stress ([Formula: see text]) mainly affects the initial [Formula: see text]. The influence of [Formula: see text] and [Formula: see text] on the [Formula: see text] value of the waste mixture is incorporated in an empirical model, which enables prediction of the permanent deformation mechanism of SFS + CW + RC mixtures with wider-ranging amounts of RC and higher cyclic deviator stresses.

Effectiveness of a Geocomposite-PVD system in preventing subgrade instability and fluidisation under cyclic loading

Instability of subgrade soil sometimes associated with soil fluidisation can lead to uncontrollable deformation and failure at a critical number of loading cycles for a given cyclic deviator stress and frequency. Although numerous laboratory experiments on the performance of Prefabricated Vertical Drains (PVDs) and geocomposites have already been carried out in the past, how effectively this combination can mitigate the potential for subgrade fluidisation under repeated (cyclic) loading is still not properly understood. The primary objective of this paper is to evaluate the integrated role of PVDs and geocomposite in preventing subgrade fluidisation using Dynamic Filtration Apparatus (DFA). Laboratory experiments show that the continuous dissipation of EPWP and the substantial reduction in drainage path lengths by PVDs can prevent subgrade fluidisation at shallow depths, while geocomposite can provide adequate surficial drainage and effective confinement at the ballast/subgrade interface. By measuring the Excess Pore Pressure Gradients (EPPGs) during cyclic loading, the test results convincingly reveal the promising performance of PVD-geocomposite combination under different loading conditions.

Post-cyclic mechanical behaviors of laterite clay with different cyclic confining pressures and degrees of reconsolidation

The post-cyclic mechanical behaviors of subgrade soil are usually assessed by conventional cyclic triaxial tests, however, the stress field induced by traffic loads consist of not only a cyclic deviator stress, but cyclic confining pressure and shear stress. Meanwhile, the pore water is allowed to be discharged under traffic loads. Furthermore, the traffic load-induced excess pore water pressure can be partially dissipated after load-cycling. Thus, different reconsolidation processes should be considered. Recognising this, cyclic loading with variable confining pressure was applied to remoulded laterite soils under partially drained conditions, and reconsolidation was allowed. The development of effective stress paths, excess pore water pressure, and undrained strength of post-cyclic shear process were analysed. Results show that the development of effective stress paths is similar and all stress paths cross the critical state line. Besides which, the remoulded laterite clay always has a positive excess pore water pressure and tend to dilate. The undrained strength will be increased under different conditions such that the greater the cyclic confining pressure, cyclic deviator stress, number of cycles, and degree of reconsolidation, the larger post-cyclic undrained strength. Moreover, the post-cyclic undrained strengths between cyclic loading with and without cyclic confining pressure were compared: the undrained strength ratio of cyclic confining pressure to that under constant confining pressure increases linearly with increasing slope of the stress path. Nevertheless, the post-cyclic undrained strength after reconsolidation can be obtained by the corresponding undrained strength without reconsolidation: the ratios of post-cyclic shear strength with and without reconsolidation increase with increasing degree of reconsolidation. At a certain slope of stress path, the undrained strength increases linearly with degree of reconsolidation.

Experimental study on particle breakage of carbonate gravels under cyclic loadings through large-scale triaxial tests

Carbonate gravels are often used as a road base filling material in island area. To evaluate the feasibility of carbonate gravels as a filling material, a large-diameter cyclic triaxial testing system (LDCTTS) was adopted to investigate the particle breakage and long-term behavior of carbonate gravels under high-cycle loadings (N = 50000). The effects of cyclic deviatoric stress, initial static deviatoric stress, effective confining pressure and drainage conditions on the long-term behavior of carbonate gravels were investigated. Fractal theory and Einav’s relative breakage index were applied for the analysis of particle breakage. Test results show that the accumulated axial strain of carbonate gravels increases with the increase of cyclic deviatoric stress and initial deviatoric stress. Particle breakage occurs during the cyclic loading tests, especially for coarse particles with diameter>10 mm. The relative breakage index increases linearly with the cyclic deviatoric stress and the initial deviatoric stress, while decreasing exponentially with the effective confining pressure for the stress range studied. In addition, carbonate gravels in undrained tests exhibit more crushing than drained tests due to the positive pore water pressures accumulated. Einav’s relative breakage index is found to be in an exponential relationship with the input of plastic deformation energy, which can be used to predict the particle breakage of carbonate gravels under cyclic loadings.

Resilient and permanent deformation behaviors of construction and demolition wastes in unbound pavement base and subbase applications

The reuse of construction and demolition wastes (C&D wastes) as unbound granular materials (UGMs) to construct pavement base and subbase courses is of great potential, while the cyclic behaviors of unbound C&D wastes under traffic loadings still lack the support of test data. To investigate the traffic-induced resilient and permanent deformation behaviors as well as the shear and particle breakage properties of the unbound recycled concrete aggregate (RCA) & recycled clay masonry (RCM) blends, a series of consolidated drained, resilient deformation and permanent deformation tests by a large-scale dynamic triaxial apparatus were performed. The RCM content in two blends made by different mixed methods was emphasized, and the factors of gradation, confining pressure and cyclic deviatoric stress amplitude were also taken into consideration. Test results show that RCM content makes great influences on the particle breakage, resilient modulus, permanent axial strain and shakedown behavior of unbound RCA & RCM blends, and the influences show obvious differences between the two mixed methods. The peak triaxial strength, particle breakage level and resilient modulus of blends 1 (B1) are generally larger than those of blends 2 (B2), and the influence of confining pressure and cyclic deviatoric stress amplitude on resilient modulus are related to the mixed method but unrelated to RCM content. The popular modified K-θ model is employed to predict Mr of B1 and B2, and the reference ranges of the regression coefficients with respect to RCM content are obtained. Based on the results, it is evaluated that when RCM content is below a certain extent (e.g. 30%), B1 perform better (and the best at around RCM content of 10%) as pavement base and subbase courses in regard to shear strength, resilient modulus and permanent strain. However, as the RCM content continues to increase, B2 may be better than B1 considering the overall performance of cyclic properties.

Microstructure Evolution of Saturated Clay Under Cyclic Shearing

Abstract Changes in soil microstructure are important for understanding the macro-behavior of soil. Studies in the past have mainly focused on analysing variations under isotropic and one-dimensional consolidation. The present study aims to investigate the microstructure evolution of saturated clay under cyclic shearing. Cyclic triaxial tests are carried out under different magnitudes of effective confining pressure, cyclic deviator stress, and overconsolidation ratio (OCR). The soil microstructure is determined through the scanning electron microscope and mercury intrusion porosimetry tests. It is observed that there is a threshold cyclic deviator stress, above which the soil specimens show significant plastic strain and eventually fail. The threshold value is found to increase almost linearly with the increase of effective confining pressure and OCR. On the other hand, when the cyclic deviator stress is higher than the threshold value, some large pores appear even though the total pore volume is kept constant (undrained condition under cyclic loads). With the appearance of some larger pores, the soil skeleton becomes weaker and eventually fails.

Damping ratio evolution of saturated Ningbo clays under cyclic confining pressure

The mechanical behaviours of soft clays under cyclic loading are not only related to loading parameters, but also the physical indices of soft clay. One-way cyclic triaxial tests with constant confining pressure were adopted, however, the stress field induced by traffic loads includes cyclic confining pressure and cyclic deviator stress. So far, the damping ratio evolution of soft clays under traffic loading has rarely been studied. To establish an empirical formula for the damping ratio, a series of cyclic triaxial tests with variable confining pressure were conducted on saturated Ningbo clay. The effects of some factors, such as cyclic stress ratio (CSR), effective consolidated confining pressure, loading frequency, and cyclic confining pressure were investigated. The trend of the relationship between the normalised damping ratio and accumulated axial strain is similar under different conditions, in which the normalised damping ratio degrades with the increase of accumulated axial strain. Besides, the damping ratio increases with an increase of CSR and effective consolidated confining pressure, while decreases with increasing loading frequency and cyclic confining pressure. Based on that, an empirical formula relating to CSR, effective consolidated effective confining pressure, loading frequency, and cyclic confining pressure is established to predict damping ratio under cyclic loading. A comparison between predicted results and measured data shows that the empirical formula cannot only characterise the trend of the damping ratio versus accumulated axial strain curve, but also provides a good prediction of the damping ratio.

Strain Accumulation in Soft Marine Clay due to One‐Way Cyclic Load with Variable Confining Pressure

The effect of variable confining pressure on the strain accumulation in soft marine clay was investigated to gain a better understanding of the deformation characteristic in the subgrade of pavements due to traffic loading. A series of variable confining pressure (VCP) experiments and corresponding constant confining pressure (CCP) experiments were conducted on Wenzhou soft clay using an advanced cyclic triaxial apparatus. A wide range of deviatoric stress amplitudes (qampl), combined with different isotropic stress amplitudes (pampl), and partially drained conditions are simulated in the experiments. The test results indicate that the variable confining pressure significantly influences the permanent axial strain and might exacerbate the potential of subgrade invalidation in soft marine clay area. The normalized permanent axial strain () after 1000 cycles is logarithmic with the normalized stress path length (L/LCCP), and one‐unit increment in the amplitude of cyclic confining pressure will induce an increment of 0.0213% in the permanent axial strain regardless of the CSR values. Based on the data from the CCP tests, a cyclic deviatoric stress ratio threshold is determined to be about 0.7, which may suggest that the upper bound of criterion will limit the cyclic traffic loadings on soft marine clayey deposit. Finally, the effect of variable confining pressure on the permanent axial strain is quantified and incorporated in a logarithmic model for the subsoil deformation prediction under traffic loading.

Critical State Soil Mechanics for Cyclic Liquefaction and Postliquefaction Behavior: DEM study

Discrete-element method (DEM) simulations of three-dimensional (3D) assemblies of ellipsoid particles were used to evaluate the critical state (CS) for both drained and undrained (constant volume) conditions. A series of conventional triaxial cyclic liquefaction tests with symmetrical cyclic deviatoric stress (σd) with initial q=0 kPa were simulated to develop a relationship between the cyclic stress ratio (CSR=σd/2σ0′) and the number of cycles required for initial liquefaction (NL), where σ0′ is the mean effective normal stress at the end of consolidation. Both cyclic mobility and instability type behaviors were observed depending on the initial void ratio (e0) and σ0′. The micromechanics quantities, i.e., the coordination number (CN), von Mises fabric (FvM), fabric anisotropy intensity (αc), and stress-strain behavior, suggested that cyclic mobility and instability may depend on the phase transformation and instability state, respectively. The cyclic resistance ratio (CRR15), i.e., CSR at NL=15, showed a unique relation with the initial state parameter (ψ0), irrespective of e0 and σ0′. Two series of postliquefaction monotonic simulations with and without reconsolidation exhibited a unique CS, which perfectly matched with the original CS line. The FvM also reached a unique, narrow range at the CS. The postliquefaction settlement during reconsolidation also showed a linear relation with ψ0.