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In order to analyze the stability of a landfill site, it should analyze some properties of waste introducing the main structural elements. Up to now, it has not been done much research on the properties of municipal solid waste. In addition, due to the differences in waste properties from one country to another and even from one to another landfill site, it is impossible to generalize the results. These conditions caused local research on the evaluation of static and dynamic parameters of municipal solid waste to be done. Because Iran is a seismic country, the short-term behavior of waste controls landfill sites stability during seismic loads; so it is necessary to know the dynamic behavior of these materials. In this paper, about 18 cyclic tests were performed, and in addition to determining the dynamic parameters of municipal solid waste of Tehran Kahrizak Disposal Site using cyclic triaxial test, the effect of confining stress and loading frequency on dynamic properties of these materials was evaluated. The results have shown that with increasing the confining stress and loading frequency, shear modulus and damping ratio was increased and decreased, respectively, and it is related to the composition of the municipal solid waste materials. [ABSTRACT FROM AUTHOR]

The red mudstone sediments are widely encountered in earthquake region northwestern China which is vulnerable to the occurrence of landslides. Previous studies focused on rain-induced shallow landslides. Some deep-seated landslides in red clay with a gentle inclination are still not well understood. A fatal landslide named as Zhengjiamo landslide, located in Tianshui, China, was investigated. The aim of this study was to study mechanism of shear surface development under earthquake using a series of cyclic triaxial tests. The test results of the red clay from the Zhengjiamo landslide revealed that the undrained shear strength and excess pore pressure increase with increasing confining stresses σ 3 and OCR. It is also observed that those stress–strain behaviors on the deviatoric stress, axial strain and pore water pressure, subsequent to the initial contractive response, the saturated clay exhibited dilation upon continued shearing. The dilated tendency of the clay becomes more prevalent with increasing confining stresses σ 3 and OCR during the dynamic response. The reduction of shear strength of the red clay is substantially caused by the increasing number of cycles N. Under earthquakes, the sliding zone may behave in a brittle- ductile pattern. [ABSTRACT FROM AUTHOR]

The foundations of nearshore and offshore structures are always subjected to long-term cyclic loading which is often a one-way, with low amplitude and a large number of cycles. Hence, the long-term dynamic behaviour of shoreline soils and sediments should be understood to avoid excessive deformation and liquefaction. As one of the most problematic soft soils in Melbourne, Coode Island Silt (CIS) at the northern shoreline of Port Phillip Bay contains a considerable but variable amount of sand. This paper explores the dynamic response of CIS containing different sand content subjected to a large number of cycles. To determine the liquefaction potential, and the effect of sand content on the resilient modulus and permanent strain of CIS, a series of long-term cyclic triaxial tests at a sinusoidal loading frequency of 1 Hz is performed. Based on the test results, it is found that CIS with varying sand content up to 30%, does not liquefy under the cyclic stress ratios and frequency applied in this study. Also, a sand content of 10% causes CIS to degrade more under cyclic loading. In the end, an empirical model to predict the permanent strain of CIS with a variable sand content is calibrated. [ABSTRACT FROM AUTHOR]

The present study reviews a series of cyclic triaxial tests to investigate the liquefaction characteristics of Babolsar sand reinforced with randomly distributed fibers using an energy-based approach. The effect of fiber content, fiber length, confining pressure, and relative density were studied. The test results revealed that the addition of fibers increased the number of cycles required to liquefaction, resulting in higher cumulative dissipated energy. This accounted for the higher cyclic shear resistance of reinforced sand compared to unreinforced sand. Capacity energy is defined as cumulative dissipated energy to onset of liquefaction. The test results showed that W liq was significantly affected by the fiber inclusion. Comparative studies demonstrated that energy-based method is a good way to evaluate liquefaction potential of fiber-reinforced sands. [ABSTRACT FROM AUTHOR]

Dynamic behavior of reinforced soil are evaluated relative to a number of factors including: strain level, density, number of cycles, material type, fine content, geosynthetic inclusion, saturation, and effective stress. This paper investigates the dynamic behavior of saturated reinforced sand under cyclic stress condition. The cyclic triaxial tests are conducted on remolded specimens under various cyclic stress ratios (CSR) which reinforced by different arrangement of non-woven geotextile. Aforementioned tests simulate field reinforced saturated deposits during earthquake or other cyclic loadings. This analysis revealed that the geotextile arrangement played dominant role on dynamic soil behavior and as geotextile close to top of specimen, the liquefaction resistance increased. Meanwhile, the results demonstrate that the effects of arrangement of reinforcement layers on deformation and shear modulus are considerable. [ABSTRACT FROM AUTHOR]

A series of cyclic triaxial tests were carried out to explore the accumulation behaviour of coarse-grained soil (CGS) with different initial static stress states. The test results show that more accumulated axial strain can be detected for the specimen with a higher initial stress ratio or a lower confining stress under identical cyclic loading. The plastic shakedown limits are then identified, which indicates that a higher initial stress ratio or a lower confining pressure yields a lower plastic shakedown limit. Furthermore, the stress states at the plastic shakedown limit for the soils with various initial static stress states are presented in the plane of p − q , and all data trended towards converging on a straight line, which is approximately parallel to the strength envelope. A united plastic shakedown criterion is then proposed for soils under different initial stress states, which provides a simple approach to predicting the plastic shakedown limit. • Cyclic triaxial tests are conducted to investigate the coarse-grained soil. • The influence of initial stress state on the accumulation behaviour are analysed. • The plastic shakedown limits with various initial stress states are determined. • A united criterion is proposed to describe the plastic shakedown limits of soils. • The accuracy of the criterion is validated via additional cyclic triaxial tests. [ABSTRACT FROM AUTHOR]

Correctly evaluating the membrane penetration and compliance effects in the element liquefaction test of saturated coral sand is important for test result applications. Therefore, the penetration volume measurement and triaxial cyclic liquefaction testing of saturated coral sand and quartz sand samples with the same grading and relative density were conducted for relatively loose and dense states, and the liquefaction resistance test results before and after membrane compliance correction were analyzed. The results showed that under the same conditions, the influence of the penetration and compliance of coral sand samples was more significant than that of the quartz sand samples. The general practice of ignoring the effect of membrane compliance in normal-scale triaxial tests is inapplicable in coral sand tests and will result in relatively unsafe analysis results. • Usage of ignoring compliance in element tests is not applicable to coral sand. • Compliance causes large overestimation of the liquefaction resistance of coral sand. • Membrane penetration contributes most of saturated coral sand sample volume change. • The two-scale method can be used to evaluate the coral sand sample membrane effect. • Irregular particles and high stiffness create the coral sand's large membrane effect. [ABSTRACT FROM AUTHOR]

Sand reliquefaction has gained increasing concern and attention due to the severe destruction and complex mechanical behavior, which differs significantly from virgin liquefaction. Previous strain history would form various fabrics that can affect reliquefaction resistance. Although some researchers have focused on the cyclic response of reliquefaction by laboratory and simulation tests, little investigation about the influence of fabric evolution caused by previous strains on reliquefaction was reported. Therefore, several simulation tests, considering the influence of pre-shear strains (both residual strains Δ and double amplitude of axial strain DA), were performed to investigate the macro behavior/microscopic fabrics of sand. Numerical results suggested that the influence of DA on reliquefaction resistance were mainly contributing to I R and Z a , and the effect of Δ was primary due to the evolution of a c. Finally, a new judging criterion for anisotropic fabric during reconsolidation is proposed for the sand experienced liquefaction history. [Display omitted] • Strain-history dependent cyclic behavior and micro fabrics are discussed carefully. • Influential micro parameters of strain-history on sand reliquefaction are revealed. • A new detecting criterion of anisotropic fabric during reconsolidation is proposed. [ABSTRACT FROM AUTHOR]

The mechanical behavior of artificial jointed rock samples with different joint dip angles was analysed on the basis of the results of cyclic triaxial tests with 1.0 Hz frequency under different stress amplitudes and different confining pressures. It was found that the dynamic strength decreases with increasing joint dip angles and increases with increasing confining pressures. The stress ratio (the ratio of the maximum stress of the cyclic loading to the static triaxial compressive strength) can comprehensively reflect the influences of joint dip angles, confining pressures and stress amplitudes. For all samples with different joint dip angles, confining pressures and stress amplitudes, the number of cycles at failure decreases with increasing stress ratios. And the evolutionary characteristics of the residual axial strain and residual dilatancy with loading cycles, as well as the evolution law of damages, are determined by the stress ratios. As the stress ratio changes, the evolution laws of the residual strain and the damages form three kinds of situations. A damage variable is defined using the sum of absolute values of the volumetric contraction and dilatancy, which can consider the initial fatigue damage of jointed rocks under cyclic loading and reflect laws of the dynamic damage evolution. During each loading cycle, the samples are slightly compacted and then dilate largely in the reloading stage, while dilate slightly and are largely compacted when unloading. The volumetric strain exhibits a series of significant changing rule within a cycle and with the increasing number of cycles, which contributes to reveal the mesoscopic damage mechanism in the cyclic loading condition. Finally, the confining pressure and the joint dip angle strongly influence the dynamic deformation and failure mechanism of jointed rock samples by affecting the generating of the weak zone along the joint plane and the initiation and propagation of micro-cracks. [ABSTRACT FROM AUTHOR]

Dynamic loading conditions, such as earthquakes, may result in the generation of high shear strain (>5%) in the soil. Conventionally, dynamic properties of soils are estimated from the tests conducted up to a shear strain of 1% by considering Symmetrical Hysteresis Loop (SHL). However, it is commonly observed that the hysteresis loops become progressively asymmetric with increasing shear strain, which leads to the over- or under-estimation of the conventionally evaluated dynamic properties. Hence, it is necessary to adopt a modified methodology of evaluating the dynamic properties of saturated sands based on the actual Asymmetrical Hysteresis Loop (ASHL). Strain-controlled cyclic triaxial tests have been conducted, for a peak shear strain range of 0.015–4.5% at 1 Hz loading frequency, on test specimens prepared at different relative density (30–90%) and confining stress (50–150 kPa). Although, the shear modulus evaluated considering SHL and ASHL are on close agreement, the damping ratio evaluated considering SHL is approximately 40–70% lesser than that obtained by considering ASHL. Moreover, in contrast to the classical curves as largely applied in geotechnical engineering, a noticeable decrement of the damping ratio is observed beyond 0.75% shear strain. [ABSTRACT FROM AUTHOR]

Cyclic triaxial test by means of the geotechnical digital system is conducted for the soil near the Guoquan Road Station of Metro Line 10 in Shanghai to analyze the strain characteristics and the variation law of saturated silty soil under subway loading. Orthogonal design method is used to arrange the experiment, considering the following factors: frequency ratio f , cyclic stress ratio σ , vibration time ratio N , and the interaction function among them. Results show that the cyclic stress ratio σ , the frequency ratio f , the vibration time ratio N , and the interaction between the cyclic stress ratio σ and the vibration time ratio N have a significant effect on the axial strain of the subway tunnel. The effect of the interaction between the cyclic stress ratio σ and the vibration time ratio N is also significant. From the analysis of variance and regression theory, the nonlinear regression equation of the cumulative plastic strain of silty soil under subway loading is established. Residual analysis proves that the equation is ideal and credible. The results have important value for the design of subway tunnels. [ABSTRACT FROM AUTHOR]

Once loose sand has liquefied, it becomes denser along with water drainage after liquefaction. Therefore, liquefied sand is regarded as more robust against liquefaction. Such sand after liquefaction is expected to liquefy again only slightly. Nevertheless, examples of repeated ground liquefaction have been reported during some earthquake events. Reliquefaction characteristics of saturated sandy ground must be estimated accurately with consideration of the liquefaction history related to past earthquakes. Moreover, the stress history affecting liquefaction strength must be considered. Cyclic triaxial tests were conducted to estimate the liquefaction strength ratio during and after liquefaction using specimens with a history of overconsolidation. The shear wave velocity, which is related strongly to the soil physical properties, was also measured in the same specimen. Results show that the stress history does not affect the specimen shear wave velocity despite increased liquefaction strength. The increased liquefaction strength induced by the stress history is eliminated by the liquefaction history. [ABSTRACT FROM AUTHOR]

We present empirically derived liquefaction resistance curve from a large database of measurements from published literature and also simple shear tests that were performed in this study. The data measured from simple shear and triaxial tests are separately compiled. The data are fitted with two empirical models to develop representative liquefaction resistance curves. Comparisons illustrate that the slope of the widely used power law is highly dependent on the range of data it is fitted to and that the power law underestimates the resistance at high number of cycles (N). The alternative empirical model is demonstrated to provide favorable fit with the measurement over a wide range of data. The representative curves are normalized by the equivalent number of uniform cycles for a magnitude (M) 7.5 event (N) to reduce the wide scatter of the measurements and to make it usable with liquefaction triggering charts that relate in situ parameter with cyclic resistance ratio for a M = 7.5 event. Comparison with published liquefaction resistance curves show that the proposed curve is lower at N ≤ N and higher at N > N. A single-parameter empirical exponential function that closely fits the normalized liquefaction resistance curves and representative values for its parameter are presented. We also propose an empirical equation to correct the liquefaction resistance curve measured from a triaxial test to match that from a simple shear test. [ABSTRACT FROM AUTHOR]

The engineering properties of tailings are important for the safety evaluation and engineering design of tailing dams. In the present study, laboratory experiments were performed to investigate the geotechnical properties of four different tailings, including two iron tailings (coarse and fine) and two copper tailings (coarse and fine). Compared to the copper tailings, the iron tailings showed higher compressibility, lower permeability, lower strength, and lower cyclic resistance. With the decrease in void ratio, the coefficient of consolidation almost kept constant for the fine iron tailings, whereas for the fine copper tailings, the coefficient of consolidation gradually increased. Under cyclic loading, the accumulation of pore water pressure was faster in the fine tailings than that in the coarse tailings. The cyclic resistance ratios (CRR) of the four tailings were found to be comparable with previous report data on other metal tailings, and the consolidation stress showed little impact on CRR. The laboratory tests provided useful information to understand the geotechnical behaviors of mine tailings including seepage, deformation, strength, as well as seismic responses. [ABSTRACT FROM AUTHOR]

Due to the ever-increasing demand for electricity, generation of fly ash in large quantities has become a problem throughout the world. The utilization of fly ash in rail and road embankments in earthquake-prone areas requires thorough understanding of its dynamic strength characteristics. A series of resonant column and cyclic triaxial tests have been carried out on fly ash to investigate the influence of various factors on its maximum dynamic shear modulus (Gmax) and dynamic damping (Ds). Correlations for predicting Gmax and Ds for fly ash have been proposed. The fly ash is found to be far more liquefiable than sand. The particle-size distribution and low unit weight play a vital role in the determination of cyclic strengths. The dynamic shear damping is found to be very much influenced by the confining pressure and induced strain, but independent of the relative density of the fly ash. The damping of sand is found to be always more than the damping of the fly ash irrespective of the confining pressure. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation using the three-dimensional discrete element method (DEM) to evaluate the macro-scale properties of saturated silt in a cyclic triaxial test. The three-dimensional particle model generated based on scanning electron microscopy (SEM) images of silt was imported into the discrete element program PFC3D and a rigid block model with different fines content was established. The effect of non-plastic fines content on the liquefaction properties of silty rigid block model was studied. The DEM results show that: (1) In the initial stage of dynamic stress loading, the axial strain of the sample develops slowly, and the stress-strain hysteresis loops almost overlap. With the increase of the number of cycles, the axial strain fluctuates violently, and the hysteresis loop becomes larger and develops toward the transverse axis. After the initial liquefaction, the dynamic elastic modulus and strength of the sample decrease significantly. (2) When the fines content increases from 0 to 30%, the liquefaction resistance of silt decrease with the increase of fines content. When the fines content increases from 30% to 100%, the liquefaction resistance of silt increases with the increase of fines content. (3) Under the same cyclic stress ratio, the number of cycles required for silt to liquefy decreases initially and then increases with the increase of fines content, and the critical fines content is 30%. The DEM results were compared with experimental results from the laboratory cyclic triaxial tests to provide insights into the underlying mechanism that governs the effects of fines content value on the liquefaction properties of silt. • Discrete element models using three-dimensional rigid block particles were developed to evaluate macro-scale properties of saturated silt in a cyclic triaxial test. • Effect of fines content on liquefaction properties of silt was investigated using DEM and compared with laboratory test results. • Particle contact state was used to reveal the underlying mechanism on the silt liquefaction properties. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop an easy procedure to diagnose the cyclic behavior of fine-grained soils, leading to liquefaction. There are approaches to this problem with reference to liquid limit (w L), plasticity index (PI), clay content, (C%), in-situ water content compared to the liquid limit (w n /w L), average grain size (D 50), and liquidity index (I L). Previous research has indicated that fine-grained soils defined as "sand-like" are prone to liquefaction. There is consensus that liquefiable silty soils have "sand like" characteristics. In the transition from sandy to clayey, it is generally accepted that it would be appropriate to make a judgment by making use of mechanical testing and that clayey soils do not liquefy. This paper presents the results of dynamic triaxial shear testing (CTX), where excess pore water pressures and axial strains are evaluated compared to the physical properties to reach the threshold for cyclic failure. Samples of undisturbed soil procured from different locations of the city of Adapazarı, Turkey, were subjected to CTX testing. The results were interpreted in the light of the physical properties to arrive at a judgment of cyclic failure. Being able to identify a liquefaction prone fine grained soil by merely measuring a few physical properties without resorting to arduous cyclic testing would be an advantage to the practising engineer. This however necessitates the elimination of the ' gray zone' for which most researchers recommended the use of cyclic testing. The main finding of this study is that samples reaching double strain amplitude (DSA) of <5% in the CTX test contain no sand and have a clay content of 20% or more. An attempt to establish a relationship between sensitivity to cyclic loading and physical properties is also made. • Seismic liquefaction in fine-grained fluvial soil. • Relationships between physical properties and cyclic triaxial test results of fine-grained soils. • Revision in the limit values of physical properties of soils for evaluation of liquefiability. [ABSTRACT FROM AUTHOR]

We present a novel method to improve liquefaction resistance in sandy soil by treating it with natural rubber latex (NRL) using a pressurised permeation technique. Sand samples treated with NRL solutions of 10%, 15%, 20%, and 30% concentrations were tested. The liquefaction resistance of the untreated and NRL-treated sand samples was evaluated by performing strain-controlled cyclic triaxial tests with 0.15%, 0.3%, and 0.5% axial strain amplitudes. We find that NRL treatment reduces excess pore pressure development in the sand, thereby increasing liquefaction resistance. Further, this study also explores the effect of NRL treatment on stiffness deterioration in the sand under cyclic loading. NRL-treated sand samples showed resistance to progressive stiffness degradation even after many cycles due to interparticle bonding developed by virtue of the solidified NRL fibres. From a pilot study on the behaviour of treated sand under stress-controlled loading, it was seen that irrespective of the pore pressure development, NRL effectively resist the strain development in sand. Hence, we propose the utilisation of NRL as an environment-friendly soil stabiliser for mitigating liquefaction. • Natural Rubber Latex's binding property can be used for liquefaction mitigation. • Liquid Rubber Latex is permeated into the soil pore spaces under pressure. • Rubber latex get coagulated within pores and bind sand grains together. • The Rubber binding prevents sand liquefaction and associated stiffness reduction. [ABSTRACT FROM AUTHOR]

In this study, cyclic behavior and dynamic properties of Renusagar pond ash samples reinforced with geotextiles have been studied. Pond ash samples were collected from the upstream side of the pond ash embankment. Laboratory tests have been carried out to obtain the material properties of the pond ash. Strain-controlled cyclic triaxial tests have been carried out on reconstituted pond ash samples with and without geotextiles, at varying confining pressures (70, 100, and 150 kPa), loading frequencies (1 and 0.5 Hz), and cyclic shear-strain amplitudes (0.5, 0.8, and 1.05%). The woven geotextiles were used as reinforcing materials, which were placed in the pond ash samples in one and three layers. Results show that the pond ash samples reinforced with geotextiles exhibit better friction angle, drainage properties, and liquefaction resistance. It may be concluded that pond ash reinforced with geotextiles can be used effectively as embankment construction material. [ABSTRACT FROM AUTHOR]

Reducing the static and seismic earth pressures on geotechnical structures, such as retaining walls, bridges abutments and buried pipes, using compressible materials is a novel idea which has received increased consideration during recent years. Despite the high compressibility of injectable polyurethane (PU) foams, their performance as a compressible inclusion material has not yet been studied. This paper presents results from a series of cyclic triaxial tests to investigate the dynamic properties of PU foam and PU foam-sand mixtures at intermediate to large strains. Furthermore, the effect of various parameters including initial deviator stress, static confining stress and foam-sand mixing percentage, on damping ratio and shear modulus are identified. The laboratory test results indicated that in pure foam, the damping ratio attenuated in elastic strain amplitudes, which remained constant once the stress was increased to near the yield point. The results of the tests on the foam-sand mixture samples with various mixing ratios demonstrated that the variation in damping ratios is a function of foam mass. So that for specimens with 5% PU foam, after a relative decrease, the damping ratio increased in the cyclic shear strain amplitudes more than 0.03–0.05%. In addition, it was observed that the dynamic behavior of the mixture is significantly affected by the content of injected foam and also confining stresses (proportional to the depth of the treatment zone). [ABSTRACT FROM AUTHOR]

A series of undrained cyclic triaxial tests were performed on sand–clay mixtures with various sand–clay mixing ratios. Prior to the primary tests, the threshold fines content was examined by consistency tests, which was found to be approximately 20%. For sand–clay mixtures with a sand-matrix (fines content less than the threshold fines content), the cyclic shear strength of low-density mixtures increases and that of high-density mixtures decreases with increasing fines content. However, for sand–clay mixtures with a fines-matrix (fines content greater than the threshold fines content), there exists a unique correlation between the cyclic shear strength and global void ratio for different fines content. The equivalent granular void ratio is introduced in this paper to account for the contribution ratio of the fines to soil skeleton. As a result, a unique relationship between cyclic shear strength and equivalent granular void ratio was observed for pure sand and sand–clay mixtures with a sand-matrix. [ABSTRACT FROM AUTHOR]

The deformation and the degradation of ballast significantly affect the performance of the railway track. In this study, the discrete element method (DEM) was used to investigate the deformation behavior and degradation characteristics of ballasts under monotonic and cyclic loading. The ballasts were simulated as crushable aggregate which is modeled by bounded discrete elementary particles together and it can be crushed under external forces. The flaw of the aggregate was also modeled by randomly distributed void. Conventional monotonic and cyclic triaxial tests were carried out to investigate the crushing of the aggregates and the associated mechanical behaviors. The effects of confining on the crushing of aggregates and the mechanical behavior were also analyzed. It was found that the permanent deformation of the aggregates significantly increases when particle crushing is considered. The crushing of aggregate is most significant in the first two or three cycles. [ABSTRACT FROM AUTHOR]

Large numbers of vehicles manufactured annually result in massive traffic and in turn creates huge numbers of waste tires entering into the environment and causing problems. Therefore, it is necessary to find reasonable applications for waste tires. They may be used to reduce seismic effects on structures due to their damping characteristics and energy absorption. Although comprehensive research studies have been carried out on static and dynamic properties of soil mixed with waste rubber, dynamic tests on layered mixtures of sand and rubber are highly demanding due to their easy to perform for practical applications. In this study, dynamic properties of sand mixed with different percentages of waste tire grains in uniform and layered forms were studied using a series of consolidated drained cyclic triaxial tests. The results show that for a given rubber percentage, layered mixtures have less shear modulus and more damping ratio than rubber-sand mixtures with uniform distribution. It has also been observed that for 50% tire content in layered sand-rubber mixtures, the Sand-Tire-Sand (STS) configuration offers lower shear modulus and a greater damping ratio than the Tire-Sand-Tire (TST) arrangement. • The influence of arrangement of tire grains in soil-rubber mixtures in layered form was investigated using cyclic triaxial tests. • Increasing the confining pressure, the shear modulus increases and damping ratio decreases. • With increasing the rubber content, the shear modulus decreases and damping ratio increases. • Uniform sand-rubber uniform mixtures have greater shear modulus and smaller damping ratio than separate layers of sand and rubber. • Layered sand-rubber mixtures show the same trend for damping ratio and especially shear modulus close to that of pure rubber. [ABSTRACT FROM AUTHOR]

Microbially induced calcium carbonate precipitation (MICP) is a new, natural, environmentally friendly treatment method for soil foundations, which can improve the resistance of calcareous sand foundations to liquefaction. Liquefaction is prone to occur under dynamic loading caused by events such as earthquakes or sea waves. Activated carbon is a porous substance that also offers the property of adsorption. In this study, the adsorption capacity of activated carbon was used to improve the retention ratio of bacteria during MICP treatment. Bacterial retention tests, cyclic triaxial (CTX) tests, and microscopic scanning tests were carried out to investigate the effects of variable activated carbon contents (namely 0%, 0.25%, 0.75%, 0.50%, 1.00%, and 1.25%, relative to the weight of the sand) on the liquefaction resistance of MICP-treated calcareous sand. The results showed that with the increasing activated carbon, the number of cycles of excess pore water pressure in the cumulative stage of the samples was increased, and the amplitude of axial strain was decreased. As the activated carbon content was increased, the bacterial retention ratio, cyclic strength, and secant modulus of the samples were found to improve considerably. On examination of microscopic scanning images, it was observed that the distribution of excessive activated carbon between the sand particles had resulted in it occupying the bacterial nucleation site and creating an obstacle to the connection between sand particles. The test using 0.75% activated carbon content best enhanced the resistance to liquefaction of calcareous sand. The outcome of this study may in the authors' view prove beneficial in improving the bacterial retention ratio and liquefaction resistance of calcareous sand when it is reinforced by microorganisms. • The effects of activated carbon on MICP-treated calcareous sand were investigated. • A series of bacterial retention tests and cyclic triaxial tests were performed. • Microscopic images which revealed the mechanism of activated carbon were obtained. • The optimal activated carbon content of liquefaction resistance was found to be 0.75%. [ABSTRACT FROM AUTHOR]

In situ survey revealed that sand that experienced liquefaction history in the mainshock may liquefy again (called reliquefaction) when suffered an aftershock. Sometimes aftershocks might cause more severe damage to infrastructure. Previous studies revealed that the reliquefaction resistance was influenced by many factors, especially the anisotropic fabric. However, the influences of initial anisotropy and stress-induced anisotropy on reliquefaction response are still unclear, especially the mechanism of the stress-induced anisotropy and its quantitative evaluation. Therefore, two groups of cyclic triaxial tests were firstly carried out on sub-angular sand, reconstituted by different methods, to illustrate the influences of anisotropy on liquefaction and reliquefaction response. According to test findings, a new parameter, named definitive anisotropy degree, was proposed to quantitatively evaluate the anisotropy. Another group of cyclic triaxial tests were also performed on spherical glass beads with no preferred orientation, based on which an explanation of the mechanism of stress-induced anisotropy for different geomaterials was given at the end. • Effects of initial and stress-induced anisotropy on reliquefaction were studied. • A parameter was proposed to quantitatively evaluate the anisotropy degree. • The mechanism of stress-induced anisotropy on reliquefaction was given. [ABSTRACT FROM AUTHOR]

Devastating ground failures at seismically active sites underlain by saturated fine-grained soils have led to a need for revealing liquefaction potential of fines and effects of the characteristics governing this potential. A cyclic pore pressure model is introduced to examine the effects of plasticity index, ratio of water content to liquid limit and cyclic stress ratio on liquefaction susceptibility of such soils. The model is developed using data of 68 cyclic triaxial tests compiled through a comprehensive literature review. By means of pore pressure behavior estimated by the model and strain tendencies observed during the tests, a critical assessment on liquefaction susceptibility criteria for fine-grained soils is provided. Beyond evaluation of the susceptible and non-susceptible fines, this assessment partially provides distinction between liquefaction-related phenomena one of which is induced by complete loss of strength, whereas the other is induced by high strain levels without complete loss of strength. [ABSTRACT FROM AUTHOR]

A series of monotonic drained and cyclic undrained triaxial tests were conducted to study the cyclic behavior of a shore sand mainly formed of silica and carbonate, under critical state soil mechanics framework. The main focus of the study was on simplifying the process of approaching to liquefaction, and predicting it using the concept of “state”. The results indicated that generation of pore water pressure from the start of cycling to liquefaction can be simplified into a bilinear-shaped trend in a semi-logarithmic space. The pore pressure response, the number of cycles needed for liquefaction and the cyclic resistance ratio were shown to depend on the initial state relative to the critical state line in space of specific volume against logarithm of mean effective stress. Analysis of the results also indicated that the bilinear trend of approaching to liquefaction and the liquefaction resistance of the soil with various densities and stress levels could be well characterized in terms of the state parameter and the cyclic stress ratio, using logarithmic, exponential and quadratic formulations. Liquefaction curves were derived in terms of the state parameter, independent of soil density and stress level. [ABSTRACT FROM AUTHOR]

Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids ( D/ D) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10% to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D/ D causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice. [ABSTRACT FROM AUTHOR]

The road base aggregate usually reaches the shakedown state under large number of cycles of traffic loads. But this shakedown state is expected to depend on the inclusion of fines and the matric suction. In this study, monotonic and cyclic triaxial tests were performed under controlled matric suctions on the road base aggregate with different fine contents (FC s) and matric suctions. Results show that the plastic creep limit of unsaturated road base aggregate is affected by the two-side effects of fines: reduction of friction angle and enhancement of matric suction. For the coarse-grain controlled soil (FC range from 0% to 4%) and fine-grain controlled soil (FC range from 8% to 16%), the plastic creep limit decreases with increasing FC due to the friction angle reduction caused by the inclusion of fines. For the transition soil (FC range from 4% to 8%) under unsaturated state, the plastic creep limit increases with the increase of FC as the dominant effect of fines shift to the enhancement of matric suction. By adopting an allowable cyclic stress ratio (CSR), a novel method is proposed, allowing prediction of the plastic creep limit based on the results from standard monotonic triaxial test for coarse-grain controlled soil and fine-grain controlled soil, and the results from post-cycle monotonic triaxial test for the transition soil. This method can be applied to road base aggregate with different FC s and matric suctions. • The effect of fines on the plastic creep limit depends on the structure of the soil. • A good correlation is found between the plastic creep limit and the regressed peak strength. • A novel method is proposed for predicting the plastic creep limit of soils with different fine contents and matric suctions. [ABSTRACT FROM AUTHOR]

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. • Cyclic triaxial tests were conducted on planar, sawtooth and natural joints at different confining pressures. • As confining pressure decreased or cyclic deviatoric stress increased, the maximum axial strain increased. • Empirical relationships were established for resilient moduli and damping ratio. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to assess the reliability of a nonlinear hysteretic model to capture the behavior of saturated silty sand mixtures under cyclic loading conditions. The parameters governing the liquefaction triggering are identified using the results of standard laboratory tests (monotonic and cyclic consolidated undrained triaxial tests as well as resonant column tests) undertaken for reconstituted soil samples. Consequently, the uncertainty related with collected samples is reduced. The numerical results, obtained after calibration of the constitutive model, are in good agreement with the experimental ones and they are analyzed through the effects of relative density, fine content, and confining pressure in the liquefaction resistance of silty sands. • Validation of the 3D Iwan-Iai hysteretic constitutive model under cyclic loading conditions. • Suitability of the 3D Iwan-Iai model for various silty sand mixtures. • Onset of liquefaction simulated for cyclic mobility and cyclic liquefaction. • Effect of fine content and relative density for liquefaction assessment. • Impact of the 'p2' liquefaction parameter (Iai model) on the excess pore water pressure build-up. [ABSTRACT FROM AUTHOR]

Historical cases show that the liquefaction of sand is an important cause of earthquake disasters. Geosynthetics are widely used to improve the performance of sand deposit. However, limited studies have been conducted on the effect of geosynthetics on mitigation of sand liquefaction. In this study, the liquefaction resistance performance of geotextile reinforced sand is discussed by a series of strain-controlled cyclic triaxial tests with different cyclic strain amplitudes and layer numbers of geotextile. The influence of geotextile layout and cyclic strain amplitude on the liquefaction behavior of saturated sand is studied. Experimental results show that the liquefaction resistance of saturated sand increases with the increase of layer number of geotextiles and decreases with the increase of cyclic strain amplitude. The increased cyclic strain amplitude leads to fast accumulation of pore water pressure. Furthermore, a single element numerical model is created based on the finished cyclic triaxial test, and parameter calibration is carried out for reinforced sand by matching the excess pore water pressure. Numerical simulation results show that the computed responses with calibrated parameters are in good agreement with the experimental ones. This will provide a valuable reference for numerical modeling and engineering application of geotextile reinforced sand. • A series of strain-controlled cyclic triaxial tests for geotextile reinforced saturated sand are performed. • The influence of geotextile and cyclic strain amplitude on the liquefaction resistance of saturated sand is explored. • A single element numerical model is developed to simulate cyclic triaxial liquefaction test. • A parameter calibration method is designed to compare the difference between computed and experimental EPWPs. [ABSTRACT FROM AUTHOR]

Recent studies on construction material technology have indicated that soil reinforcement improves resistance of soil against compression and tension. Due to the wide use of geotextile reinforcement in road construction, the potential benefit of geotextile reinforcement in cyclic loading should be investigated. In this study we performed a series of cyclic triaxial tests to examine dry silty sand reinforced with geotextile when subjected to dynamic loading. These tests were conducted on reinforced and unreinforced dry sand and sand mixed with varying amounts of silt (0–50%). The main factors affecting the cyclic behaviour, such as the arrangement and number of geotextile layers, confined pressure and silt content are examined and discussed in this paper. The results indicate that geotextile inclusion and increased confining pressure increase the axial modulus and decreased cyclic ductility of dry sand for all silt contents examined. Also, it was found that by increasing the silt content by up to about 35 percent the axial modulus in reinforced and unreinforced sand is decreased and cyclic ductility increased. With further increases in silt content, these values are increased for cyclic axial modulus and decreased for cyclic ductility. [ABSTRACT FROM AUTHOR]

Experimental investigations and modeling of linear elasticity of fiber-reinforced clayey sand under cyclic loading unloading are conducted in this paper. Experimental studies are focused on four aspects. First, a series of cyclic triaxial tests, with different confining pressures and deviator stress ratios up to 150 cycles, are performed. Impacts of fiber content, cell pressure, deviator stress ratio and loading unloading repetition that affect dynamic behavior of the composite material are discussed. It is shown that shear modulus decreases with increasing deviator stress ratio at high confining pressure and the rate of loss of shear modulus found to be much lower for fiber reinforced specimens. Other results show that increase of shear modulus with loading repetition is more pronounced at higher deviator stress ratios. Second, the optimum fiber content is experimented under cyclic loading unloading and is expressed as a power function of deviatoric stress ratio. It is shown that optimum fiber content is not constant and it is affected by deviator stress ratio. Third, a function is introduced to describe the linear stress–strain curve under cyclic loading unloading using equivalent linear analysis. The shear modulus G is expressed as a function of fiber content, confining pressure, deviatoric stress ratio and loading repetition. Finally constitutive coefficients of the model parameters are calibrated by the results of cyclic triaxial shear tests and using the linear regression. [ABSTRACT FROM AUTHOR]

Oil sands are natural deposits of sand materials that are rich in bitumen. Limited studies have been conducted to determine the dynamic behavior of oil sand materials. Recent difficulties encountered in oil sand mine fields in Canada substantiated the need to characterize the stress dependent, visco-elastic, and plastic behavior of oil sand materials under dynamic loading of off-road construction and mining equipment. This paper introduces a new cyclic triaxial test procedure for determining shear modulus and deformation characteristics of oil sand materials. The test procedure was used to characterize shear moduli of three oil sand materials with varying bitumen contents. From the test results, nonlinear shear modulus models were successfully developed to characterize temperature and stress dependent behavior of the tested oil sand materials. The research findings indicate that the new laboratory approach is an improvement on conventional tests, especially when oil sand materials need to be evaluated in the field for subgrade construction and equipment mobility. [ABSTRACT FROM AUTHOR]

The liquefaction vulnerability of fine- to coarse-graded saturated sand and gravelly sand is evaluated by stress control cyclic triaxial laboratory tests. Cyclic triaxial test on reconstituted specimens is carried out with relative density of 45 %. Cyclic triaxial tests performed by sinusoidal wave form with 1-Hz frequency and with the effective consolidation pressure equal to 100 kPa. Cyclic stress ratio which caused initial liquefaction in 15 cycles recognized as the liquefaction resistance in cyclic triaxial test of present study. The result had been used to find a relationship between liquefaction resistance and the grading characteristics (e.g., coefficient of curvature and coefficient of uniformity) of various graded sands and gravelly sands. Then, it is realized that a relationship between liquefaction resistance and any of the sizes (i.e., D, D, D, D) appears to be more practical. [ABSTRACT FROM AUTHOR]