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The effect of geotextile inclusion on the shear modulus and damping ratio of sands is evaluated in a wide range of shear strain amplitudes, from very small to fairly large, using the results of several resonant column and hollow cylinder torsional shear tests. The resonant column test results are utilized to characterize the reinforced soil behavior at the range of small to medium strains whereas the hollow cylinder torsional shear test results are exploited to assess the medium to large strain dynamic properties. The results demonstrate that the inclusion of geotextile sheets in the soil medium would increase both its shear stiffness and damping ratio in the whole range of shear strain amplitudes, thus rendering a perfect composite to resist dynamic forces applied on geo-structures in earthquake prone areas. Empirical equations are proposed to estimate the small strain and strain-dependent shear modulus and damping ratio of geotextile-reinforced sands. The effect of scaling is also accounted for by a simple analysis so that the results obtained in the current study in the element scale could be extended to the prototype scale in the field. Finally, the accuracy of the proposed scaling approach is verified against a finite element model of a geotextile-reinforced embankment. • Effect of geotextile inclusion on shear modulus and damping ratio of sands is evaluated at various shear strain amplitudes. • Dynamic properties are assessed through several resonant column and hollow cylinder torsional shear tests. • Empirical equations are proposed to estimate the dynamic properties of geotextile-reinforced sands. • Effect of scaling is accounted for by a simple analysis to generalize the results of this study to the field scale. • Accuracy of the proposed scaling approach is verified against a finite element model of a geotextile-reinforced embankment. [ABSTRACT FROM AUTHOR]

The beneficial effects of geocells on improving the soils' characteristics have always drawn researchers' attention. However, due to the geocell's large scale, more accurate analyses, such as large-scale cyclic laboratory tests, are still needed to determine the soil-geocell system's actual mechanism. In the present research, a series of large-scale triaxial tests are carried out on poorly graded sand samples with 30 cm diameter and 60 cm height reinforced by geocell with heights of 0.6, 1.0, and 1.4 of the pocket diameter and placement depths of 0.05, 0.15, 0.25, and 0.35 of the samples' height under static and cyclic loading conditions. Contrary to common opinion, the results obtained for unreinforced sands showed that the maximum bulge, instead of the middle, occurred at 0.25 of the sample's height from the top surface. Changing the bulging from the middle to the upper part reflects the role of the direction of stress applied and the accumulation of the deformation due to plastic behavior near the load position. On the one hand, the results of static tests revealed that placing geocell at this depth delivers the best performance in controlling the bulging and reducing settlement values due to the predominant lateral support to the sand particles, reducing the localized stress concentrations, increasing internal friction and interlocking, and reducing the likelihood of shear failure. On the other hand, the geocell with moderate height had higher wall rigidity and stability against deformations compared to the geocell with lower and higher height values due to higher soil confinement potential and more resistance against buckling, respectively. Cyclic loading was also performed on geocell-reinforced soils under 110 cycles with cumulative strains ranging from 0.13 to 0.155 %. The cumulative strains for the unreinforced and reinforced soils were 0.196 % and in the range of 0.130–0.154 %, respectively. The best geocell placement depth under cyclic loading mode was at 0.05 of the sample's height, which had a cumulative strain of 0.13 % in 110 cycles and reduced the cumulative strain by about 34 % compared to the unreinforced sample. The presence of geocell in the soil generally led to an increase in the shear modulus and a decrease in the slope of the damping ratio. Further, the shear modulus was reduced by increasing the geocell placement depth. • Geocell's wall rigidity has a significant impact on confinement and buckling. • Maximum bulge for static and cyclic loadings occurs at 0.25 and 0.05 of the sample's height. • The cumulative settlement of geocell-reinforced sand reduced by about 34 %. • Geocell placement effect at shallow depth was more remarkable under cyclic loading. • Shear modulus was reduced by increasing the geocell placement depth. [ABSTRACT FROM AUTHOR]

Coral silt, a type of coral soil with more than 50% silt content, is formed during the process of land reclamation. Given the frequent action of waves, wind, earthquakes and other dynamic loads, the cyclic dynamic shear characteristics of coral silt are important for determining the seismic safety of reef infrastructures. A series of symmetrical and asymmetrical cyclic simple shear tests were performed to characterize the cyclic behavior of coral silt with particular consideration given to the static-cyclic shear stress coupling. Two empirical formulas for the undrained peak shear strength and critical state strength in monotonic simple shear tests are proposed. For both symmetrical and asymmetrical-loading cyclic simple shear tests, a CSR threshold value lying between 0.05 and 0.075 controls the final failure. The cyclic shear stress significantly influences the cyclic deformation, cyclic pore water pressure, cyclic strength, and cyclic shear modulus of coral silt. • The undrained shear strength of coral silt can be estimated by the empirical formula: S up = 0.1992 σ v 0 ′ and S uc = 0.1435 σ v 0 ′ , respectively. • There is a threshold value of CSR between 0.05 and 0.075 that controls whether the final failure. • There is an inflection point in the cyclic shear strain development curve of all ultimate failure tests. • The cyclic pore water pressure development model and cyclic shear modulus significantly depend on CSR. • The dynamic strength of coral silt increases as the α and σ ′ v0 increase. [ABSTRACT FROM AUTHOR]

Abstract Characterizing the small-strain shear modulus (G 0) of sand with fines is of importance in geotechnical applications since natural sand is usually not clean but contains a certain amount of fines. This paper presents an experimental study to investigate G 0 values of several sand-fines mixtures, formed by mixing clean quartz sands of different sizes with crushed silica fines of varying quantity. Focus of the study is on the possible interplay between the influence of particle size disparity and the influence of fines contents for which current understanding is not adequate. By defining the particle size disparity as D 50 / d 50 , where D 50 is the mean size of base sand and d 50 is the mean size of fines, a critical range of size disparity is found to be approximately between 4 and 7. When the size disparity is smaller than 4, the role of fines is manifested mainly by fines content; when the size disparity is beyond 7, the contribution of fines to the load transfer gradually becomes negligible because in this case fine grains tend to roll into the voids. A new concept, referred to as combined size disparity, is proposed to capture the influence of fines content and the influence of size disparity in a collective manner. By adopting this concept, an empirical relationship is proposed for estimating G 0 values of sand-fines mixtures. The predictive performance of the relationship is then examined using literature data and a reasonably good agreement between prediction and measurement is obtained. Highlights • The small-strain shear modulus (G 0) of sand-fines mixtures was studied. • A critical range of size disparity was found to be approximately between 4 and 7. • The influences of fines content and size disparity on G 0 are strongly interplayed. • A new concept, referred to as combined size disparity, was proposed. • By using this concept, an empirical relationship was proposed for estimating G 0. [ABSTRACT FROM AUTHOR]

In offshore engineering, the dynamic properties of ultrasoft clay in the seabed could affect the stability of offshore construction under dynamic loading. The typical rheological response of ultrasoft clay is studied based on the test results from large amplitude oscillatory shear tests with a rheometer. The ultrasoft clay undergoes three phases: the solid phase, transition phase and liquid phase, under dynamic loading. Modulus overshoot is observed when a phase transition occurs. The shear modulus and damping ratio of ultrasoft clay are studied based on the relationship between rheological parameters and dynamic parameters. The results show that the maximum shear modulus of ultrasoft clay could be expressed as a function of water content. Compared with general clay, the normalized shear modulus of ultrasoft clay decreases, and the damping ratio rapidly increases with increasing shear strain. Models describing the change in the normalized shear modulus and damping ratio with the shear strain of ultrasoft clay are suggested based on our test results. This study could aid in the evaluation of the stability of submarine structures at the seabed level under dynamic loading. • Dynamic properties of ultrasoft clay were studied by large amplitude oscillatory shear tests with a rheometer. • The effect of water content on the rheological behavior of ultrasoft clay was investigated. • The phase transition of ultrasoft clay was studied based on the typical rheological response. [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]

The soil small-strain shear modulus, G 0 , is necessary for static and dynamic soil analyses and is often correlated to other soil properties such as density and void ratio, on their turn depending on gradation. The paper first presents a concise literature review of parameters influencing G 0 in detail. Secondly, a particle shape analysis is performed. Silica sand is found much more spherical than calcareous sand, and calcareous sand becomes more spherical after crushing. Bender element test results indicate that not only uniformity coefficient (C u ) but also particle characteristics including particle shape and stiffness are very important to G 0 . G 0 of calcareous sand is found higher than that of silica sand. Indeed, with less sphericity and more angularity, the variety of particle shape in calcareous sand produces a better fabric for shear wave propagation. For calcareous sand, the test results show that particle shape is the main factor affecting G 0 . Less dynamic stiffness is found for particles owning more sphericity and less angularity. The increase of C u or finer particles (at low C u ) causes a decrease in G 0 . Finally, predictions of G 0 for the tested calcareous sands using empirical equations from previous studies give very high relative errors (16.7–30%). [ABSTRACT FROM AUTHOR]

High rockfill dams experience a wide range of shear strain amplitudes during earthquakes. To provide more reliable material property descriptions for earthquake response analysis of high rockfill dams, this study investigates the dynamic properties of rockfill materials in a wide strain range by large-scale cyclic triaxial testing with a high-sensitivity laser sensor. The results reveal the considerable increase of shear modulus and decrease of damping ratio with increasing confining pressure for a given initial stress ratio and the significant effect of the initial stress ratio on the small-strain shear modulus and normalized shear modulus. Previously proposed equations were found to imprecisely depict the variation of the dynamic shear modulus of rockfill materials for a wide strain range. Furthermore, the dynamic shear modulus is dependent on the Initial stress ratio in the anisotropic stress condition. Based on the existing hyperbolic model, a modified model for rockfill materials is suggested to accurately estimate the nonlinear behavior. The applicability of the modified model and previous studies for rockfill materials are assessed in the estimation of the normalized shear modulus. The results provide a reference for evaluating the accurate shear modulus in a wide strain range for strong earthquake motions. [ABSTRACT FROM AUTHOR]

The study of site-specific dynamic properties of soil holds vital importance in many geotechnical engineering problems for the region holding high active seismicity. The Sutlej River basin, a valley and high-risk seismic zone in the north-eastern part of the Punjab state, has been considered for the study. The site-specific shear modulus reduction curves and material damping ratio curves for a range of shear strain amplitudes have been developed under varying experimental conditions of confining pressure, relative density, and loading frequency using the resonant column (RC) tests and cyclic torsional shear (CTS) tests. The study addresses the usage of two testing approaches, i.e., resonant column test (RC) and cyclic torsional shear test (CTS), for the estimation of shear modulus and damping ratio values at varying shear strain amplitudes. The regression analysis has been performed for the two testing techniques viz. RC and CTS to study the sensitivity of shear modulus values and material damping ratio values towards varying experimental conditions. The shear modulus and damping ratio values determined from cyclic torsional shear tests were observed to have great dependency on the frequency of loading. The knowledge of site-specific dynamic properties will support practical interpretation for the geotechnical engineering problems in the region. • The resonant column and cyclic torsional shear testing of Sutlej river sand have been performed under varying experimental conditions to analyze the dynamic properties. • Site-specific shear modulus reduction and damping ratio curves have been developed under varying relative density, confining pressure, and loading frequency conditions. • The influence of frequency of cyclic torsional shear loading on shear modulus and damping ratio has been analyzed. • The modified hyperbolic model has been used to assess the non-linear dynamic behaviour of sand. [ABSTRACT FROM AUTHOR]

A better understanding of soil response to dynamic loads, including earthquakes, can result in safer designs that can reduce casualties. The damping ratio and shear modulus are critical parameters in soil dynamics, and several factors affect these parameters, including density and moisture content. The non-linear and multiple influences on these two parameters make their estimation difficult. Machine learning techniques are very powerful mapping tools with a remarkable capacity to perform nonlinear multivariate function approximations. In this study, to predict sand secant shear modulus and damping ratio from input variables, artificial neural networks (ANN) and classification and regression random forests (CRRF) were used as alternative estimators. The database was created using a series of simple shear tests that accurately assessed damping ratios and secant shear modulus to predict these two dynamic parameters. The input variables of the proposed predictive models included vertical stress, relative density and cyclic stress ratio, and its outputs included secant shear modulus and damping ratio. The Bayesian Regularization (BR) back-propagation ANN model produced correlation coefficient (R) and mean absolute error (MAE) values of 0.998 and 0.006, respectively, while CRRF models gave R and MAE values of 0.995 and 66.051, respectively. Additionally, sensitivity analysis of artificial intelligence (AI) models demonstrated that vertical stress and relative density played a vital role in predicting damping ratio, while all three parameters were important in predicting secant shear modulus. In this study, two developed artificial intelligence models were compared with existing literature models. According to the results, for test database, the existing models were able to predict the shear modulus and damping ratio with R of 0.911 and 0.918, respectively. However, the proposed ANN and CRRF models were able to predict shear modulus with R of 0.993 and 0.996, and damping ratios with R of 0.992 and 0.990, respectively. The results showed that ANNs and CRRFs were more robust than existing models for predicting damping ratio and shear modulus, as well as identifying the influence of input variables on sand dynamic properties. • The Bayesian Regularization (BR) back-propagation ANN produced R and MAE values of 0.998 and 0.006, respectively, while CRRF gave R and MAE values of 0.995 and 66.051, respectively. • Vertical stress and relative density played a vital role in predicting damping ratio. • Cyclic stress ratio (CSR), vertical stress and relative density were important in predicting secant shear modulus. • Based on the developed artificial intelligence models, two important parameters, shear modulus and damping ratio, were accurately predicted. [ABSTRACT FROM AUTHOR]

Loess is a kind of world-recognized problematic soil and, as a consequence, it is a major hazard in geotechnical engineering. This study examines the small to medium strain dynamic properties of Lanzhou intact and recompacted loess through a set of resonant column (RC) tests. The influence of soil structure on the small-strain shear modulus G 0 , the variations of G / G 0, and damping ratio DT(%) with shear strain γ were analyzed and discussed. The test results show that the structure has an important influence on the dynamic properties of dry loess at small and medium strain, whereas, with the increase of moisture, its effect weakens. It is proved that a normalized correlation between G / G 0 and γ/γ 0.7 is practically identical for undisturbed and recompacted loess in Lanzhou, irrespective of soil structure, which may be useful in practical applications. • The small to medium strain dynamic properties of Lanzhou loess with metastable structure were examined. • Structure effect reduces the ductility in dynamic response for Lanzhou loess. • The correlations between G / G 0 and γ/γ 0.70 could be normalized well for Lanzhou loess, irrespective of structure effect. [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]

This paper proposes a unified model to estimate the in-situ small strain shear modulus of clays, silts, sands, and gravels based on commonly available index properties of soils. We developed a model to predict the laboratory small strain shear modulus ( G max,lab ) using a mixed effects regression of a database that contains 1680 tests on 331 different soils. The proposed model includes the effect of void ratio, effective confining stress and overconsolidation ratio as well as plasticity index, fines content, and coefficient of uniformity. We compiled a second database to estimate the in-situ small strain shear modulus ( G max,in-situ ) from laboratory ( G max,lab ) measurements. This study validated and compared the resulting model with other existing models using a third database of measured G max,in-situ values. The residuals of the proposed model had a mean and median closer to zero and the smallest standard deviation of all the models considered. By including a statistical description of the residuals, this work allows uncertainty of the small strain shear modulus to be included in probabilistic studies. [ABSTRACT FROM AUTHOR]

While volcanic soils exist in many places around the world, their mechanical behavior is however less extensively studied as compared to the conventional soil type such as quartz sand and clay. This paper presents an experimental study investigating the small-strain shear modulus ( G 0 ) and associated shear wave velocity ( V s ) of a volcanic granular soil collected from the northeast of Japan that was affected by the devastating 2011 Tohoku earthquake. Reconstituted soil specimens were tested at different packing densities and confining stress levels by using the resonant column technique, and the pressure and density dependence of shear modulus was established for the soil. The study showed that under otherwise similar conditions, the G 0 value of the volcanic soil was markedly lower than that of clean quartz sands, but it tended to increase significantly when the fine particles in the soil were removed. This finding suggests that the presence of fines plays an important role in the mechanical behavior of volcanic soils. A practical model accounting for the influence of fines and the pressure and density dependence is proposed and it is shown to provide reasonable estimates of G 0 for both volcanic soils and clean quartz sands studied. [ABSTRACT FROM AUTHOR]

An experimental study was undertaken to characterize the seismic response of high plasticity clays found in the Texoco Lake region of the Mexico City valley. Series of resonant column and triaxial tests were carried out in twin samples, and empirically-derived well known modulus degradation and damping ratio models were used to simulate the measured response. A total of forty three tests were conducted in twin samples. The results gathered appear to indicate that the reference strain, γ r , instead of the plasticity index, PI, constitutes the best parameter to properly establish the modulus degradation and damping curves for high plasticity clays, increasing the accuracy of the model predictions. Appropriate values of γ r were obtained for the high plasticity Texcoco clays directly from the experimental data, to determined modulus degradation and damping curves. The approach was validated throughout the analysis of four cases study. Site response analysis predictions were compared with actual measurements at three seismological stations and one vertical array, considering several recorded moderate to large seismic events. The computed ground motions are in good agreement with the measured response. [ABSTRACT FROM AUTHOR]

Cement stabilization is often used to improve the bearing capacity and compressibility of soft clays. The present paper aims to investigate the shear modulus degradation of cement treated clay during cyclic loading. A series of cyclic triaxial test was conducted on artificially cement treated marine clay to study the factors affecting the shear modulus degradation. The parameters considered for the study are cement content (2.5–7.5%), curing days (7–28), cyclic shear strain amplitude (0.3–1%), number of loading cycles (1–100) and loading frequency (0.1–0.5 Hz). As in the case of natural clays, cement treated clays exhibit stiffness degradation which depends on mix ratio, curing days and loading conditions. The results show that the shear modulus degradation decreases with increase in the shear strain amplitude, cement content and curing days. It is also noted that irrespective of the mix ratio and curing conditions, the degradation decreases with increase in loading frequency. An empirical relationship is proposed to predict the shear modulus degradation based on Idriss׳s degradation model. The performance of the proposed empirical model is validated with the present experimental results. [ABSTRACT FROM AUTHOR]

Realistic estimation of soil behavior is dependent on considering very small and small strain domains. Lengthy formulas proposed in the literature have limited predictive power for estimation of maximum shear modulus, G 0. The aim of this study is to overcome this drawback. Theoretical aspects of fuzzy sets and adaptive neuro-fuzzy inference system (Anfis) are presented. Then, Anfis is implemented within a logical platform that adapts itself with available data to estimate and describe G 0. • Fuzzy logic is an adequate approach for problems with variability, uncertainty and unsharp boundaries. • Adaptive neuro fuzzy inference system (Anfis) is a suitable tool for approximating soil parameters. • Anfis gives the flexibility to select trusted databases rather utilizing lengthy formulas validated for specific datasets. • Maximum shear modulus is estimated utilizing easily obtainable variables with clear physical meaning. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of the dynamic properties of the soil is of great importance as the dynamic shear modulus and damping ratio are necessary input data in finite element modeling programs. This paper presents a post-processing strategy to identify the shear modulus and damping ratio vs. shear strain curves using the experimental results of a dynamic centrifuge program. Application is presented for the Fontainebleau sand. The proposed methodology is fast, robust and able to capture the nonlinear hysteretic behavior of the material. Based on the results, specific parameters for the Fontainebleau sand are identified for the empirical equation of shear modulus and damping ratio proposed by Ishibashi and Zhang [1]. It is found that confining pressure has an important influence on both shear modulus evolution and damping ratio. [Copyright &y& Elsevier]

Determination of shear modulus along with damping ratio values in the field when shear strains exceeds those maximum strains obtained from laboratory tests has a crucial importance in the seismic design of structures whose interaction with soil is more pronounced. In this study, shear modulus of undisturbed samples, obtained from Adapazarı city center during drilling works conducted within the scope of the geotechnical investigation following the 1999 Kocaeli earthquake, were determined. Elasticity of undisturbed Adapazarı samples was measured using a cyclic triaxial test rig. The aim is to obtain relationships between the elasticity moduli from the stress–strain relations of specimens in dynamic and static loading setups, and the axial strains following termination of dynamic tests. Minimum and maximum shear moduli were determined for non-plastic soils and for soils with the plasticity index of PI = 40%. The elasticity modulus ratio (E N=20 /E N=1) for samples with plasticity index of PI = 40% is higher than those with PI = 20% at the same level of deformation. As the plasticity increases at the same deformation level, both of the E ds /E N=1 and E ds /E N=1 ratios increase. Moreover, seismic performance of a reinforced concrete frame is evaluated for both fixed and soil-structure system. Seismic demand in soil-structure model with the frame and soil profile considered in this study is observed to be higher as compared to fixed-base frames. • Shear modulus of undisturbed samples were determined following the 1999 Kocaeli earthquake. • The relationships between the elasticity moduli and the axial strains at the end of dynamic tests are shown. • Minimum and maximum shear moduli were obtained for non-plastic soils and for soils with the plasticity index of PI = 40%. • As the plasticity increases at the same deformation level, the ratio Eds/EN = 1 also increases. • Seismic demand on superstructure can result in increase due to interaction with soil. [ABSTRACT FROM AUTHOR]

It is essential to determine low strain shear modulus (G m a x ) to model dynamic soil response and estimate the site effects due to earthquakes. Several correlations have been developed between dynamic soil properties and soil penetration resistance values such as N-values from Standard Penetration Test (SPT). However, only a few of the established correlations are often used because of uncertainty over applied hammer energy (E H) and applicability in different regions. Hence, this study aims to signify the importance of E H in N-value corrections, its influence on G m a x estimation, to suggest modification factor for an existing correlation and validate with Downhole and Crosshole measurements. Different SPT corrections are studied besides the energy measurements in the analysis of the correlation between the N-value and G m a x . A previously proposed correlation between measured N-value and G m a x is improved to account for in-situ E H measurement, and the correction factors to account for different hammer energy ratios (ER) are suggested. Modified correlations compared well and agreed within the 95 % confidence bound with the freshly acquired seismic borehole tests data. • Correction factors for a previous correlation for different hammer energies are improved and validated using field data. • Non-linearity of the coefficient in correlation is compared with the energy correction factors for N-value. • Influence of hammer energy on variation of low strain shear modulus with hammer energy measurement is discussed. • Significance of hammer energy correction compared to other SPT correction factors is highlighted. [ABSTRACT FROM AUTHOR]

Dynamic behavior of sand-bitumen mixtures was investigated using a series of dynamic hollow cylinder tests. The effects of different parameters including bitumen content, loading frequency and bitumen viscosity on shear modulus and damping ratio of the mixtures were evaluated in detail. The results showed the added bitumen increased shear modulus of the mixture up to about 20% for bitumen content of 3.5% in the range of shear strains between 0.01% and 0.1%. Such an increase was negligible at shear strains beyond 0.3%. Moreover, the added bitumen boosted damping ratio of the mixtures up to about 10% for bitumen content of 3.5% at shear strains beyond 0.3% while this increase was only about 5% at shear strains less than about 0.1%. Damping ratio and shear modulus of the mixtures changed with the frequency of applied loading mainly due to the viscous behavior of the bitumen. It was also found that using more viscous bitumen augmented damping ratio and shear modulus of the mixtures. • Dynamic behavior of sand-bitumen mixtures was investigated. • Added bitumen increased shear modulus of the mixture up to about 20%. • Increase in shear modulus due to bitumen was negligible at large shear strains. • Bitumen boosted damping ratio of the mixture up to 10% at large shear strains. • Dynamic parameters of the mixtures varied with frequency of loading. [ABSTRACT FROM AUTHOR]

To investigate the shear modulus and damping ratio of granulated rubber-sand mixtures, cyclic triaxial tests were conducted on specimens prepared with different granulated rubber content (by weight) and consolidated under different consolidation ratios. The specimens were then sheared under two cyclic shear strain amplitudes of 0.002 and 0.004 up to 300 cycles. The results show that adding granulated rubber has decreased shear modulus (G) and increased damping ratio (D) under both shear strain amplitudes, but rubber has been helpful in reducing the degradation rate of the shear modulus irrespective of the initial consolidation state. Overall, anisotropic consolidation has had little effects on the variations of shear modulus and damping ratio of granulated rubber-sand mixture (GRSM) compared to clean sand. The sand-rubber mixtures have become more isotropic by increasing the rubber percentage even under anisotropic consolidation. The point that the granulated rubber has significantly contributed to reducing the degradation potential of G with number of cycles makes it attractive in executing backfills and earth structures using rubber-sand mixtures in seismically active zones. The results of this study are also promising in efficient application of granulated rubber-sand mixtures as an isolation system under the foundation of buildings. • Conducting cyclic triaxial tests under undrained conditions. • Study the effects of granulated rubber content on the shear modulus and damping ratio of granulated rubber-sand mixture. • Study the effects of anisotropic consolidation on the shear modulus and damping ratio of granulated rubber-sand mixture. • Evaluating relatively high cyclic shear strain on shear modulus and damping ratio of granulated rubber-sand mixture. • Proposing granulated rubber-sand mixture as an isolation system under the foundation of normal buildings. [ABSTRACT FROM AUTHOR]

In view of its appropriate engineering properties and environmental benefits, waste rubber is being increasingly used in engineering applications. Along with static loading, clay-rubber mixture (CRM) can be also utilized under dynamic loading. Due to a lack of detailed research on dynamic and static properties of CRMs, the effects of 0–30% rubber content on geotechnical properties of clay soil (CS) was investigated in this study through strain-controlled monotonic and cyclic triaxial tests. Moreover, the structure of the CRM and pure rubber was observed under a binocular microscope. The results indicated the effects of rubber size, rubber content, and shear strain amplitude on strength, volumetric strain, damping ratio, and shear modulus of the CRM. The results correspondingly demonstrated a good cohesion between clay and rubber grains as well as an appropriate strength and shear strain for the given mixture. According to the results of the dynamic tests, the highest damping ratio was obtained with 10% rubber content. In addition, the shear modulus showed a downward trend as the rubber content and the shear strain amplitude augmented. The use of rubber powder rather than granular rubber also enhanced the damping ratio by 10% on average. In contrast, the granular rubber boosted the shear modulus by 13% as compared with the rubber powder. Based on the results, it is recommended to use 10% rubber powder in executive operations to achieve the highest damping ratio. Considering the static strength of the CRM and its good damping ratio under cyclic loading compared with pure soil, it is suggested to be used in situations wherein soil could be subjected to low compressive loads combined with cyclic loading. • Dynamic properties of clay and recycled waste tire mixed are investigated. • This study helps in recycling and solving the problem of waste tires. • Reuse of such wastes is of both environmental and geotechnical importance. • Selecting the optimal size of waste tires in geotechnical engineering practice. • Suggestion of using recycled granular tire in geotechnical engineering projects. [ABSTRACT FROM AUTHOR]

This study investigates the effect of non-plastic fines on the anisotropic smalls strain stiffness of a calcareous sand by conducting multidirectional bender element tests. G H H , G H V and G V H are evaluated on both horizontal and vertical planes and the stiffness anisotropy, considering the effect of fine content, is studied. The models for predicting small strain shear modulus G 0 of the calcareous sands are modified. Test results show that G 0 decreases with the increase of the fine content until a threshold fine content is reached. The stiffness anisotropy drops with the increases of the fine content. The modified Hardin equation provides a better prediction than the modified Wichtmann equation and the Payan equation. • The effect of non-plastic fines on the small strain stiffness of a calcareous sand is investigated. • The stiffness anisotropy decreases with the increase of the fine content. • The stress history and fine content are introduced the Hardin model for predicting the small strain shear modulus of the calcareous sand. • The modified Hardin model shows better prediction ability than other two models in literature. [ABSTRACT FROM AUTHOR]

Among various soil improvement methods, stabilization using traditional additives (cement, lime, flyash, etc.) is very often used in soft clay soils. In recent times, nontraditional additives are used as a partial or a full replacement to the traditional additives for reducing the detrimental effect of excessive addition of these to the earth. The present study is focused on developing such a combination of non-traditional additives, which minimizes the use of traditional stabilizers. The study aims to evaluate the soil behavior under dynamic loading before and after the soft soil is treated with the optimum of Nano silica and Bioenzyme along with 1% of cement (cured for 28 days). Strain controlled cyclic triaxial tests, and piezoelectric bender element tests were conducted to evaluate the effect of treatment on various dynamic properties of the clay in particular shear modulus (G), damping ratio (D) and the small strain shear modulus (G max) respectively. The stabilization improves the shear modulus and damping ratio of the soil because the stress dissipation and energy absorption are more due to particle densification, pore volume reduction, and better bonding between the cemented particles. The results of cyclic triaxial and bender element tests indicate that the nano-silica in the presence of bioenzyme and cement can be a highly powerful technique in improving the moduli of the soil. • A new combination of cement, Nano-silica and bioenzyme is developed for soil stabilization. • The decrease in dynamic Shear modulus with the number of cycles was lower after soil stabilization. • The rise in damping ratio of treated soil implies more energy absorption by the soil and less impact during dynamic activity. • More pore pressure dissipation was observed in soil treated with the additives. [ABSTRACT FROM AUTHOR]

The stiffness properties of soils, particularly shear modulus and damping ratio, play a fundamental role in predicting the ground deformation during cyclic and dynamic loading. The dynamic properties can be used for the assessment of seismic ground response and the analysis of soil–structure interaction. This study provides a detailed dynamic characterisation of two liquefiable sandy soils, which have experienced earthquake-induced liquefaction, as historically documented. The soils were collected in the greater Lisbon area, in the south of Portugal. For this purpose, a comprehensive laboratory testing programme, which included a series of bender-element and resonant-column tests, was conducted. During the study, the effects of void ratio and mean effective stress on the soil stiffness were examined, focusing on the small-strain response. Results show shear modulus degradation and damping ratio curves, at small and intermediate shear strain levels, for saturated reconstituted samples under different stress conditions. Data obtained in the laboratory of both materials were fitted into normalised models to estimate the dynamic properties for different stress and state conditions. In addition, damping ratio curves were compared against the typical bounds of quartz materials. Stress-dependent models for estimating the maximum shear modulus and threshold shear strain amplitudes of both sands are proposed in this paper. The data provided in this study are useful for numerical analyses and geotechnical design, particularly when involving dynamic or seismic approaches. • Assessment in detail of the dynamic properties of two historically liquefiable sands. • Parameters to estimate the dynamic soil behaviour using a stress-dependency approach. • Computation of a specific void ratio function for the examined soils. • Fitting of experimental data into normalised design curves. [ABSTRACT FROM AUTHOR]

Small-strain dynamic properties of sands are commonly estimated through the correlations basically developed by the experimental results of isotropically consolidated specimens. In reality, however, the in-situ stress state of soils is not necessarily isotropic. Several resonant column tests were conducted on reconstituted samples of a coastal siliceous-carbonate sand in a variety of initial relative density and consolidation stress. The results indicate that despite the noticeable effect of initial stress anisotropy on the values of maximum shear modulus G max , the values of minimum damping ratio D min are almost independent of initial stress ratio. In a preceding paper, the authors proposed a correction factor for two siliceous and calcareous sands which correlates the shear modulus in anisotropic stress condition to the isotropic shear modulus. It is demonstrated herein that the proposed formula is precise for the siliceous-carbonate sand of the present study. The proposed empirical relationship is then compared with a correction factor proposed by others for shear modulus of sands in stress anisotropy condition. • Isotropic and anisotropic dynamic properties of a siliceous-carbonate sand are compared. • The effect of stress anisotropy on the D min and G max is investigated. • A correction factor is presented to capture the effect of stress anisotropy on G max. [ABSTRACT FROM AUTHOR]

A review of the current state of the art in the assessment of aging effects on soil liquefaction is presented in this paper. The review includes a summary of several field case histories indicating greater resistance to liquefaction in aged soils than in young uncemented soils during earthquakes, a discussion of the mechanisms that increase liquefaction resistance with time, an evaluation of proposed methods for quantifying the influence of aging processes (or diagenesis) on liquefaction resistance (K DR), and an evaluation of proposed predictor variables for K DR. The published literature indicates physical diagenetic processes tend to dominate the nature of interactions at the grain-to-grain contacts of sand deposits in the absence of sufficient cementing agents, while chemical processes tend to dominate where sufficient cementing agents are present. Variables proposed for predicting K DR include: the time since deposition or last critical disturbance; the ratio of measured to estimated small-strain shear wave velocity (MEVR); the ratio of small-strain shear modulus to cone tip resistance (G max /q c); the adjusted G max /q c (K G); and the ratio of measured to estimated adjusted G max /q c (MEK G). It is shown that MEVR , G max /q c , K G and MEK G are all ratios of measured to estimated or reference shear wave velocity. MEVR and G max /q c are slightly more robust predictors (i.e., regression equations with higher coefficient of regression and lower root mean square error) of K DR than K G and MEK G. Time is the least robust predictor of K DR. • Aging changes the soil's structure and liquefaction resistance with time. • Aging can be predicted using time, MEVR , G max /q c , K G or MEK G. • MEVR , G max /q c , K G or MEK G are ratios of measured to estimated or reference velocity. • MEVR and G max /q c are slightly more robust predictors of aging. • Time is the least robust predictor of aging. [ABSTRACT FROM AUTHOR]

Fibre-reinforcement has shown its efficacy in improving soil properties and been proposed to apply in increasing liquefaction resistance of deposits. As the contributions of fibres in real seismic conditions are yet to clarify, further investigations are needed to fill this gap. In this study, centrifuge tests have been conducted for this exploration. The dry pluviation preparation procedures for fibre-reinforced sand in centrifuge testing are disclosed in details for the first time. Results show that fibres are beneficial in preventing structure collapse of the sand matrix, but liquefaction induced excess pore pressures and ground surface settlements reduction is not apparently reduced as those in previous tests. Shear moduli are enhanced to some extent under lower confining stresses at relative larger shear strain levels, while equivalent damping ratios are increased at small strain levels. Limitation of simulating real conditions of previous element tests and 1 g shaking table tests may exaggerate the benefits of fibres. • Dry pluviation can be used to prepare fibre-reinforced sand for centrifuge tests. • Fibres have some beneficial effects on acceleration propagation in soil deposit. • Excess pore pressure and ground settlement are not apparently affected by fibres. • Fibres increase soil shear modulus. • Fibres increase soil equivalent damping ratio at small shear strain level. [ABSTRACT FROM AUTHOR]