Cyclic Simple Shear Research Articles

Detailed particle breakage of crushable granular materials under cyclic shearing conditions using dyed gypsum technique

Particle breakage of granular materials under cyclic shearing is related to a variety of engineering problems in geotechnical and transportation engineering. However, there is limited understanding regarding the detailed evolution law of breakage under cyclic shearing. To this end, a series of cyclic simple shear tests were conducted on artificially dyed gypsum particles. It was observed that, in contrast to the particle size distribution of the whole sample, the fractional particle size distributions of gap-graded samples followed a unified breakage evolution path as those of the uniformly graded ones and tended towards fractional fractal distributions. These results have inspired the introduction of the fractional breakage index. Moreover, the breakage-plastic work relationship was further extended to describe the breakage of fractional particles, incorporating the effect of the number of cycles on the plastic work distribution. Finally, based on the concept of breakage-packing, a predictive model for plastic work-breakage-deformation of crushable granular materials under cyclic shearing was proposed. These results have the potential in understanding the detailed particle breakage evolution and establishing a predictive framework for the breakage-induced deformation of crushable granular materials.

Cyclic response of unsaturated weathered red mudstone: Experimental investigation and a cyclic model

The mechanical properties and constitutive model of unsaturated soils under cyclic loading are crucial for understanding the behavior of foundations and slopes subjected to dynamic motions such as earthquakes and traffic loading. In this study, multilevel strain-controlled cyclic simple shear tests of unsaturated weathered red mudstone (WRM) were conducted. The detailed investigation focused on cyclic responses, including shear stress-strain behavior and volume change, strain-dependent secant shear modulus and damping ratio, and stress–dilatancy behavior. This study revealed the significant influences of the degree of saturation and vertical stress on these responses, with the initial static shear stress mainly affecting the shear stress-strain behavior and volume changes at the initial loading stage. Based on the experimental observations, a cyclic constitutive model was proposed for unsaturated WRM. The model incorporates a slightly revised Davidenkov model and Masing criterion to generate shear stress-strain hysteresis loops with or without initial static shear stress. Additionally, a stress-dilatancy equation was included to capture the volume changes during cyclic loading. The proposed model was verified by comparing representative test data and calculation results, demonstrating the excellent performance of the proposed model in modeling the main features of unsaturated WRM under cyclic loading.

Role of Tangential Displacement Amplitude in 3D Cyclic Simple Shear Behavior of Gravel–Steel Interface

Role of Tangential Displacement Amplitude in 3D Cyclic Simple Shear Behavior of Gravel–Steel Interface

Experimental Study on Cyclic Simple Shear Test of Coastal Tidal Soft Soil

Based on undrained cyclic simple shear tests conducted on coastal tidal soft soil under various conditions of cyclic stress ratios and moisture contents, this study investigated the influence of these factors on the dynamic properties of the soil. The findings indicated that with increasing moisture content and stress cycle ratio, the stress–strain hysteresis loop gradually expanded, resulting in a higher strain difference and a transition from a dense to a sparse curve pattern. Moreover, the symmetry of the hysteresis loop was lost in the later stages of shearing. With an increase in the number of cycles, the cumulative shear strain gradually increased, and the increase in the cyclic ratio of water content to stress reduced the number of cyclic shear cycles required to achieve failure, thereby accelerating the soil’s failure rate. A predictive formula was developed based on the experimental results to estimate the failure cycles as a function of the cyclic stress ratio and moisture content. Furthermore, the softening index decreased gradually with an increasing number of cycles, and a higher moisture content and cyclic stress ratio accelerated the soil’s softening process. It was observed that under the conditions of optimal moisture content, the soil exhibited a slower softening rate during the initial stage of shearing.

Undrained cyclic behavior of underconsolidated marine clay in multidirectional simple shear tests

In the field of marine reclamation engineering, underconsolidated marine clay often presents challenges owing to its susceptibility to multidirectional cyclic stresses and potential for excessive deformation. This research examined the undrained cyclic behavior of underconsolidated marine clay through multidirectional cyclic simple shear tests. It explored shear strain evolution, the cyclic shear stress–strain relationship, and stiffness degradation by analyzing the impacts of clay consolidation levels and phase differences in the cyclic stress. The findings indicated that as the degree of consolidation increased, the rate of cyclic shear strain development in marine clay gradually diminished. Conversely, an enhanced phase difference led to a quicker evolution of shear strain. Additionally, as loading continued, the tested clay exhibited notable softening behavior, leading to stiffness degradation. A larger phase difference resulted in more pronounced stiffness degradation, although a higher degree of consolidation effectively delayed this degradation. These findings provide new insights on the cyclic behavior of underconsolidated marine clay under multidirectional loading, offering crucial information for marine reclamation engineering.

Pore pressure development model of fiber-reinforced calcareous sand based on shear strain characteristics

In this study, the pore pressure buildup characteristics of fiber-reinforced calcareous sand were investigated by examining the influences of fiber contents and fiber length through a series of cyclic simple shear tests. The test results indicate that the generation mechanisms of pore pressure ratio and shear strain of fiber-reinforced calcareous sand are interrelated under cyclic loading. The fiber content and fiber length have a significant influence on the relationship of pore pressure ratio versus number of cycles. Nevertheless, the correlation of pore pressure ratio versus shear strain is independent of fiber content and fiber length. According to the unique relationship, a pore pressure development model based on shear strain was established, exhibiting excellent predictive accuracy in simulating the pore pressure generation of fiber-reinforced calcareous sand with various fiber content and fiber lengths under cyclic loading. Moreover, the proposed model is also applicable to clean calcareous sand and siliceous sand.

Stress-density model validation: Free-field liquefaction analysis

Liquefaction has caused severe damage to buildings and infrastructure during numerous earthquakes, leading researchers to develop constitutive models that can capture complex soil behaviour in liquefaction-induced phenomena. Constitutive models require validation against laboratory or real-world data to assess their capability. This paper first discusses the recent implementation of the stress-density (S-D) model in the OpenSees finite element platform. Subsequently, calibration and validation phases evaluate the performance of the S-D model against two previously conducted centrifuge tests. Single-element simulations of cyclic simple shear tests inform the parameter calibration for the Nevada sand, which comprises the two main layers in the centrifuge tests. The validation phase consists of eight 1-D site response analyses in OpenSees compared to the centrifuge tests in terms of accelerations, spectral accelerations, pore water pressures, and settlements. The current study shows that the model reasonably predicts the soil behaviour in terms of acceleration and pore water pressure, particularly in the liquefiable layer.

Rubber-sand infilled soilbags as seismic isolation cushions: experimental validation

This study proposes the use of soil bags filled with a rubber sand mixture (SFRSM) to address the issue of weak stability associated with rubber-sand layers for seismic isolation. To evaluate the dynamic characteristics of the SFRSM, large-scale cyclic simple shear tests were conducted to investigate the effects of rubber content, vertical pressure, shear displacement amplitude, fill percentage, and laying scheme. Furthermore, shaking table tests were carried out to evaluate the impact of vibration intensity and frequency on the seismic isolation of SFRSM layers. The results indicate that (1) Compared to the rubber-sand layer, the SFRSM exhibits a lower shear modulus and higher damping, indicating its potential for greater seismic isolation and energy dissipation. (2) The dynamic characteristics of the SFRSM were significantly influenced by the fill percentage and laying scheme, suggesting that an effective isolator capable of withstanding various external conditions could be developed. (3) The isolating effect of the SFRSM layer is attributed to its ability to dampen high-frequency vibration components effectively. Additionally, the threshold frequency required to trigger attenuation decreases with an increasing number of SFRSM layers. In summary, these experimental results provide evidence that the proposed innovative strategy enhances the strength and vertical stiffness of the original rubber-sand layer, making it well-suited for seismic design applications in low-rise buildings in less-developed regions. Highlights 1. A novel seismic isolation strategy using the soil bags filled with rubber-sand mixture (SFRSM) was proposed. 2. Large-scale cyclic simple shear tests were conducted to evaluate the dynamic properties of SFRSM. 3. The influence of key parameters on the dynamic shear modulus and damping ratio of SFRSM was analysed. 4. The proposed strategy is well suited for the seismic design of low-rise buildings in less-developed regions.

Effect of stage amplitude ratio on dynamic behaviors of sand under wind turbine loading

Offshore wind turbines are subjected to more significant wave and wind environmental loads at extreme weather conditions, making subsoil experience various loading stages with different amplitudes. To investigate the coupling effect of both cyclic shear stress ratio (CSR) and stage amplitude ratio (Ar) between normal and extreme weather conditions, a series of bi-directional simple shear tests with five different Ar and three CSR values were conducted on marine sand using the variable-direction dynamic cyclic simple shear (VDDCSS) apparatus. In the tests, soil samples were compacted under vertical stress and then sheared in undrained conditions by applying two shear stresses acting in different horizontal directions. Test results indicated that the cyclic strain, pore water pressure ratio, and cyclic strength were significantly determined by the value of stage amplitude ratios and the CSRs: at the same CSR, cyclic strains, and pore water pressure increased while cyclic strength decreased with the Ar. Comparing the test data between various cyclic stress ratios found that the CSRs can accelerate shear strains, pore pressure accumulation, and cyclic strength attenuation.

Investigating the Dynamic Behaviour of Bottom Ash Versus Sand Using Cyclic Simple Shear Tests

Investigating the Dynamic Behaviour of Bottom Ash Versus Sand Using Cyclic Simple Shear Tests

A novel experimental database on the cyclic response of mine tailings

Understanding the cyclic response of mine tailings is key for areas with moderate to high seismicity and an active mining industry (e.g. the United States, Peru, and Chile). However, assessing the cyclic response of mine tailings still relies on procedures and correlations developed for natural soils (i.e. sands and clays). This is due to information on the cyclic response of mine tailings being rather scarce compared to natural soils. Hence, it remains unclear if more efficient approaches can be implemented. This study presents an experimental database focused on the cyclic response of mine tailings compiled from various sources. The database is organized considering three classes, where all three contain cyclic simple shear (CSS) information. Class A also includes triaxial (Tx) and cone penetration testing (CPTu) information, Class B has Tx or CPTu information, and Class C contains no additional information beyond CSS. Most materials belong to Class A. It is worth noting that Class C (only cyclic information) is comparable with most databases for natural soils, hence highlighting the uniqueness of our database. In total, the database contains 129 CSS tests on 20 materials that represent a broad range of mine tailings. Thirteen materials belong to Class A, 5 to Class B, and 2 to Class C. In discussing the database, key information (e.g. the range of liquefaction resistance curves) is shared. In addition, potential assessments that can be conducted with the database are illustrated. The study closes by presenting the database organization and discussing potential uses. The database is available under the following DOI: https://doi.org/10.17603/ds2-1k0a-dt17

Cyclic liquefaction of granular materials with varied forms under multidirectional loads

Both the liquefaction resistance of granular materials under complex multidirectional cyclic loadings and the influence of particle form or morphology on that resistance are poorly understood. This paper presents an experimental investigation on this topic. Round, frosted, concave and convex glass beads as well as Hong Kong completely decomposed granite (CDG) sand were used to prepare samples with varying particle morphologies (i.e. roughness, sphericity, aspect ratio and convexity). Unidirectional and multidirectional cyclic simple shear tests were performed to examine the liquefaction susceptibility and highlight the specific role of various particle morphologies. Results show that the increase of shape irregularity and surface roughness both result in a considerable liquefaction resistance improvement. Moreover, overall shape has a more fundamental effect on liquefaction behaviour than surface roughness. An enhanced morphology index, providing a collective description for the particle geometry and surface texture, are proposed to optimise the correlation with liquefaction behaviour. In addition, it is discovered that multidirectional loading could exacerbate the generation of pore pressure and trigger a sharp increase in shear strain amplitude at a lower excess pore pressure ratio. Accordingly, a novel analytical procedure for estimating the liquefaction resistance, independent of cyclic loading patterns and particle morphology, is developed and validated by additional data in the literature.

Sand liquefaction in simple shear tests

Liquefaction is a phenomenon marked by a rapid loss of soil strength and stiffness, which generally occurs in loose saturated sandy deposit during earthquake because of the generation of excess pore water pressure. Several experimental researches concluded that liquefied soil behaves as a fluid during ground movement, but after the earthquake motion ceases, due to the dissipation of excess pore water pressure, the liquefied soil recovers its initial stiffness and returns to behave as a solid. Liquefaction resistance of sandy soil can be studied by means of Cyclic Simple Shear (CSS) test or Cyclic Triaxial (CTX) tests. While CTX tests are widely used in liquefaction studies due to their simplicity, CSS tests are more representative of stress conditions produced during an earthquake by simulating the continuous rotation of the principal stress axes. In this research the preliminary results of CSS tests carried out with confining rings on the sandy samples retrieved in the South of Sicily are reported. The apparatus is described in detail. All samples used were obtained from the same type of Italian sand by using same preparation method to minimize the number of factors influencing the results. Moreover, all tests were conducted by a single operator. All experimental results are reported in the plane cyclic resistance ratio (CRR) and number of cycles where liquefaction occurs (Nliq) in order to assess the liquefaction phenomenon.

Effects of initial static shear on liquefaction behaviour of Toyoura sand in undrained multi direction dynamic cyclic simple shear tests and DEM

Effects of initial static shear on liquefaction behaviour of Toyoura sand in undrained multi direction dynamic cyclic simple shear tests and DEM

Shear modulus prediction of landfill components using novel machine learners hybridized with forensic-based investigation optimization

The assessment of the shear modulus (G) of municipal solid waste (MSW) and leachate-contaminated soil (LCS) is of vital importance for landfill engineering investigation and achieving sustainable development goals. In this study, 153 cyclic triaxial tests on MSW (reconstructed samples under CU conditions) and 104 cyclic simple shear tests (strain controlled) on LCS were conducted to assess the shear modulus. The examined variables are plastic percentage (0–0.274), age (0–16 years), shear strain (0.075–3.63%), unit weight (9 and 12 KPa), frequency (0.1–1 Hz), and confining pressure (75 and 150 KPa) for MSW and leachate content (0–40%), shear strain (0.05–1%), frequency (0.1 and 1 Hz), and vertical load (50–350 KPa) for LCS. Laboratory assessment of cyclic parameters is costly and complicated which requires precise testing and the experts. Therefore, multiple types of ensemble models (AdaBoost, GBRT, XGBoost, and Random Forest (RF)) were utilized along with Forensic-Based Investigation Optimization (FBIO). The application of numerical and computational approaches as the main novelty of the research can be a step forward to save time and money. The performance comparison of the established models on experimental datasets showed that GBRT- FBIO model outperformed the other models for G-MSW (R2 =0.99, RMSE=0.164, MAE=0.122, MAPE=0.073, and a20-index=0.956 for testing datasets) and G-LCS (R2 =0.99, RMSE=0.477, MAE=0.385, MAPE=0.028, and a20-index=1 for testing datasets). Finally, the outcomes of the sensitivity analysis also displayed the most participation of shear strain (50.87%) and vertical load (52.1%) to the shear modulus of MSW and LCS.

Macro–Meso Mechanical Behavior of Loose Sand under Multi-Directional Cyclic Simple Shear Tests

Loose sand samples under different complex shear paths and directions of consolidation shear stress were simulated using bi-directional simple shear DEM models. Liquefaction characteristics and corresponding meso-mechanisms were analyzed, and the following conclusions were drawn. Bi-directional cyclic shear stress accelerated the drop in vertical stress, especially in the first and last cycles. Compared to uni-directional cyclic simple shear tests, the contact force between particles decreased faster in bi-directional cyclic simple shear tests. With an increased θ, the skeleton of the sample became unstable, and more particles were in a floating state, making the sample easier to liquefy. The mechanical coordination number decreased rapidly at the beginning and the end of shearing, and was relatively stable in the middle; it was around 4.2 when samples were liquefied. The magnitude of the anisotropy tensor gradually increased during shearing. Under bi-directional shear paths, the sample’s skeleton structure was subjected to a greater disturbance during the initial shear stage, caused damage to the particle skeleton and faster liquefaction. With an increased θ, the amplitude and peak value of the anisotropy tensor increased.

Cyclic response of unsaturated weathered red mudstone under various conditions of initial static shear stress and moisture content

Slope stability in weathered red mudstone (WRM) sediments during earthquakes is strongly dependent on the cyclic response of unsaturated WRM. In this paper, the cyclic simple shear tests on unsaturated WRM were conducted, and the influencing factors, including the moisture content (w), initial static shear stress (τs), cyclic stress amplitude (τcyc) and vertical stress (σv) were investigated in detail. The test results showed that the existence of τs affects the development patterns of shear stress–strain curves induced by increasing number of loading cycles (N). For specimens without τs, a closed hysteretic loop is formulated in each cycle, and no residual strain occurs. The hysteretic loop of WRM with τs is unclosed, and the residual strain accumulates with increasing N. The initial static shear stress usually exists within soil in slopping ground; thus, deformation accumulation is the main failure model under cyclic loading. The accumulated plastic shear strain was then presented in detail, and the test results indicated that the accumulated plastic shear strain at an identical cycle increases with increasing τs, τcyc and w, but decreases with increasing σv. Finally, the cyclic resistance corresponding to three identical accumulated shear strains (0.5%, 1.5%, and 2.0% in this study) was studied, and a unified cyclic stress ratio, USR, was proposed to build a united model of unsaturated WRM cyclic resistance, in which the effects of τs, σv, τcyc and w were considered uniformly.

Loading rate influence on high-cyclic loading of clays

Experimental observations reported in the literature, based on cyclic triaxial and cyclic simple shear tests, show that the loading frequency influences the excess pore pressure and strain accumulation for fine-grained soils under undrained conditions. A high-cycle accumulation (HCA) model for clay was introduced by Wichtmann (2016) and Staubach et al. (2022) to quantify the strain/pore pressure accumulation as a function of the number of applied cycles, amplitude, void ratio, stress ratio, OCR and loading frequency. This article explores the convenience of including the loading frequency factor in the HCA clay model based on the interpretation of a series of cyclic undrained triaxial tests performed on three different clay materials, namely Dorfner kaolin, Lower Rhine clay and Onsøy clay. Analysis of results shows that for those specific three clay materials, the normalization of the pore pressure accumulation rate u̇acc with the amplitude function fampl purifies the data from the influence of loading frequency and thus no explicit frequency function ff is required.

Evaluation of liquefaction strength of Japanese natural sandy soil using triaxial and simple shear tests

The aim of this note is to reexamine the stress and strain conditions of cyclic triaxial and cyclic simple shear tests for evaluating the liquefaction strength of natural sandy soil. The conventional method of determining the liquefaction strength relies on the shear stress components. However, the use of stress invariants eliminates the need to specify the stress components, thereby making it a more rational approach for determining the liquefaction strength. A comparison of the results using the conventional stress ratio and the stress invariant ratio is done in this study. A strong correlation is seen between the liquefaction strengths obtained from the triaxial and the simple shear tests when using the stress invariant ratio. Despite this strong correlation, large scattering still remains due to the effects of the soil fabric of the natural sandy soil. A torsional hollow cylindrical device is used here to perform simple shear tests on undisturbed natural sandy soil.

Monotonic and Cyclic Simple Shear Response of Well-Graded Sandy Gravel Soils from Wellington, New Zealand

In the 2016 Kaikoura earthquake, liquefaction of gravelly soils from reclaimed fills occurred in CentrePort, Wellington, New Zealand. This study presents constant volume monotonic and cyclic simple shear tests on well-graded gravel with sand collected from CentrePort. A large-scale cyclic simple shear device is utilized to evaluate the monotonic, cyclic, and postcyclic responses of the sandy gravel soils. Specimens prepared at various relative densities were subjected to a vertical effective stress of 100 kPa and then monotonically and cyclically sheared. After the cyclic loading, the postcyclic response was evaluated, including volumetric compression or monotonic shear with or without dissipation of excess pore water pressure. Shear wave velocity was measured before and after the cyclic loading. The results show that the well-graded sandy gravel has a high potential for liquefaction, with higher relative density specimens having higher liquefaction resistance. Postcyclic volumetric strain is primarily correlated with density and maximum shear strain during cyclic loading. Postcyclic reconsolidation causes densification of the liquefied specimens, resulting in higher monotonic shear resistance, while postcyclic monotonic shear without dissipation of excess pore water pressure reveals that substantial shear strain is required to develop the shear resistance. Shear wave velocity was significantly reduced after liquefaction, but recovered to slightly higher than its precyclic shear values after reconsolidation. Compared to other gravelly and sandy soils, the well-graded sandy gravel showed a similar or slightly higher liquefaction resistance than gap-graded and uniform gravels. Moreover, the well-graded sandy gravel had a relatively lower ultimate postcyclic volumetric strain due to a small variation between its maximum and minimum void ratios. The results advance our understanding of the liquefaction resistance and subsequent postcyclic responses of the well-graded sandy gravel soils.