Cyclic Triaxial Compression Tests Research Articles

Liquefaction resistance of sand reinforced with randomly distributed polypropylene fibres

This paper presents an experimental study on the effect of randomly distributed fibres on enhancing the liquefaction resistance of sand. A series of undrained cyclic triaxial compression tests and hollow cylinder torsional shear tests were conducted on saturated sand samples with and without fibres. The influencing factors (including fibre length, fibre content and relative density), which are closely related to the liquefaction resistance of sand, were investigated. The test results indicated that samples reinforced with randomly distributed fibres can sustain many more loading cycles than can samples without fibres before liquefaction occurs; that is, the inclusion of fibres can effectively improve the liquefaction resistance of sand. The liquefaction resistance increased with increasing fibre length and fibre content. The reinforcement effect is found to be significant in both medium dense samples and loose samples. The results from triaxial tests and hollow cylinder shear tests were similar, indicating that the different loading conditions in the two types of tests will not influence the reinforcement effect of randomly distributed fibres.

Practical method and application study for predicting cyclic accumulative deformations of the saturated soft clay

The distribution of saturated soft clay is greatly wide in China. The current main measures adopted to deal with soft soil foundations may lead to environmental pollution, even some engineering accidents may happen on soft soil foundations. In order to solve engineering problems of saturated soft soil foundations well, researches of mechanical properties of them are necessary. One of the most important mechanical characteristics of saturated soft clay is its cyclic accumulative deformation under cyclic loadings. For saturated soft clay, the cyclic accumulative deformation is similar to the creep behavior under static loadings. Therefore, the cyclic accumulative deformation is equivalent to the creep, the number of loading cycles is seen as the time, and this study develops a practical method for predicting the cyclic accumulative deformation of saturated soft clay with the creep theory. The method is a pseudostatic elasto-plastic finite element method implemented by ABAQUS software. A fitted equation between cyclic accumulative strain and number of loading cycles and the empirical relationship of parameters of fitted equation were established with a series of cyclic triaxial compression tests. Then with this empirical relationship of parameters, the method developed by this study was employed to predict the cyclic accumulative deformation under cyclic triaxial tension tests. Predicted results were in good agreement with test results, and the effectiveness of this method was thus validated for different stress states. The method was then applied in analyzing the cyclic accumulative deformation for soft soil foundation of a pile-supported wharf structure.

Mechanistic behaviour under traffic load of a clayey silt modified with lime

The behaviour under traffic loads of a soil modified with lime was researched through a laboratorial mechanistic approach. A clayey silty soil from Cebollatí, eastern Uruguay, and a commercial calcic lime were used. Cyclic triaxial compression tests were carried out on the soil treated with different lime contents, curing periods and dry densities in order to study its resilient behaviour. The fatigue life was investigated through cyclic indirect diametrical tensile tests by varying the lime content and curing period. A model of resilient modulus as power function of the deviator stress was found, independent of the lime content and curing period and dependent on the compaction effort. The model is similar to that observed in the natural soil, which means that the treated soil behaves as modified material. Nevertheless, the material is susceptible to fatigue cracking. The fatigue life, expressed as the number of load cycles up to break, is an inverse power function of the initial tensile strain, being most sensitive to that parameter. It was found that the fatigue life can be better explained when expressed as function of the ratio between the initial tensile strain and the tensile stain at break.

국내 철도 노반 흙재료의 반복재하에 따른 영구변형 발생 특성 및 상관성 분석

국내 철도 노반 흙재료의 반복재하에 따른 영구변형 발생 특성 및 상관성 분석

An elastoplastic bounding surface model for the cyclic undrained behaviour of saturated soft clays

A total stress-based bounding surface model is developed to predict the undrained behaviour of saturated soft clays under cyclic loads based on the anisotropic hardening modulus field and bounding-surface theories. A new hardening rule is developed based on a new interpolation function of the hardening modulus that has simple mathematic expression and fewer model parameters. The evolution of hardening modulus field is described in the deviatoric stress space. It is assumed that the stress reverse points are the mapping centre points and the mapping centre moves with the variation of loading and unloading paths to describe the cyclic stress-strain hysteresis curve. In addition, by introducing a model parameter that reflects the accumulation rate and level of shear strain to the interpolation function, the cyclic shakedown and failure behaviour of soil elements with different combinations of initial and cyclic stresses can be captured. The methods to determine the model parameters using cyclic triaxial compression tests are also studied. Finally, the cyclic triaxial extension and torsional shear tests are performed. By comparing the predictions with the test results, the model can be used to describe undrained cyclic stress-strain responses of elements with different stress states for the tested clays.

Behavior of Sand After a High Number of Cycles Application to Shallow Foundation

Considerable strains appear in the structures during accumulation of the irreversible strains of the subgrade under the effect of the cyclic loads. If the number of cycles is very large, even a small strain after accumulation becomes significant and sometimes harmful. In this study, a simple numerical modeling of the behavior of sand under cyclic loading is proposed. The suggested approach consists, in drained condition, in determining the parameters characterizing the average cyclic path of the soil under the effect of the number of cycles duly characterized and translating the cyclic effect by a volumetric strain cumulated by a variation of the module of the soil. In this study, we are interested in cyclic triaxial compression tests simulated by a finite element calculation. While proposing an analogy between the cyclic pseudo creep and the soft soil creep model (SSCM), on the first hand we propose an equivalence between the cyclic parameters and the parameters of SSCM, and on the other an equivalence time number of cycles will be established. The application of the formulation suggested on a shallow foundation under cyclic loading confirms the good adaptation of the model suggested to this type of problem.

Effects of Principal Stress Axis Rotation on Unsaturated Rail Track Foundation Deterioration

Precise assessment of cyclic plastic deformation of rail track subgrade is essential in designing cost effective rail tracks. Plastic deformation of rail tracks is often underestimated due to the omission of effects of principal stress axis rotation and water content on subgrade deformation. Moisture content of rail track subgrade is influenced by infiltration, seasonal ground water table variation and climate changes. To understand the influence of principal stress axis rotation and moisture content on the plastic deformation of soil, a series of cyclic moving wheel loading tests and cyclic triaxial compression tests were performed on unsaturated Toyoura sand, using a modified multi-ring shear apparatus. Results show that the presence of water in sand affects the cyclic plastic deformation of subgrade of rail tracks, significantly. The subgrade water content variation combined with the principal stress axis rotation further increases the accumulation of the cyclic plastic deformation of subgrade under moving wheel loads. Experimental results further conclude that the conventional experimental methods are unable to accurately assess the rail track deterioration process introduced by water content of rail track subgrade under repeated moving wheel load and highlight the requirements of realistic test methods such as the cyclic moving load multi-ring shear test, the cyclic hollow cylindrical test, or the model test in predicting rail track deterioration process of unsaturated subgrade under moving wheel loads.

Effect of film thickness on resistance to permanent deformation in asphalt mixtures

The resistance of asphalt mixtures against permanent deformation is one of important requirements that have to be verified in the design process of asphalt mixtures. In the case of asphalt concrete the European Standard EN 13108-1:2006 Bituminous Mixtures. Material Specifications. Part 1: Asphalt Concrete allows empirical (compositional recipes and requirements) or fundamental approach for testing of permanent deformation resistance. A fundamental approach specifies asphalt concrete in terms of performance-based requirements linked to limited prescription of composition and constituent materials. In this design approach a triaxial cyclic compression test is used to verify resistance to permanent deformation. The presented study investigates characteristics of resistance to rutting of asphalt concrete mixtures (eight mixtures of AC 11 from different producers) determined by triaxial cyclic compression test. The basic conclusions and statements of main factors influenced resistance to rutting (type of binder, binder content, and aggregate gradation) have been worked out from prevenient experience and experimental measuring. But measured test results presented in the following paper point out differences in resistance however the bitumen contents are relatively the same. During detailed investigation the tested asphalt mixtures had small differences in aggregate gradation. Changes in gradation make change of aggregate specific surface and the mixture needs different bitumen content to coat aggregate particles, to bound them to each other and to make stiff material resistant to rutting. The results from measuring of resistance to permanent deformation show the relation between aggregate specific surface and bitumen film thickness and permanent deformation.

Cyclic Behaviors of Granular Materials under Generalized Stress Condition Using DEM

AbstractMost behaviors of granular materials have been studied under the limit conditions of stress paths such as cyclic triaxial compression and extension tests. Furthermore, the macrobehavior and micromechanical response of granular materials under more comprehensive cyclic loading tests in the generalized stress condition are not well understood. The objectives of this paper are to ensure the ability of the Discrete Element Method (DEM), to simulate the macrobehavior of granular materials under various cyclic stress paths of the generalized stress condition, and to explore the micromechanical response. To this end, four different cyclic stress paths under generalized stress simulations, following the stress-controlled method on a sample of spheres, were conducted. To check the validity of DEM results, the experimental results of the real sand under cyclic stress programs were used. The macrobehaviors, indicated by the stress–strain–dilation relationship and the directions of principal strain increment ...

Effect of Cyclic Loading on the Lateral Behavior of Offshore Monopiles Using the Strain Wedge Model

This paper presents the effect of cyclic loading on the lateral behavior of monopiles in terms of load-displacement curves, deflection curves, andp-ycurves along the pile. A commercial software, Strain Wedge Model (SWM), was employed, simulating a 7.5 m in diameter and 60 m long steel monopile embedded into quartz sands. In order to account for the effect of cyclic loading, accumulated strains were calculated based on the results of drained cyclic triaxial compression tests, and the accumulated strains were combined with static strains representing input strains into the SWM. The input strains were estimated for different numbers of cycles ranging from 1 to 105and 3 different cyclic lateral loads (25%, 50%, and 75% of static capacity). The lateral displacement at pile head was found to increase with increasing number of cycles and increasing cyclic lateral loads. In order to model these deformations resulting from cyclic loading, the initial stiffness of thep-ycurves has to be significantly reduced.

Laboratory evaluation of asphalt concrete mixtures to permanent deformation

Several laboratory tests have been developed in order to detect the resistance of asphalt concrete mixtures to permanent deformation. Among them, the most commonly used are the wheel-tracking and the cyclic compression test. The purpose of this study was to compare the permanent deformation behaviour of asphalt concrete, under different testing procedures, when gradation and binder content was varied but within the tolerance limits. The asphalt concrete used was an AC 20 with 50/70 penetration grade bitumen. For the wheel-tracking test, three different procedures at two testing temperatures (45 and 60°C), were used: procedure A and B, in air, in accordance with EN 12697-22, and the procedure specified in BS 598-110. For the triaxial cyclic compression test, method B per EN 12697-25, was used at a testing temperature of 45°C. The results of the study showed that the aggregate gradation and the binder content even when both varied within the tolerance limits affect the performance in terms of permanent deformation. The ranking of the mixtures was found to be the same regardless of the testing procedure employed. As far as the acceptability of the mixtures was concerned it was found that by applying the limiting values set by PD 6691:2010, the BS 598-110 procedure and the small device, procedure B per EN 12697-22 gave different outcomes.

American and European Mix Design Approaches Combined

This paper describes a project that is part of NL-LAB, a larger, long-term program at Delft University of Technology, Netherlands, which aims to establish the predictive capacity of the current European functional tests for Dutch asphalt concrete (AC) mixtures. In this NL-LAB program, the functional characteristics of resistance to rutting (EN 12697–25), fatigue (EN 12679-24), stiffness (EN 12697–26), and moisture sensitivity (EN 12697-12 and EN 12697–23) are determined for specimens that are (a) mixed and compacted in the lab, (b) mixed in the plant and compacted in the lab, and (c) mixed in the plant and compacted in the road. Eventually, these tests will provide insight into the effect of mixing and compaction on the functional characteristics. The project described in this paper focused on the indirect tensile strength (ITS) and the triaxial cyclic compression test for two AC mixes. The properties found for all three stages of preparation were analyzed with the use of formalistic expressions from the NCHRP Design Guide 1–37A, Level 2, for the estimation of performance indicators. This project aimed to see if these relations remained valid for the Comité Européen de Normalisation tests, especially for mixes with high recycled asphalt pavement content. In the Netherlands, 50% reclaimed asphalt pavement is standard. It was found that the NCHRP Design Guide 1–37A expressions fit the Comité Européen de Normalisation test data quite well for the reclaimed asphalt pavement that contained mixes, especially for the ITS. Currently, another two construction projects are being sampled, and the results will be used to validate and improve the relations.

Test Study on Dynamic Deformation Behavior of Soft Rock-Concrete Sample under Cyclic Loading

Considering three contact states of good contact, containing weak interlayer and water, containing weak interlayer but no water, a series of cyclic triaxial compression tests of soft rock-concrete samples for investigation the dynamic deformation behaviors are carried out. The influence of contact states on dynamic properties of combination samples is analyzed based on the dynamic stress-strain curves and accumulative strain curves. The results show that changing the contact states has notable effects on the dynamic strain of the samples. Comparing with the good contact sample, the accumulative strain of the sample containing weak interlayer is about 2 times. The amplitude of the sample vibration increases, while the accumulative strain reduces with the increase of the vibration frequency. It can be noted that the measures such as assuring construction quality, removing weak interlayer and water, keeping good contact state between bedrock and tunnel structure can reduce the settlements and improve the tunnel service life.

Enhancing triaxial cyclic compression testing of hot mix asphalt by introducing cyclic confining pressure

Permanent deformation in terms of rutting is a major deterioration mode of bituminous bound pavements. The triaxial cyclic compression test (TCCT) is a scientifically accepted and standardised test method to assess the resistance to permanent deformation. Presently, the standard TCCT according to EN 12697-25 is carried out with cyclic axial loading and constant confining pressure. In road pavements, dynamic traffic loading due to passing tyres leads to cyclic confining pressures. Thus, to bring the TCCT closer to reality, within the study presented in this paper, (a) the radial reaction and its phase lag to axial loading in standard TCCTs is measured and (b) an enhanced TCCT with cyclic confining pressure which takes into account the viscoelastic material response in terms of radial phase lag to axial loading is introduced. In a subsequent test programme, TCCTs with various confining pressure amplitudes are run on different materials and results from standard and enhanced TCCTs are analysed and compared in terms of resistance to permanent deformation. It is shown that the resistance to permanent deformation increases significantly when the viscoelastic material response is taken into account in the TCCTs with cyclic confining pressure.

Constitutive model of saturated soft clay with cyclic loads under unconsolidated undrained condition

An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and extension tests were conducted to study the parameters of the model. Results showed that the relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain were nearly unique, when the initial octahedral shear stress ratios of specimens were equal to 0.3, 0.5 and 0.7. The relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain determined from the cyclic triaxial compression tests were basically the same as those determined from the cyclic triaxial extension tests. Furthermore, the relationships were not related to the initial stress condition, the test stress state and the octahedral cyclic shear stress ratio. The relationships determined from the cyclic triaxial tests under no deviatoric stress were basically the same as those determined from the cyclic triaxial tests under deviatoric stress. The change of the octahedral cyclic accumulative strain with the number of cycles was unique under different tests stress states. An equivalent visco-elastic constitutive model of saturated soft clay under UU condition was initially established.

Influence of asphalt compaction procedure on 3D deformation properties

In this study, the effect of various laboratory procedures for compacting hot-mix asphalt to form test specimens is investigated. Based on the triaxial cyclic compression test (TCCT) according to the European specification EN 12697-25, the resistance to permanent deformation of the specimen obtained from different types of laboratory compaction is studied. The deformation behaviour of the laboratory-compacted specimens is always compared with the deformation properties stated in TCCT for the asphalt mix specimen taken from on-site roller-compacted road pavement. As a result, the effect of the choice of laboratory compaction procedure on the resulting deformation behaviour in TCCT is assessed.

순환골재를 포함한 입상재료의 특성에 관한 실험적 연구

PURPOSES : In Korea, most designs of pavement had been mainly performed by considering CBR of granular materials before KPRP(Korea Pavement Research Program) and 86 AASHTO design method were introduced. Since then, the trend of the pavement designs gradually have moved to using mechanical characteristics throughout the resilient modulus based on the test results up to recently. In this study, we should like to research the mechanical characteristics of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. METHODS : The kinds of materials were tested; coarse grained subbase materials, refining aggregates base materials and recycled aggregates. RESULTS : The present study aims to figure out the resilient modulus of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. CONCLUSIONS : The test results revealed that the engineering properties of the recycled aggregates were more excellent than the those of others.

Fatigue Behavior of Granite Subjected to Cyclic Loading Under Triaxial Compression Condition

A series of laboratory tests were performed to examine the fatigue behavior of granite subjected to cyclic loading under triaxial compression condition. In these tests, the influences of volumetric change and residual strain on the deformation modulus of granite under triaxial cyclic compression were investigated. It is shown that the fatigue behavior of granite varies with the tendency for volumetric change in triaxial cyclic compression tests. In the stress- strain space, there are three domains for fatigue behavior of rock subjected to cyclic loading, namely the volumetric compaction, volumetric dilation with strain-hardening behavior, and volumetric dilation with strain-softening behavior domains. In the different domains, the micro- scopic mechanisms for rock deformation are different. It was also found that the stress level corresponding to the transition from volumetric compaction to volumetric dila- tion could be considered as the threshold for fatigue failure. The potential of fatigue deformation was compared with that of plastic deformation. The comparison shows that rocks exhibit higher resistances to volumetric deformation under cyclic loading than under plastic loading. The influence of residual strain on the fatigue behavior of rock was also investigated. It was found that the axial residual strain could be a better option to describe the fatigue behavior of rock than the loading cycle number. A con- stitutive model for the fatigue behavior of rock subjected to cyclic loading is proposed according to the test results and discussion. In the model, the axial residual strain is con- sidered as an internal state variable. The influences of confining pressure and peak deviatoric stress on the deformation modulus are considered in a term named the equivalent stress. Comparison of test results with model predictions shows that the proposed model is capable of describing the prepeak fatigue behavior of rock subjected to cyclic loading.

Permanent Strain Development Dynamics for Asphalt Pavement Materials

This article gives the summary of the author’s PhD thesis supervised by Prof Dr Sc Ing Juris Rihards Naudžuns and defended on 10 November 2010 at the Riga Technical University. Introduction provides characteristics of the object of the research – asphalt concrete – from chemical, physical and mechanical aspects. The current situation on the roads and in Latvian transport industry has been described, and urgency of the problem, the necessity to eliminate deficiencies and the economic effect has been substantiated. The aim and tasks of the thesis have been formulated. Chapter 1 is devoted to survey of the literature which provides new and the already known (classical) modelling methods of stress and strain of road pavement layers, as well as description of advantages and deficiencies of these methods. Chapter 2 contains description of test methods used in the Promotion thesis. Properties of experimental specimens and their raw materials have been compared. Methods of designing asphalt mixtures are described. Chapter 3 provides analysis of external factors causing asphalt concrete permanent strain – temperature and transport load. In Chapter 4, test specimens have been experimentally tested with the help of the performance testing methods (wheel tracking test, uniaxial cyclic compression test and triaxial cyclic compression test). Plastic deformations have been determined and deformation rates have been calculated. In Chapter 5, the asphalt pavement quality provision system has been developed on the basis of the analysis of the obtained results and recommendations have been provided for minimising rutting. This thesis is written in Latvian and is available on http://ortus.rtu.lv/ web page and from the author upon request.

Quantification of the properties of enzyme treated and untreated incinerator bottom ash waste used as road foundation

A substantial amount of incinerator bottom ash (IBA) waste is generated annually from burning municipal solid waste. IBA is similar to aggregate consisting of ferric metals, non-ferrous metals, brick and tile fragments, ceramic, glass, stone, dirt, etc. In this work, IBA waste was mixed with conventional limestone aggregate in an attempt to achieve a blend with acceptable mechanical properties and minimum environmental risks for use in road foundation layers. Enzyme treatment was applied in order to improve the behaviour of IBA–limestone blends. A series of laboratory tests, such as cyclic triaxial compression tests, pH monitoring and scanning electron microscope, were adopted to determine the materials' mechanistic behaviour and microstructure characteristics. Emphasis was on examining the effect of various parameters, such as IBA content, enzyme content, moisture content and curing time. Results of this study showed that IBA blends gave a favourable performance as road foundation layers in comparison with the control limestone blend. Microstructure and chemical analysis results showed that the addition of plant-based enzyme improved the mechanical properties of the control limestone blend; however, it did not have any noticeable effect on the IBA blends.