Articles de revues : « Repeated load triaxial test »

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Puppala, Anand J., Aravinda M. Ramakrishna et Laureano R. Hoyos. « Resilient Moduli of Treated Clays from Repeated Load Triaxial Test ». Transportation Research Record : Journal of the Transportation Research Board 1821, n^o 1 (janvier 2003) : 68–74. http://dx.doi.org/10.3141/1821-08.

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Three chemical stabilization methods—sulfate resistant cement (Type V), low-calcium fly-ash (Class F) mixed with sulfate resistant cement (Type V), and ground granulated blast furnace slag—were used in a series of repeated load triaxial tests on clayey soil to assess the effectiveness of these three stabilizers in enhancing resilient modulus ( MR) properties of the soil. MR results were measured from repeated load triaxial tests conducted on both control and treated soils at optimum moisture content levels. Test results were analyzed to understand the potentials of each stabilizer on MR response of the soils and to study the effects of confining and deviatoric stresses on resilient response of the treated soils. Mechanisms for MR enhancements in treated soils were developed, and a series of flexible pavement design exercises was conducted to evaluate the impact of each stabilizer on the design thickness of the asphalt surface layer of pavements.

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Lekarp, Fredrick, et Ulf Isacsson. « The Effects of Grading Scale on Repeated Load Triaxial Test Results ». International Journal of Pavement Engineering 2, n^o 2 (juillet 2001) : 85–101. http://dx.doi.org/10.1080/10298430108901719.

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Ji, Jie, Meng Chen, Zhi Suo, Jianming Wei, Jiani Wang et Lei Chen. « Rutting Prediction Model of Asphalt Mixture Based on the Triaxial Repeated Load Test ». Advances in Civil Engineering 2021 (24 juin 2021) : 1–9. http://dx.doi.org/10.1155/2021/5238680.

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This study establishes a more reasonable and effective rutting prediction model called the quadratic modified Burgers rheological model by considering dynamic loads. Use ABAQUS to simulate the rutting depths through the existing Burgers model and the quadratic modified model and compare with the measured values of the multitemperature and load rutting tests and triaxial repeated load tests. The real tests were conducted on four asphalt mixtures, including SK-90 asphalt mixture, styrene-butadiene-styrene (SBS) modified asphalt mixture, direct coal liquefaction residue (DCLR) modified asphalt mixture, and compound DCLR modified asphalt mixture. The results showed that the range of error ratio and residual sum of squares between simulated and measured rutting depth based on the two different models are 5–35%/5.0–8.74% and 3–15%/0.9–3.1%, respectively, which show that the quadratic modified Burgers rheological model has a more accurate prediction.

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Puppala, Anand J., Suppakit Chomtid et Venkat Bhadriraju. « Using Repeated-Load Triaxial Tests to Evaluate Plastic Strain Potentials in Subgrade Soils ». Transportation Research Record : Journal of the Transportation Research Board 1913, n^o 1 (janvier 2005) : 86–98. http://dx.doi.org/10.1177/0361198105191300109.

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The design and the analysis of flexible pavement systems depend on soil layer characterization, traffic loads, and number of passes. The current AASHTO design method for flexible pavements uses resilient characteristics of subsoils to characterize and determine the structural support of each layer and to design the thickness of the layers. This moduli property, however, does not fully account for the plastic strain or rutting potentials of subsoils, as in the cases in which silt and mixed soils undergo high plastic deformations but possess high resilient properties. A study was initiated to establish a test procedure to use a repeated load triaxial device to measure plastic strain potentials of subgrade soils. Laboratory-compacted soil specimens were subjected to a repeated deviatoric load, determined as a percentage of static deviatoric load at failure under un-consolidated undrained conditions. The plastic strains were monitored during 10,000 repeated load cycles, and the accumulated plastic deformations were determined. The test procedure and test results conducted on two types of soils, a coarse sand and silty sand, are presented. Effects of soil type, compaction moisture content, dry unit weight, confining pressure, and deviatoric stresses on the plastic strains were addressed.

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Xue, Guoqiang, et Xiaoming Huang. « Research on Permanent Deformation of Asphalt Mixture by Triaxial Repeated Load Test ». Journal of Highway and Transportation Research and Development (English Edition) 5, n^o 1 (mars 2011) : 13–18. http://dx.doi.org/10.1061/jhtrcq.0000035.

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Hussain, Jawad, Douglas J. Wilson, Theunis F. P. Henning et David Alabaster. « Comparing Results between the Repeated Load Triaxial Test and Accelerated Pavement Test on Unbound Aggregate ». Journal of Materials in Civil Engineering 26, n^o 3 (mars 2014) : 476–83. http://dx.doi.org/10.1061/(asce)mt.1943-5533.0000822.

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Tutumluer, Erol, Navneet Garg et Marshall R. Thompson. « Granular Material Radial Deformation Measurements with a Circumferential Extensometer in Repeated Load Triaxial Testing ». Transportation Research Record : Journal of the Transportation Research Board 1614, n^o 1 (janvier 1998) : 61–69. http://dx.doi.org/10.3141/1614-08.

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Determination of both axial and radial specimen strains in a repeated load triaxial test is essential for properly characterizing the directional dependency of resilient granular material behavior. Radial deformation measurement is not yet included in the standard AASHTO test procedure. The method of measuring radial strains adopted in this study emphasizes the use of a contact-type specimen instrumentation technique with a circumferential chain extensometer. The circumferential extensometer was successfully used in repeated load triaxial testing to measure radial strains of three aggregate samples with different material types and properties. The accuracy of the measuring system was within 10−5 (in strains) when the smallest strains recorded were on the order of 10−4. Nonlinear stress-dependent models for properly characterizing the anisotropic granular material stiffnesses were developed from measured axial and radial strains. The vertical/horizontal stiffness ratios in the triaxial sample consistently increased with increasing principal stress ratios, which often occurs in pavements under wheel loading. In general, the repeatability in radial strain measurements was deemed to be satisfactory and more reliable strains were measured at low confining pressures.

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Zhao, Yu, Jie Liu et Hong Juan Wu. « The Experimental Study on Engineering Characteristics of Improved Clay ». Advanced Materials Research 463-464 (février 2012) : 169–74. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.169.

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The rapid transit railway foundation bed bears the repeated dynamic load of train besides the static-load from upper structure. The engineering characteristics of improved clay, in especial the dynamic performance under repeated dynamic load or train, is the key factors to determine the improved clay can be used as roadbed fill material. In this paper, the dynamic triaxial test is adopted to imitate the repeated load of train, and the engineering characteristics of improved clay is studied such as dynamic stress plastic strain and elastic strain etc. which influence the running seriously.

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Tutumluer, Erol, et Umit Seyhan. « Neural Network Modeling of Anisotropic Aggregate Behavior from Repeated Load Triaxial Tests ». Transportation Research Record : Journal of the Transportation Research Board 1615, n^o 1 (janvier 1998) : 86–93. http://dx.doi.org/10.3141/1615-12.

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Determining horizontal specimen response in a repeated load triaxial test is essential to properly characterize the directional dependency of unbound aggregate resilient behavior under anisotropic loading conditions. Recent research has applied artificial neural networks (ANNs) for predicting, in the absence of lateral deformation data, the anisotropic stiffness properties of granular materials from standard AASHTO tests. Feed-forward backpropagation-type neural networks were successfully trained with two triaxial stresses (confining pressure and applied deviator stress), measured vertical deformation, and two aggregate properties (compacted dry density and crushed particle percentage) used as input variables. The output variables were the horizontal and shear moduli for which the actual (target) values were derived and computed from test results. The ANN models predicted the two moduli, with mean errors of less than 3 percent compared with those computed by using experimental stresses and strains. Both the applied stress state and the aggregate properties were found to affect the generalization and thus the prediction ability of the ANN models.

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Qiao, Yaning, Andrew Dawson, Anders Huvstig et Leena Korkiala-Tanttu. « Calculating rutting of some thin flexible pavements from repeated load triaxial test data ». International Journal of Pavement Engineering 16, n^o 6 (22 août 2014) : 467–76. http://dx.doi.org/10.1080/10298436.2014.943127.

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Nataatmadja, A., et A. K. Parkin. « Characterization of granular materials for pavements ». Canadian Geotechnical Journal 26, n^o 4 (1 novembre 1989) : 725–30. http://dx.doi.org/10.1139/t89-083.

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For design and analysis of flexible pavements, a simple elastic model that does not require cumbersome calculation and also can rank materials according to their performance is clearly desirable. Early studies indicated that the resilient modulus of a granular material can be taken to be a function of the first invariant of stress, θ, although there is evidence that it is also dependent on the repeated deviator stress, qr. The limitations of some earlier models are discussed herein and a simple model for granular materials is proposed. The model is empirical in nature and based on repeated load triaxial testing with constant confining pressure. The application of this model in situations where the confining pressure is pulsed in phase with the deviator stress is also discussed. Key words: repeated load, triaxial test, resilient modulus, granular materials, modelling, pavement.

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Zhu, Tanyong, Tao Ma, Xiaoming Huang et Siqi Wang. « Evaluating the rutting resistance of asphalt mixtures using a simplified triaxial repeated load test ». Construction and Building Materials 116 (juillet 2016) : 72–78. http://dx.doi.org/10.1016/j.conbuildmat.2016.04.102.

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XIAO, ZHENGHUA, BO HAN, HONGJIAN LIAO et AKENJIANG TUOHUTI. « EXPERIMENT STUDY ON DYNAMIC STRENGTH OF LOESS UNDER REPEATED LOAD ». International Journal of Modern Physics B 22, n^o 31n32 (30 décembre 2008) : 5825–30. http://dx.doi.org/10.1142/s0217979208051236.

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A series of dynamic triaxial tests are performed on normal anisotropic consolidation and over anisotropic consolidation specimens of loess. Based on the test results, the variable regularity of dynamic shear stress, axial strain and pore water pressure of loess under dynamic loading are measured and analyzed. The influences of the dynamic shear strength and pore water pressure at different over consolidation ratio are analyzed. The relationship between dynamic shear strength and over consolidation ratio of loess is obtained. The evaluating standard of dynamic shear strength of loess is discussed. Meanwhile, how to determine the effective dynamic shear strength index of normal anisotropic consolidated loess is also discussed in this paper. Several obtained conclusions can be referenced for studying the dynamic shear strength of loess foundation.

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Fang, Rui, Hui Gao et Xiang Qin Bian. « Three-Stage Permanent Deformation Behavior of Subgrade Soils ». Advanced Materials Research 374-377 (octobre 2011) : 1942–46. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.1942.

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The development of the permanent deformation of subgrade soils under repeated load tests may consists of three stages, namely the primary, secondary and tertiary stages, but the existing models can not describe this behavior very well, so a new model is required to be developed. Based on the creep equation of the soil under static load, a mechanistic model is developed to describe the development of the permanent deformation of the soil under repeated load tests. Triaxial repeated load tests are conducted for silty soils and results show that, under some conditions, the development of the permanent deformation of silty clay consists of three stages and the number of load repetitions corresponding to the initiation of the tertiary stage is 330,0000. The new model is used to fit the test results and the comparison of test results and fitting results prove that this model can describe all three stages of permanent deformation.

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Karasahin, Mustafa. « An anisotropic model of unbound granular material under repeated loading ». Thermal Science 23, Suppl. 1 (2019) : 295–302. http://dx.doi.org/10.2298/tsci181021043k.

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The base and subbase layers of a pavement are compacted to the desired density by rollers. This cause the anisotropy in other words the layer more stiffer in the vertical direction than the horizontal direction. In the study inherent and stress induced anisotropy were measured by using the repeated load triaxial test equipment which is able to cycle both confining and axial pressure. The test results were then modelled using the stepwise regression. A new cross anisotropic model was proposed to predict the unbound stress-strain behavior. The proposed model is able to predict the axial strain more accurately than the radial strain.

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Gaillard, Laura, Cyrille Chazallon, Pierre Hornych et Juan Carlos Quezada. « Study of the mechanical behaviour of reclaimed asphalt aggregates without binder addition ». E3S Web of Conferences 92 (2019) : 10004. http://dx.doi.org/10.1051/e3sconf/20199210004.

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The objective of this paper is to investigate a source of reclaimed asphalt aggregates without binder addition. To this end, a series of triaxial tests was performed. First, monotonic triaxial tests allowed to determine failure resistance of the material at 20°C, 50°C and at 20°C with a prior preheating at 50°C. Then, the resilient and permanent behaviours at 20°C were studied thanks to Repeated Load Triaxial (RLT) tests with different levels of loading. The results show that increasing the temperature test implies a drop of failure resistance but a higher cohesion. RLT tests reveal a stress dependent resilient behaviour. Finally, the experimental results were compared with calibrations of the non-linear elastic Boyce model.

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Sas, Wojciech, Andrzej Głuchowski et Alojzy Szymański. « Determination of the Resilient modulus MR for the lime stabilized clay obtained from the repeated loading CBR tests ». Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation 44, n^o 2 (1 décembre 2012) : 143–53. http://dx.doi.org/10.2478/v10060-011-0070-0.

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Abstract Determination of the Resilient modulusMR for the lime stabilized clay obtained from therepeated loading CBR tests. The main aim of this paper is to prove that CBR repeated test is useful to give an adequate like unconfi ned cyclic triaxial test parameters for design the pavement and subgrade soils. That parameter is the Resilient modulus (MR) which is the elastic modulus based on the recoverable strain under repeated load. Resilient modulus (MR), is an important parameter which characterizes the subgrade’s ability to withstand repetitive stresses under traffic loadings. The 1993 AASHTO guide for design of flexible pavements recommends the use of MR. The additional aim is connected with the concept of sustainable development. For many countries, where resources are at premium, it is very important that stabilized local soil can be used for road construction. For ensuring that stabilized clay can be used for pavement material standard compaction, CBR and repeated CBR tests were performed. In that paper parameter MRof the subgrade lime stabilized clay soil by laboratory CBR repeated test were determined using for calculation formulas from triaxial cyclic test. Based on AASHTO empirical equation the static CBR values using back analysis was also calculated. Finally both values of CBR determined and calculated were compared.

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Diaz-Rodriguez, J. Abraham. « Behavior of Mexico City clay subjected to undrained repeated loading ». Canadian Geotechnical Journal 26, n^o 1 (1 février 1989) : 159–62. http://dx.doi.org/10.1139/t89-016.

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This note describes a series of cyclic triaxial tests on undisturbed soil samples of Mexico City clay, obtained near the SCT building. The site is a silty clay deposit of a very high water content and soft consistency. The material exhibits elastic behavior in spite of its very high water content. Three empirical relationships describing an equivalent Young's modulus, an equivalent damping ratio, and a cyclic stress level, associated with cyclic strain level, were obtained. Test results define two different patterns of strength loss. Key words: undrained strength, repeated load, clay, modulus, damping, Mexico City.

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Zhou, Ding. « Experimental Study on Permanent Deformation of Fine Sandy Subgrade Filling in Coastal Region ». Key Engineering Materials 814 (juillet 2019) : 419–24. http://dx.doi.org/10.4028/www.scientific.net/kem.814.419.

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By using repeated load triaxial test method, test results of permanent strain of fine sand were obtained. The main factors affecting permanent strain of fine sand samples are water content, degree of compaction and deviator stress. Permanent strain of sand is less sensitive to moisture when compared to clay and silt. Well compacted fine sand subgrade is less affected by the change of water content, which illustrates a more stable long-term performance. Analyze from meso-structure, the ellipsoid shaped particle is less stable than sphere shaped one under the effect to repeated load. Fine sand with smaller amount of ellipsoid shaped particle would have better dynamic behaviors. Predicting models of permanent strain with basic soil physical properties were established using regression analysis.

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Garg, Navneet, et Marshall R. Thompson. « Triaxial Characterization of Minnesota Road Research Project Granular Materials ». Transportation Research Record : Journal of the Transportation Research Board 1577, n^o 1 (janvier 1997) : 27–36. http://dx.doi.org/10.3141/1577-04.

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Six granular materials were used as base and subbase materials in the flexible pavement test sections for the Minnesota Road Research (Mn/ROAD) project. Crushed/fractured particles are not allowed in aggregate classes CL-1Fsp, CL-1Csp, CL-3sp, and CL-4sp. Ten to 15 percent crushed/fractured particles are required for CL-5sp. One hundred percent crushed/ fractured particles are required for CL-6sp. A comprehensive laboratory testing program was established to determine pertinent engineering properties of the granular materials. Rapid shear tests and repeated-load tests were conducted to determine the shear strength parameters (friction angle and cohesion), resilient modulus, rutting potential, stress history effects on shear strength, and moisture susceptibility. The results from the rapid shear tests and permanent deformation tests show that the rutting potential of a granular material can be characterized from rapid shear test at a confining pressure of 15 psi (103.35 kPa). The rutting parameter A was a function of the shear strength of the granular materials. The shear strength results obtained from rapid shear tests performed at a confining pressure of 15 psi reflect the rutting trends observed in the low-volume road test sections at the Mn/ROAD project. Results from repeated-load tests were used to develop the parameters for K-θ, UT-Austin, and Uzan’s models for evaluating the resilient modulus of granular materials. The axial strain values calculated from the resilient modulus models appear to be in good agreement with the measured axial strain values, except for the very low shear strength material CL-1Csp.

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Cerni, G., A. Corradini, E. Pasquini et F. Cardone. « Resilient behaviour of unbound granular materials through repeated load triaxial test : influence of the conditioning stress ». Road Materials and Pavement Design 16, n^o 1 (6 octobre 2014) : 70–88. http://dx.doi.org/10.1080/14680629.2014.964294.

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Li, Ning, Hao Wang, Biao Ma et Rui Li. « Investigation of unbound granular material behavior using precision unbound material analyzer and repeated load triaxial test ». Transportation Geotechnics 18 (mars 2019) : 1–9. http://dx.doi.org/10.1016/j.trgeo.2018.10.006.

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Wang, Xiu Shan, Xiao Jun Ding et Yong Li Xie. « Permanent Deformation Prediction Model of Graded Gravel under Repeated Load ». Advanced Materials Research 168-170 (décembre 2010) : 217–21. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.217.

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In order to predict the permanent deformation of graded gravel, through to the existing flexible pavement granular base permanent deformation estimate model's contrastive analysis, combined with repeated dynamic triaxial test , selects Wei Mi permanent deformation estimate model as the loose aggregate permanent deformation of the estimate model, using 1stopt statistical analysis software carries on the nonlinear curve fit for the parameter, obtained two kinds of norms of graded broken stone aggregates forecast model of the correlation among the types : permanent deformation of the coefficient and water content and resilient modulus, and their reliability was analyzed. Analysis result shows that when load acting time reaches 10 000, the minimum and average correlative coefficients of the regression formulas is 0.4144 ,0.6340 and 0.5080, which is greater than the critical value of 0.3993, and the correlative coefficient between theoretical curve and measured one is more than 0.96. So the reliability of the proposed prediction formulas of permanent deformation for graded gravel is higher, can be used to forecast China's Asphalt Pavement Rutting.

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Kang, Mingu, Joon Han Kim, Issam I. A. Qamhia, Erol Tutumluer et Mark H. Wayne. « Geogrid Stabilization of Unbound Aggregates Evaluated Through Bender Element Shear Wave Measurement in Repeated Load Triaxial Testing ». Transportation Research Record : Journal of the Transportation Research Board 2674, n^o 3 (27 février 2020) : 113–25. http://dx.doi.org/10.1177/0361198120908230.

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This paper describes the use of the bender element (BE) shear wave measurement technology for quantifying the effectiveness of geogrid stabilization of unbound aggregate materials with improved mechanical properties from repeated load triaxial testing. Crushed stone aggregate specimens were prepared with three different gradations, that is, upper bound (UB), mid-range engineered (ENG), and lower bound, according to the dense graded base course gradation specification in Illinois. The specimens were compacted at modified Proctor maximum dry densities and optimum moisture contents. Two geogrids with different triaxial aperture sizes were placed at specimen mid-height, and unstabilized specimens with no geogrid were also prepared for comparison. To measure shear wave velocity, three BE pairs were placed at different heights above geogrid. Repeated load triaxial tests were conducted following the AASHTO T307 standard resilient modulus test procedure, while shear wave velocity was measured from the installed BE pairs. After initial specimen conditioning, and at low, intermediate, and high applied stress states, both the resilient moduli and accumulated permanent strains were determined to relate to the geogrid local stiffening effects in the specimens quantified by the measured shear wave velocities. The resilient modulus and shear wave velocity trends exhibited a directly proportional relationship, whereas permanent strain and shear wave velocity values were inversely related. The enhancement ratios calculated for the geogrid stabilized over the unstabilized specimens showed significant improvements in mechanical behavior for the UB and ENG gradations, and a maximum enhancement was achieved for the engineered gradation specimens stabilized with the smaller aperture geogrid.

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Arulrajah, A., J. Piratheepan, M. W. Bo et N. Sivakugan. « Geotechnical characteristics of recycled crushed brick blends for pavement sub-base applications ». Canadian Geotechnical Journal 49, n^o 7 (juillet 2012) : 796–811. http://dx.doi.org/10.1139/t2012-041.

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This paper presents the findings of a laboratory investigation on the characterization of recycled crushed brick when blended with recycled concrete aggregate and crushed rock for pavement sub-base applications. The engineering properties of the crushed brick blends were compared with typical state road authority specifications in Australia for pavement sub-base systems to ascertain the potential use of crushed brick blends in these applications. The experimental programme included particle-size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion, pH, organic content, and repeated load triaxial tests. Laboratory tests were undertaken on mixtures of 10%, 15%, 20%, 25%, 30%, 40%, and 50% crushed brick blended with recycled concrete aggregate or crushed rock. The research indicates that up to 25% crushed brick could be safely added to recycled concrete aggregate and crushed rock blends in pavement sub-base applications. The repeated load triaxial test results on the blends indicate that the effects of crushed brick content on the mechanical properties in terms of permanent deformation and resilient modulus of both the recycled concrete aggregate and crushed rock blends were marginal compared to the effects on dry density and moisture content.

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Raymond, Gerald P., et Richard J. Bathurst. « Repeated-load response of aggregates in relation to track quality index ». Canadian Geotechnical Journal 31, n^o 4 (1 août 1994) : 547–54. http://dx.doi.org/10.1139/t94-063.

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Track quality rating systems are briefly introduced as a background for undertaking a study of the repeated-load response of ballast aggregates. The results from a number of different laboratory investigations are reviewed and this data interpreted in terms of track quality behaviour. The paper reviews selected results from repeated-load triaxial tests used to investigate the repeated-loading response of different granular railway ballasts at stress levels comparable with those below North America heavy freight axle loads. These results are used to establish an aggregate index to predict deformation and breakdown of ballast under repeated loading. Large-scale test programs are reviewed that relate aggregate quality to simulated ballasted track formation response using a 0.9 m long by 250 mm wide tie to represent a typical loaded rail seat. The large-scale testing was restricted to one aggregate that was subjected to a range of load levels and artificial subgrade stiffness. Similar related work on coarse, single-sized aggregates recommended for drainage layers in highway pavements is reviewed to illustrate the trade-offs between support compressibility and quality of aggregate defined by the aggregate index value. The laboratory tests and model performance are compared with published data to establish a laboratory performance rating in the form of an aggregate index for prediction of those track quality indices that relate to deformation as a function of aggregate type. Key words : ballast, aggregate, hardness, toughness, railway, track quality.

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Xu, An Hua, et Jian Hong Fang. « Study on Roadbed Soil Dynamic Resilient Modulus Test ». Advanced Materials Research 671-674 (mars 2013) : 1245–53. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.1245.

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This paper draws on the successful experience from domestic and abroad researches, testing repeatedly of powder subgrade with load triaxial tests, analyzing the relationship between the subgrade soil resilient modulus, deviatoric stress, water content and degree of compaction. At the same time, conducting corresponded roadbed soil resilient modulus forecast model, and qualifying its correctness of test data model.

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Kim, Dahae, et Y. Richard Kim. « Characterization of Permanent Deformation of Asphalt Mixtures with Minimum Strain Rate, LVECD Program, and Triaxial Stress Sweep Test ». Transportation Research Record : Journal of the Transportation Research Board 2631, n^o 1 (janvier 2017) : 96–104. http://dx.doi.org/10.3141/2631-11.

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The rutting resistance of asphalt concrete is typically assessed by using flow number tests in the lab in accordance with AASHTO TP 79. However, the flow number represents the rutting resistance of the material with regard to ranking for only a specific test condition. A significant amount of testing effort is needed to evaluate rutting resistance by using the flow number test under various loading conditions and temperatures. Therefore, researchers have developed alternative test methods to reduce the testing effort. For example, the incremental repeated-load permanent deformation test and the triaxial stress sweep (TSS) test are two promising protocols that can predict the permanent deformation of asphalt mixtures efficiently and accurately. This study compares the minimum strain rates (MSRs) obtained from incremental repeated-load permanent deformation and TSS tests to examine the ability of the TSS test to analyze the MSRs of asphalt mixtures. In addition, the viscoplastic shift model calibrated from the TSS test that is implemented in the layered viscoelastic pavement analysis for critical distresses (LVECD) program was used to predict the rut depths of 16 pavement sections from four sources. The MSRs and rut depths predicted from the LVECD program were compared with actual measured rut depths. The results of this study indicated that the MSR results could only be used to rank the rutting susceptibility of single-layer asphalt pavements. For a multilayered pavement system, structural level analysis is necessary to predict the accurate rutting performance and rut depths of the test sections.

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Kim, In Tai, et Erol Tutumluer. « Unbound Aggregate Rutting Models for Stress Rotations and Effects of Moving Wheel Loads ». Transportation Research Record : Journal of the Transportation Research Board 1913, n^o 1 (janvier 2005) : 41–49. http://dx.doi.org/10.1177/0361198105191300105.

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The latest research findings on stress rotations caused by moving wheel loads and their effects on permanent deformation or rut accumulation in pavement granular layers are presented. Realistic pavement stresses induced by moving wheel loads were examined in the unbound aggregate base and subbase layers, and the significant effects of rotation of principal stress axes were indicated for a proper characterization of the permanent deformation behavior. To account for the rutting performances of especially thick granular layers, a comprehensive set of repeated load triaxial tests was conducted in the laboratory. Triaxial test data were obtained and analyzed from testing aggregates under various realistic in situ stress paths caused by moving wheel loading. Permanent deformation characterization models were then developed on the basis of the experimental test data to include the static and dynamic stress states and the slope of stress path loading. The models that also considered the stress path slope variations predicted the stress path dependency of permanent deformation accumulation best. In addition, multiple stress path tests conducted to simulate the extension–compression–extension type of rotating stress states under a wheel pass gave much higher permanent strains than those of the compression-only single path tests. The findings indicated actual traffic loading simulated by the multiple path tests could cause greater permanent deformations or rutting damage, especially in the loose base or subbase, when compared with deformations measured from a dynamic plate loading or a constant confining pressure type laboratory test.

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Miljkovic, Miomir, et Martin Radenberg. « Rutting mechanisms and advanced laboratory testing of asphalt mixtures resistance against permanent deformation ». Facta universitatis - series : Architecture and Civil Engineering 9, n^o 3 (2011) : 407–17. http://dx.doi.org/10.2298/fuace1103407m.

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Permanent deformation in asphalt layers which manifestation on pavement surface is named rutting represents one of the most significant distresses of asphalt pavements. Depending on the level, it can be a huge inconvenience for traffic safety, driving comfort, and overall pavement life-cycle. Rutting may be classified into three basic types: one-dimensional or vertical compaction, lateral flow or plastic movement, and mechanical deformation. As an addition to Superpave? mixture volumetric design three, so called, simple performance tests (SPT) were recommended. Each of these tests in conduced in uniaxial or triaxial compression of cylindrical specimens. They cover the determination of dynamic modulus, repeated load permanent deformation test (flow number), and static load permanent deformation test (flow time). These tests provide relatively good insight in on-site mixture performance. An application of these tests provides a potential link between mixture design and structural analysis that was an underlying goal of substantial amount of earlier flexible pavement researches.

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Islam, Kazi Moinul, Sarah Gassman et Md Mostaqur Rahman. « Field and Laboratory Characterization of Subgrade Resilient Modulus for Pavement Mechanistic-Empirical Pavement Design Guide Application ». Transportation Research Record : Journal of the Transportation Research Board 2674, n^o 8 (19 juin 2020) : 921–30. http://dx.doi.org/10.1177/0361198120926171.

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The resilient modulus (MR) of subgrade material is an important parameter in pavement design using the Mechanistic-Empirical Pavement Design Guide (MEPDG) and has a significant influence on pavement performance. MR can be obtained indirectly from falling weight deflectometer (FWD) data using a back-calculation tool (i.e., AASHTOWare 2017) or from empirical correlations with soil index properties. MR can also be obtained directly using repeated load triaxial tests (AASHTO T 307-99, 2017). In this study, the field test program included FWD tests and soil sampling. These field tests were performed on six asphalt pavement sections in South Carolina, U.S., to estimate the MR of the subgrade soil. This study involved extensive laboratory characterization of subgrade soils collected from underneath the pavement sections. Laboratory characterization included index tests (sieve analysis, Atterberg limits, specific gravity, moisture content, and standard Proctor density tests) on bulk samples and repeated load triaxial tests on thin-walled tube samples to obtain a direct measure of MR. Results show that the MR values found from the FWD data have similar trends to the laboratory-measured MR values. However, results from lab testing were 33%–75% lower than the back-calculated MR. Laboratory-measured MR, and back-calculated MR were used to determine a C-factor of 0.33, 0.25, and 0.29 for coarse-grained, fine-grained, and all types of soils, respectively. This parameter can be used to estimate resilient modulus for MEPDG Level 2 design inputs across South Carolina and similar geologic regions. The research studies will be facilitated by the local calibration and implementation of the MEPDG.

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Lee, Sangyum, Cheolmin Baek et Je-Jin Park. « Performance-based mix design of unmodified and lime-modified hot mix asphalt ». Canadian Journal of Civil Engineering 39, n^o 7 (juillet 2012) : 824–33. http://dx.doi.org/10.1139/l2012-067.

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This paper presents the performance evaluation of unmodified and lime-modified hot mix asphalt (HMA) mixtures at varying asphalt content using asphalt mixture performance test developed from National Cooperative Highway Research Program project 9-19 and 9-29 and the viscoelastic continuum damage finite element analysis. Test methods adopted in this study are the dynamic modulus test for stiffness, the triaxial repeated load permanent deformation test for rutting, and the direct tension test for fatigue cracking. The findings from this study support conventional understanding of the effects of asphalt content and lime modification on the fatigue cracking and rutting performance. Finally, the optimum asphalt content for both lime-modified and unmodified mixtures are proposed based on the knowledge gleaned from the performance-based mix design methodology. With additional validation and calibration, the comprehensive methodology described in this paper may serve as the foundation for a performance-based HMA mix design and performance-related HMA specifications.

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Yang, Guang Qing, Xi Zhao Wang et Bao Jian Zhang. « Dynamic Characterization of Cement-Treated High-Speed Railway Subgrade ». Advanced Materials Research 250-253 (mai 2011) : 3909–12. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.3909.

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In order to ensure the high-speed railway train running safety and stabilization, the subgrade should keep adequate strength, rigidity and long-term stabilization under the repeated train load. When the subgrade soil is poor, we can treat it with cement. Whether the performance of cement-treated soil can meet the demand of high-speed railway, so the dynamic triaxial test of cement-treated soil is studied in this paper. The dynamic performance of cement-treated soil under repeated train load is analyzed. The variation and influence factors of critical dynamic stress, accumulated plastic strain, elastic strain and resilient module of cement-treated soil are studied.When the dynamical stress more than the critical dynamical stress, the cumulate plastic strain and the elastic strain will rapidly increase with the increase of the loading time of the dynamical stress. The resilience modulus will decrease along with the increase of the dynamical stress. When the dynamical stress less than the he critical dynamical stress, the elastic strain and the resilience modulus remain constant with the increase of the loading time of the dynamical stress. And the elastic strain and the resilience modulus linearly increase with the increase of the dynamical stress.

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Tutumluer, Erol, et Marshall R. Thompson. « Anisotropic Modeling of Granular Bases in Flexible Pavements ». Transportation Research Record : Journal of the Transportation Research Board 1577, n^o 1 (janvier 1997) : 18–26. http://dx.doi.org/10.3141/1577-03.

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A new cross-anisotropic model is proposed to predict the performance of granular bases in flexible pavements. A cross-anisotropic representation has different material properties (i.e., elastic modulus and Poisson’s ratio) assigned in the horizontal and vertical directions. Repeated-load triaxial tests with vertical and lateral deformation measurements can be used to establish these anisotropic properties. Simple stress-dependent granular material models, obtained from analysis of the laboratory test data, are used in a nonlinear finite element program, named GT-PAVE, to predict pavement responses. The horizontal and shear stiffnesses are typically found to be less than the vertical. The nonlinear anisotropic approach is shown to account effectively for the dilative behavior observed under the wheel load and the effects of compaction-induced residual stresses. The main advantage of using a cross-anisotropic model in the base is the drastic reduction or elimination of significant tensile stresses generally predicted by isotropic linear elastic layered programs.

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Cabral, Wendel S., Suelly H. A. Barroso et Samuel A. Torquato. « Study of the Permanent Deformation of Soil Used in Flexible Pavement Design ». Advances in Civil Engineering 2020 (21 octobre 2020) : 1–9. http://dx.doi.org/10.1155/2020/4274926.

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The decreasing supply of soils with geotechnical parameters suitable for pavement designs is a visible problem in our environment. In order to establish more efficient designs and adequate construction criteria, it is essential to understand the performance of materials. This is a study of the permanent deformation (PD) of soil used in pavement layers, obtaining prediction models through the technique of artificial neural networks, in addition to the design of pavement structures using mechanistic-empirical and empirical methods. The multistage repeated load triaxial (RLT) test, as well as numerical analyses of stresses and displacements using the CAP3D program, was used. The results showed that both the test procedure and the prediction models performed satisfactorily in obtaining PD behavior. Moreover, designs using the methods adopted resulted in distinct structures, that is, thickness different from the granular pavement layers. It was concluded that the model and test procedure exhibit significant potential for characterizing and modeling the PD of granular materials.

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Ševelová, Lenka, Aleš Florian et Jaroslav Žák. « Influence of Plunger Stress on Resilient Modulus of Forest Subgrade Soils Obtained from Cyclic CBR Test ». Forests 12, n^o 11 (26 octobre 2021) : 1456. http://dx.doi.org/10.3390/f12111456.

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The low load-bearing capacity of subgrade soils is typical for forest roads. For the determination of the resilient modulus Mr of unbound natural as well as recycled materials, a laboratory triaxial test with cyclic loading is generally preferred. For low volume roads, including forest roads, an alternative method of the cyclic CBR test, which uses standard CBR devices for repeated loading, is being tested and applied in practice. For forest subgrade soils, the procedure for determining the modulus Mr based on cyclic loading of the specimen to a constant penetration depth of 2.54 mm was verified. This procedure was tested on an extensive dataset obtained from 11 forest roads in the Czech Republic, which was then statistically evaluated. The obtained results showed disproportionately high mean values as well as high random variability. Further data analysis revealed that the reason seemed to be the chosen test methodology. When using this procedure for forest soils, high values of plunger stress can occur, which for many types of soils greatly exceed their maximum load-bearing capacity. As result, the modulus Mr is determined at unrealistically high plunger stress values and in many cases on the disrupted specimen. The necessary solution to this shortcoming is to censor the results of the cyclic CBR test, i.e., to exclude unrealistic values of the modulus Mr determined at plunger stresses exceeding the limit values.

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Dawson, Andrew R., Michael J. Mundy et Matti Huhtala. « European Research into Granular Material for Pavement Bases and Subbases ». Transportation Research Record : Journal of the Transportation Research Board 1721, n^o 1 (janvier 2000) : 91–99. http://dx.doi.org/10.3141/1721-11.

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Two transnational European research projects in the area of granular materials for road pavements are described. The results are used to illustrate the state of practice as compared to the state of the art and are placed within the setting of a broad picture of national research within Europe. Discussed are the direction of European research, its implementation, those areas that will continue to be problematic, and the findings and strategies that suggest better-practice for non-European users. The use of the repeated-load triaxial test is shown to be an important aspect. Although the test is shown to have limitations for practical purposes, it illustrates the nature of material behavior that may be expected in situ. It is shown that a fundamental engineering understanding has been applied to granular material pavement layer technology but that there remain issues of in situ assessment, analytical methods, and variability of in situ conditions that hinder full application of current understanding.

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Yang, Jie, An-yu Yang, Yan-gong Shan, Miao-miao Yang, Jin-lei Zhao et Hang Yu. « Experimental Study on Mechanical Behavior of Lean Cemented Sand and Gravel Material in Unloading and Reloading Paths ». Advances in Materials Science and Engineering 2021 (19 janvier 2021) : 1–12. http://dx.doi.org/10.1155/2021/8893840.

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Lean cemented sand and gravel (LCSG) materials are subjected to unloading-loading when an LCSG dam is opened for water drainage and then refilled or a roadbed base is subjected to repeated wheel loads. To investigate the behavior of the LCSG materials under loading-unloading, previous studies utilized the complete loading triaxial test. In contrast, in this study, the consolidated drained triaxial tests in the unloading and reloading paths for materials with cementing agent contents of 60 and 100 kg/m3 under different confining pressures, for which each curve generates three loading-unloading cycles, were applied to investigate the unloading and reloading mechanical behavior. Experimental results indicated that the unloading and reloading behavior of the LCSG materials produced stress-strain curves exhibiting a crescent-shaped hysteresis loop, which differs from that exhibited by coarse-grained soil. Although the shape of the crescent-like hysteresis loop was preserved as stress levels increasing, it gradually expanded. Compared with that of the typical triaxial test, the cohesive force and the increasing internal friction angle increased. Further, as the confining pressure increased, the crescent-like hysteresis loops tapered, shear strength increased linearly, and the modulus of resilience increased nonlinearly; the latter’s rate of change, however, decreased. The change in volumetric strain was small during unloading as the stress level changed.

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Ševelová, Lenka, Aleš Florian et Petr Hrůza. « Using Resilient Modulus to Determine the Subgrade Suitability for Forest Road Construction ». Forests 11, n^o 11 (16 novembre 2020) : 1208. http://dx.doi.org/10.3390/f11111208.

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Forest roads are often constructed in environments with low bearing capacity of the subgrade. The subgrade then has an effect on their service life and damage. According to the methodology of the American Association of State Higway and Transportation Officiales AASHTO, the design of pavement is divided into three levels according to the intensity of the traffic load. For pavements with the highest load intensity, preparing the resilient modulus from a cyclic triaxial test is required. For other traffic load classes, including forest roads, the methodology allows the use of the estimate of resilient modulus value determined from other tests. In the laboratory at the Faculty of Forestry, Mendel University of Brno, the method from the Delft University 2009 was tested and subsequently modified, using a standard CBR machine for repeated loading. A total of 276 samples from various types of forest road subgrade from the Czech Republic were tested by the method of repeated loading on the CBR machine, from which the values of the Resilient Modulus were newly labelled Mr,CBR. The results of the statistical analysis showed a large variability of Mr,CBR values and wide intervals of its occurrence for individual types of subgrade. The variability was subjected to analysis and the influence of basic geotechnical parameters on the values of Mr,CBR was analyzed. A fundamental correlation was found between the value of Mr,CBR and the value of the plunger stress, which reached values exceeding the bearing capacity of the soil types using the Delft University method. It is necessary to limit the plunger stress during cyclic loading up to the failure limit or even better to the expected traffic load. The modified procedure results show a more consistent behavior of the modulus.

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Ullah, Salamat, Arshad Jamal, Meshal Almoshaogeh, Fawaz Alharbi et Jawad Hussain. « Investigation of Resilience Characteristics of Unbound Granular Materials for Sustainable Pavements ». Sustainability 14, n^o 11 (4 juin 2022) : 6874. http://dx.doi.org/10.3390/su14116874.

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In this study, a comprehensive laboratory testing program was designed to study the resilience characteristics of unbound granular materials (aggregate base coarse) using the repeated load triaxial test (RLTT). During the experimental program, the resilient modulus of unbound granular material was examined using different moisture content levels, material gradation using Fuller’s equation, and stress levels. The results show that the moisture content, material gradation, and stress level have a major influence on the resilient modulus of unbound granular materials. Furthermore, a linear model has been developed between moisture content and the resilient modulus. The model significantly predicts the change in resilient modulus by changing moisture content. The study also aimed to improve the modified Uzan model by adding the effect of moisture content. An improved modified Uzan stress moisture model has been developed, which shows a strong relationship between the resilient modulus, stress, and moisture content. This study can be used as a benchmark for validating other numerical data.

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Werkmeister, Sabine, Ralf Numrich, Andrew R. Dawson et Frohmut Wellner. « Design of Granular Pavement Layers Considering Climatic Conditions ». Transportation Research Record : Journal of the Transportation Research Board 1837, n^o 1 (janvier 2003) : 61–70. http://dx.doi.org/10.3141/1837-07.

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A new simple design approach that uses test results from the repeated load triaxial apparatus to establish the risk level of permanent deformations in the unbound granular layers (UGL) in pavement constructions under consideration of the seasonal effects was developed. From these data, a serviceability limit line (plastic shakedown limit) stress boundary for the unbound granular materials (UGM) was defined for different moisture contents. Below this line, the material has stable behavior. The serviceability limit line was applied in a finite-element (FE) program, FENLAP, to predict whether stable behavior occurs in the UGM. To calculate the stress in the UGL, a nonlinear elastic model (Dresden Model) was implemented into the FE program. The effects of changing moisture content during spring thaw period and asphalt temperature on pavement structural response were investigated. Additionally, permanent deformation calculations for the UGL were performed taking the stress history into consideration. The results clearly demonstrate that, for pavement constructions with thick asphalt layers, there is no risk of rutting in the granular base, even at a high number of load repetitions. The proposed design approach is a very satisfactory simple method of assessing the risk of rutting in the UGL, even without the calculation of the exact permanent deformation of the pavement construction.

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Lu, Weihua, Linchang Miao, Junhui Zhang, Yongxing Zhang et Jing Li. « Characteristics of Deformation and Damping of Cement Treated and Expanded Polystyrene Mixed Lightweight Subgrade Fill under Cyclic Load ». Applied Sciences 9, n^o 1 (4 janvier 2019) : 167. http://dx.doi.org/10.3390/app9010167.

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To investigate the deformation and damping characteristics of cement treated and expanded polystyrene (EPS) beads mixed lightweight soils, this study conducted a series of triaxial shear tests cyclic loading for different confining pressures, cement contents, and soil categories. Through repeated loading and unloading cycles, axial accumulative strain, resilient modulus, and damping ratio versus axial total strain were analyzed and the mechanical behavior was revealed and interpreted. Results show that the resilient modulus increases with increasing confining pressure and cement content. A decreasing power function can be used to fit the relationship between the resilient modulus and the axial total strain. Although sandy lightweight specimens usually own higher resilient modulus than silty clay lightweight specimens do, the opposite was also found when the axial total strain is larger than 8% with 50 kPa confining pressure and 14% cement content. For damping ratio the EPS beads mixed lightweight soil yields a weak growth trend with increasing axial total strain and a small reduction with higher confining pressure and cement content. For more cementations, the damping ratio of the sandy lightweight soil is always smaller than the silty clay lightweight soil. Nonetheless, the differences of damping ratios that were obtained under all of the test conditions are not significant.

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Rahman, Md Mostaqur, Kazi Moinul Islam et Sarah Gassman. « Estimation of Resilient Modulus for Coarse-Grained Subgrade Soils from Quick Shear Tests for Mechanistic-Empirical Pavement Designs ». Designs 3, n^o 4 (14 octobre 2019) : 48. http://dx.doi.org/10.3390/designs3040048.

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The resilient modulus represents the subgrade soil stiffness, and it is considered one of the key material inputs in the Mechanistic Empirical Pavement Design Guide (MEPDG). The resilient modulus is typically estimated in the laboratory using a repeated load cyclic triaxial test, which is complex and time consuming to perform. Technical ability is also required to prepare the test specimens, particularly for coarse-grained soils. Therefore, there is a need to estimate the resilient modulus of coarse-grained soils from other simpler tests. In this study, correlations of resilient modulus with soil index properties and quick shear (QS) test results (quick shear strength, stress at 1% strain and tangent modulus) were developed for remolded coarse-grained soils, collected from different geographic regions in South Carolina. The developed models showed good correlations of resilient modulus to tangent modulus and soil index properties. The average tangent, modulus obtained from 30% and 50% of maximum stress of the QS tests, moisture content, optimum moisture content, dry unit weight, and maximum dry unit weight showed a statistically significant effect on estimating the resilient modulus for coarse-grained subgrade soils. The validation study confirms that the developed models can be used for predicting the resilient modulus for South Carolina coarse-grained soils.

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Sebaaly, Peter E., Dan Ridolfi, Raja S. Gangavaram et Jon A. Epps. « Selecting Most Desirable Hot-Mix Asphalt Mixtures ». Transportation Research Record : Journal of the Transportation Research Board 1590, n^o 1 (janvier 1997) : 99–107. http://dx.doi.org/10.3141/1590-12.

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Aggregate properties and gradations have been shown to have a significant impact on the strength and performance of HMA mixtures. Strength properties, such as the resilient modulus and tensile strength, and performance properties, such as moisture sensitivity, permanent deformation, and low-temperature cracking, play a major role in the field performance of HMA mixtures. However, it is believed that by changing the aggregate gradation and the asphalt binder, a desirable hot-mix asphalt mixture can be achieved for any source of aggregate. The data and analysis of a laboratory research study that evaluated four gradations and four asphalt binders in conjunction with five sources of Nevada aggregates are summarized. The measured material properties include the Superpave binder and aggregate properties, the strength properties, and the permanent deformation and low-temperature cracking of the mixtures. The data analysis indicated that the resilient modulus and tensile strength tests can be used in lieu of the more complicated triaxial repeated-load test to ensure against rutting and that the binder property can be used to ensure against low-temperature cracking.

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Azam, A. M., D. A. Cameron et M. M. Rahman. « Model for prediction of resilient modulus incorporating matric suction for recycled unbound granular materials ». Canadian Geotechnical Journal 50, n^o 11 (novembre 2013) : 1143–58. http://dx.doi.org/10.1139/cgj-2012-0406.

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This paper presents experimental results on the effect of matric suction on the resilient modulus of four recycled unbound granular materials. The recycled materials were prepared at moisture contents ranging between 70% and 90% of optimum moisture content (OMC) and tested in a repeated load triaxial test (RLTT) apparatus under various stress regimes. Soil-water characteristic curves (SWCC) were established for each material by preparing samples at various moisture contents and measuring matric suction with filter papers. To obtain the wet end of the SWCC, further samples were conditioned on a tension plate at suctions controlled by the hanging water column method. Some published models for prediction of resilient modulus were applied to the experimental data, but the correlations were unsatisfactory generally, and so an improved model was sought. Subsequently, a model with four terms and six constants was developed, which followed the general power law. A single set of material constants was found for all recycled materials to provide satisfactory predictions of resilient modulus (R2 = 0.88), over a wide range of stresses and moisture states.

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Boyd, Luke J., Kevin Ball et Robert J. Aughey. « The Reliability of MinimaxX Accelerometers for Measuring Physical Activity in Australian Football ». International Journal of Sports Physiology and Performance 6, n^o 3 (septembre 2011) : 311–21. http://dx.doi.org/10.1123/ijspp.6.3.311.

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Purpose:To assess the reliability of triaxial accelerometers as a measure of physical activity in team sports.Methods:Eight accelerometers (MinimaxX 2.0, Catapult, Australia) were attached to a hydraulic universal testing machine (Instron 8501) and oscillated over two protocols (0.5 g and 3.0 g) to assess within- and between-device reliability. A static assessment was also conducted. Secondly, 10 players were instrumented with two accelerometers during Australian football matches. The vector magnitude was calculated, expressed as Player load and assessed for reliability using typical error (TE) ± 90% confidence intervals (CI), and expressed as a coefficient of variation (CV%). The smallest worthwhile difference (SWD) in Player load was calculated to determine if the device was capable of detecting differences in physical activity.Results:Laboratory: Within- (Dynamic: CV 0.91 to 1.05%; Static: CV 1.01%) and between-device (Dynamic: CV 1.02 to 1.04%; Static: CV 1.10%) reliability was acceptable across each test. Field: The between-device reliability of accelerometers during Australian football matches was also acceptable (CV 1.9%). The SWD was 5.88%.Conclusions:The reliability of the MinimaxX accelerometer is acceptable both within and between devices under controlled laboratory conditions, and between devices during field testing. MinimaxX accelerometers can be confidently utilized as a reliable tool to measure physical activity in team sports across multiple players and repeated bouts of activity. The noise (CV%) of Player load was lower than the signal (SWD), suggesting that accelerometers can detect changes or differences in physical activity during Australian football.

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Salour, Farhad, Sigurdur Erlingsson et Claudia E. Zapata. « Modelling resilient modulus seasonal variation of silty sand subgrade soils with matric suction control ». Canadian Geotechnical Journal 51, n^o 12 (décembre 2014) : 1413–22. http://dx.doi.org/10.1139/cgj-2013-0484.

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The resilient modulus of unbound materials is an important parameter in the mechanistic design of pavements. Although unbound layers are frequently in a partially saturated state, a total stress approach is conventionally used in modeling the material behaviour, and therefore pore pressure effects are not considered. In fine-grained unbound materials, the saturation state can affect their mechanical behaviour due to pore pressure effects. In this study a modified test procedure and a predictive resilient modulus model that takes into account the subgrade soil matric suction as a stress state variable is presented. Two different silty sand subgrade materials were tested in unsaturated conditions using a series of repeated load triaxial tests under controlled pore suction conditions to study its influence on the resilient modulus. The test data were further used to obtain the resilient modulus model regression parameters that account for moisture content variations through the matric suction parameter. Generally, the prediction model could effectively capture the resilient modulus behaviour of the subgrades with respect to changes in the normal stress state and the matric suction. Given the completeness of this method, this prediction model is recommended as an improved approach in capturing the moisture content effects on the material stiffness properties.

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Ghorbani, Behnam, Arul Arulrajah, Guillermo A. Narsilio, Suksun Horpibulsuk et Apinun Buritatum. « Geothermal Pavements : Experimental Testing, Prototype Testing, and Numerical Analysis of Recycled Demolition Wastes ». Sustainability 15, n^o 3 (2 février 2023) : 2680. http://dx.doi.org/10.3390/su15032680.

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Geothermal pavements have the potential to reduce the pavement surface temperature by circulating fluid in pipes within the pavement structure. This research investigated an innovative geothermal pavement system with multiple benefits, such as reducing the surface temperature and harvesting heat energy for power generation. This research aimed to provide an understanding of the mechanical properties of geothermal pavements constructed with construction and demolition (C&D) waste materials through large-scale physical testing, experimental testing, small-scale prototype testing, and numerical simulation. The mechanical properties of the geothermal pavement system were assessed under long-term traffic loading conditions using a prototype test system. The repeated load triaxial and repeated-load California bearing ratio tests were also undertaken to evaluate the effect of pipe inclusion on the permanent deformation, stiffness, and strength of the pavement base. A numerical model was subsequently developed and calibrated using the data from small-scale prototype testing. In addition, the effects of the flow rate and pipe materials on the thermal performances of the geothermal pavements were also investigated in this research. The inclusion of pipes in the pavement base layer was found to have negligible detrimental effects on the deformation behavior of RCA. The resilient moduli of recycled concrete aggregate (RCA) samples slightly decreased with the inclusion of pipes. An HDPE pipe reduced the stiffness of the RCA + HDPE mix. On the other hand, a copper pipe’s high stiffness improved the mix’s strength. The numerical simulations indicated that for the HDPE pipe, increasing the flow rate from 500 mL/min to 2000 mL/min reduced the surface temperature by approximately 1.3%, while using the copper pipe resulted in an approximately 4% further decrease in the surface temperature compared to the HDPE pipe.

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Sun, Junyu, Erwin Oh et Dominic Ek-Leong Ong. « Influence of Degree of Saturation (DOS) on Dynamic Behavior of Unbound Granular Materials ». Geosciences 11, n^o 2 (15 février 2021) : 89. http://dx.doi.org/10.3390/geosciences11020089.

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The extensive application of natural unbound granular materials (UGMs) motivates studies into the mechanical properties of alternatives such as processed crushed rocks employed commonly as base or subbase layers. The rutting and settlement generated in base and subbase layers is widely restricted in many specifications and standards. In this research, the dynamic behavior including the resilient modulus (Mr) and the plastic strain (εεp) of the crushed rocks collected from Queensland in Australia will be tested by a series of repeated load triaxial test (RLT) tests to investigate the behavior of UGMs under the fluctuation of the degree of saturation (DOS) (59%–100%). In particular, the RLT specimens were prepared in the laboratory through proper gradation under optimum moisture content (OMC) and 100% standard proctor maximum dry unit weight. Results from the RLT tests showed that UGM specimens soaked at higher DOS generated lower resilient modulus and weaker resistance to heavy traffic volumes with significant accumulation of plastic strain. The Mr and εεp of the tested aggregates under different cyclic deviator stresses of 425 kPa and 625 kPa approximately linearly decreased and approximately linearly increased as the DOS increased with a certain number of cycles up to 50,000, respectively.

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De Souza, Wana Maria, Antonio Júnior Alves Ribeiro et Suelly Helena De Araújo Barroso. « Estimating the resilient modulus of subgrade materials using visual inspection ». TRANSPORTES 30, n^o 3 (14 décembre 2022) : 2738. http://dx.doi.org/10.14295/transportes.v30i3.2738.

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The definition of the Resilient Modulus (MR) of subgrade soils is essential for the reliable implementation of mechanistic-empirical pavement design. The MR of the soil is measured through repeated triaxial load tests which require expensive equipment and complex analyses. This reinforces the need to develop accurate statistical models for the prediction of the MR of the subgrade soil to be used for paving highways, especially in developing countries, such as Brazil, where financial resources are limited. The present study used artificial neural networks (ANNs) to create a model for the prediction of the MR of subgrade soils based on a visual-manual classification. For this, the results of MR tests conducted on samples of different soils from northeastern Brazil were used to develop an ANNs model for the prediction of the MR. The results demonstrate that ANNs can predict reliably the MR of soils, with a good degree of correlation in comparison with the laboratory test data. These findings support the use of the ANN model as a cost-effective approach for the preliminary evaluation of subgrade soils for highway pavement design in northeastern Brazil.

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