Influence of Environmental Humidity on Mechanical Properties of Natural and Recycled Unbound Materials

Florian, Aleš; Ševelová, Lenka; Žák, Jaroslav

doi:10.11118/actaun201563020405

Cited by 5 publications

(5 citation statements)

References 2 publications

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“…To determine the plunger stress value acting on a material, and thus the loading force value for cyclic loading, the Finite Element Method (FEM) is currently the only correct method [4,[38][39][40]. A commonly used assumption about the angle of stress propagation α = 45 • is not fully correct for the stress distribution in pavement structures.…”

Section: The Updated Cyclic Cbr Test Proposedmentioning

confidence: 99%

“…Mostly natural materials are commonly used for forest road pavement construction, but the proportion of recycled materials is continually increasing and can be expected to become more common in the near future [4]. These materials' physical-mechanical properties are highly variable and uncertain, making it very difficult to study them in situ as well as in a laboratory.…”

Section: Introductionmentioning

confidence: 99%

“…The deformation behavior, stiffness, and strength, as well as the variability of mechanical properties, depend on many factors. These factors include soil genesis, soil type, the lay-off of unbound materials, compaction rate given by the Proctor Standard energy, liquid phase amount, the number of repeated loading cycles, and maximum load-bearing capacity [4,7,8]. The resilient modulus should consider these factors [9] and should be obtained from an appropriate laboratory test that realistically simulates expected loadings by repeated passages of transport vehicles and taking into account the expected state of stress in an actual structure.…”

Section: Introductionmentioning

confidence: 99%

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An Updated Cyclic CBR Test with Realistic Stress Values under the Plunger for Resilient Modulus Calculation

Florian,

Ševelová,

Žáková

et al. 2023

Forests

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The design and assessment of forest and rural road pavements made from unbound natural and recycled materials require the careful determination of their physical-mechanical properties. The fundamental parameter for characterizing the soil material property is considered to be the resilient modulus Mr. The generally accepted alternative solution for its calculation is the cyclic CBR test, which uses standard CBR testing equipment. To perform tests on intact specimens and under stress conditions corresponding to expected states of stress in a pavement structure, an updated cyclic CBR test is proposed. In contrast to the standard cyclic CBR test, the applied loading force for repeated loadings is not determined in the first loading step by the plunger penetration to the prescribed depth, but by the stress value that is expected in an actual pavement structure. The updated test was verified on 240 tested specimens taken from a total of 40 soil samples belonging to nine soil types according to the USCS system. The resilient modulus results obtained are compared with those obtained using the standard cyclic CBR test and the cyclic triaxial test.

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Section: The Updated Cyclic Cbr Test Proposedmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Updated Cyclic CBR Test with Realistic Stress Values under the Plunger for Resilient Modulus Calculation

Florian,

Ševelová,

Žáková

et al. 2023

Forests

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“…When applying the load to a constant penetration depth of 2.54 mm, according to the CBR standard test, high stress values are observed in the plunger, exceeding the maximum load bearing capacity of the material for many soil types. Soil is a natural, heterogeneous and discontinuous environment, the deformation behavior, strength as well as variability of mechanical properties depend on many factors-e.g., the genesis, soil type, lay-off of unbound materials, compaction rate [26,27] given by the Proctor Standard energy, the liquid phase amount [12], the number of repeated loading cycles as well as on maximum load bearing capacity. The resilient modulus must reflect these factors [28] and be obtained from an adequate laboratory test, in which the future loading by repeated passages of transport vehicles is realistically simulated with the future stress interval in the structure.…”

Section: Laboratory Analysis-cyclic Cbr Testsmentioning

confidence: 99%

Using Resilient Modulus to Determine the Subgrade Suitability for Forest Road Construction

Ševelová

Florian

Hrůza

2020

Forests

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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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“…The normal and truncated normal CDF are used for symmetrically distributed variables, the threeparametric lognormal CDF for the other case. Statistical parameters of Young modulus of recycled concrete are based on the statistical evaluation of data obtained from laboratory tests Florian et al (2015). For simplicity, the mutual statistical independence of input variables is considered with the following exception -the temperatures of the upper and the lower surface of the slabs are supposed to be fully statistically dependent.…”

Section: Input Random Variablesmentioning

confidence: 99%

Reliability Analysis of Temperature Influence on Stresses in Rigid Pavement Made from Recycled Materials

Florian¹,

Ševelová

Žák

2016

Acta Univ. Agric. Silvic. Mendelianae Brun.

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Complex statistical and sensitivity analysis of principal stresses in concrete slabs of the real type of rigid pavement made from recycled materials is performed. The pavement is dominantly loaded by the temperature field acting on the upper and lower surface of concrete slabs. The computational model of the pavement is designed as a spatial (3D) model, is based on a nonlinear variant of the finite element method that respects the structural nonlinearity, enables to model different arrangement of joints, and the entire model can be loaded by thermal load. Four concrete slabs separated by transverse and longitudinal joints and the additional structural layers including soil to the depth of about 3 m are modeled. The thickness of individual layers, physical and mechanical properties of materials, characteristics of joints, and the temperature of the upper and lower surface of slabs are supposed to be random variables. The simulation technique Updated Latin Hypercube Sampling with 20 simulations is used for the reliability analysis. As results of statistical analysis, the estimates of basic statistics of the principal stresses σ1 and σ3 in 106 points on the upper and lower surface of slabs are obtained. For sensitivity analysis the sensitivity coefficient based on the Spearman rank correlation coefficient is used. As results of sensitivity analysis, the estimates of influence of random variability of individual input variables on the random variability of principal stresses σ1 and σ3 are obtained.

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Influence of Environmental Humidity on Mechanical Properties of Natural and Recycled Unbound Materials

Cited by 5 publications

References 2 publications

An Updated Cyclic CBR Test with Realistic Stress Values under the Plunger for Resilient Modulus Calculation

An Updated Cyclic CBR Test with Realistic Stress Values under the Plunger for Resilient Modulus Calculation

Using Resilient Modulus to Determine the Subgrade Suitability for Forest Road Construction

Reliability Analysis of Temperature Influence on Stresses in Rigid Pavement Made from Recycled Materials

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