scholarly journals The application of the principles of the theory of shakedown to the calculation of pavement layers of granular materials in shear

2018 ◽  
Vol 239 ◽  
pp. 05019 ◽  
Author(s):  
Anatoly Aleksandrov ◽  
Gennadiy Dolgih ◽  
Vitaly Ignatov ◽  
Aleksander Kalinin
Keyword(s):  
Granular Material ◽  
Granular Materials ◽  
Residual Deformation ◽  
Pavement Layers ◽  
Plastic Shakedown ◽  
Dangerous Point

In the report ways of application of the theory of shakedown of material to calculation of coverings and the bases of pavements from the granulated materials are considered. The basic limits of shakedown are given, which include the limits of resilient, elastic and plastic shakedown. The results of three-axis tests are given, on the basis of which the character of accumulation of residual deformation is divided into damped, steady and progressive. These data allow to predict the nature of deformation and provide damped deformation of the granular material, limiting the stress at the most dangerous point.

scholarly journals A frictional Cosserat model for the slow shearing of granular materials

2002 ◽  
Vol 457 ◽  
pp. 377-409 ◽  
Author(s):  
L. SRINIVASA MOHAN ◽  
K. KESAVA RAO ◽  
PRABHU R. NOTT
Keyword(s):  
Angular Velocity ◽  
Granular Material ◽  
Shear Layer ◽  
Granular Materials ◽  
Layer Thickness ◽  
Couette Flow ◽  
Velocity Fields ◽  
Cosserat Continuum ◽  
Cosserat Model ◽  
Cylindrical Couette Flow

A rigid-plastic Cosserat model for slow frictional flow of granular materials, proposed by us in an earlier paper, has been used to analyse plane and cylindrical Couette flow. In this model, the hydrodynamic fields of a classical continuum are supplemented by the couple stress and the intrinsic angular velocity fields. The balance of angular momentum, which is satisfied implicitly in a classical continuum, must be enforced in a Cosserat continuum. As a result, the stress tensor could be asymmetric, and the angular velocity of a material point may differ from half the local vorticity. An important consequence of treating the granular medium as a Cosserat continuum is that it incorporates a material length scale in the model, which is absent in frictional models based on a classical continuum. Further, the Cosserat model allows determination of the velocity fields uniquely in viscometric flows, in contrast to classical frictional models. Experiments on viscometric flows of dense, slowly deforming granular materials indicate that shear is confined to a narrow region, usually a few grain diameters thick, while the remaining material is largely undeformed. This feature is captured by the present model, and the velocity profile predicted for cylindrical Couette flow is in good agreement with reported data. When the walls of the Couette cell are smoother than the granular material, the model predicts that the shear layer thickness is independent of the Couette gap H when the latter is large compared to the grain diameter dp. When the walls are of the same roughness as the granular material, the model predicts that the shear layer thickness varies as (H/dp)1/3 (in the limit H/dp [Gt ] 1) for plane shear under gravity and cylindrical Couette flow.

scholarly journals Frictional properties between geocells filled with granular material

2021 ◽  
Vol 20 (2) ◽  
pp. 332-345
Author(s):  
Gökhan Altay ◽  
◽  
Cafer Kayadelen ◽  
Taha Taskiran ◽  
Baki Bagriacik ◽  
...  
Keyword(s):  
Granular Material ◽  
Normal Stress ◽  
Granular Materials ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Frictional Properties ◽  
Geotechnical Structures ◽  
Series Of Experiments ◽  
Restricted Volume

The parameters concerning the interaction between geocell and granular materials is required for the design of many geotechnical structures. With this in mind, a series of experiments using simple direct shear tests are conducted in order to understand the frictional properties between geocells filled with granular materials. The 54 test samples are prepared by filling the geocell with granular materials having three different gradations. These samples are tested at three different relative densities under three different normal stress levels. As a result, it was observed that interface resistance between the geocells filled with granular material is found to be generally greater than in the samples without geocells. Additionally, these samples with geocells are found to be stiffer; this is due to the fact that the samples with geocell gained more cohesion because geocells confined the grains within a restricted volume.

scholarly journals Laboratory Evaluation of Gradation Improvement of Marginal Materials for Foamed Bitumen Stabilisation

2020 ◽  
Vol 10 (12) ◽  
pp. 4224
Author(s):  
Greg White ◽  
Roberto Espinosa
Keyword(s):  
Granular Material ◽  
Effective Treatment ◽  
Granular Materials ◽  
Laboratory Evaluation ◽  
Variable Effect ◽  
Construction Specifications ◽  
Average Modulus ◽  
Indirect Tensile ◽  
Foamed Bitumen ◽  
Pavement Construction

Foamed bitumen stabilisation is an attractive technology for increasing the use of marginal materials in pavement construction and rehabilitation. However, by their very nature, marginal materials do not meet the prescriptive requirements of many standard specifications. Consequently, performance-related evaluation is required. For foamed bitumen stabilised marginal materials, the cured and saturated moduli are common performance-related parameters that are also used for characterisation during structural pavement design. In this research, the indirect tensile moduli of three foamed bitumen stabilised marginal granular materials were compared to the modulus of a standard or premium material, in both cured and saturated conditions, after 3, 7 and 14 days of accelerated laboratory curing. The results indicated that the magnitude of granular material marginality was not related to the stabilised material modulus. Furthermore, the gradations of the two most marginal materials were improved by blending with another granular material and the improved marginal materials were also stabilised and tested. The gradation improvement had a variable effect on the stabilised material modulus, with the average modulus increasing by more than 20%. The modulus increase associated with the gradation improvement was related to the basis and magnitude of granular material marginality, with the saturated modulus of the most plastic marginal material increasing by the greater amount after improvement. It was concluded that foamed bitumen stabilisation is a particularly effective treatment for marginal granular materials. Furthermore, when used in combination with gradation improvement, the resulting foamed bitumen stabilised material can perform similarly to standard materials, based on cured and soaked modulus values. However, to allow the use of foamed bitumen stabilised marginal materials in pavement construction, specifications must be more performance-related and the current limits on plasticity and gradation must be relaxed.

Calculation of Residual Deformations of Granulated Materials from Exposure to Repeated Loads

2020 ◽  
Vol 992 ◽  
pp. 828-835
Author(s):  
A.S. Aleksandrov ◽  
T.V. Semenova ◽  
N.P. Aleksandrova
Keyword(s):  
Granular Materials ◽  
Triaxial Compression ◽  
Residual Deformation ◽  
Load Application ◽  
Crushed Stone ◽  
Integral Calculus ◽  
Short Period ◽  
Residual Deformations ◽  
The Impact ◽  
Repeated Loads

The analysis of the models for calculating residual deformations accumulated by granular materials under the influence of repeated loads is performed. Determined the hereditary nature of the accumulation of deformation of granular materials. This allowed the use of integral calculus for the analytical solution of the problem of the dependence of residual deformation on the number of repeated loads, the value of the main stresses. The solution is obtained in the form of logarithmic and power-law functions that associate the accumulated deformation with the deformation arising from the first load application with the number of applied loads. The deformation from the first load application is represented by the sum of the two components, instantaneous irreversible and viscoplastic. The viscoplastic component of the deformation is a consequence of stress relaxation in a relatively short period of time equal to the duration of the impact of the load. The analysis of experimental data on the triaxial compression of various granular materials is carried out and the parameters obtained for the power and logarithmic functions are determined. The materials studied include: granite, gneissic, granodiorite and diorite crushed stone, sand and gravel and crushed stone and gravel mixtures with a mineral part from various rocks, fortified sands. The possibility of application of the obtained solutions for the calculation displacement of the surface of the pavement layers of granular materials is shown. The tasks of further research are formulated.

Application of simulation technologies in the analysis of granular material behaviour during transport and storage

2005 ◽  
Vol 219 (1) ◽  
pp. 43-52 ◽  
Author(s):  
P Chapelle ◽  
N Christakis ◽  
J Wang ◽  
N Strusevich ◽  
M. K. Patel ◽  
...  
Keyword(s):  
Granular Material ◽  
Granular Materials ◽  
Large Scale ◽  
Computational Models ◽  
Research Programme ◽  
Size Segregation ◽  
Materials Handling ◽  
Simulation Tools ◽  
And Storage

Problems in the preservation of the quality of granular material products are complex and arise from a series of sources during transport and storage. In either designing a new plant or, more likely, analysing problems that give rise to product quality degradation in existing operations, practical measurement and simulation tools and technologies are required to support the process engineer. These technologies are required to help in both identifying the source of such problems and then designing them out. As part of a major research programme on quality in particulate manufacturing computational models have been developed for segregation in silos, degradation in pneumatic conveyors, and the development of caking during storage, which use where possible, micro-mechanical relationships to characterize the behaviour of granular materials. The objective of the work presented here is to demonstrate the use of these computational models of unit processes involved in the analysis of large-scale processes involving the handling of granular materials. This paper presents a set of simulations of a complete large-scale granular materials handling operation, involving the discharge of the materials from a silo, its transport through a dilute-phase pneumatic conveyor, and the material storage in a big bag under varying environmental temperature and humidity conditions. Conclusions are drawn on the capability of the computational models to represent key granular processes, including particle size segregation, degradation, and moisture migration caking.

Application of Tubes Filled With Granules for Crashworthy Design of Automobiles

2007 ◽  
Author(s):  
Dong Wook Lee ◽  
Zheng-Dong Ma ◽  
Noboru Kikuchi
Keyword(s):  
Granular Material ◽  
Granular Materials ◽  
Effective Thickness ◽  
Analytic Model ◽  
Specific Design ◽  
Model Based ◽  
Highly Effective ◽  
Crashworthiness Design ◽  
Empty Tube ◽  
Granular Particles

An innovative means for improving crashworthiness is to use tubes filled with a granular material to absorb energy during the process of a crash. In this paper, we will study how to use granular materials in the tubes found in the front posts of automobiles for improved safety. The focus will be on a specific design of tubes filled with a granular material. Note that granular particles can create enormous friction through their interactions; therefore a tube filled with a granular material can absorb much more crash energy than an empty tube. The application of granular materials to a crashworthiness design is very challenging but highly effective. In this paper, we will develop an analytic model based on the effective thickness theory of a tube filled with granules.

scholarly journals Effects of adding old shingles to granular material and hot mix asphalt : laboratory and field investigation

2021 ◽  
Author(s):  
Narayan B Shrestha
Keyword(s):  
Granular Material ◽  
Granular Materials ◽  
Hot Mix Asphalt ◽  
Field Investigation ◽  
Freezing And Thawing ◽  
Optimum Amount ◽  
Graded Material ◽  
Control Section ◽  
The Stability ◽  
Potential Use

This thesis evaluates the potential use of processed tear-off shingles in road works. Six types of granular materials were investigated to determine the type of material that benefitted the most from using the shingles. The effects of shingles on the stability, as measured by California Bearing Ratio, were found to depend on properties such as gradation and fines content. In general shingles enhanced the stability of materials of relatively low CBR, but decreased the stability of angular well graded material of CBR larger than 100%. Optimum amount of shingles were found to enhance the resistance of stabilized granular materials to cycles of freezing and thawing; however, amounts higher than optimum decreased the resistance to freezing and thawing. In terms of permeability, the addition of shingles did not have a significant effect on the drainage characteristics of the tested materials. A trial road was constructed and showed that after one week of construction dust generated by the control section was found to be twice the amount of dust generated by the shingle section.

A continuous, laboratory-size density separator for granular materials

1965 ◽  
Vol 35 (271) ◽  
pp. 536-541 ◽  
Author(s):  
M. P. Jones
Keyword(s):  
Grain Size ◽  
Granular Material ◽  
Granular Materials ◽  
Standard Laboratory ◽  
Continuous Density

SummaryDetails are given for the construction of a continuous, density separator from standard laboratory glassware and equipment. The separator can treat up to 5 g/min of granular material from 150 to 2000 µ in grain size, and the liquid used is continually recirculated by a simple airlift.

scholarly journals A numerical toolkit to understand the mechanics of partially saturated granular materials

2015 ◽  
Vol 770 ◽  
pp. 1-4 ◽  
Author(s):  
J.-N. Roux
Keyword(s):  
Granular Material ◽  
Phenomenological Models ◽  
Granular Materials ◽  
Lattice Boltzmann ◽  
Discrete Element ◽  
Mechanical Effect ◽  
Saturation Level ◽  
Partially Saturated ◽  
Mechanical Effects ◽  
Granular Assemblies

The mechanisms by which a wetting, non-saturating liquid bestows macroscopic cohesion and strength to a granular material are usually not accessible to micromechanical investigations for saturations exceeding the pendular regime of isolated menisci, easily studied by discrete element models (DEM). The paper by Delenne et al. (J. Fluid Mech., 2015, vol. 762, R5) exploiting a multiphase lattice Boltzmann approach, pioneers the simulation of the micromorphology and of the mechanical effects on grains of an interstitial liquid, in equilibrium with its vapour, for the whole saturation range. Interestingly, in accordance with some experiments and phenomenological models, the results suggest that the mechanical effect of capillary forces is maximized for some intermediate saturation level (near 40 % in the model), well beyond the pendular range. In general, the proposed simulation technique opens the way to many studies of partially saturated granular assemblies, for different saturation or imbibition processes and histories.

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