coarse grained and fine grained soil

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The results show that the moisture content has a significant effect on the deformation of coarse-grained soil. In order to better simulate the indoor triaxial test at an acceptable speed, the minimum diameter of soil particles is fixed to 0.5mm. [21] and Chen et al. Therefore, in the follow-up studies, the effects of various factors on the mechanical properties of the coarse-grained soil as embankment filler should be comprehensively considered. This may be related to the uneven spatial distribution of particles with different particle sizes in addition to the loading anisotropy. Can. The authors stated that there is a clear relation between the microscale parameters and the overall specimen response. Ranjith. The moisture content of coarse-grained soil as an embankment filler usually falls between 5% and 10%, so three moisture contents (i.e., =6.9%, 7.8%, and 9.1%) are used in the simulation; on the other hand, different deviatoric stress amplitudes (i.e., =25kPa, 45kPa, and 60kPa) and loading frequencies (i.e., f=0.5Hz, 1.0Hz, and 3.0Hz) are selected considering the vehicle loading conditions [28, 3842]. A. Schrefler, Modelling of cutting toolsoil interactionpart II: macromechanical model and upscaling,, N. Cho, C. D. Martin, and D. C. Sego, A clumped particle model for rock,, J.-W. Park and J.-J.

Kim, Y.W. Under the action of cyclic loading, the coarse-grained soil is continuously compacted, thus reducing the porosity. K.V.

With the increase of the loading frequency, the macroscopic performance is that the axial permanent deformation increases; moreover, the tensile force chain is less and more concentrated on the upper and lower surfaces at the mesoscopic level. Simulation scheme for dynamic triaxial tests. Afterward, the changes in the porosity, force chain, and particle movement of coarse-grained soil samples were analyzed, and the mesoscopic deformation behavior of coarse-grained soil under cyclic loading was investigated. Zhong-Ming He, Da Xiang, Ya-Xin Liu, Qian-Feng Gao, Han-Bing Bian, "Deformation Behavior of Coarse-Grained Soil as an Embankment Filler under Cyclic Loading", Advances in Civil Engineering, vol. In engineering practice, the embankment filled with coarse-grained soil may present large settlements and local road sections even slide under seasonal rainfall and long-term vehicle loading. S. Tripathy, M.Y.M Tadza and H.R. It is observed from Figure 6(c) that the axial permanent deformation increases significantly with the increase of loading frequency.

It is noted that as the cyclic loading progresses, the porosity decreases continuously. The weighted average radius of soil particles is calculated by [37]where is the average particle radius; is the content of particles smaller than a certain size; and is the weighted number of a certain particle size.

Wang and Wang [23] investigated the liquefaction behavior and mesomechanism of gravelly soil under cyclic loading with constant strain amplitude.

Eng. Singh. During the cyclic loading process, the history command is used to monitor the deviatoric stress exerted by the loading plate and the axial permanent deformation of the sample.

For instance, Sazzad and Suzuki [19] investigated the micromechanical behavior of granular materials with different inherent anisotropies during cyclic loading using DEM. Thus, the yield stress is used as an intermediate variable to derive the relationship between the moisture content and the particle bond strength [45, 46]. In essence, coarse-grained soil can be regarded as a typical granular material, particularly when its fines content is low. Ren et al. Figure 6(a) presents that the axial permanent deformation of the sample increases rapidly during the first 1000 loading cycles, reaching 80% of the final permanent deformation, and then the deformation slowly increases and gradually tends to be a fixed value. Selecting this option will search the current publication in context. The changes in the porosity, force chain, and particle movement of coarse-grained soil samples are examined, and the mesoscopic deformation behavior of coarse-grained soil under cyclic loading is analyzed. They also explained the mechanism of particle breakage based on the evolution of micromechanical parameters such as the distribution of the contact force and bond force. The dynamic expansion method is used to generate soil particles. It shows that the weighted average radius of the soil particles is 2.768mm. The membrane particles are bonded following the contact bonding model to ensure the particles only transmit force but not moment. Park and Song [18] examined the effects of the geometrical features and the properties of a joint on its shear behavior by an extensive series of direct shear tests using the PFC3D code. OSullivan et al.

Ju et al. The behavior of coarse-grained soil was also studied based on the continuous medium assumption. Karim and D. Mohamed. Figures 10(a) and 10(b) present that the absolute value of the velocity is increasing from the center axis of the test sample to the edge of the test sample, indicating that the particles have a velocity of moving outwards during the test. The coarse-grained soil is continuously compacted under cyclic loading, thus reducing the porosity. 2019IC13). [11] investigated the strength, deformation, elastic modulus, failure process, and particle breakage of coarse-grained soil by DEM. To control the deformation and stability of the coarse-grained soil embankment, it is necessary to have a better understanding of the deformation behavior of coarse-grained soil during cyclic loading. Jiang et al. With the increase of moisture content, the soils lubricating effect is enhanced under long-term cyclic loading, and the friction between particles is reduced.

During the road operation period, heavy-duty vehicles should be restricted to reduce the stress transmitted to the embankment and thus reduce the permanent deformation of the embankment. S. Rahimi and S. Siddiqua. Cui et al., Effects of fines and water contents on the mechanical behavior of interlayer soil in ancient railway sub-structure,, H. L. Wang, Y. J. Cui, F. Lamas-Lopez et al., Permanent deformation of track-bed materials at various inclusion contents under large number of loading cycles,, H.-L. Wang, Y.-J. Therefore, to reduce the permanent deformation of the embankment filled with coarse-grained soil, the internal stress of the granular layer should be considered when designing the embankment. The results will provide a reference for embankment filling with coarse-grained soil in engineering practice. Table 3 shows the simulation scheme for dynamic triaxial tests, which is completely consistent with that employed in the laboratory tests. The application of confining pressure is realized by applying equivalent concentrated forces to the membrane particles.

Read the winning articles. It was found that the liquefaction resistance of gravelly soil increases significantly with the increasing gravel content because of the growth in number of gravel-to-gravel contact.

The authors declare that there are no conflicts of interest regarding the publication of this paper. The authors reported that the problem of shear bands originated from the bifurcation characteristics of the soil. The position of particles inside the embankment constantly changes during road operations.

Indraratna et al. The porosity has the smallest change and fluctuates around 22% at the measurement circle 3. Padmakumar and D.N. V. N. Trinh, A. M. Tang, Y.-J. Particle contact will form contact force chains throughout the entire model. Numerical dynamic triaxial tests were performed on coarse-grained soil using the discrete element software PFC3D. It is noted that with the increase of the moisture content, the axial permanent deformation increases at the macroscopic level. Soil Science Society of America Journal. Also, with the increase of deviatoric stress amplitude, the moisture content, and loading frequency, the deformation of the sample at the same number of loading cycles increases and the ability to resist deformation decreases in different degrees. For this reason, the particles of excess size were removed. Soil Science Society of America Journal. Annals of Nuclear Energy. [37] is used to modify the particle group that is smaller than 1mm. [15] examined the effects of different confining pressures, porosity, and particle rotations on the mechanical properties of granular materials using both laboratory triaxial tests and DEM simulations. Song et al., Insight into relationships between macroscopic and grain-scale parameters in calculating three-dimensional discrete element of unsaturated soils,, M. Jiang, H.-S. Yu, and S. Leroueil, A simple and efficient approach to capturing bonding effect in naturally microstructured sands by discrete element method,. Geol. The commonly used calibration method is to compare numerical data and test results until the difference between them is smaller than a certain value. When the moisture content is 6.9%, the axial permanent deformation of the sample after 10,000 loading cycles is 0.06%, and when the moisture content increases from 6.9% to 9.1%, the axial permanent deformation increases up to 0.15% after 10,000 loading cycles.

According to Figure 10, the velocity and displacement in the three directions of the sample are not uniformly distributed but exhibit obvious anisotropy, which may also be related to the uneven spatial distribution of particles with different particle sizes in addition to the loading anisotropy. In the PFC3D software, the porosity is defined as the ratio of the volume of pores in a measurement circle to the volume of the measurement circle. Int. Schematic diagram of lateral wall and loading plates. Calibration process of mesoscopic parameters of coarse-grained soil. Selecting this option will search all publications across the Scitation platform, Selecting this option will search all publications for the Publisher/Society in context, The Journal of the Acoustical Society of America, Faculty of Civil Engineering and Earth Resources, Universiti Malaysia Pahang, Faculty of Mechanical & Manufacturing Engineering, Universiti Malaysia Pahang, https://doi.org/10.1061/(ASCE)1090-0241(2005)131:11(1330), https://doi.org/10.1680/geot.2006.56.2.81, https://doi.org/10.1016/j.enggeo.2006.10.002, https://doi.org/10.1016/j.enbuild.2005.03.001, https://doi.org/10.1061/(ASCE)1532-3641(2008)8:2(114), https://doi.org/10.2136/sssaj1969.03615995003300030009x, https://doi.org/10.2136/sssaj2000.6441285x, https://doi.org/10.1061/(ASCE)0733-9410(1989)115:12(1683), https://doi.org/10.1016/j.enggeo.2012.10.001, https://doi.org/10.1016/j.enggeo.2017.03.007, https://doi.org/10.1016/j.anucene.2007.05.011, https://doi.org/10.1016/j.enggeo.2013.06.014, https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000380, On thermal characteristics of coarse grained and fine grained soils in ground heat exchanger applications. (b) Vertical cross section. If you need an account, pleaseregister here, The thermal properties of soils and rocks is an important property for the design of thermally active ground structures such as geothermal energy foundations and heat exchange systems.

H.R. It shows that the grading curve modified by the weighted average method is basically consistent with that used in laboratory tests. J of Geomechanics ASCE, T.E. The aim of this study is thus to examine the deformation behavior and internal mechanism of coarse-grained soil as an embankment filler under cyclic loading using the PFC3D software. The cylindrical wall is modeled by a flexible particle membrane composed of particles of identical sizes (Figure 2(b)). The contact force is relatively even in the downward direction while dispersed near the edge of the sample. Thomas, H.T.

Soc. However, both the traditional geotechnical test and continuous medium analysis are not able to characterize the mesoscopic properties of coarse-grained soil.

Meanwhile, the bottom of the sample is less affected by the cyclic load. Thomas. unified plasticity Uday, G.P. Deformation Behavior of Coarse-Grained Soil as an Embankment Filler under Cyclic Loading, Road Catastrophe Prevention and Traffic Safety Engineering Research Center of Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China, School of Traffic & Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China, Laboratory of Civil Engineering and Geo-Environment, University of Lille, Lille 59000, France. Hanson and W.L. M.Y.M Tadza, N.S.M. [20] simulated the particle-scale mechanics of the response of samples of uniform spheres to 50 cycles of loading with various strain amplitudes. From the figure, the contact force chain distribution of the discrete element sample can be seen intuitively. During the entire shearing process, the work required to overcome the friction between particles is less than the work performed at the optimum moisture content, resulting in increased axial permanent deformation. Firstly, according to the characteristics of PFC3D software and triaxial test, the porosity of the numerical model is determined, and then the particle contact stiffnesses and are calibrated so that the simulated permanent deformation curve is approximately the same as the test curve, and then the stiffness of flexible particle membrane and is determined; finally, repeatedly adjust the interparticle friction coefficient and linear bond strength and until the shapes, slopes, and peak values of the numerical curves are broadly consistent with the experimental ones, and the difference between the test results and the numerical simulation results is controlled within 20%. Can. The PFC3D software can monitor the change of internal porosity in real time, which plays a positive role in analyzing the permanent deformation mechanism of coarse-grained soil under cyclic loading. Amer.

Park. Reeder. As the number of loading cycles increases, the deformation difference becomes smaller and smaller, and the final deformation difference is less than 10%. The contact force is relatively even in the downward direction while dispersed near the edge of the sample. This means that the particles at the bottom are less affected by loads and the internal evolution of soil samples conforms to its macroscopic deformation behavior during cyclic loading. Figure 7 shows the contact force chain diagram of discrete element samples with a moisture content of 6.9% under a loading frequency of 1Hz and different deviatoric stress amplitudes after 1000 cyclic loads.

The undetermined parameters involved in the numerical simulation include tangential contact stiffness , normal contact stiffness , interparticle friction coefficient , density , and porosity .

To determine the mesoscopic parameters, repeated tentative calculations are conducted following the procedure shown in Figure 5. However, the environment of a practical embankment is much more complicated.

For this purpose, additional expensive techniques such as computed tomography and scanning electron microscopy should be incorporated into traditional tests [8, 9]. Engineering Geology, H.M. Abuel-Naga, D.T. Cleall. Figure 8 shows the contact force chains in samples with three different moisture contents under a deviatoric stress amplitude of 60kPa and a loading frequency of 1Hz after 1000 cyclic loads. The arrow in the figure indicates the direction of particle movement. In such cases, it is usually recommended to properly adjust the grading curve [3436]. The discrete element method (DEM) is a discontinuous numerical method, which solves the complex practical problems by simulating the motion of spheres and particles.

(2)Under the same moisture content and loading frequency, with the increase of the deviatoric stress amplitude, the force chain distribution gradually changes from sparse to dense; meanwhile, the force chain changes from thin to thick, the number of stressed skeleton particles increases, and the contact force between the particles gradually increases. When the particle generation is performed based on the minimum radius and the ratio of the maximum radius to the minimum in DEM, the generation probability of the particle radius from the smallest to the largest is the same according to the random command. Traditional geotechnical tests are the most commonly used means to determine the mechanical properties and deformation behavior of coarse-grained soil. They found that the friction coefficient was the most important factor governing the shear strength and dilation angle. N.H. Abu-Hamdeh, and R.C. Brandon and J.K. Mitchell. 2020, Article ID 4629105, 13 pages, 2020. https://doi.org/10.1155/2020/4629105, 1Road Catastrophe Prevention and Traffic Safety Engineering Research Center of Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China, 2School of Traffic & Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China, 3Laboratory of Civil Engineering and Geo-Environment, University of Lille, Lille 59000, France. From Figures 6(a)6(c), one can note that the laboratory experimental results and the numerical data have a good consistency on the whole. 51978084 and 51678073), the Natural Science Foundation of Hunan Province (grant no. Bergado and A. Bouazza. Figure 3 shows an example of the generated cylindrical sample. Permanent deformations of samples in laboratory tests and numerical simulations. Jiang et al. They found that the differences in inherent anisotropy obviously affect the stress-strain-dilative behavior of granular materials. The maximum dry density and optimum moisture content of the studied coarse-grained soil were measured by heavy compaction tests. Basic physical and mechanical properties of coarse-grained soil. According to the Chinese standard for soil classification (GB 50145-2007) [1], this material was classified as coarse-grained soil. Geotech. W.J.

[22] performed DEM simulations of the permanent deformation and degradation behavior of railway ballast under cyclic loading. The California bearing ratio (CBR) and resilient modulus were also determined using a CBR device and the loading plate method [25, 26]. As a matter of fact, the drying-wetting cycles and the temperature change will also affect the service performance of the embankment filled with coarse-grained soil. 3rd National Conference on Knowledge Transfer, J.C. Santamarina, K.A. Geol. Figure 10(d) shows the displacement track of particles. The expression of the deviatoric stress at time t is as follows:where is the maximum value of semisinusoidal stress; is the duration of each loading; and T is the duration of one loading cycle. The velocity is timely adjusted considering the gap between the calculated stress and the target value.

Wierenga, R.M. The black chain represents compression, the red chain represents tension, and the thickness of the chain represents the magnitude of the contact force between the particles. The upper loading plate compresses the sample, and the bottom loading plate remains stationary during the simulation process. The conventional test cannot directly measure the change of the porosity during the test, and the indirect method is easy to cause disturbance to the sample and affect the test results.

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