Experimental Research on Physical and Mechanical Properties of High-Speed Railway Subgrade Filler

2014 ◽  
Vol 496-500 ◽  
pp. 2533-2537
Author(s):  
Xiong Shi ◽  
Jia Sheng Zhang ◽  
Guo Dong Deng ◽  
Fei Meng
Keyword(s):  
Mechanical Properties ◽  
Strain Hardening ◽  
High Speed ◽  
Large Scale ◽  
Axial Strain ◽  
Volumetric Strain ◽  
Bottom Layer ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Dry Density

In order to reveal the mechanical properties of the subgrade fillers, they are studied by screening test of coarse-grained soils, compaction test and large-scale triaxial test in the track-subgrade model in high-speed rail laboratory of Central South University. The experimental results show that the coarse particle content for filler of the bottom layer is larger than that of the underlying embankment. The optimum water content of the filler of the bottom layer is less than that of the underlying embankment, while the maximum of dry density is similar, All samples have shown strain hardening characteristic, the higher the confining pressure is, the more obvious the strain hardening characteristic is. the volumetric strain of samples changes from shear contraction to shear dilation with the increment of axial strain. The cohesion and internal friction angle for filler of the bottom layer is greater than that of the underlying embankment. The tangent modulus for filler of the bottom layer is larger than that of the underlying embankment, and with the confining pressure increases, the difference also increases.

scholarly journals New Structure for Strengthening Soil Embankments

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Fang Xu ◽  
Wuming Leng ◽  
Rusong Nie ◽  
Qishu Zhang ◽  
Qi Yang
Keyword(s):  
Shear Modulus ◽  
Large Scale ◽  
Dynamic Stress ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Additional Stress ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Critical Dynamic

A new prestressed reinforcement device (PRD) consisting of two lateral pressure plates (LPPs) and a reinforcement bar is developed to strengthen soil embankments by improving the soil confining pressure and providing lateral constraint on embankment slopes. The reinforcement effects of PRDs were demonstrated by investigating the beneficial effects of increasing confining pressure on the soil behavior via the performance of a series of large-scale static and cyclic triaxial tests on a coarse-grained embankment soil. The results show that PRDs can effectively improve the soil shear strength, bearing capacity, ability to resist elastic and plastic deformation, critical dynamic stress, and dynamic shear modulus, and empirical methods were also developed to determine the critical dynamic stress and initial dynamic shear modulus of the embankment soil. Moreover, 3D finite element analyses (FEAs) with an LPP width of 1.2 m were performed to analyze the additional stress field in a prestressed heavy-haul railway embankment. The FEAs showed that the additional stress at a given external distance from the border of an LPP first increased to a maximum value and then gradually decreased with increasing depth; the additional stress was transferred to the zones where the subgrade tends to have higher stresses with peak stress diffusion angles of 34° (slope direction) and 27° (longitudinal direction); and a continuous effective reinforcement zone with a minimum additional stress coefficient of approximately 0.2 was likely to form at the diffusion surface of the train loads, provided that the net spacing of the LPPs was 0.7 m. The reinforcement zone above the diffusion surface of the train loads can act as a protective layer for the zones that tend to have higher stresses. Finally, the advantages and application prospects of PRDs are discussed in detail. The newly developed PRDs may provide a cost-effective alternative for strengthening soil embankments.

scholarly journals Use of Basalt Fiber-Reinforced Tailings for Improving the Stability of Tailings Dam

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1306 ◽  
Author(s):  
Binbin Zheng ◽  
Dongming Zhang ◽  
Weisha Liu ◽  
Yonghao Yang ◽  
Han Yang
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Fiber Length ◽  
Basalt Fiber ◽  
Confining Pressure ◽  
Dry Density ◽  
Tailings Dam ◽  
Fiber Reinforced ◽  
Tailings Dams ◽  
The Stability

As one of the largest artificial geotechnical structures on earth, the tailings dams are classified as one of the high-risk sources in China’s industry. How to improve the stability and safety of tailings dams remains a challenge for mine operators currently. In this paper, an innovative method is presented for improving the stability of tailings dams, in which the basalt fiber is used to reinforce tailings. The mechanical properties of tailings used for dam-construction have a great influence on the stability of tailings dam. In order to investigate the mechanical performance of basalt fiber-reinforced tailings (BFRT), a series of laboratory triaxial tests were conducted. The effects of five parameters (fiber length, fiber content, particle size, dry density and confining pressure) on the mechanical properties of BFRT were studied. The microstructure and the behavior of interfaces between basalt fibers and tailings particles were analyzed by using scanning electron microscopy (SEM). The triaxial experimental test results show that the mechanical properties of BFRT increase with the increases of fiber length and content, particle size, dry density and confining pressure. The SEM results indicate that the interfacial interaction between fibers and tailings particles is mainly affected by particle shape.

Influence of Grain Size on Mechanical Properties in a Fe-9Ni-12Mn-2.5Si-1.0C TWIP Steel

2011 ◽  
Vol 197-198 ◽  
pp. 655-661
Author(s):  
Ze Bin Yang ◽  
Ding Yi Zhu ◽  
Wei Fa Yi ◽  
Shu Mei Lin ◽  
Cheng Mei Du
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Strain Hardening ◽  
Twip Steel ◽  
Optical Microscope ◽  
Coarse Grained ◽  
Microstructure Observation ◽  
Transmission Electron ◽  
Average Grain Size

We investigate the influence of grain size on mechanical properties in a Fe-9Ni-12Mn-2.5Si-1.0C TWIP steel by unidirectional tensile. Meanwhile the microstructures of the TWIP steel were observed and analyzed by optical microscope (OM) and transmission electron microscope (TEM). The experimental results show that the TWIP steel’s yield strength and tensile strength decrease with the increasing of grain size, whereas the plasticity increases with it. When the average grain size reaches to 27μm, the tensile strength is 1080MPa, the elongation percentage is 77%, and the strength-plasticity product achieves the 83160MPa•%. Steel’s strain hardening rate can be changed from three-stage to four-stage with the increasing of grain sizes, the areas of strain hardening by twin deformation mechanism are expanded. Through the microstructure observation we found that, coarse-grained TWIP steel conducts to twinning formation, the high density twins can increase the alloy’s ductility by splitting the grain.

Microstructural Evolution of Synthetic Forsterite Aggregates Deformed to High Strain

2004 ◽  
Vol 467-470 ◽  
pp. 579-584 ◽  
Author(s):  
A. Kellermann Slotemaker ◽  
J.H.P. de Bresser ◽  
C.J. Spiers ◽  
M.R. Drury
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Grain Growth ◽  
Microstructural Evolution ◽  
Large Scale ◽  
High Strain ◽  
Confining Pressure ◽  
Size Reduction ◽  
Coarse Grained ◽  
Fine Grained

Microstructures provide the crucial link between solid state flow of rock materials in the laboratory and large-scale tectonic processes in nature. In this context, microstructural evolution of olivine aggregates is of particular importance, since this material controls the flow of the Earth’s upper mantle and affects the dynamics of the outer Earth. From previous work it has become apparent that if olivine rocks are plastically deformed to high strain, substantial weakening may occur before steady state mechanical behaviour is approached. This weakening appears directly related to progressive modification of the grain size distribution through competing effects of dynamic recrystallization and syn-deformational grain growth. However, most of our understanding of these processes in olivine comes from tests on coarse-grained materials that show grain size reduction through dynamic recrystallization. In the present study we focused on fine-grained (~1 µm) olivine aggregates (i.e., forsterite/Mg2SiO4), containing ~0.5 wt% water and 10 vol% enstatite (MgSiO3), Samples were axially compressed to varying strains up to a maximum of ~45%, at 600 MPa confining pressure and a temperature of 950°C. Microstructures were characterized by analyzing full grain size distributions and textures using SEM/EBSD. We observed syndeformational grain growth rather than grain size reduction, and relate this to strain hardening seen in the stress-strain curves.

Effect of Coarse-Grained Ring on Mechanical Properties and Cutting Performance of 2011 Aluminum Alloy Extruded Bar

2021 ◽  
Vol 1035 ◽  
pp. 114-118
Author(s):  
Chang Liang Shi ◽  
Yan Ping Niu ◽  
Yi Min Lin ◽  
Quan Hu ◽  
Xin Zhang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Aluminum Alloy ◽  
Tensile Testing ◽  
High Speed ◽  
Testing Machine ◽  
Eutectic Phase ◽  
Cutting Performance ◽  
Coarse Grained ◽  
Tensile Testing Machine

The effects of coarse-grained ring on the mechanical properties and cutting performance of 2011 aluminum alloy extruded bars were studied by metallographic microscope, scanning electron microscope, tensile testing machine and high-speed lathe. The results show that the microstructure of aluminum alloy extruded bar was composed of α-Al phase, Al7Cu2Fe phase, CuAl2 phase and SnBi eutectic phase. There was a coarse-grained ring in the aluminum alloy extruded bar. The coarse-grained ring reduced the mechanical properties and cutting performance of the aluminum alloy extruded bar. The aluminum alloy extruded bar with a diameter of 30 mm had a coarse-grained ring depth of 9 mm and lower mechanical properties, whose the tensile strength was 287.9 MPa, the elongation was 17%, the cutting performance was poor and the chips were long. The aluminum alloy extruded bar with a diameter of 40 mm had a coarse-grained ring depth of 1 mm, higher mechanical properties and better cutting performance, whose the tensile strength was 394.5 MPa, the elongation was 23.5%, the chips were fine and uniform.

scholarly journals A Strain-Based Percolation Model and Triaxial Tests to Investigate the Evolution of Permeability and Critical Dilatancy Behavior of Coal

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 127 ◽  
Author(s):  
Dongjie Xue ◽  
Jie Zhou ◽  
Yintong Liu ◽  
Sishuai Zhang
Keyword(s):  
Axial Strain ◽  
Triaxial Compression ◽  
Sudden Change ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Percolation Model ◽  
Triaxial Tests ◽  
Transition Behavior ◽  
Orthogonal Experiments ◽  
Stress Dependent

Modeling the coupled evolution of strain and CH4 seepage under conventional triaxial compression is the key to understanding enhanced permeability in coal. An abrupt transition of gas-stress coupled behavior at the dilatancy boundary is studied by the strain-based percolation model. Based on orthogonal experiments of triaxial stress with CH4 seepage, a complete stress-strain relationship and the corresponding evolution of volumetric strain and permeability are obtained. At the dilatant boundary of volumetric strain, modeling of stress-dependent permeability is ineffective when considering the effective deviatoric stress influenced by confining pressure and pore pressure. The computed tomography (CT) analysis shows that coal can be a continuous medium of pore-based structure before the dilatant boundary, but a discontinuous medium of fracture-based structure. The multiscale pore structure geometry dominates the mechanical behavior transition and the sudden change in CH4 seepage. By the volume-covering method proposed, the linear relationship between the fractal dimension and porosity indicates that the multiscale network can be a fractal percolation structure. A percolation model of connectivity by the axial strain-permeability relationship is proposed to explain the transition behavior of volumetric strain and CH4 seepage. The volumetric strain on permeability is illustrated by axial strain controlling the trend of transition behavior and radical strain controlling the shift of behavior. A good correlation between the theoretical and experimental results shows that the strain-based percolation model is effective in describing the transition behavior of CH4 seepage in coal.

scholarly journals Effect of Grain Refinement and Dispersion of Particles and Reinforcements on Mechanical Properties of Metals and Metal Matrix Composites through High-Ratio Differential Speed Rolling

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4159 ◽  
Author(s):  
Ahmad Bahmani ◽  
Woo-Jin Kim
Keyword(s):  
Mechanical Properties ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
High Speed ◽  
Large Scale ◽  
High Ratio ◽  
Speed Ratio ◽  
Matrix Composites ◽  
Differential Speed Rolling ◽  
Differential Speed

A differential speed rolling (DSR) technique that provides capability of producing large-scale materials with fine grains and controlled texture in a continuous manner has attracted several researchers and industries. In this study, we tried to review the articles related to DSR and especially the high-ratio DSR (HRDSR) technique that is associated with a high speed ratio between the upper and lower rolls (≥2) and compare the change in microstructure and mechanical properties after HRDSR with the results obtained by using other severe plastic deformation (SPD) techniques to see the potential of the HRDSR technique in enhancing the mechanical properties of metals and metal matrix composites. The reviewed results show that HRDSR is an important technique that can effectively refine the grains to micro or nano sizes and uniformly disperse the particles or reinforcement throughout the matrix, which helps extensively in improving ambient and superplastic mechanical properties of various metals and alloys.

Study on Particle Breakage of Coarse-Grained Soil Based on Large-Scale Triaxial Test

2014 ◽  
Vol 937 ◽  
pp. 585-589
Author(s):  
Fu Yong Chu
Keyword(s):  
Power Function ◽  
Triaxial Test ◽  
Large Scale ◽  
Confining Pressure ◽  
Particle Breakage ◽  
Plastic Work ◽  
Coarse Grained ◽  
Earth Dam ◽  
Relationship Of ◽  
Coarse Grained Soil

Using large-scale shearing device, isotropiclly consolidated-drained triaxial test under different confining pressures are performed for overburden material of ShuangJiangKou earth dam which relative density is 0.8. The relationship between particle breakage of coarse-grained soil and input plastic work under loading and between particle breakage and confining pressure and between particle breakage and strength of coarse-grained soil. The results show that the particle breakage of coarse-grained soil and the input plastic work under loading is closely related. The particle breakage of coarse-grained soil increase with the input plastic work and there is a relationship of power function between Bg andWp. the increase of confining pressure will lead to the increase of particle breakage of coarse-grained soil, and there is a relationship of power function between Bg and. the increase of particle breakage of coarse-grained soil will lead to the decrease of strength of coarse-grained soil, and a relationship of linear between Bg andφ.

Relationship of Fractal Structure and Compactibility of Coarse Grain Soil in High Speed Railway Subgrade

2013 ◽  
Vol 438-439 ◽  
pp. 1108-1111 ◽  
Author(s):  
Ya Bing Huang ◽  
Yan Jun Li ◽  
Tan Jiao
Keyword(s):  
High Speed ◽  
Fractal Theory ◽  
Fractal Dimensions ◽  
Coarse Grained ◽  
Dry Density ◽  
Maximum Dry Density ◽  
High Speed Railway ◽  
Compaction Characteristics ◽  
Relationship Of ◽  
The Relationship

As an important factor that affects the compaction characteristics of the coarse grained fillers in the high speed railway subgrade, the grain composition is characterized by the application of the fractal theory. Several types of the coarse grained fillers were selected for testing and the results indicated that the relationship actually exists between the compaction characteristics and the fractal dimensions. The variation law of the maximum dry density fluctuating with the quality fractal dimension was analyzed and the results were supposed to estimate the compaction characteristics of the coarse grained fillers.

Acoustic Emission Characteristics of Sericite Schist Coarse Aggregates under Consolidated Undrained Triaxial Tests

2013 ◽  
Vol 423-426 ◽  
pp. 909-913
Author(s):  
Lan Qiang Yang ◽  
Shang Lin Qin ◽  
Hui Gao ◽  
Shan Xiong Chen
Keyword(s):  
Acoustic Emission ◽  
Large Scale ◽  
Sliding Friction ◽  
Axial Strain ◽  
Confining Pressure ◽  
Rolling Friction ◽  
Triaxial Tests ◽  
Emission Characteristics ◽  
Coarse Aggregates ◽  
Ae Signals

In order to study the acoustic emission characteristics of coarse aggregates, improved of large-scale triaxial apparatus is used to do the consolidated undrained triaxial tests of sericite schist coarse aggregates, with the acoustic emission signals monitoring. The test results show that a large number of AE signals of sericite schist coarse aggregates are generated in the initial stage. Before the axial strain reach 10%, AE counts are relatively quiet. But after 10%, they become anomalous and emerge obvious leap values. When the confining pressure up to 200kPa, AE signals are mainly generated by sliding friction. With confining pressure increasing, the proporation of rolling friction and particle breakage is more and more obvious.

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