scholarly journals Numerical Simulations of the Soil–Rock Mixture Mechanical Properties Considering the Influence of Rock Block Proportions by PFC2D

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5442
Author(s):  
Wenwei Gao ◽  
Hairong Yang ◽  
Le Wang ◽  
Ruilin Hu
Keyword(s):  
Mechanical Properties ◽  
Numerical Models ◽  
Axial Strain ◽  
Strain Curve ◽  
Physical And Mechanical Properties ◽  
Rock Block ◽  
Particle Flow Code ◽  
Random Structure ◽  
Block Rotation ◽  
Deformation And Failure

Soil–rock mixtures (S-RMs), as a kind of special engineering geological material, need to be studied because of the special structure and complex movement mechanism of their rock blocks, their physical and mechanical properties, and the factors underlying rock block movement in the process of their deformation and failure. In this paper, a series of discrete-element numerical models are constructed in particle flow code software (PFC2D). First, the random structure numerical models of S-RMs with different rock block proportions are established. Then, the parameters of the soil meso-structure are inversed by the biaxial simulation test, and a series of biaxial compressive tests are performed. The characteristics of stress and strain, deformation and failure, and rock block rotation and energy evolution are systematically investigated. The results show the following. (1) As the rock block proportion (confining pressure 0.5 MPa) increases, the peak strength of increases, the fluctuations of the post-peak become more obvious, and the dilatancy of the sample increases. (2) As the rock block proportion increases, the width of the shear band increases, the distribution of cracks becomes more complex and dispersed, and the range of the shear zone increases. (3) The number of rock blocks with rotation also increases significantly as rock block proportion increases, and the rotation angles are mostly between −5° and 5°. (4) The strain energy of S-RMs with different rock block proportions follows the same change rule as axial strain, showing a trend of first increasing and then decreasing, like the stress–strain curve.

scholarly journals Experimental Study on Physical Mechanical Properties and Microstructure of Diatomite Soil in Zhejiang Province, China

2021 ◽  
Vol 12 (1) ◽  
pp. 387
Author(s):  
Lei Gao ◽  
Yi Luo ◽  
Yingeng Kang ◽  
Mingjun Gao ◽  
Omar Abdulhafidh
Keyword(s):  
Mechanical Properties ◽  
Strain Curve ◽  
Physical And Mechanical Properties ◽  
Friction Angle ◽  
Confining Pressure ◽  
Zhejiang Province ◽  
Dry Density ◽  
High Porosity ◽  
Engineering Project ◽  
Geotechnical Tests

Diatomite soil is a kind of bio-siliceous soil with complex composition and special structure, the physical and mechanical properties of diatomite soil are very important for the engineering project. In this paper, the physical properties, mechanical properties, and microstructure of diatomite soil in Zhejiang Province are studied by geotechnical tests and microscopic tests from the macroscopic and microscopic perspective. The results show that: (1) The diatomite soil has special properties different from other soils, including small particle size, low specific gravity value, high liquid-plastic limit, and low compressibility, and the strength indexes c and φ of diatomite soil will decrease with an increase in soil water content; (2) in the triaxial test, when the dry density of diatomite soil increases from 1.30 g/cm3 to 1.50 g/cm3, the effective internal friction angle of diatomite soil increases from 5.6° to 14.5° and the effective cohesion increases from 30.9 kPa to 49.6 kPa. The stress–strain curve of diatomite soil changes from weak softening type to weak hardening type when the confining pressure is above 200 kPa; (3) the diatomite soil has high porosity due to its unique microstructure; it is rich in aluminum oxides and minerals, which will greatly reduce the engineering performance of diatomite soil.

scholarly journals Parametric analysis related to dimensioning of tubular steel columns filled with concrete in a fire situation

2022 ◽  
Vol 15 (2) ◽  
Author(s):  
Fábio Masini Rodrigues ◽  
Armando Lopes Moreno Júnior ◽  
Jorge Munaiar Neto
Keyword(s):  
Mechanical Properties ◽  
Numerical Modeling ◽  
Temperature Field ◽  
Moisture Content ◽  
Numerical Models ◽  
Physical And Mechanical Properties ◽  
Sensitivity Study ◽  
Steel Tube ◽  
Structural Elements ◽  
Steel Columns

ABSTRACT For the dimensioning of structural elements in fire situation, simplified equations and parameters are commonly used in analytical equations or numerical models. More complex equations or simplified values can be chosen by the designer for determine materials properties in high temperature in numerical models, however, numerical modeling can be quite sensitive to the variation of some of the physical and mechanical properties. In this paper, the sensitivity of the numerical model in relation to the values according to the level of simplification chosen was evaluated, presenting an analysis in relation to the results found to contribute to the choice of these parameters and presenting the indications found in the literature. In this sense, this work presents a study of sensitivity to the variation of the values of steel and concrete properties, presented in the Eurocode and Brazilian standards, in addition to the moisture content and emissivity of the surface exposed to fire, for the dimensioning, in a fire situation, of steel tube columns, of circular and square section, filled with concrete. The studies were carried out via numerical modeling developed in the software ABAQUS. It was verified that the resulting emissivity values equal to 0.7 or 0.8, recommended in the literature, are conservative, and the choice of either does not bring significant changes in the temperature field obtained for the structural elements under analysis. It was also verified that the concrete moisture content is a relevant aspect for the formation of its temperature field, also affecting, but to a lesser extent, the steel temperature. Regarding the physical and mechanical properties of the materials, this sensitivity study suggests the adoption of the values from the equations presented in Eurocodes, without simplifications, and with the specific heat and thermal conductivity of the concrete, adopted in accordance with the Eurocode 4.

scholarly journals Recycling of Foundry Sand Wastes in Self-Compacting Mortars: Use as Cementitious Materials and Fine Aggregates

2019 ◽  
Vol 9 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Ghania Sebki ◽  
Brahim Safi ◽  
Kahina Chahour
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Compressive Strength ◽  
Strain Curve ◽  
Physical And Mechanical Properties ◽  
Cementitious Materials ◽  
Fine Aggregate ◽  
Stress Strain Curve ◽  
Foundry Sand ◽  
Fine Aggregates

Abstract This work aims to study the possibility recycling of foundry sand wastes (FSW) as a cementations additive and fine aggregate in self-compacting mortars (SCM). For this, an experimental study was carried out to evaluate physical and mechanical properties of SCM. Firstly, sand is substituted by the foundry sand waste at dosages (0%, 10%, 30%, and 50%) by weight of the sand. Secondly cement is partially substituted by crushed foundry sand waste at different ratio (0%, 10%, 20%, 30%, and 50%) by weight of cement. The obtained results show that up to 50%, (FSW) can be used as fine aggregate for mortars without affecting the essential proprieties of mortar. However, beyond 50% of sand substitution, mortars lose their fluidity. The compressive strength of the mortars with 50% of cement substitution decreased compared to the control mortar. Value of the highest compressive strength recorded at 28 days, is of the order of 50 MPa for the mortar with 20% of cement substitution. Also, stress-strain curve show an acceptable mechanical behavior of FSW-based mortar at 50% of sand substitution.

scholarly journals Effect of the Interaction between Cavities and Flaws on Rock Mechanical Properties under Uniaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Jianwang Li ◽  
Yu Zhou ◽  
Wei Sun ◽  
Zheng Sun
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Three Dimensional ◽  
Strain Curve ◽  
Ct Scanning ◽  
Two Dimensions ◽  
Particle Flow Code ◽  
Uniaxial Compression Test ◽  
Fracture Evolution ◽  
Microcrack Propagation

Cavities and flaws are common types of defects in rock specimens that have an important impact on the mechanical properties of rockmass. In this paper, cement mortar was used to prefabricate a rock-like specimen with two cavities and a single flaw, and the uniaxial compression test was carried out. The process of fracture evolution on the specimen surface was obtained by using photography technology. The evolution regularity of a fracture was monitored by utilizing acoustic emission (AE) technology during the process of the specimen failure. Moreover, three-dimensional (3D) tomograms of specimens after uniaxial compression were obtained by using computerized tomography (CT) scanning technology, investigating the development characteristics of microcracks and the distribution of the final macrofractures. The particle flow code in two dimensions (PFC2D) program was used to simulate the mechanical behavior of brittle rock combining with microcrack propagation. The calculated stress-strain curve, AE features, and fracture distribution of the specimen obtained from the PFC2D simulation were relatively consistent with the experimental results.

scholarly journals Deformation and Failure Characteristics of Soil-Rock Mixture considering Material Composition and Random Structure

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Shengnian Wang ◽  
Tingting Ji ◽  
Qinpei Xue ◽  
Zhifu Shen ◽  
Qiang Zhang
Keyword(s):  
Shear Strain ◽  
Progressive Failure ◽  
Rock Block ◽  
Random Structure ◽  
Bond Failure ◽  
Frictional Material ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Composition And Structure ◽  
Significant Phenomenon

The soil-rock mixture is a cohesive-frictional geomaterial subjected to impacts of composition and structure seriously. When it suffers from gravity or other kinds of loadings, the loss of its bearing capacity always appears a progressive failure. In this study, the ultimate criterion of the frictional material changing from the deformation stage to the failure stage is analyzed first and then the deformation and failure characteristics of the soil-rock mixture with different compositions and structures are discussed by the discrete element method. The results indicate that the deformation and failure of the soil-rock mixture under axial pressure appear a significant phenomenon of detouring around rock blocks. The bond failure zones and the ultimate shear strain increase with the increase of rock block proportion. The distribution of the bond failure zones always has a good uniformity with the inclination of rock block inclinations. The increase of cementation degree between particles expands the distribution of the bond failure zones but minifies the ultimate shear strain.

scholarly journals Study on the mechanical properties of outwash deposits with random structure method

2021 ◽  
Author(s):  
Chaojun Jia ◽  
Qiang Zhang ◽  
Mingfeng Lei ◽  
Jun Yu ◽  
Rubin Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Spatial Distribution ◽  
Shear Zone ◽  
Large Scale ◽  
Physical And Mechanical Properties ◽  
Peak Stress ◽  
Displacement Curve ◽  
Random Structure ◽  
Direct Shear Tests ◽  
Outwash Deposit

ABSTRACT Outwash deposit is one of the major threats to the safety and stability of railway transit engineering in the Sichuan–Tibet area. In this paper, different samples of outwash deposits were prepared based on the random structure method, and a series of large-scale direct shear tests were carried out under different normal stresses. The influence of stone content and the spatial distribution of stone blocks on the physical and mechanical properties of outwash deposits were studied. The results show that with the increase of stone content, the shear stress-displacement curve changs from strain softening to strain hardening. The shear zone is larger, and its shape is more tortuous due to the movement and rotation of stone blocks. The internal frictional angle increases linearly while the cohesion diseases with the increase of stone content. The main influence of the spatial distribution of stone blocks on the mechanical properties of outwash deposits is the peak stress. The shear zone is mainly determined by the distribution of the stone blocks near the shear zone.

scholarly journals Effect of Layer Thickness on the Physical and Mechanical Properties of Sand Powder 3D Printing Specimens

2021 ◽  
Vol 9 ◽  
Author(s):  
Qing Xu ◽  
Lishuai Jiang ◽  
Changqing Ma ◽  
Qingjia Niu ◽  
Xinzhe Wang
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Layer Thickness ◽  
Uniaxial Compression ◽  
Strain Curve ◽  
Physical And Mechanical Properties ◽  
Image Correlation ◽  
Ductile Material ◽  
Compression Tests ◽  
Failure Patterns

The application of sand powder three-dimensional (3D) printing technology in the field of rock mechanics and mining engineering has tremendous potential, but it is still in the preliminary exploration stage. This study investigated the effect of printing layer thickness on the physical and mechanical properties of rock-like specimens with sand powder 3D printing. Quartz sand powder was used as the printing material, and the specimens were prepared with three different layer thicknesses of 0.2, 0.3, and 0.4 mm. Uniaxial compression tests with a combination of digital image correlation (DIC), acoustic emission (AE) and 3D microscope observations were performed to analyze the mechanical properties and failure patterns of the specimens during loading. Experimental findings showed that increasing the layer thickness from 0.2 to 0.4 mm would result in a decrease in the weight, density, uniaxial compression strength, and elastic modulus of the specimens. The stress-strain curve, deformation and failure patterns, crack growth process, and AE characteristics of the specimens with a layer thickness of 0.2 mm are similar to the AE characteristics of rock-like material, whereas the specimens with layer thicknesses of 0.3 and 0.4 mm deform like a ductile material, which is not appropriate for simulation of coal or rock mass. In future studies, rock-like specimens should be prepared with a small layer thickness.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

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