scholarly journals Deterioration Characteristics and Energy Mechanism of Red-Bed Rocks Subjected to Drying-Wetting Cycles

2021 ◽  
Author(s):  
Kai Huang ◽  
Fusheng Zha ◽  
Bo Kang ◽  
Xianguo Sun ◽  
Yunfeng Li ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Failure Process ◽  
Microstructural Analysis ◽  
Strain Curve ◽  
Rock Failure ◽  
Dissipated Energy ◽  
Uniaxial Compression Strength ◽  
Stress Strain ◽  
Energy Mechanism ◽  
Red Bed

Abstract The red-bed rocks were chosen and studied by using uniaxial compressive experiment and scanning electron microscopy to investigate the effect of drying-wetting (D-W) cycles on the mechanical properties and microstructural characteristics of red-bed rock. Additionally, the energy mechanism of specimens subjected to drying-wetting cycles was also explained. Experimental results showed that, the stress-strain could be divided into four characteristic stages in the compression failure process. After subjecting to cycles of D-W, the stress-strain curve gradually changed from softening to hardening. At the same time, uniaxial compression strength (UCS) and elastic modulus dropped obviously, while Poisson’s ratio gradually raised. Microstructural analysis results indicated that the microstructure of the specimen surface was no longer dense and uniform, and the porosity of tested specimens significantly increased with D-W cycles increasing. As the porosity grew, UCS and elastic modulus gradually declined. According to the first law of thermodynamics, the process of rock failure was an event of energy transfer and conversion. As the number of D-W cycles increased, the energy density of specimens all present linear fell. From the perspective of the theory of energy dissipation, the dissipated energy was essential for rock failure, and closely related to the strength of the specimen. With D-W cycles increasing, the specimens were more prone to failure, and the dissipated energy required for failure decreased gradually.

Properties of Low-Density Lightweight Aggregate Concrete under Uniaxial Loading

2011 ◽  
Vol 105-107 ◽  
pp. 1638-1643
Author(s):  
Cong Mi Cheng ◽  
Da Gen Su ◽  
Chu Jie Jiao ◽  
Juan He
Keyword(s):  
Elastic Modulus ◽  
Failure Process ◽  
Strain Curve ◽  
Lightweight Aggregate ◽  
Expanded Polystyrene ◽  
Uniaxial Loading ◽  
Lightweight Aggregate Concrete ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Oblique Crack

The aim of this study is to investigate the influence of EPS content on failure mode, stress-strain relationship and elastic modulus of expanded polystyrene aggregate concrete (PAC) with density lower than 900 kg/m3under uniaxial loading. The results show that PAC performs a good compressibility in the compression failure process. Apparent oblique crack appears in the case of uniaxial compression specimen damage; the lower the density is, the smaller the tilt angle of oblique cracks will be. Stress-strain curve of PAC with density larger than 422 kg/m3maintains a straight line relationship on ascending segment but varies with the density on the descent segment. The lower the density is, the larger PAC residual relative stress will become. Elastic modulus of PAC is proportional to 5.85 times index of relative density.

scholarly journals Mechanical Characteristics and Failure Mechanism of Siltstone with Different Joint Thickness

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Huigui Li ◽  
Zhengkai Yang ◽  
Huamin Li
Keyword(s):  
Elastic Modulus ◽  
Failure Mechanism ◽  
Uniaxial Compression ◽  
Compression Strength ◽  
Damage Model ◽  
Strain Curve ◽  
Compression Tests ◽  
Uniaxial Compression Strength ◽  
Stress Strain ◽  
Joint Thickness

The mechanics of rock mass is significantly affected by joints, but many existing studies of jointed rocks make simplifications that do not consider the joint thickness. To further study the influence of joint thickness on rock mechanics (mechanical properties, failure mechanism, damage model, etc.), we fabricated jointed siltstone specimens with different joint thickness (5, 10, 15, and 20 mm) and the specimens were subjected to uniaxial compression tests. The effects of joint thickness on the uniaxial compression strength (UCS), the strain at UCS, the elastic modulus, and the stress-strain curves were thus analyzed. For the stress-strain curve, with rising joint thickness, the upper concave in the initial compression stage intensified, the slope of the stress-strain in the elastic stage decreased, and the sudden stress drop after peak strength became more obvious. Both the peak compression strength and the elastic modulus gradually decreased with rising joint thickness, but a positive correlation was found between the strain at UCS and the joint thickness.

Experimental Research on Mechanical Properties of Recycled Aggregate Concrete under Uniaxial Loading

2013 ◽  
Vol 671-674 ◽  
pp. 1736-1740
Author(s):  
Xue Yong Zhao ◽  
Mei Ling Duan
Keyword(s):  
Elastic Modulus ◽  
Coarse Aggregate ◽  
Strain Curve ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Peak Strain ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate

The complete stress-strain curves of recycled aggregate concrete with different recycled coarse aggregate replacement percentages were tested and investigated. An analysis was made of the influence of varying recycled coarse aggregate contents on the complete stress-strain curve, peak stress, peak strain and elastic modulus etc. The elastic modulus of RC is lower than natural concrete (NC), and with the recycled coarse aggregate contents increase, it reduces. While with the increase of water-cement ratio (W/C), recycled concrete compressive strength and elastic modulus improve significantly. In addition, put forward a new equation on the relationship between Ec and fcu of the RC.

scholarly journals Experimental and Theoretical Investigation on the Thermo-Mechanical Properties of Recycled Aggregate Concrete Containing Recycled Rubber

2021 ◽  
Vol 8 ◽  
Author(s):  
Yunchao Tang ◽  
Wanhui Feng ◽  
Zheng Chen ◽  
Yumei Nong ◽  
Minhui Yao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Microstructural Analysis ◽  
Strain Curve ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Recycled Rubber

The utilization of recycled aggregates made from construction wastes and recycled rubber made from waste tires is an effective method to realize the sustainable development. Thus, this study aims to determine the feasibility of using recycled aggregate concrete containing rubber, named rubberized recycled aggregate concrete (RRAC) as a new type of green-building material. The experimental carbon emissions test verified RRAC as a low-carbon material. In addition, the residual mechanical properties of RRAC were investigated under elevated temperatures. After exposure at 200, 400, and 600 C for 60 min, the stress−strain curve, compressive strength, energy absorption capacity, and spalling resistance of RRAC with recycled aggregate replacement ratios of 50 and 100%, rubber contents of 0, 5, 10, and 15% were explored with microstructural analysis. Moreover, empirical models were proposed to describe the effects of heated temperatures and rubber contents on the stress–strain relationship of RRAC. The results indicated that the rubber particles could reduce the spalling of specimens based on the vapor pressure theory. Therefore, this study provided scientific guidance for the design of structures made with RRAC for resisting high temperatures.

scholarly journals Identification of Initial Crack and Fracture Development Monitoring under Uniaxial Compression of Coal with High Bump Proneness

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Zuoqing Bi ◽  
Han Liang ◽  
Qianjia Hui
Keyword(s):  
Rock Burst ◽  
Uniaxial Compression ◽  
Failure Process ◽  
Strain Curve ◽  
Initial Crack ◽  
Internal Crack ◽  
Uniaxial Compression Test ◽  
Stress Strain ◽  
Crack Distribution ◽  
Fracture Development

The rock burst proneness of coal is closely related to the coal mass structure. Therefore, the initial crack distribution of high burst proneness coal, its fracture development, and failure process under loading conditions are of great significance for the prediction of rock burst. In this study, high burst proneness coal is used to prepare experiment samples. The surface cracks of the samples are identified and recorded. The internal crack of the sample is detected by nuclear magnetic resonance (NMR) technology to determine the crack ratio of each sample. Then, 3D-CAD technology is used to restore the initial crack of the samples. Uniaxial compression test is carried out, and AE properties are recorded in the test. The stress-strain curve, the distribution of the fractural points within the sample at different stress states, and the relationship between ring count and stress are obtained. Results show that the stress-strain curves of high burst proneness coal are almost linear, to which the stress-ring count curves are similar. The distributions of fractural points in different bearing states show that the fracture points emerge in the later load stage and finally penetrate to form macrofracture, resulting in sample failure. This study reveals the initial crack distribution of coal with high burst proneness and the fracture development under bearing conditions, which provides a theoretical basis for the prediction technology of rock burst and technical support for the research of coal structure.

The Research of Test on Stress-Strain Constitutive Relations of Straw Concrete

2014 ◽  
Vol 584-586 ◽  
pp. 987-992
Author(s):  
Wei Liu ◽  
Wei Xi ◽  
Yi Lu Zhang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Fly Ash ◽  
Constitutive Relations ◽  
Strain Curve ◽  
Green Building ◽  
Corn Straw ◽  
Stress Strain Curve ◽  
Stress Strain

As a new green building material, straw concrete are introduced about its mechanical properties and characteristics. Mechanical properties test such as prism compressive strength, elastic modulus and Poisson's ratios use standard prismatic blocks. Under different rate of corn straw, cement, sand and fly ash, test gets the full stress-strain curve. Results show that with increase of volume of corn straw, the prism compressive strength reduces significantly. Comparing with natural concrete, elastic modulus of straw concrete can reduces greatly. Poisson’s ratio reduces with increase of volume of corn straw. Fly ash could improve property of the material and replace cement, but excessive replacement will reduce the strength of material.

Experimental Study on Compressive Property of Basalt Fiber Reactive Powder Concrete

2020 ◽  
Vol 984 ◽  
pp. 239-244
Author(s):  
Lu Liang Wang ◽  
Hai Long Zhao ◽  
De Hong Wang ◽  
Jun Feng Bai
Keyword(s):  
Test Piece ◽  
Failure Process ◽  
Basalt Fiber ◽  
Strain Curve ◽  
Reactive Powder Concrete ◽  
Compressive Property ◽  
Fiber Volume ◽  
Stress Strain ◽  
Reactive Powder ◽  
Relationship Of

In order to study the stress-strain relationship of basalt fiber reactive powder concrete (RPC), the compressive stress-strain curve test of four groups of basalt fiber RPC was carried out. The test parameters including two kinds of basalt fiber length and three fiber volume fractions showed that the deformability of the test piece was improved and the failure process was delayed after incorporating basalt fiber. The optimum fiber fraction of the test piece with 12 mm long fiber was 0.10%. According to the experimental data, the stress-strain of the basalt fiber RPC was drawn. For the curve, the constitutive relation is fitted by the piecewise equation, and compared with the experimental curve, the fitting result is better.

Research on Compressive Deformation Characters of Mortar-Free Grouted Concrete Masonry

2014 ◽  
Vol 1004-1005 ◽  
pp. 1531-1536 ◽  
Author(s):  
Xi Xi He ◽  
Ye Lin
Keyword(s):  
Elastic Modulus ◽  
Compressive Stress ◽  
Test Data ◽  
Strain Curve ◽  
Compressive Deformation ◽  
Filling Rate ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Concrete Masonry

Compressive experiments on mortar-free grouted concrete masonry composed with hollow blocks were studies in this essay. Characteristics of compressive stress-strain curve were analyzed by utilizing test data of 15 specimens with 100% filling rate of grouted concrete. Further more, elastic modulus formula was proposed according to results of previous and present work.

A Mathematical Treatment of a Theory of Rubber Structure

1935 ◽  
Vol 8 (1) ◽  
pp. 23-38
Author(s):  
T. R. Griffith
Keyword(s):  
Elastic Modulus ◽  
Plastic Flow ◽  
Strain Curve ◽  
The Other ◽  
Stress Axis ◽  
Mathematical Treatment ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Joule Effect ◽  
Vulcanized Rubber

Abstract A brief consideration of the work that has been done on the structure of rubber convinces, one that the elasticity is wholly or at least mainly explained by a consideration of the kinetics involved. The fact that when a strip of stretched rubber, one end of which is free, contracts when it is warmed, contrary to the behavior of most bodies, and that it becomes warmed on stretching, commonly known as the Gough-Joule effect, pp. 453–461, would lead one to suspect .that there is a connection between the kinetic energy of the rubber molecule and its elasticity. Lundal, Bouasse, Hyde, Somerville and Cope, Partenheimer and Whitby and Katz have reported observations, principally stress-strain curves, which show that vulcanized rubber has a lower modulus of elasticity at higher temperatures, i. e., it becomes easier to stretch as the temperature is raised. On the other hand, Schmulewitsch, Stevens, and Williams found that the elastic modulus increases with the temperature. Williams shows that the softening of vulcanized rubber with rise of temperature is due to an increase of plasticity. In order to get rid of plastic flow, he first stretches the specimen several times to within about 50 per cent of its breaking elongation, and then obtains an autographic stress-strain curve of the rubber stretched very quickly. He finds that in this case the rubber actually becomes stiffer with rise of temperature, increasing temperatures causing the stress-strain curves to lean progressively more and more toward the stress axis. He concludes that rise of temperature has two effects, one a softening due to increase of plasticity, rendering plastic flow more easy, the other an actual stiffening of the rubber due to rise of temperature. It is not easy to explain the latter effect on any theory which does not take kinetics into account.

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