scholarly journals Experimental Study on Damage and Failure of Coal-Pillar Dams in Coal Mine Underground Reservoir under Dynamic Load

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Qiangling Yao ◽  
Liqiang Yu ◽  
Ning Chen ◽  
Weinan Wang ◽  
Qiang Xu
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Water Content ◽  
Dynamic Loading ◽  
Coal Pillar ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Underground Reservoir

The stability of coal-pillar dams in underground hydraulic engineering works is affected not only by long-term water erosion but also by dynamic loading induced, for example, by roof breaking or fault slipping. In this paper, the water absorption characteristics of coal samples from western China were studied by nondestructive immersion tests, and a high-speed camera was used to monitor SHPB tests on samples of varying water content and subjected to various strain rates. Besides, the coal-pillar dam is numerically simulated based on the experimental data and the actual engineering conditions. The results show that, given low strain rate and high water content, the compaction stage accounts for most of the stress-strain curve, whereas the elastic stage accounts for only a relatively small fraction of the stress-strain curve. The dynamic compressive strength and elastic modulus follow exponential and logarithmic functions of strain rate, respectively, exhibiting a significant positive correlation. As the water content increases, the dynamic elastic modulus increases almost linearly, and the compressive strength decreases gradually. Under the same impact load, samples with greater water content fail more rapidly, and the failure is exacerbated by the propagation of parallel cracks to staggered cracks. The average size of coal fragments decreases linearly with increasing strain rate and water content. Simulations indicate that dynamic loading increases the stress concentration on both sides of the dam and expands the high-stress area and plastic zone. The results provide guidance for designing waterproof coal pillars and underground reservoir dams.

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.

scholarly journals Evaluasi Blok Tegangan Tekan Ekuivalen Balok Beton Bertulang Agregat Limbah Batu Onyx Tulungagung

2021 ◽  
Vol 15 (1) ◽  
pp. 45-50
Author(s):  
Bobby Asukmajaya R. ◽  
◽  
Edhi Wahjuni S. ◽  
Wisnumurti Wisnumurti ◽  
◽  
...  
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Coarse Aggregate ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Normal Concrete ◽  
Aggregate Concrete ◽  
Average Compressive Strength ◽  
Stress Block

Normal aggregate replacement to the onyx waste aggregate will certainly make the compressive strength and modulus of elasticity different, so it will affect the value of the compressive stress block equivalent (β1) as a result of the extent of the changing stress strain curve. In this study, trying to compare between the experimental β1 value of onyx concrete, while analytically the β1 value for normal concrete was obtained in accordance with SNI 2847 - 2019. To get the experimental β1 value from onyx concrete, it is made by looking for the compressive strength, elastic modulus and ꜫ0, for later the stress strain curve of the concrete is made to find the experimental β1 value of the onyx concrete. The results were obtained if the average β1 value of 18 specimens of onyx coarse aggregate concrete with an average compressive strength of 32.92 MPa was 0.868 while the analytical β1 value based on SNI 2847-2019 was 0.839, This shows that the B1 value for concrete with other aggregates is different, so it needs to be checked experimentally.

scholarly journals Experimental Study of Rubberized Concrete Stress-Strain Behavior for Improving Constitutive Models

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2245 ◽  
Author(s):  
Kristina Strukar ◽  
Tanja Kalman Šipoš ◽  
Tihomir Dokšanović ◽  
Hugo Rodrigues
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Curve ◽  
Experimental Results ◽  
Nonlinear Material ◽  
Rubberized Concrete ◽  
Rubber Content ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Failure Patterns

Inclusion of rubber into concrete changes its behavior and the established shape of its stress-strain curve. Existing constitutive stress-strain models for concrete are not valid in case of rubberized concrete, and currently available modified models require additional validation on a larger database of experimental results, with a wider set of influential parameters. By executing uniaxial compressive tests on concrete with rubber substituting 10%, 20%, 30%, and 40% of aggregate, it was possible to study and evaluate the influence of rubber content on its mechanical behavior. The stress-strain curve was investigated in its entirety, including compressive strength, elastic modulus, strains at significant levels of stress, and failure patterns. Experimental results indicated that increase of rubber content linearly decreases compressive strength and elastic modulus, but increases ductility. By comparing experimental stress-strain curves with those plotted using available constitutive stress-strain models it was concluded that they are inadequate for rubberized concrete with high rubber content. Based on determined deviations an improvement of an existing model was proposed, which provides better agreement with experimental curves. Obtained research results enabled important insights into correlations between rubber content and changes of the stress-strain curve required when utilizing nonlinear material properties.

scholarly journals Elastic modulus and stress-strain curve analysis of a tungsten mine waste alkali-activated concrete

2019 ◽  
Vol 274 ◽  
pp. 02003
Author(s):  
Pedro Silva Humbert ◽  
João Paulo De Castro Gomes ◽  
Luis Filipe Almeida Bernardo ◽  
Clemente Martins Pinto ◽  
Natalia Paszek
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Raw Materials ◽  
Mine Waste ◽  
Strain Curve ◽  
Portland Cement Concrete ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Glass Waste ◽  
Tungsten Mine

In the paper the compressive strength, the elastic modulus and the stress-strain curve of an alkaliactivated concrete were studied. A tungsten mine waste mud (TMWM), aggregate (also from the tungsten mine), glass waste and metakaolin were used as raw materials. Sodium silicate and sodium hydroxide were used as activators. First, TMWM chemical composition was determined by scanning electron microscopyenergy dispersive spectroscopy (SEM-EDS). The maximum particle size was 18mm. Two cubes with side dimension of 15cm were prepared from the mixture. Samples were cured at 60°C for 24 hours. A concrete mixer, vibration table and an oven were used in the process. After the curing process, cubes were cut into seven prisms and one cube with the dimensions 15x7.4x7.4cm and 7.4cm respectively. After 28 days, the laboratory tests were performed. During the compressive strength tests, the displacements were also recorded which allowed drawing the stress-strain curve of the samples. The compressive strength ranged from 17.27 to 28.84MPa. The elastic modulus was calculated by four different standards: ASTM, LNEC and European standard. The elastic modulus ranged from 2.48 to 7.49GPa what showed that the material is more elastic than ordinary Portland cement concrete.

scholarly journals Study on Characteristic and Energy of Argillaceous Weakly Cemented Rock under Dynamic Loading by Hopkinson Bar Experiment

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3215
Author(s):  
Lingdong Meng ◽  
Lijun Han ◽  
Qingbin Meng ◽  
Kexiang Liu ◽  
Maolin Tian ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Dynamic Loading ◽  
Impact Velocity ◽  
Wave Amplitude ◽  
Impact Resistance ◽  
Strain Curve ◽  
Hopkinson Pressure Bar ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Pressure Bar

To study the mechanical properties of argillaceous weakly cemented rock under dynamic loading, a sample reconstituted and graded loading scheme is firstly designed, and then the reorganization rock sample is used as the research object. Using a Hopkinson pressure bar test, the responses of an argillaceous weakly cemented rock mass under different reorganization loads and different impact velocities is studied, and changes in specimen shape after impact are also analyzed. The study found that with increased of the recombination load, the amplitude of the transmitted wave increases. With increasing impact velocity, the rate of the increase in the incident wave amplitude is much larger than that of the transmission wave amplitude. The dynamic stress–strain curve can be divided into a compaction stage, an approximate linear elastic stage, a microcrack growth stage and a strain softening stage. The larger the reorganization load is, the less obvious the compression stage of the stress–strain curve is, and the greater the elastic modulus is. The peak strength and elastic modulus increase with increasing strain rate before 500 s−1. When the reorganization load is increased, the deformation decreases, and its impact resistance increases. With increasing impact velocity, the deformation of the specimen increases.

Experimental Study on the Dynamic Compressive Mechanical Properties of Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 17-21 ◽  
Author(s):  
Ji Shu Sun ◽  
Yuan Ming Dou ◽  
Bo Li ◽  
Zhao Xia Chen
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Concrete Strength ◽  
Strain Curve ◽  
Plain Concrete ◽  
Stress Strain Curve ◽  
Growth Trend ◽  
Stress Strain ◽  
Compressive Strength Of Concrete

Dynamic compressive tests of plain concrete specimens (C30 and C40) are carried out on MTS, with the uniaxial strain rate ranging from 10-5/s to 10-2/s. The impacts of strain rates on concrete strength are studied systematically. The mechanical properties of compressive strength, elastic modulus and compressive stress-strain curve of concrete under different stain rates are also analyzed. The experiental relationships between strain rate and compressive strength of concrete are established. It is found that the compressive strength of concrete increases with the strain rate increasing. Modulus is also showing a growth trend, but the growth rate varies greatly; and the stress-strain curve under dynamic loads is similar to the one under static loads. These research achievements can provide us with a more accurate grasp of concrete actual working conditions and provide some guidance to structural design of concrete. These are important to build the dynamic damage constitutive models, too.

Understanding Dynamic Recrystallization Behavior through a Delay Differential Equation Approach

2007 ◽  
Vol 558-559 ◽  
pp. 441-448 ◽  
Author(s):  
Jong K. Lee
Keyword(s):  
Differential Equation ◽  
Strain Rate ◽  
Critical Strain ◽  
Strain Curve ◽  
Single Peak ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Behavior ◽  
Delay Differential

During hot working, deformation of metals such as copper or austenitic steels involves features of both diffusional flow and dislocation motion. As such, the true stress-true strain relationship depends on the strain rate. At low strain rates (or high temperatures), the stress-strain curve displays an oscillatory behavior with multiple peaks. As the strain rate increases (or as the temperature is reduced), the number of peaks on the stress-strain curve decreases, and at high strain rates, the stress rises to a single peak before settling at a steady-state value. It is understood that dynamic recovery is responsible for the stress-strain behavior with zero or a single peak, whereas dynamic recrystallization causes the oscillatory nature. In the past, most predictive models are based on either modified Johnson-Mehl-Avrami kinetic equations or probabilistic approaches. In this work, a delay differential equation is utilized for modeling such a stress-strain behavior. The approach takes into account for a delay time due to diffusion, which is expressed as the critical strain for nucleation for recrystallization. The solution shows that the oscillatory nature depends on the ratio of the critical strain for nucleation to the critical strain for completion for recrystallization. As the strain ratio increases, the stress-strain curve changes from a monotonic rise to a single peak, then to a multiple peak behavior. The model also predicts transient flow curves resulting from strain rate changes.

Influence of strain rate on the stress-strain curve in the range of Lüders strain

1996 ◽  
Vol 67 (11) ◽  
pp. 495-500 ◽  
Author(s):  
Essam El-Magd ◽  
Herbert Scholles ◽  
Herbert Weisshaupt
Keyword(s):  
Strain Rate ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain

High Strain Rate Test of a Steel Plate under Blast Loading from High Explosive

2013 ◽  
Vol 767 ◽  
pp. 144-149 ◽  
Author(s):  
Tei Saburi ◽  
Shiro Kubota ◽  
Yuji Wada ◽  
Tatsuya Kumaki ◽  
Masatake Yoshida
Keyword(s):  
Strain Rate ◽  
Dynamic Stress ◽  
Steel Plate ◽  
High Strain ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Time Deformation ◽  
Rate Test ◽  
High Strain Rate Test

In this study, a high strain rate test method of a steel plate under blast loading from high explosive was designed and was conducted by a combined experimental/numerical approach to facilitate the estimation process for the dynamic stress-strain curve under practical strain rate conditions. The steel plate was subjected to a blast load, which was generated by Composition C4 explosive and the dynamic deformation of the plate was observed with a high-speed video camera. Time-deformation relations were acquired by image analysis. A numerical simulation for the dynamic behaviors of the plate identical to the experimental condition was conducted using a coupling analysis of finite element method (FEM) and discrete particle method (DPM). Explosives were modeled by discrete particles and the steel plate and other materials were modeled by finite element. The blast load on the plate was described fluid-structure interaction (FSI) between DPM and FEM. As inverse analysis scheme to estimate dynamic stress-strain curve, an evaluation using a quasistatic data was conducted. In addition, two types of approximations for stress-strain curve were assumed and optimized by least square method. One is a 2-piece approximation, and was optimized by least squares method using a yield stress and a tangent modulus as parameters. The other is a continuous piecewise linear approximation, in which a stress-strain curve was divided into some segments based on experimental time-deformation relation, and was sequentially optimized using youngs modulus or yield stress as parameter. The results showed that the piecewise approximation can gives reasonably agreement with SS curve obtained from the experiment.

Sign in / Sign up

Export Citation Format

Share Document