scholarly journals Mechanical Properties and Damage Behavior of Rock-Coal-Rock Combined Samples under Coupled Static and Dynamic Loads

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Jinzheng Bai ◽  
Linming Dou ◽  
Piotr Małkowski ◽  
Jiazhuo Li ◽  
Kunyou Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Rock Burst ◽  
Wave Velocity ◽  
Dynamic Load ◽  
Dynamic Loads ◽  
Height Ratio ◽  
Damage Behavior ◽  
Research Results ◽  
Coal Rock ◽  
Static And Dynamic Loads

This research is aimed at investigating the influence of the coal height ratio on the mechanical properties and damage behavior of rock-coal-rock combined samples (RCRCS) under coupled static and dynamic loads. For this purpose, a uniaxial cyclic dynamic loading experiment with four different coal height ratios of RCRCS was conducted. Mechanical properties, failure modes, and wave velocity evolution of RCRCS were analyzed; the process of rock burst under coupled static and dynamic loads in rock-coal-rock combined structure was discussed. The following research results are obtained. (1) The peak strength of RCRCS under static and dynamic load decreases with the increasing coal height ratio as an inverse proportional function. (2) The loading and unloading modulus remains consistent for the same levels of dynamic load; the coal height ratio of 40% may be the limit for the stable value of modulus. (3) The increase of the coal height in RCRCS leads to a gradual increase of the energy release rate; the cracks develop preferentially in coal and then extend to rock sample. The distribution of AE events and damage is consistent with the distribution of passive wave velocity. The research results provide important scientific bases for the guidance of early warning of rock burst.

scholarly journals Dynamic Mechanical Characteristics of Impact Rock under the Combined Action of Different Constant Temperatures and Static and Dynamic Loads

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Enlai Zhao ◽  
Enyuan Wang ◽  
Zesheng Zang ◽  
Xiaojun Feng ◽  
Rongxi Shen
Keyword(s):  
Mechanical Properties ◽  
Dynamic Load ◽  
Incident Energy ◽  
Dynamic Mechanical Properties ◽  
Image Correlation ◽  
Dynamic Loads ◽  
Dissipated Energy ◽  
Dynamic Mechanical ◽  
Combined Action ◽  
Static And Dynamic Loads

The complex mechanical environment of deep coal and rock masses leads to obvious changes on their dynamic mechanical properties. However, there are few reports on the dynamic mechanical properties of rocks under the combined action of medium temperature (normal temperature ∼100°C) and static and dynamic loads. In this paper, a dynamic load and temperature combined action Hopkinson pressure bar experimental system is used to experimentally study the impact type of a fine sandstone under temperature conditions of 18°C, 40°C, 60°C, 80°C, and 100°C, an axial static load of 3 MPa, a gas chamber pressure of 0.06 MPa, and a constant temperature time of 4 h. The dynamic characteristics of the change law of the fine sandstone and the energy dissipation characteristics of the load process are analyzed, and the characteristic law of the fine sandstone surface response is analyzed using digital image correlation technology. Our results indicate the following. (1) Under conditions in which the other experimental conditions remain unchanged, the dynamic stress-strain of the fine sandstone presents a bimodal shape with a “rebound” phenomenon. Increasing temperature causes the peak strength of the fine sandstone to increase; however, the relative strength can increase or decrease. The relative increase in the strength is 1.14 MPa (°C) when the temperature increases from 40°C to 60°C, 0.15 MPa (°C) when the temperature increases from 60°C to 80°C, and 0.62 MPa (°C) when the temperature increases from 80°C to 100°C. (2) The digital image correlation results show that, under the action of a dynamic load stress wave, the fine sandstone experiences a displacement vector change on the sample surface; furthermore, under the combined action of the temperature and dynamic and static loads, the fine sandstone experiences macroscopic shear failure. The surface strain in the propagation direction of the stress wave is obviously higher and can even reach values of more than 10 times that of the strain in other directions. (3) From the perspective of energy dissipation, the incident energy, reflected energy, and dissipated energy of the fine sandstone under an impact load have the same change law. After being affected by a dynamic load, the energy rapidly increases to a certain value and then remains relatively stable. The transmitted energy is relatively small and can be approximated as a horizontal line. As the temperature increases, the incident energy, reflected energy, and dissipated energy tend to first decrease and then increase, and most of the incident energy in the fine sandstone is dissipated in the form of reflected waves.

The Mechanical Properties Comparative Analysis for Socked and Non-Socketed Composite Pile

2014 ◽  
Vol 1061-1062 ◽  
pp. 748-750
Author(s):  
Heng Chen ◽  
Ke Sheng Ma
Keyword(s):  
Mechanical Properties ◽  
Comparative Analysis ◽  
Seismic Performance ◽  
Dynamic Loads ◽  
Vertical Load ◽  
Interlayer Thickness ◽  
Static Loads ◽  
Soil Stress ◽  
Composite Pile ◽  
Static And Dynamic Loads

For socked and non-socketed piles in the different mechanical behavior under static and dynamic loads, the paper use ABAQUS to model, simulate the pile , the soil interlayer thickness between the bottom of the pile and bedrock are 2m, 4m under vertical load and Earthquake, cushion cap, pile and pile soil stress situation found non-socketed piles when the soil interlayer thickness within a certain range, the composite pile small subside under dynamic, static loads, the non-socketed piles can better take advantage of the pile soil has a good seismic performance in the earthquake.

Mechanical properties and failure behavior of rock with different flaw inclinations under coupled static and dynamic loads

2020 ◽  
Vol 27 (10) ◽  
pp. 2945-2958
Author(s):  
Peng Xiao ◽  
Di-yuan Li ◽  
Guo-yan Zhao ◽  
Quan-qi Zhu ◽  
Huan-xin Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Dynamic Loads ◽  
Failure Behavior ◽  
Static And Dynamic Loads

scholarly journals STATIC AND DYNAMIC LOADS ON THE BOTTOM ROW OF ARMOUR UNITS: A THEORETICAL AND PHYSICAL MODEL STUDY

2012 ◽  
Vol 1 (33) ◽  
pp. 44
Author(s):  
Michael Alexander Van de Koppel ◽  
Michiel Muilwijk ◽  
Henk Jan Verhagen
Keyword(s):  
Physical Model ◽  
Dynamic Load ◽  
Packing Density ◽  
Single Layer ◽  
Dynamic Loads ◽  
Model Study ◽  
Static And Dynamic Loads

A physical model study on the row averaged static and dynamic load on the bottom row of single layer armour units in order to investigate the influence of various parameters such as the number of rows on the slope of a breakwater and the initial relative packing density.

scholarly journals Mechanical Properties of Roof Rocks under Superimposed Static and Dynamic Loads with Medium Strain Rates in Coal Mines

2021 ◽  
Vol 11 (19) ◽  
pp. 8973
Author(s):  
Kun Zhong ◽  
Wusheng Zhao ◽  
Changkun Qin ◽  
Hou Gao ◽  
Weizhong Chen
Keyword(s):  
Mechanical Properties ◽  
Energy Density ◽  
Failure Mode ◽  
Dynamic Loading ◽  
Loading Rate ◽  
Dynamic Loads ◽  
Strain Rates ◽  
Static And Dynamic Loads ◽  
Roof Rocks ◽  
Rock Specimens

Roof rocks in coal mines are subjected to the combination of in situ stresses and dynamic stresses induced by mining activities. Understanding the mechanical properties of roof rocks under static and dynamic loads at medium strain rates is of great significance to revealing the mechanism of rock bursts. In this study, we employ the digital image correlation (DIC) technique to investigate the energy concentration and dissipation behaviors, failure mode, and deformation characteristics of roof rocks under combined static and dynamic loads. Our results show that both the static pre-stress and dynamic loading rate have significant effects on the uniaxial compressive strength of rock specimens. From the energy principle, when the static pre-stress is the same, both elastic strain energy density and dissipated energy density increase with increasing dynamic loading rate. The hazard of rock bursts increases with decreasing static pre-stress and increasing dynamic loading rate. At higher dynamic loading rates, more cracks are generated, and the failure becomes more violent. The crack initiation, propagation and coalescence processes are identified, and the failure mode is closely related to the evolution of the global principal strain field of the rock specimens.

scholarly journals Mechanical Properties and Failure Behavior of Composite Samples

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Hongwei Zhang ◽  
Zhijun Wan ◽  
Yuan Zhang ◽  
Dong Wu
Keyword(s):  
Mechanical Properties ◽  
Distinct Element ◽  
Element Model ◽  
Failure Behavior ◽  
Underground Coal Mining ◽  
Height Ratio ◽  
Uniaxial Compression Strength ◽  
Coal Rock ◽  
Coal Bursts ◽  
Distinct Element Model

In underground coal mining systems, the occurrences of coal burst hazards and pillar failures relate not only to the condition of stress distribution but also the geometry of roof-coal-floor structures. To study the failure response of these structures, the rock-coal-rock (RCR) sample, in which a coal component is sandwiched between rocks, is always employed as the experimental subject. In this study, the effect of height ratio (a ratio represents the height percentage of coal component in an RCR sample) on the mechanical properties and deformation behavior of RCR samples was numerically investigated by using the distinct element model (DEM). The results reveal the following. (1) The uniaxial compression strength (UCS) of the RCR sample decreases with increasing height ratio as an inverse proportional function. (2) With increasing height ratio, the elastic modulus of the RCR sample decreases exponentially, while the postpeak modulus is strengthened in an inverse proportional manner. (3) Microcracking activity of the RCR sample is different from that of the pure sample during loading. Specifically, a reactive period always occurs after the quiet and active periods in the RCR sample. (4) The RCR sample fails in a progressive manner, in which cracking bands develop preferentially in coal and then extend to rocks. Expectably, the mechanical properties and failure behavior of RCR samples are height ratio dependent, which may contribute to predicting the hazard of coal bursts and estimating the failure of rock-coal-floor structures.

scholarly journals Numerical Analysis of Roadway Rock-Burst Hazard Under Superposed Dynamic and Static Loads

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3761 ◽  
Author(s):  
Kong ◽  
Jiang ◽  
Jiang ◽  
Wu ◽  
Chen ◽  
...  
Keyword(s):  
Energy Density ◽  
Rock Burst ◽  
Elastic Energy ◽  
Dynamic Load ◽  
Static Loading ◽  
Static Load ◽  
Dynamic Loads ◽  
Loading Conditions ◽  
Static Loads ◽  
Elastic Energy Density

Microseismic events commonly occur during the excavation of long wall panels and often cause rock-burst accidents when the roadway is influenced by dynamic loads. In this paper, the Fast Lagrangian Analysis of Continua in 3-Dimensions (FLAC3D) software is used to study the deformation and rock-burst potential of roadways under different dynamic and static loads. The results show that the larger the dynamic load is, the greater the increase in the deformation of the roadway under the same static loading conditions. A roadway under a high static load is more susceptible to deformation and instability when affected by dynamic loads. Under different static loading conditions, the dynamic responses of the roadway abutment stress distribution are different. When the roadway is shallow buried and the dynamic load is small, the stress and elastic energy density of the coal body in the area of the peak abutment stress after the dynamic load are greater than the static calculations. The dynamic load provides energy storage for the coal body in the area of the peak abutment stress. When the roadway is deep, a small dynamic load can still cause the stress in the coal body and the elastic energy density to decrease in the area of the peak abutment stress, and a rock-burst is more likely to occur in a deep mine roadway with a combination of a high static load and a weak dynamic load. When the dynamic load is large, the peak abutment stress decreases greatly after the dynamic loading, and under the same dynamic loading conditions, the greater the depth the roadway is, the greater the elastic energy released by the dynamic load. Control measures are discussed for different dynamic and static load sources of rock-burst accidents. The results provide a reference for the control of rock-burst disasters under dynamic loads.

Stiffness of Magnetic Bearings Subjected to Combined Static and Dynamic Loads

1992 ◽  
Vol 114 (4) ◽  
pp. 785-789 ◽  
Author(s):  
D. K. Rao ◽  
G. V. Brown ◽  
P. Lewis ◽  
J. Hurley
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Dynamic Stiffness ◽  
Load Ratio ◽  
Magnetic Bearing ◽  
Dynamic Loads ◽  
Approximate Design ◽  
Critical Gap ◽  
Gap Fraction ◽  
Static And Dynamic Loads

This paper investigates the stiffness of a magnetic bearing that is subjected to the combined action of static and dynamic loads. Since their sum cannot exceed the saturation load, a large static load will imply that the bearing can carry only a small dynamic load. This smaller dynamic load together with the practical vibration amplitude define a practical upper bound to the dynamic stiffness. This paper also presents approximate design formulas and curves for this stiffness capacity as a function of the ratio of dynamic and static loads. In addition, it indicates that vibrations larger than a certain gap fraction can destabilize the magnetic bearing. This gap fraction, called the critical gap fraction, depends on the dynamic and static load ratio. For example, if the dynamic load is half of the static load, the use of more than 25 percent of gap can destabilize the bearing.

Combined Magnetic Pulsed Compaction of Powder Materials

2017 ◽  
Vol 746 ◽  
pp. 235-239 ◽  
Author(s):  
Irina Belyaeva ◽  
Viktor Mironov
Keyword(s):  
Magnetic Field ◽  
Powder Material ◽  
Dynamic Load ◽  
Pulse Magnetic Field ◽  
Dynamic Loads ◽  
Powder Materials ◽  
Static And Dynamic Loads ◽  
Hybrid Technologies ◽  
Experimental Researches

Upgrading the quality of compaction of powder materials is achieved by the use of hybrid technologies when the powders are acted upon by two or more sources of loading. The present paper describes compaction of a powder under the action of static and dynamic loads. A pulse-magnetic field is used as a dynamic load. The procedure and technique of experimental researches are described. Porosity (compactness) and structure of the material are evaluated for various combinations of loads, geometrical sizes and shapes of products. The conclusion is made about significant upgrading of quality of the powder material when used the hybrid technology compared to the static compaction.

Sign in / Sign up

Export Citation Format

Share Document