TY - THES

T1 - Experimental study on dynamic failure characteristics of confined coal under cyclic impact load

AU - Dong, Chunyang

N1 - no embargo

PY - 2022

Y1 - 2022

N2 - In this paper, a triaxial pressure SHPB experimental platform was used to perform 60 impact tests on 22 selected specimens. The mechanism of the occurrence of downhole impact ground pressure is simulated to study the damage characteristics of pressurized coal under cyclic impact loading. The experimental platform was used to test the coal samples with and without the surrounding pressure conditions, different number of damage impacts and different impact velocities. The characteristics of changes of elastic modulus, stress-strain, damage degree and impact energy of the specimens were analyzed to study the damage evolution law and dynamic mechanical properties of the coal body under cyclic impact loading. The main conclusions obtained are: (1) The specimens are cyclically impacted under triaxial pressure conditions, and they will go through the compression-density stage in the early stage, and when the damage impact reaches a certain number of times, the compression-density rate of the specimens and the rate of crack development and expansion are not on, and the specimens begin to produce damage. (2) experienced four times 0.2MPa low strength impact specimens accumulated damage are negative values, respectively -5.77%, -7.11%, -10.01% and -13.95%. (3) The coal body has a significant strain rate effect under triaxial pressure conditions. (4) Under the triaxial pressure conditions, the incident energy of the specimen is larger with the increase of the crushing impact velocity, and the average incident energy is 178.8 J, 229.2 J, 271.8 J and 325.4 J in order, corresponding to the more serious damage or crushing produced. The research in this paper provides experimental basis and reference for the in-depth understanding of the damage mechanism of coal body under dynamic load and the damage mechanism of cumulative damage form impact ground pressure.

AB - In this paper, a triaxial pressure SHPB experimental platform was used to perform 60 impact tests on 22 selected specimens. The mechanism of the occurrence of downhole impact ground pressure is simulated to study the damage characteristics of pressurized coal under cyclic impact loading. The experimental platform was used to test the coal samples with and without the surrounding pressure conditions, different number of damage impacts and different impact velocities. The characteristics of changes of elastic modulus, stress-strain, damage degree and impact energy of the specimens were analyzed to study the damage evolution law and dynamic mechanical properties of the coal body under cyclic impact loading. The main conclusions obtained are: (1) The specimens are cyclically impacted under triaxial pressure conditions, and they will go through the compression-density stage in the early stage, and when the damage impact reaches a certain number of times, the compression-density rate of the specimens and the rate of crack development and expansion are not on, and the specimens begin to produce damage. (2) experienced four times 0.2MPa low strength impact specimens accumulated damage are negative values, respectively -5.77%, -7.11%, -10.01% and -13.95%. (3) The coal body has a significant strain rate effect under triaxial pressure conditions. (4) Under the triaxial pressure conditions, the incident energy of the specimen is larger with the increase of the crushing impact velocity, and the average incident energy is 178.8 J, 229.2 J, 271.8 J and 325.4 J in order, corresponding to the more serious damage or crushing produced. The research in this paper provides experimental basis and reference for the in-depth understanding of the damage mechanism of coal body under dynamic load and the damage mechanism of cumulative damage form impact ground pressure.

KW - cyclic impact load

KW - damage evolution of coal

KW - triaxial confining pressure SHPB

KW - different impact velocity

KW - dynamic mechanical properties

KW - cyclic impact load

KW - damage evolution of coal

KW - triaxial confining pressure SHPB

KW - different impact velocity

KW - dynamic mechanical properties

M3 - Master's Thesis

ER -