Research on Coal Mechanical Properties Based on True Triaxial Loading and Unloading Experiment

Abstract

To study the safety issues caused by coal mine excavation, self-developed simulation of earth interior atmosphere and sound test system was used to perform true triaxial loading and unloading tests of coal. An acoustic emission detection system was used to record the damage evolution trend of coal under different intermediate principal stress states. The experimental results show that in the true triaxial unloading test, as the intermediate principal stress increases, the failure state of coal changes from shear failure to partial shear tension failure, finally leading to overall yield failure. In the stress-strain curves, with the increase in intermediate principal stress, the strain in the direction of intermediate principal stress gradually changes from compression to expansion, and typical expansion occurs. The Mogi–Coulomb strength criterion better reflects the strength failure characteristics of coal during unloading. The stress-acoustic emission diagrams show that the increase in intermediate principal stress causes the internal cracks of the coal to grow unsteadily and exponentially, and the increase in intermediate principal stress makes the coal lose its ability to continue to bear the load. Studying the influence of the intermediate principal stress on the mechanical properties of coal has practical significance for coal mine safety production.

Ink-Based Additive Manufacturing of a Polymer/Coal Composite: A Non-Traditional Reinforcement

“…Notably, coal demonstrates high compression strength and a favorable modulus, albeit weaker tensile properties. 43 , 44 According to the rule of mixtures, incorporating a reinforcement with a higher modulus into a matrix leads to an increase in the composite’s net modulus, aligning with the observed trend in the experimental results. 45…”

“…Coal, serving as a ceramic-type reinforcement, exhibits an anisotropic nature, implying a lack of preferential direction in properties and randomness in all directions. Notably, coal demonstrates high compression strength and a favorable modulus, albeit weaker tensile properties. , According to the rule of mixtures, incorporating a reinforcement with a higher modulus into a matrix leads to an increase in the composite’s net modulus, aligning with the observed trend in the experimental results…”

“…Notably, coal demonstrates high compression strength and a favorable modulus, albeit weaker tensile properties. 43,44 According to the rule of mixtures, incorporating a reinforcement with a higher modulus into a matrix leads to an increase in the composite's net modulus, aligning with the observed trend in the experimental results. 45 As anticipated, the UTS of the composite declined with an increase in reinforcement concentration, consistent with the expected outcome given the weak tensile properties of the reinforcement.…”

Experimental Study on the Damage and Crack Evolution Characteristics of TS-RCR Structural Bodies under Cyclic Loading and Unloading

“…Te AF value of the detected wave signal collected by acoustic emissions was low, and vice versa. Te AF value [45][46][47][48][49][50] is defned as the ratio of acoustic-emission ringing count to duration, and its unit is KHz. Figure 13 shows the time history of acoustic-emission AF values of the TS-RCR structural bodies with diferent lithologies.…”