TY  - EJOU
AU  - Teng,  
AU  - Cai, Yuhe 
AU  - Wang, Linchao 
AU  - Zhu, Yanzhao 

TI  - Effects of Temperature and Liquid Nitrogen (LN2) on Coal’s Mechanical and Acoustic Emission (AE) Properties
T2  - Fluid Dynamics \& Materials Processing

PY  - 2024
VL  - 20
IS  - 6
SN  - 1555-2578

AB  - Liquid nitrogen has shown excellent performances as a good fracturing medium in the extraction of unconventional natural gas, and its application in coalbed methane extraction is currently a research hotspot. This study focuses on the acoustic emission properties of coal specimens treated utilizing liquid nitrogen with varying initial temperatures in a three-point bending environment. Through examination of the load-displacement curves of the considered coal samples, their mechanical properties are also revealed for different initial temperatures and cycling frequencies. The findings demonstrate a gradual decline in the maximum load capacity of coal rock as the temperature rises. Similarly, when subjected to the same temperature, an escalation in the cycling frequency leads to a reduction in the peak load of coal rock. This suggests that both temperature and cycling frequency exert a notable impact on the fracturing efficacy of liquid nitrogen. Freeze-thaw cycling treatments and exposure to high-temperature conditions can activate preexisting damage in the coal rock, and, accordingly, influence its mechanical properties. In particular, throughout the progressive loading of coal rock samples, the failure mechanisms are predominantly characterized by the occurrence of tensile cracks, succeeded by the development, spread, and fracture of shear fissures.
KW  - Liquid nitrogen fracturing; three-point bending experiment; mechanical characteristics

DO  - 10.32604/fdmp.2023.044532