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Open Access

ARTICLE

Effects of Temperature and Liquid Nitrogen (LN2) on Coal’s Mechanical and Acoustic Emission (AE) Properties

Teng Teng1,2, Yuhe Cai3, Linchao Wang3,*, Yanzhao Zhu2
1 Inner Mongolia Research Institute, China University of Mining and Technology-Beijing, Ordos, 017001, China
2 Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources, China University of Mining and TechnologyBeijing, Beijing, 100083, China
3 School of Civil Engineering and Architecture, Xi’an University of Technology, Xi’an, 710048, China
* Corresponding Author: Linchao Wang. Email: wanglc@cumt.edu.cn
(This article belongs to the Special Issue: Fluids, Materials and Related Disasters in Geotechnical and Mining Engineering)

Fluid Dynamics & Materials Processing https://doi.org/10.32604/fdmp.2023.044532

Received 01 August 2023; Accepted 07 November 2023; Published online 21 December 2023

Abstract

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.

Keywords

Liquid nitrogen fracturing; three-point bending experiment; mechanical characteristics

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