Investigation on coal damage and fracture extension law of liquid nitrogen injection pre-cooling and fracturing under true triaxial stress  

作　　者：Botao Li Haifei Lin Jianping Wei Hongtu Zhang Shugang Li Zongyong Wei Lei Qin Pei Wang Rongwei Luo Zeran Liu 

机构地区：[1]School of Safety Science and Engineering,Henan Polytechnic University,Jiaozuo 454003,China [2]State Key Laboratory Cultivation Base for Gas Geology and Gas Control,Henan Polytechnic University,Jiaozuo 454003,China [3]State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization,Henan Polytechnic University,Jiaozuo 454003,China [4]College of Safety Science and Engineering,Xi’an University of Science and Technology,Xi’an 710054,China [5]Key Laboratory of Shaanxi Province Universities of Gas Disaster Prevention and Control in Western Coal Mines,Xi’an 710054,China

出　　处：《International Journal of Mining Science and Technology》2025年第2期213-229,共17页矿业科学技术学报(英文版)

基　　金：financially supported by the National Natural Science Foundation of China(Nos.51874236 and 52174207);Shaanxi Science and Technology Innovation Team(No.2022TD02);Henan University of Science and Technology PhD Funded Projects(No.B2025-9)。

摘　　要：To more accurately describe the coal damage and fracture evolution law during liquid nitrogen(LN_(2))fracturing under true triaxial stress,a thermal-hydraulic-mechanical-damage(THMD)coupling model for LN_(2) fracturing coal was developed,considering the coal heterogeneity and thermophysical parameters of nitrogen.The accuracy and applicability of model were verified by comparing with LN_(2) injection pre-cooling and fracturing experimental data.The effects of different pre-cooling times and horizontal stress ratios on coal damage evolution,permeability,temperature distribution,and fracture characteristics were analyzed.The results show that the permeability and damage of the coal increase exponentially,while the temperature decreases exponentially during the fracturing process.As the pre-cooling time increases,the damage range of the coal expands,and the fracture propagation becomes more pronounced.The initiation pressure and rupture pressure decrease and tend to stabilize with longer precooling times.As the horizontal stress ratio increases,fractures preferentially extend along the direction of maximum horizontal principal stress,leading to a significant decrease in both initiation and rupture pressures.At a horizontal stress ratio of 3,the initiation pressure drops by 48.07%,and the rupture pressure decreases by 41.36%.The results provide a theoretical basis for optimizing LN_(2) fracturing techniques and improving coal seam modification.

关 键 词：Liquid nitrogen fracturing Thermal–hydraulic-mechanical-damage coupling Heterogeneous coal True triaxial stress Fracture morphology 

分 类 号：TD315[矿业工程—矿井建设]