液氮循环冷冲击作用下高温花岗岩I型断裂特性研究  

Mode I fracture characteristics of high-temperature granite under cyclic liquid nitrogen cooling

作　　者：薛熠 杨博鹍 刘勇[2] 孙强[2] 张云 曹正正 XUE Yi;YANG Bo-kun;LIU Yong;SUN Qiang;ZHANG Yun;CAO Zheng-zheng(Institute of Geotechnical Engineering,Xi’an University of Technology,Xi’an,Shaanxi 710048,China;State Key Laboratory Cultivation Base for Gas Geology and Gas Control,Henan Polytechnic University,Jiaozuo,Henan 454000,China;College of Energy Engineering,Xi’an University of Science&Technology,Xi’an,Shaanxi 710054,China)

机构地区：[1]西安理工大学岩土工程研究所,陕西西安710048 [2]河南理工大学瓦斯地质与瓦斯治理国家重点实验室培育基地,河南焦作454000 [3]西安科技大学能源学院,陕西西安710054

出　　处：《岩土力学》2025年第2期422-436,共15页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.52274096,No.12202353);瓦斯地质与瓦斯治理国家重点实验室培育基地开放基金(No.WS2023A03)。

摘　　要：液氮循环压裂技术是一种环境友好且高效的新型无水压裂方法,通过多次液氮冷却作用在干热岩中产生显著的热应力,从而有效地对干热岩储层进行致裂和增渗。为了揭示液氮循环冷冲击作用对干热岩断裂特性及损伤特征的影响机制,对花岗岩试样进行不同循环次数的高温加热-液氮冷却处理,通过三点弯曲试验对处理后的花岗岩试样物理力学特性(包括断裂韧度和破裂特征)进行了分析。基于三维激光扫描技术和分形理论对三点弯曲试验后花岗岩断口表面形貌特征及断面粗糙度进行了定量评价。采用数值方法,利用随机四参数生成法重构非均质花岗岩基质,建立了热-力耦合的混合相场模型,对不同液氮循环次数下高温花岗岩的微裂隙演化及宏观断裂过程进行模拟,分析了液氮循环冷冲击作用对高温花岗岩宏观断裂特性的影响。试验和数值结果表明:高温加热-液氮冷却循环作用会加剧花岗岩的损伤程度,导致断裂韧度等力学参数显著下降。断面分形维数以及形态特征参数与循环次数呈显著正相关,在高循环次数下断面展现出复杂曲折的宏观主裂纹扩展路径。热-力耦合混合相场模型能够有效再现高温加热-液氮冷却循环作用下花岗岩的热-力开裂行为。花岗岩的热损伤主要集中在最大拉伸应变能区域。液氮循环作用下,高温花岗岩的微破裂主要由温度梯度和相邻矿物颗粒之间的热膨胀变形差异引起。液氮循环冷却诱导的微裂隙使得花岗岩I型断裂的扩展路径更加曲折和复杂。Liquid nitrogen cyclic fracturing is an environmentally friendly and efficient waterless fracturing technology that induces significant thermal stress in hot dry rock(HDR)through repeated liquid nitrogen cooling cycles,effectively enhancing fracturing and permeability in HDR reservoirs.To investigate how cyclic liquid nitrogen cooling affects the fracture characteristics and damage behavior of HDR,granite samples underwent high-temperature heating and liquid nitrogen cooling treatments with varying cycle numbers.The physical and mechanical properties,such as fracture toughness and behavior,were evaluated using three-point bending tests.Surface morphology and roughness of fracture surfaces generated during bending tests were quantitatively analyzed using three-dimensional laser scanning technology and fractal theory.Additionally,a numerical method was employed to reconstruct the heterogeneous granite matrix using a stochastic four-parameter generation approach.A thermo-mechanically coupled hybrid phase-field model was developed to simulate microcrack evolution and macroscopic fracture processes of high-temperature granite under different liquid nitrogen cycles,providing insight into the impact of cyclic cooling on macroscopic fracture behavior.Experimental and numerical results show that repeated high-temperature heating and liquid nitrogen cooling exacerbate granite damage,significantly reducing mechanical parameters such as fracture toughness.The fractal dimension of fracture surfaces and surface morphology parameters showed a significant positive correlation with cycle numbers.At higher cycle numbers,fracture surfaces displayed complex and tortuous crack propagation paths.The thermo-mechanical hybrid phase-field model accurately replicated the thermo-mechanical cracking behavior of granite under high-temperature heating and liquid nitrogen cooling.Thermal damage in granite was primarily concentrated in regions with the highest tensile strain energy.Microcracking observed in high-temperature granite during cycli

关 键 词：液氮 花岗岩 断裂韧度 断面粗糙度 相场法 

分 类 号：TU454[建筑科学—岩土工程]