不同低温与加载速率下冻结饱和砂岩Ⅱ型动态断裂特性  

Characteristics of dynamic mode Ⅱ fracture of frozen saturated sandstones under varying low temperatures and loading rates

作　　者：赵涛[1] 崔朝 贾海梁[1] 杨光宇 ZHAO Tao;CUI Zhao;JIA Hailiang;YANG Guangyu(School of Civil Engineering and Architecture,Xi’an University of Science and Technology,Xi’an 710054,China)

机构地区：[1]西安科技大学建筑与土木工程学院,陕西西安710054

出　　处：《煤田地质与勘探》2025年第4期191-202,共12页Coal Geology & Exploration

基　　金：国家自然科学基金面上项目(42271148)。

摘　　要：【背景】研究动力扰动下冻结饱和砂岩Ⅱ型断裂,包括临界应力强度因子(断裂韧度)变化特征以及能量耗散机制,对煤矿冻结井筒安全钻爆掘砌至关重要。【方法】利用分离式霍普金森压杆装置,在不同温度和不同加载速率下进行一系列动态SCC试验,分析了冻结饱和砂岩应力强度因子-时间曲线、断裂韧度和能量耗散机制随温度和加载速率的演化规律。总结宏观与微观层面上砂岩剪切断裂面特征,并利用核磁手段揭示了冻结效应的微观影响机制。此外,基于有限元模拟,进一步分析了断裂特性的加载速率效应。【结果和结论】结果表明:(1)随温度下降,冻结饱和砂岩断裂过程中岩石断裂韧度增大,相应地砂岩吸收的能量增加,能量利用率呈现一定的增长趋势。随加载速率增加,砂岩断裂韧度呈线性增加,岩石断裂吸收的能量也呈现增加趋势,而能量利用率呈现减小的趋势。(2)试件剪切面存在2种不同的断裂模式:“阶梯状”剪切滑移和“断口状”剪切滑移。(3)依据核磁数据总结了孔隙水冻结的3个阶段:过冷阶段,此阶段未冻水含量不变;快速冻结阶段,此阶段自由水与毛细水基本相变,大部分结合水冻结,断裂韧度迅速增加;缓慢冻结阶段,此阶段少部分结合水冻结,断裂韧度缓慢提升。(4)模拟应变-时间曲线与试验应变-时间较为吻合,表明模拟结果合理可靠,经模拟发现岩桥上出现明显的应力集中现象,并且随加载速率的增加剪应力呈现增加趋势,砂岩的断裂韧度与断裂吸收能均存在加载速率强化机制。研究成果对西部富水软岩地层冻结井筒的钻爆掘砌具有指导作用。[Background] Investigating the mode Ⅱ fracture of frozen saturated sandstones under dynamic disturbances,including changes in their critical stress intensity factor(SIF;i.e.,fracture toughness) and energy dissipation mechanisms,is crucial for the safe excavation of frozen wellbores through drilling and blasting in coal mines.[Methods] Using a split Hopkinson pressure bar(SHPB),this study conducted experiments on the dynamic mode Ⅱ fracture of a sandstone specimen using the short core in compression(SCC) method(also referred to as dynamic SCC experiments) under varying temperatures and loading rates.Accordingly,this study analyzed the SIF versus time curves of the frozen saturated sandstones,as well as the evolutionary patterns of their fracture toughness and energy dissipation mechanisms varying with the temperature and loading rate.Furthermore,it summarized the characteristics of the shear fracture planes of the sandstone specimen at macroscopic and microscopic scales and revealed the microscopic mechanisms behind the lowtemperature strengthening effect using nuclear magnetic resonance(NMR).Additionally,this study further analyzed the effects of the loading rate on fracture characteristics using finite element simulation.[Results and Conclusions] The results indicate that with a decrease in temperature,the frozen saturated sandstones exhibited intensifying fracture toughness.Accordingly,energy absorbed during sandstone fracture increased,and the energy utilization ratio showed an increasing trend.With an increase in the loading rate,the fracture toughness increased linearly,energy absorbed during sandstone fracture also showed an increasing trend,but the energy utilization ratio exhibited a decreasing trend.Two different fracture modes were observed on the shear planes of the SCC specimen:stepped and fracture-shaped shear slips.The NMR data revealed that the pore water freezing of the sandstones can be divided into three stages:supercooling,rapid freezing,and slow freezing sequentially.In the first stage,the

关 键 词：Ⅱ型动态断裂 冻结饱和砂岩 断裂韧度 能量耗散 低温强化机制 加载速率 

分 类 号：TD313[矿业工程—矿井建设]