煤田地质与勘探2025，Vol.53Issue(4)：191-202,12.DOI:10.12363/issn.1001-1986.25.02.0106
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
摘要
Abstract
[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 mechan-isms,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 sand-stone 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 satur-ated sandstones,as well as the evolutionary patterns of their fracture toughness and energy dissipation mechanisms vary-ing 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 low-temperature 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 res-ults indicate that with a decrease in temperature,the frozen saturated sandstones exhibited intensifying fracture tough-ness.Accordingly,energy absorbed during sandstone fracture increased,and the energy utilization ratio showed an in-creasing 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 dif-ferent 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 unfrozen water content remained unchanged.In the rapid freezing stage,the free and capillary water roughly experienced phase transition,and most of the bound water froze,leading to rapidly enhanced fracture toughness.In the slow freezing stage,a small amount of bound water froze,with fracture toughness increasing slowly.The strain versus time curves derived from numerical simulation agreed well with those obtained using experiments,suggesting reasonable and reliable simulation results.The simulation results re-vealed significant stress concentration on the rock bridge of the SCC specimen and that the shear stress showed an in-creasing trend with the loading rate.Moreover,both the fracture toughness of the sandstones and energy absorbed dur-ing sandstone fracture increased with an increase in the loading rate.The results of this study can serve as a guide for the excavation of frozen wellbores through drilling and blasting in water-rich soft rock formations in West China.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Key words
dynamic mode Ⅱ fracture/frozen saturated sandstone/fracture toughness/energy dissipation/enhancing mechanism under low temperature/loading rate分类
矿业与冶金引用本文复制引用
赵涛,崔朝,贾海梁,杨光宇..不同低温与加载速率下冻结饱和砂岩Ⅱ型动态断裂特性[J].煤田地质与勘探,2025,53(4):191-202,12.基金项目
国家自然科学基金面上项目(42271148) （42271148）
