摘要
为明晰水压作用下砂岩孔隙结构的演化规律,揭示其动态变化机制,借助核磁共振(NMR)技术开展试验研究。首先,制备规格为50 mm×25 mm的砂岩试件并分组,经清洗、烘干等预处理后,设定不同饱水压(5、10、20 MPa)与饱水时间(2、4、6、8、48 h);然后,通过NMR系统测试不同条件下砂岩的T_(2)谱、孔隙率和含水率等参数,分析孔隙结构变化特征;最后,从物理机制层面探讨T_(2)谱变化规律,并梳理其工程应用方向。结果表明:不同水压下T_(2)谱核磁信号幅度各异,随饱水压上升,T_(2)谱曲线右移且偏移幅度减小,T_(2)谱面积与孔隙率随饱水压的增加而增大,但增速逐渐放缓;t=0~4 h内砂岩含水率与孔隙体积快速增加,t≥6 h后孔隙结构趋于稳定;相同饱水时间下,水压升高使岩石内部产生损伤,压力达10 MPa后岩芯吸水稳定,孔隙裂隙发育至稳定阶段,孔隙结构与压力形成动态平衡。砂岩含水率越高,其孔隙连通性越好、岩石强度越低。
To clarify the evolution law of sandstone pore structure under water pressure and reveal its dynamic change mechanism,an experimental study was conducted using nuclear magnetic resonance(NMR)technology.First,sandstone specimens with a size of 50 mm×25 mm were prepared and grouped;after pretreatment such as cleaning and drying,different water saturation pressures(5,10,20 MPa)and water saturation times(2,4,6,8,48 h)were set.Then,the NMR system was used to test parameters such as T_(2) spectrum,porosity,and water content of sandstone under different conditions,and the variation characteristics of pore structure were analyzed.Finally,the variation law of T_(2) spectrum was discussed from the perspective of physical mechanism,and its engineering application directions were sorted out.The results show that the amplitude of NMR T_(2) spectrum signals varies under different water pressures;as the water saturation pressure increases,the T_(2) spectrum curve shifts to the right with a decreasing shift amplitude,and the T_(2) spectrum area is positively correlated with porosity and water saturation pressure but with a decreasing growth rate;the water content and pore volume of sandstone increase rapidly within t=0~4 h,and the pore structure tends to be stable after t≥6 h;under the same water saturation time,the increase in water pressure causes damage inside the rock,and after the pressure reaches 10 MPa,the pore structure becomes stable and the rock is completely damaged;the higher the water content of sandstone,the better the pore connectivity and the lower the strength.
作者
胡海峰
李鹏
陈明浩
张柏林
吴少康
HU Haifeng;LI Peng;CHEN Minghao;ZHANG Bailin;WU Shaokang(CHN Energy Shendong Coal Group,Erdos Inner Mongolia 017200,China;College of Safety and Emergency Management Engineering,Taiyuan University of Technology,Taiyuan Shanxi 030024,China)
出处
《矿业科学学报》
北大核心
2025年第6期1130-1139,共10页
Journal of Mining Science and Technology
基金
国家自然科学基金(42102222)。
关键词
饱水压
饱水时间
核磁共振(NMR)技术
T_(2)谱
孔隙率
含水率
saturated water pressure
saturated water time
nuclear magnetic resonance(NMR)
T_(2)spectrum
porosity
water content
