动静载作用下充填节理砂岩应力波传播特性研究

Study on stress wave propagation characteristics of filled jointed sandstone under dynamic and static loading

为研究节理角度和不同围压作用下的充填节理岩石的动态力学特性和应力波传播规律,利用改造后的动静组合加载霍普金森压杆(split Hopkinson pressure bar, SHPB)装置,对充填节理厚度为8 mm的砂岩试样进行冲击试验,研究不同围压等级(0、4、6和8 MPa)和不同节理倾角(0°、15°、30°、45°)下充填节理试样的动态力学特性和应力波传播的规律,采用应力波斜射理论并进行验证。试验结果表明:(1)完整砂岩的反射波幅值最小,以0 MPa为例,反射波幅值从0.194×10^(-3)增长到0.299×10^(-3),与倾角成正相关,透射波幅值与倾角成负相关,且从0.169×10^(-3)减小到0.053×10^(-3);以0°为例,反射波幅值与围压呈负相关,且从0.194×10^(-3)减小到0.074×10^(-3),透射波幅值相反从0.169×10^(-3)增长到0.257×10^(-3);(2)在冲击动载作用下,一定程度围压可以起到限制变形,抑制胶结面分离,提高承载能力;节理倾角越大的充填节理产生的变形越大,承载状态越差;(3)倾角试件随着围压增大反射能力降低,透射能力提高,0°倾角试件的反射系数从0.603减小到0.147,透射系数从0.569均匀增加到0.789,围压试件随着倾角的增大反射能力增大,透射能力降低与理论分析规律一致;(4)节理倾角与试样吸收能密度呈负相关,围压与试样吸收能密度呈正相关,与围压作用下的透反射规律一致。

In order to study the dynamic mechanical characteristics and stress wave propagation law of filled joint rocks under different confinement angles and different confining pressures,the impact test was carried out on sandstone specimens with a filling joint thickness of 8 mm by using the modified dynamic and static combination loading(split hopkinson pressure bar,SHPB)device.The dynamic mechanical characteristics and stress wave propagation laws of filled joints under different confining pressure grades(0,4,6 and 8 MPa)and different joint inclination angles(0°,15°,30°and 45°)were studied,and the stress wave oblique emission theory was used and verified.The experimental results show that①The reflected amplitude of intact sandstone is the smallest.Taking 0 MPa as an example,the reflected amplitude increases from 0.194×10^(-3) to 0.299×10^(-3),which is positively correlated with the inclination,and the transmission amplitude is negatively correlated with the inclination angle from 0.169×10^(-3) to 0.053×10^(-3).Taking 0°as an example,the reflected amplitude is negatively correlated with the confining voltage,which decreases from 0.194×10^(-3) to 0.074×10^(-3) and the transmitted amplitude increases from 0.169×10^(-3) to 0.257×10^(-3).②Under the action of impact dynamic load,a certain degree of confining pressure can limit deformation,inhibit cementation surface separation,and improve bearing capacity.The larger the inclination angle of the joint,the greater the deformation of the filling joint,and the worse the bearing state.③With the increase of confining pressure,the reflectivity decreases and the transmission capacity increases.The reflection coefficient of the 0°inclination specimen decreases from 0.603 to 0.147,and the transmission coefficient increases uniformly from 0.569 to 0.789.With the increase of inclination angle,the reflection capacity of the confining pressure specimen increases,while the transmission capacity decreases,which is consistent with the theoretical analysis law.④The joint inclination angle is negatively correlated with the absorption energy density of the sample,but the confining pressure is positively correlated with the absorption energy density of the sample,which is consistent with the transmission reflection law under the action of confining pressure.