3种岩石动态拉伸力学性能试验与对比分析

Comparative analysis on dynamic tensile mechanical properties of three kinds of rocks

为研究不同岩性岩石动态拉伸力学性能的差异,选用岩石工程中较为常见且波阻抗差别较大的3种岩石:红砂岩、灰砂岩和花岗岩,利用分离式霍普金森压杆(SHPB)试验系统分别对3种岩石巴西圆盘试件进行不同冲击速度下的动态劈裂拉伸试验,同时结合超高速数字图像相关(DIC)试验系统对试样表面应变场变化过程及其动态拉伸破坏过程进行了观测。对比研究分析了3种岩石的拉伸应变场和剪切应变场的动态演化规律,不同冲击速度和不同加载率下3种岩石的动态拉伸强度、拉伸敏感系数和破坏形态的变化规律,以及波阻抗对岩石动态拉伸力学性能的影响。研究结果表明:①3种岩石破坏形态的差异主要体现在圆盘试件两端的楔形局部剪切破碎区,且局部剪切破碎区面积受冲击速度的影响。②3种岩石动态拉伸强度随冲击速度和加载率的增大均表现出良好的线性增大的关系,且相同冲击速度下,花岗岩加载率和动态拉伸强度>灰砂岩>红砂岩。③红砂岩拉伸强度对加载率最敏感,花岗岩次之,灰砂岩敏感性最弱,且随冲击速度和加载率的增大,3种岩石拉伸敏感系数均呈线性增大关系。④相同应力波作用下,岩石的应力波传播过程、加载历史以及动态拉伸力学性能受岩石波阻抗影响,且几者之间存在递进影响的关系。

Red sandstone,gray sandstone and granite are three kinds of rocks that are common in rock engineering and have large differences in wave impedance.The dynamic splitting tensile test of three kinds of Brazilian disc specimens at different impact velocities was carried out by using the split Hopkinson pressure bar(SHPB)test system to study the difference of dynamic tensile mechanical properties of different lithologic rocks.At the same time,the ultra-high speed digital image correlation(DIC)test system was used to observe the strain field change process and the dynamic tensile failure process of rock samples.The tensile strain field and shear strain field of three kinds of rocks were studied comparatively.The dynamic tensile strength,tensile sensitivity and failure morphology of rock samples under different impact velocities and different loading rates were compared and the effects of wave impedance on dynamic mechanical properties of rock were studied.The results show that:①The difference of failure modes of three kinds of rocks is mainly reflected in the wedge-shaped local shear fracture zone,and the area of the fracture zone is affected by the impact velocity.②The dynamic tensile strength of three kinds of rocks increases linearly with the increase of impact velocity and loading rate.At the same impact velocity,the loading rate and dynamic tensile strength of granite are the largest,followed by gray sandstone and red sandstone.③The tensile strength of red sandstone is the most sensitive to loading rate,granite is the second and gray sandstone is the weakest.With the increase of impact velocity and loading rate,the tension sensitivity coefficients of three kinds of rocks increase linearly.④Under the same stress wave,the stress wave propagation process,loading history and dynamic tensile properties of rock are affected by wave impedance of rock,and there is a progressive relationship between them.