应力波斜入射下砂岩层裂破坏的试验研究

Experimental study on the spalling failure of sandstone under the oblique incidence of stress waves

在地下工程结构中,爆破或地震等产生的动载荷会以任意方向作用于围岩,容易导致其发生层裂破坏。为了研究应力波斜入射对砂岩试样层裂破坏特性的影响,利用50 mm杆径的霍普金森压杆装置开展了应力波在0°、30°、45°和60°入射下砂岩试样的层裂试验,并利用高速摄影仪记录试样的层裂破坏过程。试验结果表明,试样初始层裂长度和层裂强度受应力波入射角度影响显著。在相同冲击气压下,试样初始层裂长度随着应力波入射角度的增大而增大;而试样层裂强度随着应力波入射角度的减小而增大。此外,采用离散元代码(particle flow code, PFC)对本次试验进行了数值模拟,模拟结果与试验结果较为吻合。在模拟中,进一步研究了冲击速度对应力波斜入射下砂岩层裂破坏的影响,在较高冲击速度下,应力波垂直入射造成的层裂裂纹数量与较低冲击速度下变化程度不大,而应力波在斜入射下造成的层裂裂纹数量显著增多,且损伤较为明显。

In underground engineering structures,the surrounding rock is prone to spalling under the action of stress waves generated by blasting or earthquake.As the stress waves usually propagate in any direction in the surrounding rock,the effect of oblique incidence of stress waves on the spalling failure characteristics of sandstone specimens was aimed to be investigated.A split Hopkinson pressure bar device with a diameter of 50 mm was utilized to conduct spalling failure tests on the sandstone specimens under stress waves incident at angles of 0°,30°,45°,and 60°.A high-speed camera recorded the spalling failure processes of the specimens.The test results reveal that the incident angle of the stress wave significantly influences the initial spalling position and spalling strength of the specimens.With the increasing of incident angle,the initial spalling length increases,while the spalling strength decreases.Furthermore,the simulation results obtained using the particle flow code(PFC)are in good agreement with the test results.In the simulation,the influence of impact velocity on the sandstone spalling failure under the oblique incidence of stress waves was further studied.It is found that comparing to the case of lower impact velocities,the failures caused by stress waves under vertical incidence haven’t significant change,while the number of spalling cracks and the extent of damage increase significantly under oblique incidence.