振动荷载对砂岩峰后损伤变形特性的影响

Damage and Deformation of Siltstone in Post Peak Affected by Vibration Load

岩石峰后力学特性的理论研究对于深部煤炭的安全开采至关重要。开展粉砂岩的峰后振动循环和加卸载试验:首先以0.1 MPa/s的速率将围压增至20 MPa,然后以60 k N/min速率施加轴向荷载直至峰值q,再进行轴向卸载至0,最后轴向施加10~80次的正弦振动荷载。通过总结振动荷载对粉砂岩强度、变形、损伤和弹性模量的作用规律,研究了振动荷载对砂岩峰后损伤变形特性的影响。结果表明:少量的振动荷载有利于粉砂岩变形损伤的闭合,可以提高岩石的弹性模量,使岩石变得相对坚硬;但过多次数的循环荷载会引起岩石的变形进一步发展,产生新的损伤,同时也会使岩石变软。峰后阶段的振动荷载会促进新裂纹的产生、发展和贯通,最终产生多组破裂面。

The researches of post peak mechanism of rock are very important for the safety work in deep mining.This paper was devoted to the vibration cyclic load experiments of the siltstone in post peak. In the experiments,loading pattern was specially designed: firstly,20 MPa confining pressure was loaded at 0. 1 MPa/s rate and kept steadily through the experiments; secondly,the pressure in axial was loaded at 60 k N/min rate until the sample reached the stress peak q,then unload the axial pressure to 0; thirdly,the vibration load in sine wave shape which varied from 0 to 0.6 q was loaded on the sample for appointed times,then unload the pressure. According to the data of the vibration cyclic load experiments,the sample(siltstone) characteristics such as strength,deformation,damage and elastic modulus were analyzed with figures and images. The results show as follows: adequate vibration loading can reduce the deformation damage and increase the elastic modulus of rock in the post peak state. However,superabundant times of vibration loading will induce more damage,develop the deformation and make the rock softening. The vibration loading in post peak will increase the cracks and turning more failure surfaces.