矿柱偏心承载特性与失稳破坏机制

Eccentric Bearing Performance and Failure Mechanism of Pillar

荷载重心与矿柱截面形心不重合的偏心承载普遍存在于地下开采工程之中。为揭示矿柱偏心压缩承载特性与失稳破坏力学机制,采用一种模拟偏心压缩的试验装置,开展了五组不同偏心距条件下矿柱轴向压缩试验,得到了偏心压缩时矿柱抗压强度及失稳破坏特征。利用MV-XG280相机监测了加载过程中矿柱表面的散斑图像,结合数字图像相关方法分析了偏心距为1/6矿柱宽度时其表面位移场与应变场演化过程。结果表明:1)矿柱的抗压强度和弹性模量随偏心距增加呈降低趋势,偏心距越大矿柱越容易达到强度极限而破坏,与均匀压缩相比,偏心荷载作用大大降低了其承载能力;2)偏心荷载下矿柱的破坏特征为小偏心受压破坏和大偏心受拉破坏。偏心压缩使矿柱受力和力矩的共同作用,表现出偏心距越大整体弯曲变形程度越严重;3)偏心距为矿柱宽度的1/6时,位移场及应变场反映了试件变形破裂的演化过程,随着荷载的增加,位移场最大位移区域进一步集中,应变场出现明显的局部化带,形成最终导致矿柱破坏的宏观裂隙。

The problem of eccentric bearing that the center of load does not coincide with section center of the pillar generally exists in the practice of underground mining engineering.In order to reveal eccentric compression bearing performance and instability failure mechanical mechanism of pillar with different eccentricity,a test device simulating eccentric compression was used to carry out axial compression tests on five sets of pillar under different eccentricity conditions.The compressive strength and instability failure characteristics of the pillar samples under eccentric compression were obtained.The MV-XG280 camera was used to monitor the speckle image of the surface of the pillar during the loading process.Combined with the digital image correlation method,the evolution process of the surface displacement field and strain field was analyzed when the eccentricity was 1/6 pillar width.The results show that:1)The compressive strength and elastic modulus of the pillar decrease with the increase of the eccentricity.The larger the eccentricity,the easier it is for the pillar to reach the strength limit and damage.Compared with uniform compression,the eccentric load greatly reduces its bearing capacity.2)The failure characteristics of the pillar under eccentric load are small eccentric compression failure and large eccentric tension failure.Eccentric compression makes the interaction of the force and moment of the pillar,showing that the greater the eccentricity,the more serious the overall bending deformation.3)When the eccentricity is 1/6 of the width of the pillar,the displacement field and the strain field reflect the evolution process of the deformation and fracture of the specimen.With the increase of the load,the maximum displacement area of the displacement field is further concentrated,and the strain field shows obvious localization zone,forming a macroscopic crack that eventually leads to the failure of the pillar.