无约束径向载荷下不规则砂岩强度的颗粒尺寸效应研究

Effect of particle size on strength of irregular sandstone under unconstrained radial load

为探究无约束径向载荷下不规则砂岩颗粒的尺寸效应,采用物理试验与数值模拟分别研究相同高度、不同高厚比及不同高度、相同高厚比时砂岩颗粒的力学参数、破坏形式和能量规律,探讨不规则砂岩颗粒尺寸效应规律及影响因素。研究结果表明:在相同高度h、不同高厚比h/δ下,试件厚度增加,破坏形式由剪切破坏到劈裂破坏再到拉剪混合破坏,抗压强度和弹性模量增加,且当1≤h/δ≤1.25时趋于稳定;能量与厚度呈正相关;长度效应由端面摩擦主导;对不同高度相同高厚比试件而言,小尺寸砂岩颗粒峰值强度大,声发射次数多且分散;大尺寸砂岩颗粒峰值强度小,声发射次数少而集中;尺寸对砂岩颗粒破坏形式影响较小;体积效应由非均质性主导,均质度增加,体积效应减弱。

In order to investigate the size effect of irregular sandstone under diametral loading without confinement, the mechanical parameters, failure forms and energy laws of specimens with the same height,different ratios of height to thickness and the same height-to-thickness ratio at different heights were studied by physical test and numerical simulation. Moreover, the size effect laws and influencing factors of irregular sandstone were discussed. The results show that the thickness of specimens with the same height and different ratios of height to thickness increases, and the failure forms change from shear failure to splitting failure and to tensile-shear mixed failure. The compressive strength and elastic modulus increase and tend to be stable when 1≤h/δ≤1.25. The energy of the specimen is positively correlated with its thickness. The length effect of specimen is dominated by end friction. For the specimens with different heights and the same height-thickness ratio, the peak strength of small-sized specimens is large, and the acoustic emission occurs frequently and dispersedly. The peak strength of large-size specimens is small, and the frequency of acoustic emission is small and concentrated, while the size has little influence on failure mode. The volume effect of specimen is dominated by heterogeneity, and decreases with the increase of homogeneity.