石灰岩孔道试样压缩条件下变形与强度特征的试验研究

Experimental study on deformation and strength properties of hollow cylindrical specimens of limestone under compression

为了分析非均匀应力分布对石灰岩孔道试样变形、强度及破坏特征的影响，利用孔径为6～25mm的石灰岩孔道试样，在RMT-150B岩石力学试验系统进行单轴和内孔压为0的常规三轴压缩试验。结果表明：（1）单轴压缩时，孔道试样的峰值强度、弹性模量与孔径没有明显关系，破坏特征以张剪性破坏为主，孔道没有出现坍塌迹象。（2）三轴压缩时，孔径对试样在屈服阶段以前变形特性的影响不明显，对峰值后的变形特征影响显著，孔道试样的弹性模量与孔道尺寸、围压的关系不大。（3）利用修正的Coulomb预测材料强度高出单轴压缩峰值强度11％左右，与完整试样试验回归结果大致相等，其值与孔径和围压没有直接关系；而以修正的双剪切强度准则预测材料强度受试样孔径、围压的影响较为复杂，孔径小于11mm预测材料强度与孔径、围压的关系不明显，而孔径大于16mm时预测材料强度随孔径、围压增加而降低。（4）三轴压缩时孔道试样的破坏特征受孔径、围压的双重影响，孔径较大时更有利于屈服破坏承载能力降低。

A series ofuniaxial and pseudo-triaxial compression tests on hollow cylinder specimens with 50 mm in outer diameter and 6 - 25 mm in inner diameter were carried out to study the effects of nonuniform stresses on the deformation, strength and failure characteristics. The test results show that： （1） There is no significant difference among peak strength, elastic modulus and hole diameter under uniaxial compression, failure patterns of specimens are tensile-shear failure, the hole remain hasn＇t occur to collapse; （2） The effect of inner diameter on deformation characteristic isn＇t obvious before yield stage under the triaxial compression, but it has significant effect on the deformation characteristics of post-peak strength. There is no obvious difference between elastic modulus, inner diameter and and confining pressure; （3） The material strength of modified Coulomb prediction is more about 11%than uniaxial compression peak strength, which equals to regression results of intact specimen and has no direct connection to inner diameter and confining pressure. The effect of inner diameter and confining pressure is complex, when material strengths are predicted by modified twin-shear strength criterion. The predictive value of material strength is no significant difference between hole diameter and confining pressure when the inner diameter is less than l 1 ram, it decreases as the inner diameter or confining pressure increase when hole diameter is more than 16 mm; （4） The failure characteristic of hollow specimens are affected by hole diameter and confining pressure under triaxial compression, the bearing capacity will decrease when the inner diameter is bigger.