岩样三轴压缩的破坏形式和Coulomb强度准则

尽管岩样轴向承载能力与围压成线性关系,但岩样在围压下轴向压缩破坏的断面,并不能由Coulomb准则准确预示。截面倾角在45°±φ/2附近时,基于粘聚力和内摩擦力的承载能力变化不大,实际破坏面的方位与岩样内部层理、缺陷等有关。砂岩具有明显的颗粒,岩样破裂面通常含有部分圆锥面,并不完全是平面,而石灰岩、煤的颗粒细微,破裂面则多是平面。对高径比为2的圆柱岩样,在围压影响系数大于4或内摩擦角φ达到36.87°之后,倾角45°±φ/2的平面将起止于岩样的端面,而不是侧面,难以利用Coulomb准则分析岩样的承载特性。

DESTROY CHARACTER AND COULOMB CRITERION OF ROCK SPECIMEN IN PSEUDO-TRIAXIAL COMPRESSION

The relation is linear between axial supporting capacity of specimen and confining pressure,but the crack angle of specimen can not be given by Coulomb criterion.The axial supporting capacity of sections with angle around 45°+φ/2 is nearly the same based on the concept of cohesion and internal friction.So the real crack face usually resulted from the bedding and defect in the specimen.The failure of specimen for sandstone that is made of clearly particles is usually diagonal crack with part cone,but one for coal and limestone which is made of tiny particles is plane crack.For specimen with the ratio 2 of length to diameter,the plane with angle 45°+φ/2 will connect the upper and lower face of the specimen,not the surround face when the internal friction angle is larger than 36.87° or the influencing coefficient of confining pressure on the strength is larger than 4.And it is difficult to analyze the supporting character of specimen with Coulomb criterion.