复杂应力条件下岩石的拉剪变形及破坏准则研究

根据不同围压条件下的粉细砂岩三轴压缩全程试验,分析了围压对砂岩峰值强度和破坏方式的影响,研究了压缩过程中砂岩的拉、剪变形随围压的变化规律。结果表明:粉细砂岩峰值强度与围压的关系是一条有拐点的折线,围压低于拐点对应的临界围压σ3L时,粉细砂岩的破坏方式仍为剪切破坏,但其强度受到张拉变形影响而低于Coulomb准则的计算值,岩石破裂面与最小主应力夹角大于(45°+φ/2);围压高于σ3L时,粉细砂岩的破坏仅受剪切变形控制,张拉变形对强度的影响可以忽略,岩石进入完全剪切破坏状态,破裂面角度与(45°+φ/2)吻合。在此基础上,提出了反应砂岩破坏过程中张拉应变和剪切应变相互关系的指标值ft/fγ,并据此推导了砂岩在不同围压下的强度准则,与实际情况较为吻合。

Research on the Tension-shear Deformation and Failure Criterion of Rock Under Complex Stress

Based on the mechanical tests of fine siltstone which were conducted under different confining pressures,the effect of confining pressure to peak strength and failure form was analyzed,and the law between tension-shear deformation and confining pressure of whole process was researched.The study results showed as follows.The relationship curve of peak strength and confining pressure of fine siltstone is a polygonal line which has a inflexion.When confining pressure is less than the σ3L of inflexion,the failure of fine siltstone is controlled by shear deformation,and its strength is influenced by tension deformation,so it will be less than the strength calculated by the Coulomb rule,and its rupture angle is larger than(45°+φ/2).When the confining pressure is higher than the σ3L,the failure of fine siltstone is only controlled by shear deformation,its strength and rupture angle are as same as the Coulomb rule gives.Based on this,the index ft/fγ which is a reflection of tension deformation and shear deformation in the failure process was given,and the strength rule of fine siltstone under different confining pressures was constituted,which accorded with fact.