温度作用后大理岩加-卸荷破裂特性试验研究

Loading and unloading test on fracture characteristics of marble after heating

文章开展了常温和200℃作用后锦屏大理岩的单轴、常规三轴及三轴卸围压试验,分析了温度作用对大理岩破裂特征及强度的影响规律。研究表明:温度作用对大理岩破坏形式有较大影响,在相同的应力路径下,温度作用后的试件更容易出现张拉破坏特征。单轴试验中,试件均发生剪切和张拉组合破坏,未受温度作用的试件以剪切破坏为主,而温度作用后的试件以张拉破坏为主;在常规三轴试验中,未受温度作用的试件主要是剪切破坏,而温度作用后的试件有单剪、剪切和张拉组合破坏形式;三轴卸围压试验中,未受温度作用的试件有单剪、共轭剪切、剪切和张拉组合破坏等形式,而温度作用后的试件包括单剪、剪切和张拉组合、共轭剪切和张拉组合破坏等形式;常规三轴试验中,温度作用后试件的内摩擦角基本没有变化,而内聚力略有增加;卸围压试验中,温度作用后试件的内摩擦角有所增加,而内聚力则降低;采用Mogi-Coulomb强度准则对温度作用后的大理岩加、卸荷强度的回归效果优于Mohr-Coulomb强度准则。

To investigate the influence of temperature on fracture characteristics and strength of marble in Jinping, the uniaxial and triaxial compression, and unloading confining pressure tests on marble samples under natural state and heated at 200 ℃ were carried out. The results show that the thermal treatment has great influence on the failure forms of marble samples. The samples heated at high temperature tend to fail in tension. In uniaxial compression tests, the specimens fail in tension-shear, shear failure is predominant for the natural sample, and tensile failure predominant for the heated sample. In triaxial compression tests, the natural samples fail in shear, but the heated samples fail in simple shear or tension-shear. In unloading confining pressure tests, the natural samples fail in simple shear, conjugate shear and tension-shear, but the heated samples fail in simple shear, tension-shear, and coupling of conjugate shear and tension. For the heated specimens, the inner friction angle is unchanged and cohesion increases slightly in the triaxial compression tests; on the contrary, the inner friction angle increases slightly and cohesion is reduced in unloading confining pressure tests. It is more reasonable for using Mogi-Coulomb failure criterion to analyze loading and unloading strength of the marble samples under natural or heated condition than Mohr Coulomb criterion.