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有关岩石强度的理论和实验研究已有许多报道。目前在岩石力学中应用较多的是莫尔-库仑理论。但这一理论只考虑了最大剪应力τ_(13)及其相应面上正应力σ_(13)的作用,而未考虑中间主剪应力τ_(12)或τ_(23)的作用,即没有考虑中主应力σ_2的影响,所以莫尔-库仑理论也可称之为单剪理论。有些实验表明这与实际不符,例如茂木清夫(Mogi,K.)经过多年研究认为σ_2对岩石破坏的影响是相当大的,因此曾建议采用修正的八面体剪应力条件,并提出了如下形式的破坏准则,τ_8=f(σ_1+σ_3+ασ_2);此外,文献[5]给出了一个岩石的三维破坏准则,该准则以第一和第三应力不变量表达,但这似乎只是一种数学上的组合,缺乏物理意义。另外,还有许多半经验形式的准则等。
There have been many reports on theoretical and experimental studies of rock strength. At present, more Mohr-Coulomb theory is widely used in rock mechanics. However, this theory only considers the effect of the maximum shear stress τ_(13) and the normal stress σ_(13) on its corresponding surface, but does not consider the role of the intermediate principal shear stress τ_(12) or τ_(23), ie it does not consider The influence of the principal stress σ_2, so the Mohr-Coulomb theory can also be called the single shear theory. Some experiments show that this is inconsistent with the reality. For example, Mogi (K.) after years of research, it was found that σ_2 has a great impact on rock failure. Therefore, it has been proposed to adopt a modified octahedral shear stress condition and put forward the following forms: The failure criterion, τ_8=f(σ_1+σ_3+ασ_2); In addition, the literature [5] gives a three-dimensional damage criterion for rocks, which is expressed by the first and third stress invariants, but this seems to be only a mathematical On the combination, lack of physical significance. In addition, there are many semi-empirical forms of guidelines and so on.