有关岩土材料剪胀的讨论

Some discussion on the dilatancy of geotechnical materials

剪胀是岩土材料一个非常重要的特性,但目前对于剪胀的描述并不统一。剪胀角在滑移线场理论中主要有两种定义:①是实际塑性应变ε与剪切应变γ之间的夹角;②是破坏面(应力滑移线)与速度矢量方向的夹角(此时也称膨胀角)。在有限元计算中剪胀角则通过塑性势函数来定义,但对塑性势函数的选择比较随意,只是将屈服函数中的内摩擦角换成剪胀角,此时的剪胀角已没有明显的物理意义,只能在一定程度上反映材料的剪胀特性。阐明了滑移线场理论中有关剪胀的描述,推导了平面应变条件下考虑剪胀角影响并与Mohr-Coulomb准则精确匹配的广义Mises准则,研究了剪胀对浅基破坏模式的影响。

Dilatancy is a very important property of geotechnical materials, but now there＇re different definitions about it in geotechnical engineering. In slip line theory there＇re two definitions： one is the angle between the plastic strain e and the shear strain γ, the other is the angle between the failure surface （stress slip line） and the strain slip line. In FEM analysis the dilatancy angle is defined by the plastic potential function at discretion which can only express the dilatancy property to a certain extent. The two definitions of dilatancy in slip line theory are clarified, and the generalized Mises yield criterion matching Mohr-Coulomb yield criterion in plane strain condition is put forward where the effect of dilatancy can be considered. Finally, the effect of dilatancy on the failure modes of shallow foundations is studied.