三维离散元计算参数选取方法研究

SELECTION STUDY OF COMPUTATIONAL PARAMETERS FOR DEM IN GEOMECHANICS

简要分析了岩体力学计算中比较重要的几何参数和物理参数的选取问题。通过对几种离散元方法接触关系的比较,讨论了在不同的计算模型中结构面刚度所代表的物理意义。指出在刚性块体模型中,结构面的刚度是包含了岩块和结构面物理特性的等效刚度,而在可变形块体模型中,只有当块体间的接触弹簧刚度取足够大时,才能客观地反映岩体的特性。太大的接触刚度影响计算的可靠性,为此给出了一种简单的处理方法。通过量纲分析的方法给出了岩体结构振动的阻尼表达式,指出可以通过岩体的振动实验确定阻尼比,并进而给出特征时间。量纲分析得到的特征时间为计算时间步长提供了参考值。最后,介绍了离散元法的计算控制及滑动与失稳的判据。

A brief analysis is made on the selection of geometric and physical parameters for the computation of geomechanics. By comparison of several different DEM contact relationships, the physical meaning of joint stiffness in different computational models is discussed. In rigid block model, the joint stiffness is an equivalent stiffness reflecting the stiffness of rock block and joint. As for the deformable block model, the spring stiffness between blocks should be large enough to reflect the real characteristics of rock mass. In general, oversized contact stiffness may influence the computational reliability, and a simple treatment to get rid of the influence is proposed. The damping expression of structural vibration for rock mass is given by dimensional analysis, and the damping ratio can be obtained through vibration test. The characteristic time obtained from dimensional analysis offers a reference value for computational time step. In the end, the criteria of computing control, slide and failure in DEM are introduced.