PFC^(2D)平节理模型细观参数标定方法

Calibration method of meso-parameters of PFC^(2D) flat-joint model

细观参数的快速准确确定对PFC正确模拟岩石力学性能非常重要。目前,平节理模型细观参数的标定研究均未考虑对泊松比和压拉比有很大影响的黏结比例φ_(b)和影响岩石强度及裂纹产生难易程度的黏结强度变异系数R_(sd)这两个细观参数,且未考虑作为判断围岩损伤范围重要指标的宏观参数起裂强度σ_(ci)。在参数中新增φ_(b),R_(sd)和σ_(ci),采用正交数值试验方法研究了平节理模型8个细观参数与岩石6个宏观参数之间的相关性,确定了各宏观参数与主要细观参数之间的拟合关系,并分析了宏细观参数间的趋势关系。在此基础上,提出了平节理模型细观参数的标定流程,然后根据片麻花岗岩物理试验的宏观力学参数确定了模型的细观参数并进行数值试验,模拟结果与物理试验结果基本吻合,说明标定流程可行。

The rapid and accurate calibration of meso-parameters is of utmost importance for the correct simulation of mechanical properties of a rock in PFC.Thus far,the calibration methods for flat-joint model(FJM)meso-parameters have not considered the bonding ratio,φ_(b),which significantly influences both Poisson’s ratio and compression-tension ratio,and the coefficient of variation of bonding strength,R_(sd),which significantly influences rock strength and difficulty of crack formation.Crack initiation strength,σ_(ci),is a macro-parameter that has not been considered;however,it is an important index to judge the damage range of the surrounding rock.Therefore,φ_(b),R_(sd),and σ_(ci) were included in parameter calibration study.Orthogonal numerical tests were conducted to study the correlation between the eight meso-parameters of the FJM and the six macro-parameters of the rock.The fitted relationships between each of the macro-parameters and main meso-parameters were determined;furthermore,an analysis of the trend relationships between the macro-and meso-parameters was conducted.Based on the above,a FJM meso-parameters calibration method was proposed,and the calibration method was used to calibrate the meso-parameters of the gneiss granite,whose macro-parameters have already been experimentally determined.The calibrated numerical model was used to perform a series of numerical experiments,and the calibration method is verified to be feasible because the results of the numerical experiments are close to those of the physical experiments.