岩石粘弹塑性本构关系及改进的Burgers蠕变模型

软弱岩石一般具有粘弹塑性共存特性,而典型的Burgers蠕变模型只能描述材料第三期蠕变以前的粘弹性规律,因此,本文基于Mohr-Coulomb准则,提出了新的塑性元件,该元件假定材料屈服后完全服从Mohr-Coulomb塑性流动规律。将该元件与典型的Burgers模型串联,形成了能模拟粘弹塑性偏量特性和弹塑性体积行为的改进型Burgers蠕变模型,推导了相应的粘弹塑性本构关系。给出了模型参数的求解方法,编制了相应的数据处理程序,并结合工程实例,对蠕变模型参数进行了拟合和加权平均取值。应用结果表明:试验曲线与理论计算曲线吻合,改进的Burgers蠕变模型能较好的描述岩石的蠕变特性。

Visco-elastop-lastic constitutive relationship of rock and modified Burgers creep model

The classic Burgers creep model could only describe the viscoelastic behaviour of rock material before the third creep-phase, but weak rock usually was visco-elasto-plastic. So according to this shortage of Burgers model, a new plastic cell was developed based on Mohr-Coulomb criterion, which was assumed to be in absolute accordance with the plastic flow law of Mohr-Coulomb when rock failed. And then the plastic cell acted in series with the classic Burgers model, and a modified Burgers creep model was built and the corresponding visco-elasto-plastic constitutive relationships were deduced. The modified model could simulate visco-elasto-plastic deviatoric behavior and elasto-plastic volumetric behavior. In addition, some methods to solve model parameters were given and some corresponding programs were developed to deal with the test data. And the model parameters of an engineering example were fitted and the values were obtained through weighted mean ones. It was shown that the creep testing curves were coincident well with the theoretic curves, validating that the modified Burgers creep model was felicitous to characterize the creep behaviour law of rock.