破损参数是用来描述岩土材料由胶结状态向无胶结状态转化的变量，合理地描述结构性土的破损演化规律是建立结构性土本构模型的关键。目前，大多损伤规律的研究先假设破损参数的表达式，随后通过拟合室内试验结果获取相关参数，从而确定损伤规律，这些损伤规律的合理性及适用性有待验证。为得到统一的具有微观意义的结构性砂土损伤规律显式数学表达式，提出了一种基于符号回归的损伤规律预测模型。首先，基于具有微观物理意义的破损参数定义式，建立不同离散元(distinct element method，DEM)损伤数据库。其次，采用组合输入变量的方法在等向压缩和等p真三轴压缩应力路径上进行参数筛选(p为平均有效应力)，结合基于遗传编程的符号回归(genetic programming-based symbolic regression，GPSR)算法，得到不同复杂度的损伤表达式。最终对比不同表达式的预测误差和泛化误差，选择表现最好的表达式为结构性砂土损伤规律，即GPSR损伤规律。对比前人经典损伤规律表达式，在不同DEM损伤数据库上进行适用性分析。结果表明，GPSR损伤规律将破损参数表示为塑性偏应变εs、归一化的平均有效应力p/py以及中主应力系数b的函数，可以很好地反映结构性土向重塑土转变的过程;GPSR损伤规律在不同损伤数据库上良好的预测精度进一步证明了其在不同岩土材料上的适用性。研究成果对建立结构砂土本构模型具有一定参考价值。
Damage law of structured sand using symbolic regression algorithm
The damage parameter is a variable used to describe the transition of geomaterials from a bonded state to an unbonded state.The correct expression of the damage evolution of structured soil is crucial in establishing constitutive models for structured soils.Currently,research on damage laws typically involves assuming expressions for damage parameters and then fitting these parameters using experimental results to establish the damage law.The rationality and applicability of these damage laws are yet to be validated.To derive a unified expression for the damage law of structured sands incorporating microscopic mechanisms,a prediction model based on symbolic regression is proposed.Firstly,using the definitions of damage parameters with microscopic physical significance,various damage databases are constructed using the distinct element method(DEM).Secondly,preliminary parameter screening is conducted on isotropic compression and constant p true triaxial compression stress paths using a method that combines input variables.p is the average effective stress.Combined with the genetic programming-based symbolic regression(GPSR),damage expressions with different complexities are derived.Finally,the best-performing expression is selected as the damage law for structured sand,namely the GPSR damage law,based on an analysis of prediction and generalization errors.The applicability of different expressions is compared using various DEM damage databases.The results show that the GPSR damage law represents damage parameters as functions of plastic deviatoric strain εs,normalized mean effective stress p/py and coefficient of intermediate principal stress b.It effectively reflects the transition from structured soil to remolded soil.The outstanding prediction ability of the GPSR damage law on different damage databases further demonstrates its applicability to various geomaterials.The research findings are valuable to establish constitutive models for structured sands.
structured sanddistinct element method(DEM)machine learningsymbolic regressiondamage law
万方数据
维普
