Intelligent Inversion Analysis Of Macro-And Micro-Parameters Of Rockfill Based On Discrete ElementMethod And It’s Engineering Application

As an essential engineering construction material,rockfill is a kind of granular material with high-pressure compaction,strong permeability,high shear strength and small settlement deformation.It widely used in dam construction,embankment,road,airport,port and marine engineering.At the same time,with the further improvement of water resources development in China and even in the world,water conservancy project construction is facing a new challenge of cold,high altitude,high steep slope,high seismic intensity,and deep overburden.Rockfill,the material of rockfill dams as the recommended dam type,urgently need to study its physical and mechanical properties.Therefore,through the improvement,series and optimization of machine learning,the strong nonlinear relationship between multi-scale variables of rockfill is established in this paper,which makes the mechanical parameters of rockfill materials more in line with the engineering practice.Then these parameters are applied to the micro-mechanic research of rockfill and the solution of practical problems in rockfill engineering.The main contents and achievements of this paper are as follows:(1)To further improve the calculation accuracy,an adaptive inversion analysis model based on harmony search algorithm and multi-output multi-kernel correlation vector machine is established based on structural monitoring data for rockfill macroscopic constitutive model parameters.This model can quickly and accurately realize the adaptive back analysis of different projects and monitoring items.For many uncertain factors in the design,construction and construction of rockfill dam,an uncertainty inversion analysis model combining relevance vector machine and stochastic finite element method is established.This stochastic inversion analysis model can comprehensively consider the uncertainty of numerical calculation and input-output to back analysis of the variation coefficient of parameters of rockfill dam.The average absolute error of the settlement after back analysis is 1.930.(2)Based on summarizing the research progress of rockfill characteristics and microscopic contact model,a refined discrete element triaxial test model of rockfill is established,and the influence mechanism of microscopic parameters on rockfill deformation characteristics is analyzed in depth.To calibration of rockfill microscopic parameters influenced by many factors and time-consuming,a calibration model based on quantum genetic algorithm and support vector machine is established for rockfill microscopic parameters using on the stress-strain curves.Furthermore,aiming at the more widely used in engineering,a calibration model of rockfill microscopic parameters based on quantum genetic algorithm and relevance vector machine is proposed using the macroscopic constitutive model.So,the error of the different confining pressure stress-strain curve is less than 0.21 MPa.Finally,the microscopic mechanism of rockfill is analyzed qualitatively and quantitatively.(3)To make sure the micro parameters of rockfill harmony with the actual operation of the project,based on the measured deformation data of the structure,a calibration model of the micro-parameters of rockfill is proposed.The micro-parameters of contact model of rockfill dam can be calibrated according to the measured deformation values of a rockfill dam.To maximum the theoretical advantages of discrete element simulation in structure,the discrete element method is used to simulate the rockfill dam,and the calculation results of discrete element and finite element are compared.Based on the above research,the inversion models are integrated into an inversion analysis software of rockfill materials to realize the fast and accurate conversion between multi-scale parameters of rockfill materials.(4)Aiming at determining the height of retaining wall in practical engineering,the discrete element model of rockfill slope is established with the above parameter inversion analysis method,and the instability process of rockfill slope under construction,operation,rockfall and reinforcement measures is simulated.To reflection and superposition of seismic wave at the artificial boundary,the viscous boundary of the discrete element is established,and the model response under different boundary is compared.The seismic condition of rockfill slope is analyzed.Though the above analysis,the instability process and influence range of rockfill slope are clarified,and it is suggested that the concrete retaining wall of the rockfill slope be increased to 11 m,which provides a reference for the design of similar slope engineering protection measures.