Stiff servo-controlled numerical test method based on mixed higher order discontinuous deformation analysis#br#
LU Bo,WU Aiqing,Xu Dongdong,Yang Maocai#br#
(Key Laboratory of Geotechnical Mechanics and Engineering of the Ministry of Water Resources,Yangtze River Scientific Research Institute,Wuhan,Hubei 430010,China)
Abstract:Compared with the traditional mechanical test,the numerical test method has the advantages of low cost,flexibility and convenience,and is not affected by the performance of test machines and the dispersion of rock samples. The meso-mechanism of rock deformation and failure can be conveniently studied by analyzing rock meso-structure and parameter sensitivity. As a useful supplement to the macroscopic mechanical test,the mesoscopic numerical test method has gradually developed into an important means to study the mechanical properties of rocks in recent years. Based on the discontinuous deformation analysis method,a numerical micromechanical test method was established to realize the ideal rigidity of a rigid testing machine and the servo control of an electro-hydraulic servo testing machine. Under the framework of mixed high-order discontinuous deformation analysis,the block elements that make up the rock sample can adopt the displacement mode of constant strain element or higher-order polynomial,and the block elements that simulate the loading frame adopt the rigid-body displacement mode,so as to achieve the ideal rigidity of the loading system. The numerical simulation of the closed-loop control mechanism of the electro-hydraulic servo testing machine is realized by the real-time feedback control of the loading rate and its magnitude. The application of calculation strategies such as“loading step withdrawal”and“binary search”makes the loading rate and its magnitude in the numerical test always adapt to the bearing capacity of the rock sample,so as to get a more realistic post-peak curve. The validity of the servo numerical simulation program was verified by two simplified models. After that,uniaxial compression test was carried out with the developed program,and the stress-strain whole-process curve was obtained. The servo numerical test method based on mixed higher order DDA provides a new research method for the numerical micromechanical study of basic mechanical properties of rock.
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