Meso-expression Of Resistance Of Granular Structure System Based On Stress Composition Analysis

The mechanical property of granular materials is among the most interesting field of mechanics because this kind of material has been applied widely.Disclosing its essential mechanism from a micro-and meso-scale level and describing it theoretically is the overall developing trend to understand the relevant problems.Based on the analysis of the shear strength of granular materials and the force source to resist loads,this thesis involves three aspects.By analyzing the stress composition of structural resistance of solid particle system,the author discloses the source and influencing factors of structural resistance of solid particle system;constructing the force model of the granular particles and establishing the microscopic expression of structural resistance of solid particle system when the particles is affected by the external loadings.The rationality of the microscopic expression of structural resistance of solid particle system is verified by the direct shear test.The main research progress is summarized as follows.(1)The structural resistance of solid particle system reflects the resistance of the particle's physical properties to resist the variation of the particle system.Whether there is additional load or internal disturbance,the structural resistance of solid particle system exists inside the particle system.The shear strength is the macro performance of this structural resistance of solid particle system.The results reveal the different roles of stress source(gravity,additional load and regional conditions)and particle composition characteristics(particle size,morphology,gradation,density and arrangement)in the structural resistance of solid particle system.(2)In order to understand the interactions of granular particles,the author introduces the concepts of the resistance stress analysis unit of the granular structure system and the internal stress balance interface of the granular system.Then the numerical simulation is applied to determine the effect of the microscopic properties of the particles on the structural resistance of solid particle system.A balance interface of internal stress within the granular system is used to establish the theoretical model of structural system resistance by means of incorporating the microscopic physical parameters of the particles.(3)Based on the analysis method of the structural resistance of the granular medium structure system,the loading process and the result data of the direct shear test are quantitatively analyzed.The results show the feasibility and rationality of the structural resistance of solid particle system to understanding the mesoscopic mechanism of the shear strength of the granular materials.The internal stress transfer expansion angle of the particle system has a correlation with the shear strength parameters(only the internal friction angle for quartz sand),which can provide a cutting-edge idea for further analysis of the meso-mechanism of the granular mechanical process.