Macroscopic And Mesoscopic Study On Deformation Mechanism Of Soil Around Underground Grain Storage Silos Under Flowing Water

Currently,the research on anti buoyancy of underground granaries mostly focuses on the selection of granary shapes,optimization of waterproof materials,structural design of granaries,and reduction factors,while ignoring the beneficial factors of soil mass on the resistance to buoyancy of underground granaries.Moreover,the problems of flowing water and silo soil interaction are key topics in the field of underground granary stability research,and have long been concerned by geotechnical workers.Based on the general project of the National Natural Science Foundation of China(No.51978247),this thesis developed a corresponding visual test system for the deformation of soil around the warehouse under the action of groundwater.Combining digital image technology,considering the effects of soil compaction and water level,the deformation characteristics of soil around underground granaries under the action of groundwater were studied from a microscopic perspective,and the deformation mechanism of soil was analyzed.Finally,it is verified from a macro perspective through numerical simulation.The main research contents and conclusions are as follows:(1)In this thesis,Solidworks software is used to model the model warehouse,and then the slicing software Ultimakercura is used to optimize and print the model warehouse.Combining digital image technology,a visual model test system for underground grain warehouses under the action of groundwater is developed by ourselves.The accuracy of non-contact video measurement systems and particle image velocimetry systems in data analysis methods is analyzed.The experiment proves that the system is feasible in analyzing the characteristics of soil around underground granaries under the action of groundwater with different compactness and water levels,and can obtain full field displacement with high accuracy,which has obvious advantages over traditional contact method.(2)Using digital image processing technology,the captured soil displacement images are analyzed to obtain the displacement time history curves of the silo in the horizontal and vertical directions,as well as the contour vector nephogram of the soil around the silo.From the vertical section,the changes in the displacement field of the soil around the silo and the displacement of the silo are studied at a micro and micro level.It can be concluded that due to the action of groundwater,under various working conditions with different initial compactness,the displacement of the silo body in the vertical direction is significantly greater than that in the horizontal direction,and the deformation amount generated during the soil movement stage is greater than the deformation amount generated during the soil saturation stage and the soil destruction stage.In the loose sandy soil sample with Dr=0.3,the soil particles around the bin can easily backfill into the void below the bin along the funnel wall,and form a circular flow around the underground grain bin,forming a local flow failure mode.In a dense sand sample with Dr=0.7,an inverted trapezoidal range is formed as the upward displacement increases.During failure,some soil particles will backfill into the surrounding of the silo,forming overall shear failure during the soil movement stage,with only a small portion being flow failure.(3)By collecting sequence images before and after soil deformation at different water levels,and drawing contour vector nephogram,the mesoscopic movement laws of soil particles around the warehouse under different water levels are systematically explored,and the most unfavorable working conditions are obtained.It can be concluded that: the change and development process of soil around the warehouse with different compactness is basically consistent when the water level is at the bottom of the warehouse or at a low level,and the soil at the upper part of the warehouse bottom is greatly affected by capillary water zones.As the water level rises,the displacement of the silo increases,the maximum displacement of the soil mass increases,and the matrix suction gradually disappears,weakening the mechanical properties of the soil mass.The range of influence of the displacement of the soil mass also extends to the distal ends of both sides of the silo.Moreover,due to the lubrication of water,the adhesion of the interface between the silo and soil is further weakened,thereby destroying the stability of the silo soil system,leading to instability and damage of the silo.(4)The flowing water action will gradually increase the pore pressure of the soil around the silo,causing changes in the mechanical parameters in the soil.The increased pore pressure will gradually affect the effective stress between particles,leading to increased interaction between soil particles,leading to changes in soil stress,leading to deformation and destruction of the soil.This thesis is closely related to the current research frontier.Through model tests of underground granaries,combined with comprehensive analysis of digital image processing technology and finite element numerical simulation results,it analyzes the development and influencing factors of the displacement field of soil around granaries,comprehensively and deeply studies the macro and micro laws of soil deformation around underground granaries under the action of groundwater,providing a reference for subsequent silo construction and optimization.