Experimental Study On Static And Dynamic Direct Shear Properties Of Soybean And Soybean-steel Granary Interface

Food security reserve is not only related to military supplies and civil food,but also closely related to national security and social stability.As a functional structure for grain storage,granary is the most basic guarantee for grain storage safety.The mechanical characteristics of the grain stored in granary,the grain and the granary interface are the key parameters for the granary structural design.In the process of storage,grain is not only affected by static load,but also by dynamic load such as earthquake,loading and unloading,vibration,etc.The interaction between grain and granary will occur,which will affect its static and dynamic characteristics.Soybean is not only one of the important food crops in China,but also an important economic crop for extracting edible oil.Based on soybean in granary as the research object,this paper uses the grain dynamic direct shear apparatus to carry out the static and dynamic direct shear test of soybean and soybean-steel granary interface,in order to study the influence of different factors on the static and dynamic shear properties of soybean and soybean-steel granary interface.The specific contents are as follows:(1)Carrying out the soybean monotonic direct shear test by a grain dynamic direct shear apparatus,the effects of different vertical stress and porosity on the strength and body deformation characteristics of soybean were studied.It is commended that the smaller vertical pressure,the smaller shearing strength,bigger dilatancy angle and more obvious dilatancy under the same porosity of soybean sample.It is also concluded that the smaller porosity,the bigger shearing strength,internal friction angle,dilatancy angle at the same vertical pressure.(2)Cyclic direct shear test of soybean and post-cycle monotonic direct shear test were carried out to discuss the effect of different shear amplitude,vertical stress and porosity on soybean strength characteristics,body deformation characteristics,shear stiffness and damping ratio during cyclic shearing process,involving the comparative analysis of the test results of monotone direct shear and monotone direct shear after cycling.The results show that the curves of shear stress and shear displacement of soybean expand from inside tooutside under different influence factors,and shear hardening occurs.In a single cycle,with the alternation of shear shrinkage and shear expansion,the bulk deformation shows shear shrinkage as a whole;at the same cycle number,the shear stiffness and damping ratio increase with the increase of the shear amplitude,and the increase of vertical stress causes the shear stiffness to increase and the damping ratio to decrease,the shear stiffness and damping ratio increase with the decrease of porosity;after cyclic shear,the internal friction angle of the same porosity increases compared with the monotonic direct shear test.(3)Through the monotonic direct shear test of soybean-steel granary interface,the strength and volume deformation characteristics of the interface under different vertical stress and porosity were studied.The test results show that under the same porosity,the larger the vertical stress is,the larger the shear strength is,the less the softening phenomenon of the strength curve is,and the larger the volume shear shrinkage is;under the same vertical stress,the smaller the porosity is,the larger the shear strength is,the more obvious the softening phenomenon is,and the larger the friction coefficient is,the smaller the volume shear shrinkage is.(4)By the cyclic direct shear test and the post-cycle monotonic direct shear test of soybean steel interface,the influence of different vertical stress and porosity on the strength and volume change characteristics of the interface in the cyclic process was studied,including the comparison between the post-cycle monotonic direct shear test results and monotonic direct shear test results.The results show that under different vertical stress and porosity,the interface shear stress-shear displacement curve shrinks from the outside to the inside,resulting in shear softening.The soybean in the upper shear box shows shear shrinkage as a whole.After cyclic shear,the interface shear strength under different influence factors is lower than that of the monotonic direct shear test,and the shear shrinkage is stronger than that of the monotonic direct shear test.