Development Of Grain Temperature-controlled Direct Shear Apparatus And The Dynamic Characteristics Of Wheat-concrete Silo Wall Interface

Grain supply chain is a security chain related to the livelihood of our country.Grain storage security is an indispensable key link in the grain supply chain,and grain storage security in granary is the basic guarantee to effectively guarantee grain storage security.Studying the interaction mechanism between grain and the wall of grain storage is an important part of the structural design and optimization of grain storage.In this paper,the grain temperature controlled static and dynamic direct shear apparatus was improved,and the monotonic shear test,cyclic shear test and single shear test after cyclic shear test of wheat concrete silo wall interface were carried out considering the effects of different temperature,normal stress,void ratio and cyclic shear displacement.To simulate the static and dynamic interaction between wheat and concrete granary wall in the actual grain storage process,the static and dynamic parameters under different grain storage conditions were tested,so as to provide basic test data reference for structural safety design and dynamic analysis of concrete granary.The main contents of this paper are as follows:(1)In order to simulate the grain storage state under different temperature conditions and study the influence of temperature difference on the static and dynamic shear characteristics of wheat-concrete interface,based on the existing grain dynamic direct shear apparatus,a temperature control system was added and a grain temperature controlled static and dynamic direct shear apparatus was developed to realize the temperature control of the shear interface.The performance of the instrument is verified by comparing with the existing test results.(2)The monotonic and cyclic shear tests of wheat-concrete interface under the same normal stress and void ratio at 20℃,35℃ and 50℃ were carried out by using the grain temperature controlled static and dynamic direct shear apparatus to explore the influence of temperature change on the interface shear stress and normal displacement,and analyze the static and dynamic shear characteristics of the interface.The results show that the dynamic modulus and the mean shear strength of wheat-concrete interface increase with the change of temperature.(3)A series of monotonic shear tests under different normal stress and void ratio were carried out to study the static shear strength and deformation characteristics of wheat-concrete interface.The test results show that: under the same void ratio,the higher the normal stress,the higher the shear strength,the more obvious the shear stress softening and shrinkage;under the same normal stress,with the increase of void ratio,the lower the shear strength,the more obvious the shear shrinkage,the greater the internal friction angle and cohesion under the peak and residual.(4)A series of cyclic shear tests were carried out considering the effects of normal stress,void ratio and cyclic shear displacement amplitude.The test results show that: under the same void ratio,the increase of normal stress and cyclic shear displacement amplitude will lead to the increase of cyclic shear strength and vertical displacement reduction of wheat-concrete interface;under the same normal stress,the higher void ratio,the smaller cyclic shear strength and the greater normal displacement reduction.(5)The single shear test after cycle is carried out based on the cyclic shear test,and compared with the monotone shear test.The results show that the development law of shear stress is similar to that of monotone shear,but the shear stress,internal friction angle and cohesion are improved.The normal displacement of single shear test is different from monotone shear.After the cycle,the interface of wheat-concrete only shows slight shrinkage,even shows small expansion under some normal stress and void ratio.