Research On Unloading And Storage Load Distribution In Frustum-shaped Silo

Grain security is always the foundation of economic development and social harmony.Silo plays an important role in grain storage.Based on the model of existing assembly-type steel silos,a large round frustum-shaped steel-Cable-Bamboo modular silo architecture is put forward.The storage load is the main load for the silo,and it is also the key point of researches on silo.The aim of this paper is to investigate in detail on the distribution of storage and emptying load in frustum-shaped silo structure.Firstly,the unloading experiments by early stage of the project group are simulated by EDEM.The simulation results are compared with the experimental results to get more accurate EDEM parameter settings.At the same time,the possibility and rationality of EDEM software simulation in silo loading and unloading are also verified.Then,frustum-shaped silos with 6 ratios of height to diameter(for shallow siloes:0.8,1.0 and2.2;for deep siloes:2.0,2.2 and2.4)and 4 dip angles(0°,3°,5°and 7°)are simulated with full storage and point-line symmetry unloading.Through the detailed comparison between the simulation results and calculation results of theoretical formula,the distribution law of the static and dynamic lateral pressure in the deep and shallow frustum-shaped silo is studied;Based on the Janssen hypothesis,the formula of lateral pressure of deep frustum-shaped silo is derived,and the relevant verification is carried out by the discrete element simulation.Finally,the standard of deep and shallow frustum-shaped siloes is put forward,verifying from formula coupling and discrete element simulation.Through these series of studies,we can reach the following conclusions:(1)The density of particle is adjusted in modeling,and the total mass of particles generated in the EDEM model is equal to the total mass of the real particles(the principle of equal mass),which can reduce the error between the simulated value and the experimental value and the theoretical value.(2)When the pressure coefficient k takes the active earth pressure coefficient(k=tan~2(45-/2)),the calculation value of lateral pressure in cylindrical deep silo is less 20%~30%than the simulated and experimental values,but it agrees well with simulated and experimental values when k takes the value of the international standardization organization specification(k=1.1(1-sin)).The calculation value of lateral pressure in frustum-shaped deep silo agrees well with the simulation value when k takes the active earth pressure coefficient.(3)Frustum-shaped silo reduces the silo capacity,but the lateral pressure is obviously smaller than the cylindrical silo.It can effectively reduce or even eliminate overpressure in the upper silo.(4)The overpressure coefficient of shallow and deep frustum-shaped silo and shallow cylindrical silo is in a"triangle distribution",that of deep cylinder is in a"spindle distribution".The overpressure coefficient of both frustum-shaped and cylindrical silo increases with the increase of the dip angles and the ratios of height to diameter.The overpressure phenomenon of line symmetry unloading is more serious than point symmetry unloading,especially away from the discharge opening,where the maximum overpressure coefficient is up to 2.75.(5)As the dip angle of frustum-shaped silo in[3°,7°],the ratio of height to diameter of deep and shallow frustum-shaped silo dividing is in(1.5,1.65).