Lateral Wall Pressure Analysis And Three-dimensional Foundation Consolidation Analysis Of Large Diameter Silos

Silos are widely used in a variety of industries, such as coal, chemicals, electric power, metallurgy, building materials and food. With the development of production, the capacity and diameter of silos is becoming bigger and bigger, and the mechanical behavior of silos is becoming more complex. However, up to date, there is little research on the structural behavior, lateral wall pressure, ground deformation and failure mechanics for large-diameter silos. The current design is more referring to the present design standard for general silos, without reliable theory is built to design a large scale silo. In view of this situation, a series of studies on lateral wall pressure and ground consolidation of circular silos were carried out in this paper. This work includes three parts as below.The first part is relevant to upper bound limit analysis method of lateral pressure of large-diameter silos.1. According to the specific fracture surface of bulk materials in large-diameter silos, lateral wall pressure of deep and shallow silos was respectively analyzed used upper bound limit analysis method. Analytical expression of lateral wall pressure was obtained. The correctness of this formula was proved through numerical examples. On the basis of this, the influence of silo height and radius on the lateral wall pressure is systematically investigated. The result shows that the lateral wall pressure increases with the increase of silo radius. However, the lateral pressure doesn't increase linely with silo radius, but more and more slow increasing trend between the lateral pressure and silo radius can be shown.2. The critical ratio of height to diameter between deep and shallow silo was studied based on the upper bound limit analysis approach. The formula was obtained, and the influence of internal friction angle of bulk solid, top-surface inclination angle of bulk solid and friction angle between bulk solid and silo wall on the critical ratio was comprehensively analyzed. The result shows that the critical ratio of height to diameter increases with the decreasing of the friction angle between bulk solid and silo wall. The critical ratio also increases with the decreases of top-surface inclination angle of bulk solid. When the top-surface inclination angle of bulk solid is zero, the critical ratio decreases firstly, and then increases with the increase of the internal friction angle. When the top-surface angle of bulk solid is the natural angle of repose, the critical ratio decreases monotonically with the increase of the internal friction angle. The second part is three-dimensional finite element analysis of lateral wall pressure of silos.Elasto-plastic finite element analysis was carried out by using a large commercial software ADINA. Three-dimensional finite element models are respectively built when bulk material in silos was assumed at rest, at filling process and at discharge process. Then the lateral wall pressure under three kinds of conditions was studied. The result shows that wall pressure obtained by FEM is in good agreement with the measured value. It is feasible to study on the lateral wall pressure of silos with FEM. Lateral wall pressure of large-diameter silo at the end of filling process is not larger than the static one. At the beginning of discharge process, the lateral wall pressure increases suddenly at the intersection of the rupture surface and the silo wall. The maximum pressure at the beginning of discharge is at the silo bottom. The lateral pressure at the beginning of discharge is much larger than static lateral pressure. At the intersection of the rupture surface and the silo wall, the lateral wall pressure of discharge is2-3times to static lateral pressure. Lateral pressure at the beginning of discharge should be paid sufficient attention in silo design. In addition, the influence of material parameters on lateral wall pressure is also analyzed.The third part is three-dimensional Biot consolidation analysis of transversely isotropic saturated soil ground under axisymmetric variable loading.In general, the loading of silos on foundation is an axially symmetric and variable problem. In view of this situation, three-dimensional Biot consolidation of transversely isotropic saturated soil under round and circular load is analyzed. In the analysis process, effective stress and joint Laplace-Hankel integral transformation were used. Analytical solution of Biot consolidation was obtained. The accuracy of this analytical solution was verified by two simple examples. Then, the loading of filling and discharge process of silos is simplied to trapezoidal cyclic loading, the surface subsidence at the center at the silo base is calculated. The result shows that there is little difference on the maximum settlement induced between simplified cyclic loading and constant loading. This is because the process of the loading cycle is very long. Based on the above analysis, the process of loading and unloading is not necessary to consider in the final settlement calculation in actual project. Lastly, the influence of soil anisotropy on foundation settlement was studid. The result shows that soil anisotropy has a great impact on foundation settlement.