Influences of the ground conveying corridors on the pressure of the wall and corridor in squat silos

Abstract: In order to facilitate later maintenance, the underground conveying corridor is moved up to the inside of the squat silo. This process reform is bound to have an impact on the pressure distribution of the wall and corridor. In this study, the loading and discharge experiments of the reduced-scale silo models with different aspect ratios and eccentricity ratios were carried out. Three kinds of PMMA cylinders with different heights were used to simulate the wall. The outer diameter of the cylinder is 1 000 mm, the wall thickness is 10 mm, and the height is 392 mm, 642 mm, and 892 mm, respectively. Three different lengths of ground conveying corridors are made of 10 mm thick steel plate, which are one main corridor and two secondary corridors. The strip eccentricity of the main corridor is zero, and that of the two secondary corridors is 300 mm. In order to consider the influence of eccentricity ratios, five discharge openings are set on the top wall of the main corridor to simulate central and eccentric discharge. In order to explore the influence of aspect ratios, three silos with different aspect ratios (0.44, 0.69, 0.95) are used. The cylinder and the corridors are placed on the steel support. A total of three main and secondary corridors were placed in the silo model, and the manual loading mode was adopted. All the openings on the top wall of the corridors were blocked first, and then the stored material was loaded from the top of the model. When the stored material in the full state of the model was completely stable, the pressure data were recorded by the test system. The results of the loading tests showed that the lateral pressure at the bottom of the silo wall was affected by the corridors. The lateral pressure of the wall in the corridor height range is significantly smaller than the predicted value of the silo standard. The whole discharge process can be summed up as a process of continuous undercutting of the inverted cone, and the vertex of the inverted cone is always located directly above the discharge opening. The phenomenon that the overpressure coefficient increases with the eccentricity of discharge was not observed. The overpressure coefficients of the wall and corridor were generally small when the aspect ratio was below 0.69, and the overpressure coefficients of the wall and corridor increases rapidly when the aspect ratio was close to 1.0. If the conveying corridor was determined as a deep buried corridor according to the standard GB 50077-2017, the predicted value of corridor pressure was obviously less than the test value. It was more reasonable to calculate the static pressure on the top and side wall of the main and secondary corridors according to the shallow buried formula proposed in this study, in which the storage height should be taken as the actual storage height of the corridor. It is suggested that the coefficient of overpressure on the top and side wall of the corridor should be considered properly in the design of squat silos, which can be 1.2-1.3.