Experimental study on side pressure of grain silo under storage and discharging state

Abstract: Pressure especially dynamic pressure on the silo wall is crucial for the silo design, and it is difficult and intractable to study and discuss the pressures on the silo wall during discharging. In order to study the static pressure in the state of grain storage and the dynamic pressure under the state of central discharging, the model silo with a diameter of 400 mm and height of 700 mm which based on a reinforced concrete silo was made by aluminum. Taking the wheat as the storage material, the pressure tests of static storage and central discharging were carried out under the conditions of 100%, 80% and 50% volume of silo respectively, and the measured results of pressure were compared with the calculation results of relevant standards of China, Europe and the United States The experiments results of the static side pressure showed that the deviations rate between the measured value of the static side pressure of the model silo with the calculated value of China stangards were the smallest, while it was biggest compared with the United States standard. The three measured values of the static side pressure were more than the calculated values of China's standard, that was 600 mm away from the top surface of the storage under 100% of silo volume, 160 mm away from the top surface of the storage under 80% of silo volume and 250 mm away from the top surface of the storage under 50% of silo volume, but the measured values were less than the calculated values after security correction. The measured values of static side pressure of the model silo were all less than those of European and the United States standards, the European and the United States standards were more security than China's, the China's standard safety margin should to be adjusted. The test results of the dynamic side pressure of the silo wall showed that the dynamic side pressure of the same measuring points were different when the top of storage was in the whole flow state for the different initial silo volume when the storage was discharged to the same height, The dynamic side pressure of C1 (100 cm from the lower edge of sido wall) was 3.376 kPa when the 100% silo volume was discharged to 50% silo volume, and it was 1.528 kPa when the 80% silo volume was discharged to 50% silo volume. The phenomenon of overpressure occurred in the process of wheat from mass flow to tubular flow. The maximum overpressure coefficients of the 100%, 80% and 50% silo volume were 2.76, 2.90 and 2.68. The positions of occurring tubular flow gradually decreased at 100%, 80% and 50% silo volumes, it indicated that the location of tubular flow was related to the initial storage volume, the smaller the initial storage volume, the lower the location of tubular flow occurred on the top surface of storage. When discharging at the same port, the slope of the curve of grain height with time was about 16.1, i.e. the rate of grain unloading was the same, and the peak time of dynamic side pressure at the lower measuring points was later than that of the upper measuring points The study could provide a basis for the compilation and revision of silo standard and a reference for the design of grain silo.