Test And Calculation Method Of Elastic Modulus And Poisson Ration For Grain Heap

A grain pile belongs to bulk materials. When it is simplified to be continuum media, andthe distribution of pressure of grain and the lateral pressure of grain and friction acting on thewall is being studied either by theoretical analysis or numerical simulation, the modulus ofelasticity and poisson’s ratio of grain pile are the indispensable and major parameters.Experimental study and theoretical analysis were combined to study how to determine themodulus of elasticity and poisson’s ratio of wheat. The main conclusions are as follows:1. The relation between axial deformation and compression time for a sample wasobtained by uniaxial compression test. Initially, the sample’s axial deformation was larger,then it tended to be stable, and the smaller the axial compressive force was, the shorter thestabling time was. The axial deformation rebounded along with the compression time, thevalue of rebound increased with the axial compressive force.2.The compression modulus of grain pile was achieved by uniaxial compression test. Thecompression modulus was varied with the axial compressive force, and it increased with theaxial compressive force. As the axial compressive force reached a certain value, while thecompression modulus decreased with the axial compressive force.3.The elastic modulus under four different confining pressure conditions were obtainedby triaxial compression test, namely, the range of elastic modulus was from337kpa to1793kpa as the applied confining pressure was50kpa; the range of elastic modulus wasfrom418kpa to5574kpa as the applied confining pressure was100kpa; the range of elasticmodulus was from578kpa to6880kpa as the applied confining pressure was150kpa; therange of elastic modulus was from1535kpa to9414kpa as the applied confining pressurewas200kpa. When the confining pressure is constant, the elastic modulus decreased with theincrease of axial stress deviation. Under the same axial stress deviation, the elastic modulusincreased with the confining pressure.4. Based on the theory of elastic mechanics, the analytic solution of sth to triaxialcompression test specimen was derived. According to the stress characteristics of compressedsample, a calculation formula of poisson’s ratio of grain was proposed on the basis ofanalytical solution. And then, according to the corresponding experimental data, using theproposed formula for poisson’s ratio to calculate the poisson’s ratio of wheat under those fourconfining pressures, and four corresponding relation curves of the poisson’s ratio versus axial pressure were plotted.5. The sample’s lateral deformation was confined due to the confining pressure, so as theconfining pressure increased, the lateral deformation decreased under the same axial pressure,and the poisson’s ratio was reduced as well. When the confining pressure was constant, thepoisson’s ratio decreased with the increase of axial pressure. After the axial pressure increasedto about1.2times as much as the confining pressure, the poisson’s ratio kept constant, andcould be regarded as a constant that is about0.2.