Contact stiffness parameters of soil particles model for discrete element modeling using static packing pressure test

摘要

Compression test is the dominating experimental procedure used for determining the strength and stress-strain properties of soils and other granular materials. Static Packing Pressure Test was conducted in order to calibrate the stiffness ratio which is normal contact (kn) and shear contact (ks) stiffness of soil particles model. These micro-behaviors are important parameters in any numerical modeling with regards to soil model using Discrete Element Modeling (DEM). However, for this study, the apparatus used is Static Packing Pressure Test as alternative experimental tool to replace the Biaxial Test. Three different mean size distributions of silica sands were used as soil media, which are D_(50)=1.357mm, D_(50)=0.571mm and D_(50)=0.286mm. Meanwhile, the DEM software used is Particles Flow Code 2-Dimensional (PFC 2D) in order to model the Static Packing Pressure Test. For experimental test, sand samples were poured into mould size of 23 cm in height X 10 cm of diameter. Then, the plunger was located in the mould and compressed until the movement of vertical displacement stopped. The load and displacement were recorded in the data lodger. The elastic modulus (E_e) of sample can be determined from stress strain plot. The elastic modulus (E_e) is necessary in order to obtain the stiffness of the soil particles model. The determinations of contact stiffness initially are based on the interpolation of assumed contact stiffness with the identified elastic modulus from experimental test. By using PFC 2D, the hundreds disks were modeled as discrete, which represent the soil particles. It has been proved that the contact stiffness of soil particles were successfully identified using the Static Packing Pressure Test.