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Paper 107

Influence of Microscopic Factors on Lateral Earth Pressure using the Discrete Element Approach

M.-C. Weng and C.-C. Cheng
Department of Civil and Environmental Engineering, National University of Kaohsiung, Taiwan

Keywords: discrete element method, particle mechanics, PFC2D, lateral earth pressure.

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In designing geotechnical structures such as retaining walls and structure foundations, the earth pressure is an important design parameter. Conventionally, the soil is idealized as a continuum to estimate the earth pressure. However, it should be pointed out that soils may not be described as a continuum. Like sands or gravels, they exhibit granular characteristics and have the property of particle separation. Therefore, it is of key interest to investigate the influence of inter-particle interactions on the development of earth pressure from the viewpoint of particle mechanics.

This study adopts the discrete element method (DEM) to explore the key influencing factors on the variations of lateral earth pressure, including packing type, interior friction angle, particle stiffness and particle size. The reference parameters for the DEM model were retrieved from direct shear tests of a rod assembly. Based on the reference parameters, the evolution of lateral earth pressure is further simulated, and a parametric study was conducted. The results showed that:

  1. The greater interior friction angle led to a lower active coefficientand increased the passive coefficient. These tendencies agreed with that of the conventional limit equilibrium theory, but the values of the two analysis methods exhibited significant differences.
  2. Increasing inter-particle stiffness decreased the active coefficient and increased the passive coefficient. The larger particle size led to the higher active coefficient and the lower passive coefficient.
  3. When the assembly was arranged in order, such as dense packing, it exhibited much larger lateral pressure than for the random packing.
The packing type, particle stiffness and particle size are not considered in the conventional limit equilibrium theory. The DEM analysis in this study has shown that these factors indeed affect the evolution of lateral earth pressure.