01043884

Component

This paper presents a coupled discrete element model to analyze the seepage of water through a pavement filter as an alternative to conventional seepage analysis. First, the particle size distributions for simulated subbase and subgrade of the filter system are selected to satisfy U.S. Army Corp of Engineers’ criteria. Then, the water pressure which provides an average hydraulic gradient as a multiple of the critical hydraulic gradient is applied at the bottom of the subgrade to initiate seepage. The two-dimensional discrete element code, Particle Flow Code (PFC-2D), is employed to model the soil skeletons as assemblies of discrete particles. The interstitial pore water motion is idealized using time-dependent Navier-Stokes equations. First, the flow rates obtained from the discrete element method and finite element method based on conventional analysis are compared. Then, the localized porosities, water velocities and hydraulic gradients within the pavement layers are determined under transient and steady-state seepage conditions. It is observed that the transient local hydraulic gradients and water velocities at the subgrade-subbase interface, which cannot be identified using conventional seepage analysis, are excessively large compared to both the average values across the entire filter and the corresponding values under steady state conditions. Finally, commonly used empirical relationships among permeability, porosity and grain size are also investigated using the coupled discrete element model. Since this effort involves modeling of the very properties that cause instability of pavements, it can be envisioned that the results of this preliminary investigation would shed light on issues concerning malfunction of pavement filters due to critical transient and local seepage forces.

01042056

07-2831

English

21p

2007

Transportation Research Board 86th Annual Meeting

CD-ROM

Figures (15) ; References (9) ; Tables (1)

Filters; Pavement design; Pavement distress; Pavement layers; Pavement performance; Pavements; Permeability coefficient; Seepage; Subbase (Pavements); Subgrade (Pavements); Water

Navier Stokes equations

Design; Highways; Hydraulics and Hydrology; Pavements; I22: Design of Pavements, Railways and Guideways; I23: Properties of Road Surfaces

Transportation Research Board Annual Meeting 2007 Paper #07-2831

TRIS, TRB

Feb 8 2007 7:32PM