Simulations of air and water flow in a model dike during overflow experiments

Abstract

Flow in flood dikes, earth dams, and embankments occurs in variably saturated conditions, with pores of the earth material filled partly with water and partly with air. In routine engineering analysis, the influence of pore air is neglected and the air pressure is assumed equal to atmospheric. In some circumstances, for example, during overtopping of the dike by water, the effect of pore air on water flow and stability of the structure can be important. These features cannot be captured with the commonly used Richards equation. In this paper, we analyze earlier experiments on the overtopping of a model dike made of fine sand. During the experiments, a significant amount of air was trapped near the outer slope of the dike, which later escaped through a fracture formed in wet sand. The observations were compared with numerical simulations using the Richards equation and the two-phase immiscible flow model. The deformation and damage of the dike were not modelled, but the initial evolution of the entrapped air pressure (before damage occurred) was in a good agreement with two-phase flow simulations.

Estimation of the Critical Infiltration Rate for Air Compression During Infiltration

“…In field studies it has been observed that during the periods of intense rainfall, compressed air may break up through the soil surface, thereby leading to excessive runoff and soil erosion (e.g., Banerjee et al, 2010;Navarro et al, 2008;Weeks, 2002). Despite these practical concerns, when handling infiltration problems air pressure is usually assumed to be at equilibrium with atmospheric pressure (e.g., Grismer et al, 1994;Tisler et al, 2019).…”