20 research outputs found
Numerical Unsaturated Flow Model of Railway Drainage Systems
Substandard drainage assets are considered to be a major cause of flooding, earthwork failures, and deficient track geometry. Considering the deterioration of track materials due to cyclic loads and tamping forces, the impact of more frequent extreme rainfall events is likely to lead towards higher rates of hydraulic overloads in the drainage system, earthwork failures, and service disruptions. Therefore, the development of a numerical model could be able to describe the ageing track bed materials and provide an alternative tool for the simulation of the flow through the porous media used in the construction of railway tracks. In this paper the model HYDRUS is tested to simulate the drainage of trackbed materials under laboratory controlled conditions prior its application on actual railway drainage case studies
A Bayesian assessment of an approximate model for unconfined water flow in sloping layered porous media
The prediction of water table height in unconfined layered porous media is a difficult modelling problem that typically requires numerical simulation. This paper proposes an analytical model to approximate the exact solution based on a steady-state Dupuit–Forchheimer analysis. The key contribution in relation to a similar model in the literature relies in the ability of the proposed model to consider more than two layers with different thicknesses and slopes, so that the existing model becomes a special case of the proposed model herein. In addition, a model assessment methodology based on the Bayesian inverse problem is proposed to efficiently identify the values of the physical parameters for which the proposed model is accurate when compared against a reference model given by MODFLOW-NWT, the open-source finite-difference code by the U.S. Geological Survey. Based on numerical results for a representative case study, the ratio of vertical recharge rate to hydraulic conductivity emerges as a key parameter in terms of model accuracy so that, when appropriately bounded, both the proposed model and MODFLOW-NWT provide almost identical results
Dupuit-Forchheimer Analyses of Steady-State Water-Table Heights due to Accretion in Drained Lands Overlying Undulating Sloping Impermeable Beds
Long Term Efficiency Analysis of Infiltration Trenches Subjected to Clogging
In recent years, limitations linked to traditional urban drainage
schemes have been pointed out and new approaches were developed introducing
more natural methods for retaining and/or disposing of stormwater. Such
practices include infiltration and storage tanks in order to reduce the peak flow
and retain part of the polluting components. The impact of such practices on
stormwater quantity and quality is not easily assessable because of the complexity of physical and chemical processes involved. In such cases, integrated
urban drainage models may play a relevant role providing tools for long term
analysis. In this study, the effect of the clogging phenomenon has been assessed
by means of a simplified conceptual modelling approach developed in previous
studies has been employed and different soils as well as different design criteria
have been considered. On the basis of a long-term simulation of 6 years rain
data, the performance as well as the effectiveness of an infiltration trench
measure are assessed. The study confirmed the important role played by the
clogging phenomenon on such infiltration structures