Investigation of movement of rain water in railway track ballast and subballast layers

Ahmadkhani, Sina (2021). Investigation of movement of rain water in railway track ballast and subballast layers. University of Birmingham. Ph.D.

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Abstract

Railway track system of a country plays a vital role in providing a suitable transportation. Railway track drainage has a considerable impact on the efficiency of tracks in terms of stability and response of the components to passing trains loads. A good track drainage system identifies the entire sources of water adjacent to track structure and resulted from precipitation and delivers an appropriate method for removing them as swiftly as possible.

The necessity of adequate drainage system underneath the rail tracks, track drainage principles along with the design procedures are summarised in the literature. Ballast fouling is identified, and different sources of fouling are investigated.

A study is undertaken to assess the effect of fouling on ballast permeability and drainage characteristics of this layer. The fouling materials corresponded different sources of ballast fouling. The fouling agents are considered as crushed ballast, sand and kaolin.

Hydraulic flume test is conducted in order to investigate the effect of different sections and rainfall characteristics on water level and discharge out of ballast and subballast subsequently. The mentioned variables recognised as rainfall intensity, rainfall duration, subgrade slope, and ballast fouling index or hydraulic conductivity.

The presented research evaluates findings of a laboratory-based hydraulic flume test. A numerical model based on multi-variable linear regression is developed in order to estimate the experimental data for water level and discharge out of ballast. The conducted study highlights the impact of section slope on the rate of the flow out of ballast and subballast and the remaining gravitational water. The model is used for developing a non-linear relationship between the rainfall duration and the initial ballast discharge values collected during the rainfall event.

The proposed numerical model has specific application regarding prediction of the water level and system discharge as well as evaluation of ground water conditions underneath the tracks. Therefore, it can be used in the designing procedure of drainage systems in an area where average rainfall characteristics, rainfall return-period and proposed subgrade slope can be estimated.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):