Numerical modelling of a geosynthetically reinforced sand mass undermined by a subgrade void.
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Date
2016
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Abstract
The South African railway network is highly developed and the vast span of existing rail lines
require maintenance and upkeep to ensure smooth running of locomotives. One of the problems
faced by the rail industry is instability in the formation level due to the development of
sinkholes. Sinkholes and voids commonly form in karstic topography as a result of dolomite
related subsidence but may also result from man-made processes such as mining. Roads and
railway lines extend for hundreds of kilometres, occasionally over terrain prone to sinkhole
formation, making construction over such terrain unavoidable. In order to prevent catastrophic
failure in a railway line, the formation must be reinforced over sinkhole prone areas.
Geosynthetic reinforcement is identified as a potential means of spanning developing subgrade
voids by providing a temporary means of support in the event of a sinkhole. A laboratory model
using single and multiple layers of geosynthetic reinforcement was thus developed at the UKZN
geotechnical laboratory. Building physical models however is often expensive and time
consuming. The research contained in this dissertation explored the use of numerical modelling
in simulating the behaviour of a geosynthetically reinforced sand mass when undermined by a
subgrade void. Finite element analysis software was used to provide a numerical representation
of the physical laboratory model. Exploration into how best FEM can be used in predicting the
behaviour of a reinforced fill layer undermined by a subgrade void is thus required. The FEM
simulation should provide results within a reasonable degree of accuracy when compared to the
experimental model. Through the course of the investigation the parameters governing the
behaviour of the finite element model were identified and modified/varied in order to improve
the accuracy of the numerical results. In addition to the numerical model, an analytical
investigation in which design methods for reinforcement are used to predict the behaviour of a
reinforced fill layer took place.
Description
Master of Science in Engineering. University of KwaZulu-Natal, Durban 2016.
Keywords
Railway engineering., Sinkholes., Geotechnical engineering., Numerical modelling., Geosynthetic fabric.