As an essential component of the ballast track, the ballast layer
provides functionali-ties such as drainage, load distribution, as well
as strength and stability for the rail-way track. The mechanical
behaviors of ballast track such as its permanent settle-ment, breakage,
force propagation and void ratio are in a great extent influenced by the
form distribution of ballast stones. Its reasonable design will greatly
improve the mechanical behaviors, and thus prolong the maintenance cycle
of ballast track, or reduce the number of ballast stones needed for
construction. This dissertation focuses on proposing optimized ballast
stones in the ballast aggre-gate in regard to their geometrical forms.
As the first step, a ballast random form gen-erator, which is designed
to generate ballast form databases with different form dis-tributions,
is proposed. 15 databases are created for further usage. Afterwards,
Dis-crete Element Method (DEM) based simulations are performed to
investigate the mechanical behaviors of ballast aggregates. The
simulation model is established based on a box test, whose result is
presented firstly. Establishment and calibration process of the model
are expatiated afterwards. A parameter study regarding to cru-cial
modeling parameters is also performed. Using the validated parameters
and the 15 generated form databases, DEM simulation models with
different form distribu-tions of ballast stones in the ballast aggregate
are proposed. Simulative methods to quantify the mechanical behaviors
are elaborated. Based on the obtained results, the interrelation between
mechanical behaviors of ballast aggregate and the form effect on
mechanical behavior of the ballast aggregates are studied. The optimized
ballast aggregate is proposed based on the findings stated above. The
proposed optimized ballast aggregate is expected to be a reference for
construc-tion of ballast track in real world. The modeling technic and
the calibrated modeling parameters can be used fo
