ABSTRACT
The degradation of ballast is one of the major substructure problems which leads to increased track settlement, increased ballast fouling and reduced drainage. There are several factors affecting ballast deformation and particle breakage, as discussed earlier in Chapter 3. Ballast gradation is a prime factor for the stability, safety and drainage of tracks. A specified ballast gradation must provide the following two key objectives:
• Ballast must have high shear strength to provide increased stability and minimal track deformation. This can be achieved by specifying broadly-graded (wellgraded) ballast.
