In the design of flexible paving the following requirements must be met :- 1. The elastic deformation, or deflection, must not exceed certain specific limits. 2. The plastic deformation, or settlement, must not exceed certain specific limits. 3. The shear stresses induced in the pavement must not exceed the shear resistance of the system. The discrepancies between measured deflections and calculations based on the elastic theory are largely due to the fact that no distinction has been made in the past between elastic deformation and plastic deformation. This paper descriptionbes a method for evaluating both elastic and plastic deformation. It formulates certain theories of deformation and it introduces approximate methods for estimating both elastic and plastic deformations in multi-layered systems.
The writer is particularly interested in the results of the drilling into the decomposed Malmesbury shales, as he has recently encountered a similar problem at a bridge site in Paarl. Here too the dip of the rock is nearly vertical, and a considerable thickness of weathered material is found over the solid rock. Much of this weathered material shows the near vertical laminated structure of the parent rock.