PLANNING OF ROAD PROJECTS-EARTHWORKS-WEST GERMANY

A successful program is described which provides the optimization of road gradients against a number of criteria. The optimization of the ground plan of the road and graphical data processing are in development. A few non-linear digital terrain models have been developed which provide for use in the computer the digital description of the relevant terrain surfaces with good accuracy, starting from limited initial data. In the field of geotechnical preliminary investigations, guide rules have been worked out which define the extent of the investigations and the grouping of the results. The testing of refraction-seismology shows good correlation between the dynamic rigidity modulus calculated from the wave velocity, and the modulus of compressibility measured by means of the oedometer. The discussion on earthworks covers such aspects as physical investigations, compaction' properties, optimum degree of saturation and water content, deformation properties, and the practical application of the results. The relationship is described between the grain size characteristic and the resistance to deformation characterized by the CBR value of continuously and discontinuously graded gravel and sand mixtures. The compaction and deformation properties of mixed soils consisting of sand, gravel, stones and cohesive components such as silt and clay depend to a very great extent on the water content of the cohesive component and particle grading. The effect on the design of the superstructure of the stabilization of the top course is discussed. Control tests with nuclear gauges in the execution of earthworks is reviewed. The effect of thermal insulation in the protection against the effects of rain and frost is also reported.