2. Innovative contributions of the GTR guide

2.1 Material classification

For reference purposes, we list below the main improvements made by the GTR compared with the former RTR recommendation of 1976:

• the clear distinction between loose soil and rocky terrain;

• extension and clarification of the classification of category F materials: organic soils and industrial by-products;

• taking into account the nature of the matrix (the fine clay or sand fraction) of coarse soils;

• the use of new, more significant parameters (see definitions in ) to assess the suitability...