The green part at the bottom of the picture is the depth range of the roadbed; the red line is the excavation line; the yellow circle in the side ditch is masonry or bricks; when calculating the excavation area, it is calculated in red, and It doesn't count as yellow.

Based on the horizontal and vertical section design of the route, as well as super-height and widening calculations, the lateral dimensions and design elevations of each part of the road width can be obtained, thereby determining the filling and excavation of the roadbed cross-section, and then based on the geology and hydrology Other conditions will determine the shape and size of the parts outside the road width. Due to the differences in topography, geology, hydrology, filling and excavation, etc., the cross-section of the roadbed shows various forms.

As the expressway extends from flat areas to mountainous areas, the selection and design of roadbed section forms, which are mostly laid out on steep slopes on one side of the mountain and in vertical and horizontal valley areas, have added new content and connotations.

Extended information:

Using the advantage of the highway central separation zone to divide the road bed into two sections, up and down, with unified and coordinated horizontal and vertical linear shapes and fixed spacing distances, one section A bridge is used, and the other is a combination of half-fill and half-excavation, or fill, or excavation. It is a "combination" idea.

The half-side bridge roadbed has the advantages of small land occupation, small mountain excavation, low project investment, relatively independent and coordinated upstream and downstream connections, and close horizontal connections. It is widely used in mountainous highways and expansion and construction. Highway reconstruction projects, especially those with steep cross-slope terrain. The survey and design should pay attention to the coordination between the two, the connection between the two ends, and the treatment of interception and drainage.

The light anchor retaining wall roadbed is a steep road section on a mountain slope. In order to reduce the excavation surface or disturbance range of the foundation of the half-filled and half-excavated retaining project, the anchor principle is used to expand the stress surface of the structural base. Reducing the number of roadbed projects is a "walking on stilts" approach.

Lightweight retaining wall roadbed has the characteristics of small excavation area, simple construction, low project investment, easy control of backfill quality, and project safety. It is especially suitable for areas with good bedrock integrity and steep slopes. Half fill, half dig.

Baidu Encyclopedia--Roadbed Cross Section