(1) Construction method. A graded gravel transition section is provided at the connection between the embankment and the hard rock cutting. Within 20m of the transition section, the surface layer of the subgrade bed shall be filled with gravel mixed with 5% cement, and the lower surface layer of the subgrade bed shall be filled with cement-stabilized graded gravel (mixed with 5% cement, layer thickness 0.15cm) in layers. A filler transition section is provided at the connection between the embankment and soft rock, strongly weathered hard rock and soil cuttings. The transition section adopts horizontal excavation steps, and the backfill is set with the same filling material as the embankment. The step height of the transition section between the embankment and the cutting is 0.6m, and a horizontal drainage blind pipe is set at the top of the step. The transverse transition section is shown in Figure 3.

When constructing half-filled, half-excavated roadbed and roadbed with different rock and soil combinations, the following methods should be followed: ① The cutting earthwork construction is mainly carried out by mechanical excavation, and manual excavation according to the design requirements Steps at the connection; ② The road cutting and ballast disposal are constructed using excavators and dump trucks. The embankment is filled in layers using loaders and dump trucks to transport the filler. Bulldozers are used for paving. Manual work with graders is used for fine leveling and vibration compaction. ③ Embankment The cutting drainage and protection project follows the filling operation, and artificial hanging wires are used to ensure that the roadbed bed is not washed away by rainwater.

(2) Construction technology. Manual excavation and slope shaping are carried out manually with machinery, and temporary drainage ditches are built at any time according to the excavation height of the road cutting. The subgrade bed is cleaned, shaped and rolled to the design requirements, and then the connecting steps are manually excavated. The subgrade bed is filled and rolled in layers, and each layer is filled with a 4% cross slope as required. After the filling is completed, the surface layer of the subgrade bed is constructed, followed by the subgrade filling, masonry protection and drainage engineering.

(3) Construction points. When the bottom of the excavation and replacement foundation soil is a soil roadbed, impact compaction should be carried out. When the bottom layer is weak, stability and deformation analysis should be carried out. The bottom of the excavation and replacement foundation soil should be provided with a 4% transverse drainage slope tilting outward; steps. The joints are rolled longitudinally along the steps, and small vibrators are used for construction where large machines are inconvenient.

(4) Precautions. Subgrade drainage and protection should be carried out closely following subgrade filling to prevent rainwater erosion; during the layered filling process, subgrade cross slopes should be made according to design requirements to facilitate surface drainage; road cutting protection should be carried out closely following road cutting excavation.

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