Filling requirements of subgrade construction

Requirements for subgrade construction fill, including filling stratification, water content control, fill width, transverse slope of subgrade surface, land requisition sideline, construction access road, subgrade fill height and other requirements.

Layered filling and layered rolling

Subgrade must be filled and rolled in layers. The maximum compaction thickness of each layer shall not exceed 20cm (the compaction mechanical energy can ensure the compaction degree, and the compaction thickness can be appropriately increased after passing the field test), and the compaction thickness of the last layer on the top surface of the road bed shall be 20cm (in case of special circumstances that do not meet the design requirements, the minimum compaction thickness shall not be less than 10cm).

Water content control

The water content should be controlled within 2% of the optimum water content for compaction.

Filling width and pin slope

Each side of subgrade filling width is 30cm wider than the design width of filling layer, the compaction width is not less than the design width, and finally the slope is nailed.

Transverse slope of subgrade surface

The subgrade surface should have an outward transverse slope of 2% ~ 4% to prevent water accumulation.

Land requisition and sideline business

When filling subgrade, in order to prevent subgrade slope from being washed by rain, it is required to set up temporary drainage dam and drainage facilities two meters away from the downhill foot of subgrade. Centralized soil borrowing is prohibited on both sides outside the land requisition line/within the range of kloc-0/0m.

Xianfeng road

It is strictly prohibited to use it as a construction access road within the scope of subgrade filling.

Uniform and dense

Subgrade filling should be uniform and dense, and the transverse slope of subgrade top surface is consistent with the transverse slope of road arch.

Height of subgrade fill

Height of subgrade fill The minimum height of subgrade fill must ensure that the stability is not affected by groundwater, surface water, capillary water and frost heaving. This project is an urban road, and the minimum filling height of subgrade design should be greater than the critical height of subgrade in wet or moderately wet state.