1, drainage:
Before construction, we should carefully understand the terrain and hydrogeological conditions. For surface water and groundwater that may endanger the strength and stability of subgrade, effective temporary or permanent measures should be taken to discharge water from subgrade quickly. The surface of the road bed should be kept in a good drainage state; The transition ditch must be built from cutting to embankment, and shall not be blocked; Each layer of fill should have road arch, so that there is no water on the surface; After construction, all kinds of ditches, pipes, wells and culverts can form a complete and effective drainage system.
2. Embankment:
(l) Original ground treatment: In areas with poor hydrogeological conditions and wet and soft soil, gravel with a thickness of not less than 30cm can be laid on the surface, or local excavation and replacement treatment can be carried out.
When the height of the embankment is less than 20cm (including the excavation part), loosen the soil by 30 ~ 50 cm and compact it in layers, with the compaction degree of 93% ~ 95%. Expressway and the first-class highway take the upper limit, and other highways take the lower limit.
(2) Filler: soil with good water stability should be selected to fill the subgrade; Coarse-grained soil with good water stability and frost resistance should be selected for the upper part of subgrade affected by freezing injury; It is forbidden to fill each layer of embankment with frozen soil, impervious over-wet soil and humus soil; The water content during compaction should be controlled within 2% of the optimal water content.
(3) Earth borrow yard: centralized earth borrow yard should be set up, especially in areas with difficult drainage.
(4) Rolling: Before the surface of each layer is rolled, the road arch shall be leveled and trimmed with a grader to effectively control the loose laying thickness and the uniformity of the filler. After compaction, measure the smoothness of each layer surface with a three-meter ruler, and the gap height shall not be greater than 20mm；; Check the strength of the top surface of the formed bed according to regulations or check whether there is "soft elasticity" by rolling with a roller of not less than 20t.
(5) Embankment height: Subgrade should be dry or moderately wet all the year round; When repairing low embankment, corresponding technical measures should be taken according to the specific situation.
(6) In order to make the strength and stability of subgrade meet the design requirements, various prevention methods of freeze-thaw and frost boiling can be comprehensively selected during construction.
3. Cutting:
(1) Qualified stone slag shall be selected for the overbreak backfill part of the stone section, and the compaction degree shall not be less than 95%; It is forbidden to use inferior cutting materials or cover soil for backfilling or leveling; When the overbreak part is irregular or less than 8cm, it can be repaired and leveled with concrete; The leveling layer should be made of semi-rigid materials such as graded macadam, cement stabilized macadam and lime-fly ash stabilized macadam.
(2) If the subgrade compaction degree of soil cuttings or weathered argillaceous shale which disintegrates and softens when meeting water does not meet the provisions of Article 7.5. 1, loosen the soil and compact it, or according to the soil conditions, fill in good soil with sufficient thickness to meet the requirements of subgrade strength and compaction, and then strengthen drainage measures, such as shoulder sealing and mortar ditch.
(3) For areas with fissure water, interlayer water, diving and spring caves, measures such as cutting, cutting and lowering should be taken respectively according to the provisions of Chapter 8, such as deepening side ditches, setting seepage ditches, seepage pipes and seepage wells.
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