Before construction, the leveling points and traverse points shall be closed for measurement, and the measurement results shall be reported to the engineer for review. After confirmation, the center line survey, slope toe, cutting top and subgrade land boundary stake lofting and cross-sectional survey shall be carried out, and the outline shall be marked and reported to the supervision engineer for approval.
Second, the site cleaning and backfilling
Manually cooperate with bulldozers, loaders and dump trucks to clean up the surface rotten soil, cut down trees and shrubs, dig out roots, dismantle masonry and other masonry structures, and backfill and tamp the pits and grooves caused by the demolition construction in layers, with the compactness greater than or equal to 90%. The impacted subgrade within the construction scope shall be inspected in time, and the next step of construction can be carried out only after it is approved by the supervision engineer. Topsoil should be stored separately from other excavated materials. If topsoil is used to build embankment slopes, topsoil should be stored or scattered in places that will not pollute farmland or areas designated by the Engineer. After storage or paving, the topsoil shall be smooth and free of weeds, roots, turf and large stones. In case of soft soil subgrade, the foundation should be reinforced. When the cross slope of the ground is steeper than 1: 5, the original ground should be dug into steps and filled with soil. When the ground cross slope is steeper than 1: 2.5, special treatment should be taken to prevent the embankment from sliding along the base.
Three, filling technical requirements, material test and mechanical equipment
(1) Before subgrade filling, the following aspects shall be completed:
A, check the soil quality of users in the proposed borrow yard and subgrade excavation;
B, particle analysis, water content, compactness, liquid plastic limit, standard compaction test and CBR filling;
C, the construction of subgrade filling test section, subgrade filling test section should do the following work:
(1) Type of compaction equipment;
② the best combination mode;
③ Rolling times and rolling speed;
(4) Construction technology of construction machinery;
⑤ Loose laying thickness of each layer of material;
6. Water content of materials, etc. , and report to the supervision engineer for approval.
After the report of subgrade test section is approved by the supervision engineer, the construction can be carried out according to the results of the completed subgrade filling test section.
(2) Inspection items of earthwork subgrade
Earthwork subgrade survey project
Inspection method and frequency of specified value or allowable deviation of project inspection.
highway
First-class highway connecting line
second-class highway
1△ pressure
solid
Degree (%) zero
Excavation (m) 0~0.30 ≥96 ≥95 Density method: every 200m.
Each compacted layer shall be measured at four locations.
0.3~0.80 ≥96 ≥95
be filled/suffused/brimming with
(m) 0~0.80 ≥96 ≥95
0.80~ 1.50 ≥94 ≥94
> 1.50 ≥93 ≥92
3 longitudinal elevation (mm)+10,-15+10, -20 level: every 200m.
Measuring part 4
4 centerline deviation (mm) 50 100 total station: measure 4 points every 200m.
5 The width (mm) shall not be less than the design meter scale: 4 places shall be measured every 200m.
6 flatness (mm) 15 20 3m ruler: every 200m.
Measure 2 x10 foot.
7 Cross slope (%) 0.3 0.5 level: every 200m.
Measure 4 parts
8 slope is not steeper than the design value. Measure 4 places every 200 meters.
(3) In order to ensure the compactness of the slope, when filling the subgrade, each side should be filled with 30-50cm width, and the compaction should be strengthened. For the temporary discontinuity that cannot be constructed at the same time, when filling the newly filled road section, the excavation step method should be adopted and the rolling should be strengthened.
(4) During the earthwork filling construction of subgrade, the subgrade should be provided with 2% cross slope, and drainage should be done well to avoid the harm of water to subgrade.
(5) After inspection by the engineer, the unqualified backfill shall be reworked, repaired and reinforced according to the engineer's instructions.
(6) The main machinery for highway subgrade construction are bulldozers, scrapers, excavators and loaders. These machines will be used on site after inspection and approval by the supervision engineer.
Four, fill subgrade construction technology
Reasonable earthwork allocation and earthmoving route are very important. According to the location and topography of the borrow site, determine the economical and reasonable earth-moving route. When laying soil, the number of unloading trucks should be calculated according to the compaction thickness that the roller can achieve. Dump trucks transport the soil from the borrow yard to the paving site, and lay it in rows from one end to the left and right at equal distances.
(1) Construction procedure: cleaning, measuring and setting out of the basement → cleaning and rolling of the basement before filling → detection of the basement → layered filling of hauling earthwork → paving and leveling by bulldozer → rolling by roller → quality inspection → next construction.
(2) Surveying and setting out: firstly, set out the center line of subgrade, one at every 20m, and then tie piles at appropriate positions on both sides of subgrade. Then, according to the elevation of the top surface of each filling layer, the boundary line of each filling layer is released. The sideline is controlled by steel drill, with one pile every 20m, and a red triangulation flag must be inserted on the pile. The length of drill pipe is generally about 60cm.
(3) Virtual paving thickness: The virtual paving thickness of filler is generally controlled at 30cm. The control method of virtual paving thickness adopts side pile steel hanging line method.
(4) Elevation control: During site construction, the original elevation shall be the compaction elevation of the original ground. In general, the elevation of three layers of subgrade filling in each section is detected to verify the filling thickness of each layer. At the same time, the center line deviation is detected, so that the center line deviation can be corrected at any time during construction.
(5) Feeding quantity control: According to the virtual paving thickness, average width and length of each layer, calculate the required material consumption of each section scheme.
(6) Feeding: Dump trucks are used for packaging and transportation, and dump trucks should use the same model as far as possible. After the filler is transported to the site by the dump truck, it is unloaded according to the determined unloading distance and the number of vehicles. Organize vehicles reasonably, direct traffic, and prevent traffic jams of materials-carrying vehicles. It is forbidden to use soil materials from different borrow sites for mixed filling in the same road section.
(7) Leveling: In order to control the thickness of virtual paving, the soil on the side must be leveled. Bulldozers are used for rough leveling. In the process of leveling, the virtual laying thickness of the sideline is controlled by hanging line, and the sideline is straight and the slope is consistent, which meets the design requirements.
(8) Rolling: After the water spraying meets the requirements, use a vibratory roller for the first static compaction, the second, third and fourth vibratory compaction, and the fifth static compaction. When rolling, it should be slow first and then fast, from both sides to the middle, from low to high, with each axis overlapping 50cm, and the maximum speed should not exceed 4 km/h. When rolling, it should ensure uniformity, no pressure leakage, no dead angle and no obvious wheel tracks.