Construction preparation work

First, carry out construction lofting, and then remove topsoil and root turf or humus. In paddy field area, embankment is built on the road land in front of the construction, vertical and horizontal drainage ditches are excavated in the embankment, and the slope of the ditch bottom is greater than 0.5%, and the drainage ditches are connected to drain the topsoil. Compaction shall be carried out before foundation filling, and the compactness of the foundation shall not be less than 85%. When the height of filled soil is less than the thickness of subgrade, the compactness of basement is not less than the standard of subgrade. When the thickness of loose layer of basement is more than 30cm, it should be backfilled and compacted by layers after excavation.

3) Slope accumulation

Before the rockfill embankment is poured, the slope should be piled up, and the stone particle size should be greater than 30cm. The piled stone should be as neat, tight and dense as possible, without obvious holes and looseness. The bearing contact surface between the blocks is slightly inclined inward. When the filling height is less than 6.0m, the stacking thickness is1.0m; ; When the height is greater than 6.0m, the stacking thickness is 2.0m, and the slope can be stacked in steps.

4) Material transportation and paving

Stone is made of uniform, unweathered and crack-free hard materials. Stone strength is not less than 15MPa, and it is transported by excavator and dump truck. When filling, try to mix the filler evenly to avoid excessive concentration of large-size filler. At the same time, arrange the stone transportation route. According to the level of stratification, first low and then high, first on both sides and then discharged in the middle. Rock-filled embankment should be piled up and paved at the same time, directly on the rough surface of paving, and paved forward with high-power bulldozer, and the loose paving thickness should be controlled within 60cm. After the bulldozer paving is initially completed, the oversized stones will be broken manually to meet the requirements of the specification.

For stones with large material diameter, leveling should be done manually, and the stones should be close to the bottom and face down. In the same position, stones with large particle size should not overlap. For the road sections with obviously less fine materials, a layer of gravel or stone chips, accounting for about 15%-20% of the large aggregate, shall be paved on the surface of the initially paved rockfill, and the gaps between the large aggregates shall be ensured. After paving fine materials, the surface will remain relatively flat, which is beneficial to rolling construction.

5) rolling

Because there is no cohesive force between granular materials in rock-filled embankment, it mainly depends on the mutual embedding and close bite between fillers to achieve enough friction to resist subgrade deformation, so a large-tonnage vibratory roller is needed. During the construction, 15t vibratory roller is used for rolling construction. When rolling, the speed is 2.0 ~ 4.0km/h and the frequency is about 30Hz. First static pressure, then vibration for 6 ~ 8 times, and finally static pressure. The rolling sequence starts from two sides to the middle, and then from the middle to both sides, and the staggered wheels are required to be 1/3 wheel width each time. For places with obvious cavities and pores, fine materials should be added and then rolled. If there are still loose stones, small stones with appropriate particle size should be embedded and rammed.

3. Quality control of rock-filled embankment

The construction quality is mainly controlled by the construction process and quality inspection. In each construction process, especially the maximum particle size, compaction thickness, compaction times, compaction settlement difference and so on. The proportion of fillers shall be strictly controlled according to the specified requirements. During construction, technicians should record the compaction thickness, compaction times and particle size of each layer of filler in detail, so that the supervisor can verify it at any time.

After the completion of each floor, it is necessary to carry out intermediate inspection, and resolutely rework the unqualified sections to ensure the quality is foolproof and leave no future trouble.

After the subgrade is completed, the deflection detection is carried out before the pavement construction, and the results fully meet the requirements of the specification. Determination of compaction standard

1) Through the test section, the quality control standard of rock-filled embankment is established. According to the temporary regulations of Party A, the degree of compaction can be detected by differential compaction settlement method or dry compaction density method. Considering the actual construction situation, the compaction settlement method is adopted for compaction degree detection.

2) detection method.

First, the compacted embankment is longitudinally distributed along the embankment with an interval of about 8.0m, and the horizontal interval depends on the site conditions. Make eye-catching marks with paint on the paved points. When measuring the elevation with a level, in order to reduce the error, prepare a 20cm×20cm steel pad on the measuring point. Then use 15t vibratory roller for rolling detection (rolling parameters: 2.0 ~ 4.0km/h, frequency 30Hz, rolling twice), and there should be no obvious wheel tracks after rolling. Then use a level to measure the elevation of each point. The height difference of each measuring point before and after rolling is the compaction settlement difference of the measuring point.

In the interim provisions of Party A, the average value of compaction settlement difference should be less than 5mm, and the standard deviation should be less than or equal to 3 mm. The detection frequency is 65438 02 points per 2000 cm2; When the compacted area is less than 200cm2, at least 4 points should be detected.

3) Test some results.

Before the construction of the rockfill embankment, the compaction test was carried out, and the 15t vibratory roller was used as the compaction machine, and the construction technology and suitable filling thickness, particle size and other parameters of the rockfill embankment were determined, which are summarized as follows.

The loose laying thickness is divided into 40cm, 60cm and 80cm, and the length of * * * is 100m. It can be clearly seen from the table that the loose coefficient of fillers varies greatly due to the heterogeneity of fillers. When the loose laying thickness is 40cm, the vibratory roller will roll it for 5 times, and the compaction settlement difference meets the requirements; When the loose laying thickness is 60cm, rolling for 6 times can also meet the requirements; At 80cm, rolling 10 times still fails to meet the requirements.

Considering the construction organization, economic benefits, construction progress, machinery utilization rate and other factors, it is decided to adopt loose paving thickness of 60cm and rolling times of not less than 8 times.

4) In rock cutting excavation, it is also important to choose reasonable blasting scheme and parameters to minimize the rock particle size after blasting. The combined blasting scheme is adopted, which is mainly based on the pot gun and supplemented by the vertical hole. For different rocks, more practical parameters are determined by trial blasting. Through the full crushing of the tank gun, the part whose particle size exceeds the particle size limit of the filler is concentrated in the excavation area for loosening and vertical blasting to reduce the particle size, so that the filler basically meets the requirements.

Answer over.