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After the construction of the cement mixing pile pile cap is completed and the soil backfill between the piles is completed, the gravel cushion is filled in the upper part, the thickness of the cushion is 50cm, and it is filled and compacted in two layers, each layer is 25cm, and a layer of two-way geogrid is laid in the middle of the cushion, and the slope slope ratio is 1:1.5.

The crushed stone for the cushion should be made of unweathered clean gravel or rolled gravel, with good gradation, and no plant residues, garbage and other debris.

Lay a geogrid in the cushion, first lay a layer of 0.25m thick gravel cushion, roll compact, lay a layer of geogrid, fold back 2.0m at both ends, and then lay 0.25m thick gravel cushion, rolling compacted (K30≥110MPa/m. After the construction of the upper part of the fill.

Before the geogrid is laid, a white line is drawn on the paving layer according to the width, and then the end of the grid is fixed with U-shaped iron nails. After fixing the ends, use the paver to slowly pull the grille forward. Each 10-metre-long shop is manually tightened and straightened once until one roll of grating is laid, and then the next roll is laid. After laying a roll, roll it over with a roller. The lap between the grille and the grille is 10~15cm.

6.3.2 Construction technology and requirements

Packing requirements

The filler below the embankment bed is filled with group A, B, and C fillers or improved soil, and the thickness of each layer of filler is not more than 300mm after compaction. The thickness of the compacted layer that fills to the last layer of the top surface of the roadbed is not less than 100mm, and the filling section is paved and smoothed with a bulldozer or grader according to the grid distribution, so that the filling layer is smooth and uniform in the longitudinal and transverse directions, so as to ensure that the surface of the roller roller can be basically evenly touched with the layer for compaction, so as to achieve the best rolling effect.

The surface layer of the positive line base bed is a group A filler, and the maximum particle size of the filler is required to be no more than 15cm; The bottom layer of the foundation bed is group A and group B filler, and soil improvement or reinforcement measures are taken for the filler that does not meet the requirements, and the maximum particle size is not more than 20cm, or 2/3 of the paving thickness. The basic body of the road is gravel, gravel and block stone in group A and group B filler and group C filler, and the maximum particle size is not more than 30cm. or 2/3 of the paving thickness;

The surface layer of the station line bed is a and B group of fillers, and the maximum particle size of the filler is not more than 15cm, and soil improvement or reinforcement measures are taken for the fillers that do not meet the requirements; The bottom layer of the foundation bed is group A, group B, group C packing (plasticity index shall not be greater than 12. The liquid limit shall not be greater than 32%), and soil improvement or reinforcement measures shall be taken for fillers that do not meet the requirements, and the maximum particle size shall not be greater than 20cm, or 2/3 of the paving thickness. The basic body of the road is group A, group B filler and gravel, gravel and block stone in group C filler. The maximum particle size is not more than 30cm, or 2/3 of the paving thickness;

Basic construction principles

After the surface has been treated in accordance with the design and relevant specifications. First of all, the construction of the test section is carried out, after obtaining the construction parameters, the construction is carried out in strict accordance with the principle of "from low to high, longitudinal segmentation, and horizontal layering" in accordance with the filling, and the embankment below the foundation bed is strictly organized in accordance with the "three stages, four sections, and eight processes".

Filling method

The roadbed is excavated by excavator, loaded by loader with excavator, transported by dump truck, paved by bulldozer and initially leveled, grader finely leveled, and vibrating roller rolled. Slope trimming by hand.

Construction process

1) Layered filling

The embankment filling adopts the full width of the cross section and the longitudinal segmentation for layered filling. In order to ensure the compaction of the subgrade, the thickness of the loose paving must be controlled by 90% of the thickness of the subgrade fill in the test section, and the thickness of each layer of loose paving is not more than 30cm, and the thickness of each layer is about 25cm after compaction. During construction, a ruler rod is erected at the shoulder position to control the paving thickness, and each layer of filling is in place once according to the thickness of the loose paving, and the unloading is commanded by a special person. If the ground has a slope, start from a low place to carry out layered filling, layered filling, the ground cross slope is steeper than 1:10 on the slope must dig steps, digging steps need to be carried out from top to bottom. The width of the longitudinal steps along the line is not less than 2m, and it is leveled and rolled. Which design to choose, is to change the environment, illegally cross the Dadu River, the economy is more profound, and the feeling is affirmative, the telephone exchange, hahahaha, the division and merger, the urgency, the urgency, the ancient times

2) Paving leveling

At the same time as unloading the soil in the filling section, the grader is used to level it, and attention should be paid to the road crown that is set up in each layer according to the requirements. After the bulldozer has completed the bulldozing of a section. The scraper is used for leveling, and the pit is filled with manual cooperation to ensure the quality of compaction. The subgrade slope with a fill height of more than 6m and less than 15m is filled every 0.6m from the surface to the surface of the foundation bed, and a layer of three-way soil is laid in accordance with the requirements of the drawings within the horizontal range of the embankment slope

Before the filler is rolled, the water content is tested and controlled within the allowable water content of the construction. Then crush. When the moisture content of the filler is low, take sprinkling measures, and in winter, it must be sprinkled at noon when the temperature is relatively high, and it is strictly forbidden to sprinkle when the temperature is low. When the water content is too large, the method of digging and drying in the soil extraction site can be adopted to reduce the water content.

4) Rolling and tamping

According to the layered construction drawings and different filler conditions, select the appropriate rolling machinery, and the heavy-duty vibrating roller is used for the filling compaction operation, and the excitation force of the roller is 25~50t. The rolling sequence is from both sides to the middle of the forward and backward rolling, the curve section is first inside and then outside, the transverse joints overlap more than 0.5m or about one-third of the wheel width, and the front and rear adjacent sections overlap more than 1m.

According to the type of filler, the thickness of the filler and the standard of compactness, the number of compaction times obtained in the test section is controlled. First static pressure 2 times, then vibration pressure, in general, the number of vibration compaction times: 6~8 times for the surface layer of the roadbed, 5~6 times for the bottom layer of the roadbed, and 4~5 times for the basic body of the road. For compaction near the slope, the shoulder is preliminarily compacted by a bulldozer to the shoulder without landslide, and then the roller is used to roll it. The outer wheel rim of the roller is kept about 30cm away from the edge line of the overfilled roadbed to ensure the safety of the roller. For the places where the roller should not be rolled, a small tamping machine is used to tamp it.

5) Test visa

Before sampling or testing, the tester should ensure whether the filler meets the requirements, whether the rolling section is compacted evenly, and whether the thickness of the filling layer exceeds the specified thickness. The quality inspection of subgrade fill compaction is detected with the layered filling and rolling construction. On the basis of the quality of the filler, the thickness of the filling, the uniformity of the longitudinal and horizontal direction of the filling layer, etc., the sand filling method and the K30 load plate are used to determine the compaction coefficient and foundation coefficient of the fine-grained soil, and the coarse-grained soil and gravel soil are tested by the K30 load plate and the nuclear densitometer, and the next layer of filling is carried out after reaching the specification and design standard.

6) Subgrade refurbishment

After the embankment is filled according to the design elevation, it is repaired and measured. Restore the middle line, set up a pile every 20m, measure the horizontal elevation, calculate the trimming height, cast the shoulder side pile, build the road arch, and roll it again with a flat roller, so that the roadbed surface is smooth and clean without floating soil, and the transverse drainage slope meets the requirements. For the fine-grained soil slope, according to the shoulder edge line pile, the overfilled part is brushed with a hanging line according to the design slope rate, and the renovation is carried out. After the renovation, the slope reaches the turning point with obvious ridge lines, straight lines, and smooth changes, so that the slope surface is smooth and there is no concave and convex, and the compaction density is qualified.

The renovation includes the drainage cross slope, flatness, slope and other renovation contents of the subgrade surface, and the subgrade renovation is carried out in strict accordance with the design structure size to meet the requirements of technical standards. Slope trimming release subgrade edge line pile, according to the requirements of the design specification, for the widening part of the artificial hanging line brush to overfill part, trim the vertex, trim the turning point to reach the edge line obvious, straight line, curve smooth.

(1) Scope of construction

The DK16+179.33~DK16+625.53 section is reinforced with one-way cement mixing piles, with a pile length of 7m-9m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement.

DK16+642.49~DK18+291.8 section is reinforced with one-way cement mixing pile, with a pile length of 9m-11m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement. The DK18+291.8~DK18+321.8 section is reinforced with two-way cement mixing piles, with a pile length of 12m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement.

The roadbed of DK26+592.24~DK26+622.24 is reinforced with multi-directional cement mixing piles, with a pile length of 12m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement. The roadbed of DK26+622.24~DK26+973.32 is reinforced with multi-directional cement mixing piles, with a pile length of 11m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement.

The DK27+218.18~DK27+536.64 section is reinforced with one-way cement mixing piles, with a pile length of 11m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement. DK27 + 536.64 ~ DK27 + 650.00 section is reinforced with one-way cement mixing pile, the specific pile length is subject to 0.5m driven into the sandstone, the pile diameter is 0.5m, the pile spacing is 1.3m, and the square is arranged.

DK28+071.25~DK28+101.25 section is reinforced with one-way cement mixing pile, with a pile length of 6m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement.

DK28+228.85~DK28+962.62 section is reinforced with one-way cement mixing pile, with a pile length of 6m-7m, a pile diameter of 0.5m, a pile spacing of 1.3m, and a square arrangement.

1) Do a good job of the construction site of the three links (road pass, water pass, electricity pass) one level (remove the obstacles on the construction site), find out the location of the underground pipeline and determine the location and height of the overhead wire; Do a good job in the drainage of the construction site, dig temporary drainage ditches on both sides of the road, and ensure that there is a 4% lateral drainage slope, and harden the cement pavement of the main road in the construction site, so as to form an overall smooth road.

2) The cement mixing pile must be qualified 42.5 grade ordinary Portland cement. Before use, the sample of cement is sent to the central laboratory or the laboratory designated by the supervising engineer for inspection;

(3) Construction process

Pile lofting→ drilling rig in place→ checking, adjusting the drilling rig → opening one, two, three (to be continued.) )